Adsorption of azithromycin pharmaceutical by polypyrrole and polypyrrole/zinc ferrite@magnetite (PPy/ZnFe2O4@Fe3O4) adsorbents synthesized from deep eutectic solvent: Kinetic, isothermic, and thermodynamic studies

Ahmad F. Hamasdiq; Hani K. Ismail; Rebaz A. Omer

doi:10.25259/AJC_635_2025

View/Download PDF

Buy Reprints

PDF

Translate this page into:

Original Article

2025

:18;

6352025

doi:

10.25259/AJC_635_2025

Adsorption of azithromycin pharmaceutical by polypyrrole and polypyrrole/zinc ferrite@magnetite (PPy/ZnFe₂O₄@Fe₃O₄) adsorbents synthesized from deep eutectic solvent: Kinetic, isothermic, and thermodynamic studies

Ahmad F. Hamasdiq, Hani K. Ismail^,*, Rebaz A. Omer

Department of Chemistry, Faculty of Science and Health, Koya University, Koya 44023, Kurdistan Region – F.R., Iraq

*Corresponding author: E-mail address: hani.khalil@koyauniversity.org (H. Ismail)

Received: 2025-06-03, Accepted: 2025-07-26, Epub ahead of print: 2025-09-22, Published: 2025-10-15

Licence

This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License, which allows others to remix, transform, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.

Abstract

The aim of this study was to use novel polypyrrole (PPy)/zinc ferrite@magnetite (PPy/ZnFe₂O₄@Fe₃O₄) and PPy compounds as adsorbents to remove azithromycin (AZM) from aqueous solutions. These adsorbents were made by chemical polymerization in a deep eutectic solvent (DES) known as oxaline. A range of techniques, such as Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), vibrating sample magnetometer (VSM), Brunauer-Emmett-Teller (BET), and zeta potential, were employed to comprehensively evaluate the synthesized adsorbents. Additionally, adsorption tests were conducted to examine the influences of AZM concentration, pH, contact duration, and adsorbent dose. The ideal results indicate that AZM removal effectiveness was 62.3% for PPy and 98.5% for PPy/ZnFe₂O₄@Fe₃O₄ under the following conditions: pH 6, with 80 mg of PPy and 60 mg of PPy/ZnFe₂O₄@Fe₃O₄ adsorbents, a drug concentration of 100 mg/L, and stirring for 180 min. The adsorption process was thoroughly investigated using the kinetic and isothermal models. The pseudo-second-order kinetic and Langmuir models were identified as the most accurate representations of AZM adsorption for both adsorbents at 298 K. Additionally, the data demonstrated that pure PPy had an adsorption capacity of 80.13 mg/g, but the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite had a high adsorption capacity of 183.73 mg/g. Thermodynamic analysis revealed that the adsorption process was spontaneous and endothermic. The adsorbent exhibited exceptional regenerative properties, allowing for reuse throughout five cycles. The study also investigated the adsorption of AZM medicines from real tablet samples utilizing the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite. These results showed the good absorbent capacity of PPy/ZnFe₂O₄@Fe₃O₄ in the efficient removal of AZM from water sources.

Keywords

Adsorption

Azithromycin

Conducting polymer composite

Deep eutectic solvents

Kinetic and isotherms

Polypyrrole

Show Related Articles from PubMed

1. Introduction

Recently, the spread of pharmaceutical residues in the environment has gained significant attention from researchers due to their significant risk to ecosystems and the contamination of aquatic ecosystems [1,2]. Pharmaceutically active chemicals (PhACs) have been widely utilized globally. When these substances are present in the environment, they typically have detrimental effects on aquatic life and can infect organisms, accumulating within them, adversely affecting the quality of existing water resources via deliberate or inadvertent release into aquatic environments [3,4]. Pharmaceutical effluents represent a potential source of water pollution and have infiltrated the environment via various means [5,6]. The largest sources of pharmaceutical waste for the environment and water bodies are human activities, hospital wastes, pharmaceutical waste, and veterinary therapy. Pharmaceutical residues have been identified and documented in sewage effluent, rivers, lakes, and groundwater [4,7]. There are many pharmaceuticals widely used to treat humans and animals that are very harmful to the environment after disposal due to their chemical composition and use. Antibiotics constitute a significant amount of these medications [8]. They possess a very resilient structure and constitute 15% of global medication use. The presence of antibiotics and their metabolites in aquatic ecosystems has raised significant concerns in recent years [9,10]. Azithromycin (AZM) is an important antibiotic that has a special 14-atom structure (Figure 1) and is used to treat bacterial infections. Owing to the absence of effective procedures for the removal of AZM, this chemical and its metabolite are discharged into municipal sewage after ingestion. AZM exhibits relative stability and low biodegradability, enabling prolonged presence in aquatic systems [11,12]. Environmental rules stipulate that the permissible AZM concentration is around 1 mg/L; exceeding this threshold heightens the risk of the medication entering the human body, potentially resulting in adverse effects and allergies. In addition, AZM can disrupt aquatic ecosystems, affecting microbial communities and contributing to antibiotic resistance [13].

Various methods have been used to remove antibiotics from water and wastewater, including physical methods like adsorption, membrane filtration, and reverse osmosis; chemical methods like electrocoagulation; and biological methods such as aerobic or anaerobic processes [14,15]. Adsorption remains a favored method because it is straightforward and offers many advantages, such as better effectiveness, easy recovery and recycling of the adsorbent, high efficiency in removing antibiotics on a large scale, and being a more affordable and flexible option for getting rid of these pollutants [16,17]. The creation of adsorbents for the effective elimination of concurrent chemical substances is essential. A variety of materials, including metal oxide nanocomposites [18], chitosan [19], carbon-based substances such as graphene oxide, graphene, activated biochar/charcoal, and carbon nanotubes and their derivatives, have been utilized to eliminate pharmaceutical contaminants from aqueous matrices and to be applied in separation science [20,21]. The efficacy of an absorbent relies on its non-toxicity, simplicity of preparation, high capacity, ability to absorb pollutants, and recyclability [22]. Conducting polymers (CPs) such as polypyrrole (PPy), polyaniline, polythiophene, and their composites have been thoroughly examined as effective adsorbents for various pharmaceutical contaminants due to their advantageous characteristics, including chemical and thermal stability, cost-effectiveness, high environmental stability, a distinctive doping mechanism, ability to extract polar analytes, and ease of manufacture [23-25]. In addition, CPs are a category of materials that exhibit notable characteristics due to their chemical and physical properties, facilitating their use in applications such as electrodes, sensors, rechargeable batteries, and, more recently, as adsorbent materials [26,27]. Nevertheless, CPs exhibit several disadvantages in their unadulterated form, including inadequate mechanical properties and restricted characterization of porosities, surface area, and cycle life stability; however, their incorporation with other materials may alleviate these issues [28,29]. The adsorption efficacy relies on porosity and surface area; hence, magnetic nanoparticles are widely employed in environmental disinfection due to their low toxicity, facile separation, and diminutive size. Iron oxides are valued for their several properties, including non-toxicity, chemical stability, magnetic qualities, and cost-effectiveness [15,30]. The incorporation of PPy and iron oxides into a singular adsorbent material can enhance its adsorption characteristics. Some adsorbents made from natural polymers have been reported in the literature [31-33].

Surface functionalization makes Fe₃O₄ nanoparticles better for different applications by adding specific molecules to their surfaces. Incorporating organic or inorganic molecules into Fe₃O₄ may enhance stability, prevent aggregation, and improve interaction selectivity. Recent studies on surface-functionalized Fe₃O₄ nanoparticles for water treatment have demonstrated remarkable efficacy in removing pollutants. Their stability, regenerative capacity, and extensive surface area enable them to eliminate contaminants from water, safeguard public health, and ensure access to clean water for all [34]. The incorporation of iron oxide with metal ferrite is a tactic to mitigate instability concerns. Multiple studies have demonstrated the considerable effectiveness of mixed iron oxide and metal ferrite nanoparticles, such as ZnFe₂O₄, in the remediation of organic-contaminated water, including pharmaceutical waste [35].

CPs can be readily produced in both aqueous and nonaqueous (ionic liquids) conditions by chemical or electrochemical processes [36]. Strong inorganic acids, including nitric acid, sulfuric acid, and hydrochloric acid, have been utilized as dopants in the production of conductive polymers. Nonetheless, the application of CPs in aquatic environments with these acids presents multiple challenges. They release hydrogen gas as a result of employing potent, dangerous inorganic doping acids. This leads to the embrittlement of polymers, reduced heat stability, and associated hazards, as well as alterations in morphology [26,37]. Deep eutectic solvents (DESs) may serve as alternatives to aqueous solutions lacking strong inorganic acids. This has garnered more attention than inorganic acids. DESs are innovative solvents that operate in a manner akin to ionic liquids [38]. In 2003, Abbot et al. identified distinctive green solvents known as DESs [39]. Cost-effective, simpler to produce than ionic liquids, devoid of hazardous strong inorganic acids in aqueous solutions, high solute solubility, significant ionic conductivity, and non-toxic. It comprises a eutectic mixture of quaternary ammonium salt that acts as a hydrogen bond acceptor (HBA) with a hydrogen bond donor (HBD) compound. The HBD compounds possess a hydrogen atom bonded to a moderately electronegative atom such as fluorine, oxygen, or nitrogen, while HBA compounds have a partial positive charge [40,41].

This study involved the synthesis of PPy with and without core/shell nanoparticles of zinc ferrite and magnetite (ZnFe₂O₄@Fe₃O₄) utilizing DESs (choline chloride: oxalic acid, known as oxaline) via a chemical polymerization procedure, employing ammonium persulfate (APS) as the initiator. This endeavor led to the development of a new multifunctional adsorbent, the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite, intended for the adsorption of AZM from water solutions. The functionalization of PPy with ZnFe₂O₄@Fe₃O₄ derived from DESs can augment the adsorption capacity and efficiency of the new adsorbent for pharmaceutical removal from aqueous solutions compared to PPy alone. This improvement is due to the presence of diverse functional groups on its surface, such as π-electron systems, nitrogen, and oxygen groups, along with an augmented surface area enabled by the integration of magnetic nanoparticles featuring a core/shell architecture and electrostatic interactions.

This modification of PPy/ZnFe₂O₄@Fe₃O₄ nanocomposites has not been employed for drug removal in the past, and there is currently no data on it. This study demonstrates that PPy/ZnFe₂O₄@Fe₃O₄ nanocomposites have enhanced removal efficiency and rapid adsorption rates for AZM in comparison to PPy alone. This adsorbent nanocomposite can be easily extracted from the solution and reused. The adsorbent of PPy/ZnFe₂O₄@Fe₃O₄ nanocomposites was characterized through multiple techniques, including Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), Brunauer-Emmett-Teller (BET) analysis, and vibrating sample magnetometer (VSM). The influence of several physical parameters, such as solution pH, drug concentration, adsorbent dosage, contact duration, and temperature, on adsorption efficiency was examined. The adsorption results were assessed using thermodynamic and kinetic models, as well as isotherm processes.

2. Materials and Methods

2.1. Chemicals and reagents

All materials were analytical grade. Chemicals utilized in this study include pyrrole monomer (Py) (Macklin, purity 98%), ammonium persulfate (APS, Bio Chemo Pharma), oxalic acid (C₂H₂O₄·2H₂O, Sigma-Aldrich, purity 99%), choline chloride (Bidepharm, purity 97%), iron (III) chloride hexahydrate (FeCl₃·6H₂O, Bio Chemo Pharma), zinc chloride (ZnCl₂, Carlo-Erba), and iron (II) chloride (FeCl₂, Bidepharm, purity 99.50%). Hydrochloric acid (HCl, 37%, Bio Chemo Pharma), hydrogen peroxide (H₂O₂, Sigma-Aldrich), MeOH and EtOH (extra pure 99.9%, Fisher), and sodium hydroxide (NaOH, Carlo Erba) were used. Methylene blue ((MB), ≥85%,), methyl orange ((MO),85%), Nickel (II) chloride hexahydrate (NiCl₂·6H₂O, 99.9%), copper (II) chloride powder (CuCl₂, 97%), and cadmium nitrate tetrahydrate (Cd(NO₃)₂·4H₂O, 99.99%) were purchased from Merck. All chemicals were used as received without further purification. AZM pure chemical was ordered from the company of Awamedica – Committed to Quality in Erbil, whereas AZM tablets (Brand name, VELPHARM, as shown in Figure S1) were purchased from local pharmacies in Erbil city.

Figure S1

Download

2.2. Preparation of Fe₃O₄ nanoparticles

FeCl₂·4H₂O (1.98 g) and FeCl₃·6H₂O (5.4 g) were combined in a 1:2 molar ratio and dissolved in 50 mL of deionized water; the solution was mechanically agitated at 80°C for 15 min, after which NaOH solution (1 M) was incrementally added until the pH reached 10. After 30 min, the black precipitate was isolated using magnetic decantation, washed at least five times with distilled water, followed by EtOH, and then dried under vacuum at 80°C for 10 h [42], as shown in Figure 2.

2.3. Preparation of ZnFe₂O₄ nanoparticles

3.3637 g of FeCl₃·6H₂O and 0.8481 g of ZnCl₂ were dissolved in 50 mL of distilled water. The flask was maintained under stirring and reflux at 80°C, the pH of the reaction mixture was raised to about 10 by the addition of a 10% NaOH solution, and stirring was sustained for 3 h. The precipitate was collected, centrifuged, washed at least five times with distilled water, followed by EtOH, and then dried under vacuum at 100°C for 6 h. The resultant dark brown powders were pulverized and then calcined at 450°C for 3 h [42], as shown in Figure 3.

2.4. Preparation of ZnFe₂O₄@Fe₃O₄ nanoparticles

To synthesize ZnFe₂O₄@Fe₃O₄ (Figure 4) at a 2:1 weight ratio of ZnFe₂O₄ to Fe₃O₄, 0.23 g of magnetite nanoparticles (Fe₃O₄) and 0.47 g of zinc ferrite nanoparticles (ZnFe₂O₄) were incorporated into 20 mL of deionized water. The reaction mixture was agitated for 1 h. The pH of the reaction mixture was then adjusted to 8 using a 1M NaOH solution and stirred under reflux for 3 h. Ultimately, ZnFe₂O₄@Fe₃O₄ nanoparticles were retrieved from the reaction vessel using an external magnet, thereafter washed at least five times with distilled water, followed by EtOH, and dried in an oven at 80°C [42].

2.5. Preparation based DES

In our investigation, DES was synthesized by amalgamating choline chloride (ChCl) and oxalic acid (Oxa) in a 1:1 molar ratio, referred to as oxaline (Figure 5), and then heated in an oven at 60°C for 1 h. Subsequently, we agitated the solution on the magnetic hotplate at 60°C for an additional 2 h until a clear, homogeneous solution was achieved, as indicated in earlier works [36,43,44].

Synthesis and structure of the proposed Oxaline-DES.

2.6. Chemical polymerization

2.6.1. Synthesis of PPy

PPy was synthesized using chemical polymerizations, 2.5 g of pyrrole monomer dissolved in 30 mL of oxaline-DES solvent, and stirred for 30 min, referred to as solution 1. A prepared oxidant solution of APS was utilized as the initiator by dissolving 4 g of it in 25 mL oxaline-DES as a dopant, resulting in solution 2. Subsequently, solution 2 was transferred to a separating funnel, where the initiator was added dropwise to the monomers in solution 1 over the course of one hour, with continuous stirring at 25°C to initiate the polymerization of the monomer. Upon completion of the dropwise addition, approximately 3 mL of H₂O₂ was introduced in several stages to enhance the polymerization process. Upon completing 8 h of polymerization with agitation, allow the solution to rest overnight. The next day, the product was filtered via a Buchner funnel and then rinsed many times with deionized water until a clear solution was achieved. The wet polymer output was then processed in an oven at 70°C for 5 h to produce dry polymer powder. The proposed structure and reaction process for the synthesis of PPy have been shown in Figure 6(a).

In-situ oxidative polymerization process for synthesis of (a) PPy and (b) PPy/ZnFe2O4@Fe3O4 nanocomposite.

2.6.2. Synthesis of PPy/ZnFe₂O₄@Fe₃O₄ composite

The PPy/ZnFe₂O₄@Fe₃O₄ composite was synthesized via chemical polymerization using the pyrrole (Py) monomer and equal proportions of ZnFe₂O₄ powder and Fe₃O₄ nanoparticles, maintaining a weight ratio of 1:1 between ZnFe₂O₄ and Fe₃O₄. Initially, varying weight ratios of ZnFe₂O₄:Fe₃O₄ nanoparticles were combined in 35 mL of oxaline-DES solvent, as shown in Table 1. The solution was sonicated for 2 h and thereafter placed on a magnetic hotplate with stirring. Subsequently, 2.5 g of pyrrole monomer was used for each distinct ratio (see Table 1). In addition, an oxidant solution of APS was prepared as the initiator by dissolving 4 g of it in 25 mL of oxaline-DES as a dopant. Subsequently, the oxidant solution was transferred to a separating funnel, where it was added dropwise to the monomers and composite solution over 1 hour while continuously stirring to initiate the polymerization of the monomer. Next, approximately 3 mL of H₂O₂ is added into a polymerization solution in several stages to enhance the polymerization process. The polymerization procedure was conducted for 8 h at 25°C, followed by an overnight incubation of the solution. Finally, the product was filtered via a Buchner funnel and then rinsed many times with deionized water until a clear wastewater solution was achieved. The wet polymer output was then processed in an oven at 70°C for 5 h to produce dry polymer composite powder, and the chemical polymerization reaction has been shown in Figure 6(b).

Table 1. The weight ratio of metal oxide to monomer in PPy/ZnFe₂O₄@Fe₃O₄ composite polymer synthesis.

Samples	Py monomer (g)	Fe₃O₄@ZnFe₂O₄ (g)
1	2.5	0
2	2.5	0.25
3	2.5	0.5
4	2.5	0.75
5	2.5	1.00
6	2.5	1.25

2.7. Preparation of AZM pharmaceutical stock solution

To prepare a stock solution with a concentration of 500 mg/L, the pure AZM powder was dissolved in deionized water containing 10% absolute MeOH to ensure complete dissolution of the medication. The amount of AZM was determined based on its molecular weight.

2.8. Ultraviolet-visible spectroscopy

Spectroscopic analysis of AZM was conducted using a UV/Vis Spectrometer (Alegent Cary Series 100 UV-Vis spectrometer) equipped with a 1 cm quartz cell to ascertain λ_max. The absorbance value at the λ_max of 213 nm was recorded and analyzed, as seen in Figure S2. The stock solution of AZM in a MeOH-water combination was appropriately diluted, and calibration was performed within a concentration range of 2 to 60 mg/L. Subsequently, λ_max 213 nm was used to establish the AZM calibration curve, yielding a correlation coefficient (R²) of 0.9973, as shown in the supplemental information (Figure S3). The λ_max value corresponded with the literature [45,46].

Figure S2

Download

Figure S3

Download

2.9. pH points of zero charges (pH_pzc)

The pH at point of zero charge (pH_pzc) of the pure PPy and PPy/ZnFe₂O₄@Fe₃O₄ composite was determined by adding 40 mg of each material to 100 mL of solutions that had an initial pH of 2 to 10 (adjusted with 0.1 N NaOH and HCl solutions). The final pH was measured after 24 h of equilibrium at 298 K. The variation in pH during equilibration, ∆pH (the difference between final and initial pH), was subsequently graphed against the initial pH. The pH_pzc was ascertained by the intersection of the initial and final pH values [25]. This procedure has been executed in duplicate.

2.10. Adsorption study

The adsorption tests were carried out at room temperature using a 0.1 M solution of HCl and NaOH to change the pH of the solution using a pH meter (Adwa (AD8000)). In each experiment, the samples were mixed with a certain amount of the adsorbent at 200 rpm for a predefined amount of time using a shaker (GFL Shaking Incubator 3031). The impact of multiple parameters was then investigated, including temperature (298-313 K), adsorbent dosage (20 to 140 mg), initial pharmaceutical pollutant concentration (20–200 mg/L), reaction time (10–300 min), and pH (2–10). A UV/Vis Spectrometer (Alegent Cary Series 100 UV-Vis spectrometer) was used to measure the concentrations of AZM separately before and after adsorption by the adsorbent at wavelengths of 213 nm [45,46]. For further information, refer to Figures S2 and S3 in the supplemental information. The equilibrium adsorption capacity (q_e) and pharmaceutical adsorption percentage (Removal% %), Eq. (1-2), of the synthesized adsorbent were examined with variations in the adsorbent dosage and AZM concentration.

(1)

R e m o v a l % = \frac{(C_{i} - C_{e})}{C_{i}} \times 100

(2)

q_{e} = \frac{(C_{i} - C_{e}) V}{M}

C_i is the initial concentration of the drug at time 0, C_e is the equilibrium concentration in mg/L, V is the volume of the drug solution in liters (L), and M is the mass of the adsorbent in gramd=s (g). Furthermore, the mean adsorption from three measurements and the relative errors of the experimental findings were ± 5%.

2.11. Adsorption modelling studies

Kinetic adsorption experiments were conducted for durations ranging from 10 to 300 min, utilizing aqueous solutions containing 100 mg/L of AZM. The pH level was optimized, and further parameters have been detailed in the figure captions. The selected kinetic models for visualizing the experimental data comprise pseudo-first-order, pseudo-second-order, and Elovich models. The linear versions of these equations have been shown in section 3.3.1. Isothermal tests were performed with increasing AZM concentrations ranging from 20 to 200 mg/L at the appropriate pH and contact time. The isotherms were obtained using linear regression of the experimental data utilizing the Langmuir, Freundlich, and Temkin models, as presented in section 3.3.2. The remaining AZM in the solution was measured via UV spectroscopy.

2.12. Regeneration of PPy/ZnFe₂O₄@Fe₃O₄ adsorbent

For the adsorption-desorption studies, 60 mg of the adsorbent was added to 100 mL of AZM solution (100 mg/L) in a sealed conical flask. The mixture was then stirred for 180 min. Subsequently, the PPy/ZnFe₂O₄@Fe₃O₄ adsorbent was isolated by magnetic means (Figure S4), and Eq. (1) was employed to determine the adsorption percentage. For the desorption process, 50 mL of MeOH was combined with the identical adsorbent-loaded AZM. The adsorbent was collected by magnetic means and repurposed for adsorption. This technique was conducted three times to ensure consistent and favorable results. The UV-Vis spectrophotometer was utilized to analyze the supernatant solution. The desorption % was calculated using Eq. (3).

Figure S4

Download

(3)

D e s o r p t i o n % = \frac{A m o u n t o f d r u g d e s o r b e d}{A m o u n t o f d r u g a d s o r b e d} \times 100

2.13. Environmental application

This study examines the effectiveness of synthetic nanocomposites in removing AZM from wastewater samples by analyzing various tap water samples containing actual tablets of these medications. The experimental configuration aligned with prior descriptions. The designated weight of the medications (comprising 50 mg/L of AZM) was dissolved in deionized water, tap water, and modified wastewater samples (incorporating 10 mg of methyl orange, methylene blue, Ni, Cu, and Cd ions). The undissolved AZM powder was removed from the solution by filtration with Whatman No. 41 paper.

2.14. Instrumental

A variety of techniques were used for the characterization and analysis of the PPy, ZnFe₂O₄@Fe₃O₄, and PPy/ZnFe₂O₄@Fe₃O₄ nanocomposites. The FTIR spectra were obtained using a (Bruker, VBCTOR 22, USA) spectrophotometer via the KBr-disc method as the background medium. FTIR Spectra were acquired throughout the wavenumber range of 400-4000 cm^-1 to determine the functional groups of the PPy composite. A powder XRD analysis was carried out by (GNR Explorer, Via Torino, 7 28010 Agrate Conturbia (NO) - Italy) to examine the crystalline characteristics of the samples, with deviation angles recorded from 5° to 80°. The BET using nitrogen adsorption-desorption isotherms within the P/P0 range of 0-1 and pore size distributions from 1 to 100 nm was used to evaluate the surface area and pore diameter distribution. The surface morphology was examined with field-emission SEM (FESEM-TSCAN) at an accelerator voltage of 10 keV. EDX was used to characterize the elements contained in the deposited polymer composite. The magnetic properties of pure ZnFe₂O₄@Fe₃O₄ and PPy/ZnFe₂O₄@Fe₃O₄ nanocomposites were evaluated utilizing a vibrating sample magnetometer (Kavir Magnet Company) to acquire magnetization loops for the synthesized materials.

3. Results and Discussion

3.1. Characterization of polymeric samples

3.1.1. FTIR study

FTIR was utilized to investigate the substance’s molecular bond properties, chemical makeup, and the existence of functional groups. Figure 7 displays the FTIR spectra of ZnFe₂O₄@Fe₃O₄, PPy, and the ternary composite PPy/ZnFe₂O₄@Fe₃O₄. In the FTIR spectra of the produced ZnFe₂O₄@Fe₃O₄ (black line), the hydroxyl group −OH, which results from absorbed water, is responsible for the broad band that developed at about 3438 cm⁻¹. The M-O-H (M=Fe and Zn) absorption peaks were found in-plane at 1384 cm^-1 and out-of-plane at 1630 cm^-1 [27]. Furthermore, in composite ZnFe₂O₄@Fe₃O₄, the stretching vibration of the M-O bond is responsible for the intrinsic absorption peaks in the following manner: The peaks between 721 and 640 cm^-1 are ascribed to the tetrahedral sublattice and the octahedral configuration of Fe-O, respectively [47]. However, the metal tetrahedral and octahedral sites of Zn-O in composite ZnFe₂O₄@Fe₃O₄ are represented by the high absorption peak at 558 cm^-1 and a faint signal at 444 cm^-1, which are suggestive of intrinsic vibrational modes [48].

FTIR spectra for ZnFe2O4@Fe3O4, PPy, and the PPy/ZnFe2O4@Fe3O4.

The absorption bands corresponding to pure PPy, illustrated in Figure 7 (pink line), are identified at wavenumbers of 784, 920, 1030, 1188, and 1377 cm^-1, which can be attributed to the C–H out-of-plane bend, =C–H bend of alkenes, C–H in-plane stretch, conjugated C–N stretch, and C–C vibration of the aromatic ring in PPy, respectively. Additionally, the bands at 1550, 1643, 2919, and 3428 cm^-1 are attributed to the stretching vibrations of C–C bonds, C–N bonds, C–H stretches, and N–H bonds (associated with absorbed water) of the pyrrole ring. The identified peaks correspond with existing literature on the polymerization of PPy [3,41,44].

On the other hand, the FTIR spectra of PPy/ZnFe₂O₄@Fe₃O₄ (Figure 7, brown line) show changes in the functional groups and chemical composition when compared to PPy and ZnFe₂O₄@Fe₃O₄ individually. In addition, the FTIR spectra of ZnFe₂O₄@Fe₃O₄ and PPy two moieties were observed in the FTIR spectrum of the PPy/ZnFe₂O₄@Fe₃O₄ composite, which confirms that the two have combined. Broadband at 3423 cm^-1 demonstrated the combination of the –OH group of ZnFe₂O₄@Fe₃O₄ particles with the –NH of PPy into the composite structure. Moreover, the specific peaks of Fe–O and Zn–O at 600 and 680 cm^-1 are distinctly observable, affirming that the structural integrity of the ferrite phase was preserved during the production of the composite. This confirms the incorporation of Fe₃O₄@ZnFe₂O₄ particles into the PPy matrix through electrostatic and hydrogen bonding interactions. Regarding FTIR peaks of PPy, they are evident in the PPy/ZnFe₂O₄@Fe₃O₄ composite; however, they are significantly shifted in their position, as clearly depicted in Figure 7. Furthermore, the peak intensities for the PPy/ZnFe₂O₄@Fe₃O₄ composite displayed discrepancies relative to those of pure PPy, signifying a notable interaction between ZnFe₂O₄@Fe₃O₄ and PPy within the PPy/ZnFe₂O₄@Fe₃O₄ matrix.

3.1.2. XRD study

Figure 8 displays the powder XRD patterns for ZnFe₂O₄@Fe₃O₄, PPy, and PPy/ZnFe₂O₄@Fe₃O₄ composites. XRD can identify the crystalline and amorphous regions of the polymers. In general, broad, low-intensity peaks in a polymer’s matrix suggest amorphous behavior, whereas sharp, high-intensity peaks indicate crystalline behavior. The ZnFe₂O₄@Fe₃O₄ sample exhibits strong crystallization in its structure, as evidenced by the diffraction peaks around 2θ = 18.27°, 30.31°, 33.21°, 35.77°, 41.03°, 43.26°, 49.61°, 54.07°, 57,51°, 62.68°, and 74.62°. These peaks are attributed to the (111), (220), (300), (311), (222), (400), (420), (422), (511), (440), and (533) crystalline planes of the spine, respectively, as reported in previous works [42,49]. Additionally, the interplanar distance was compared with JCPDS data (JCPDS card no. 10-325, 22-1086) to index the peaks, which correspond to ZnFe₂O₄@Fe₃O₄. The diffraction pattern of pure PPy has a prominent peak at 25.10°, presumably associated with the (200) crystal plane. This peak indicates that the PPy chain demonstrates an amorphous characteristic, as corroborated by other research [44,50].

XRD spectra for Fe3O4@ZnFe2O4, PPy, and the PPy/Fe3O4@ZnFe2O4.

Amorphous PPy and crystalline ZnFe₂O₄@Fe₃O₄ nanoparticles are confirmed to exist in the PPy/ZnFe₂O₄@Fe₃O₄ composite by the presence of diffraction peaks typical of both PPy and Fe₃O₄@ZnFe₂O₄ particles. Additionally, compared to pure PPy, the XRD peak of PPy was found to have a reduced intensity and to be displaced to 24.96° in the PPy/ZnFe₂O₄@Fe₃O₄ composite. Additionally, the crystalline planes of Fe₃O₄@ZnFe₂O₄ are observed for the PPy/Fe₃O₄@ZnFe₂O₄ composite at (111), (220), (311), (222), (400), (420), (422), (511), and (440). However, they are shifted to at 2θ around 18.72°, 29.86°, 36.89°, 40.58°, 42.81°, 49.14°, 54.60°, 57.75°, and 63.34°, respectively. Some of these planes vanish entirely after being incorporated with the amorphous structure of the PPy (Figure 8, brown line). These findings indicate the strong interaction between amorphous PPy and ZnFe₂O₄@Fe₃O₄ nanoparticles. The incorporation of PPy with ZnFe₂O₄@Fe₃O₄ nanoparticles led to a decrease in the overall crystallinity of the composite, as evidenced by reduced peak intensities and partial vanishing of crystalline planes. The observed peak shifts and broadening may be due to strain induced by polymer encapsulation, strong interfacial interactions, or potential partial oxidation of Fe₃O₄ to Fe₂O₃ under the influence of oxidizing agents used during polymerization.

3.1.3. Surface morphology study

FE-SEM, as illustrated in Figure 9(a-c), was used to examine the surface morphologies of the prepared substances (ZnFe₂O₄@Fe₃O₄, PPy, and PPy/ZnFe₂O₄@Fe₃O₄). As shown in Figure 9(a), the FE-SEM micrograph of ZnFe₂O₄@Fe₃O₄ demonstrated interconnected particles that produced an agglomerated structure with oval morphologies. The insert Figure 9(a) illustrates the range of sizes of the particles, which are in nanometers. Figure 9(b) shows the SEM of pure PPy, which is characterized by somewhat porous aggregates and typically has an irregular spherical form. However, the surface morphology of the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite is completely changed when PPy is mixed with ZnFe₂O₄@Fe₃O₄ nanoparticles, as shown in Figure 9(c). The surface of the nanocomposite sample exhibits significant irregularity and a rough, porous morphology, contrasting with the surface of pure PPy. This research demonstrates that ZnFe₂O₄@Fe₃O₄ was effectively grafted onto the surface of PPy. Moreover, a notable disparity in grain size (within the nanostructure) and a more fragmented, network-like morphology were detected in comparison to PPy. This open configuration enables the ingress of adsorbate pharmaceuticals onto the interior surface of PPy/ZnFe₂O₄@Fe₃O₄. These findings may thus be regarded as promising evidence for the utilization of PPy/ZnFe₂O₄@Fe₃O₄ as an adsorbent material in wastewater treatment.

SEM pictures illustrating the surface morphology of (a) ZnFe2O4@Fe3O4, (b) PPy, and (c) PPy/ZnFe2O4@Fe3O4. Elemental EDX spectra of (d) ZnFe2O4@Fe3O4, (e) PPy, and (f) PPy/ZnFe2O4@Fe3O4.

Elemental analysis can determine the number of atoms in a sample and yield important information about the structure and composition of an adsorbent. Figure 9(d-f) depicts the EDX of the synthesized samples. The inclusion of C, O, N, Zn, and Fe in the composition of PPy/ZnFe₂O₄@Fe₃O₄ is shown in Figure 9(f), in contrast to those components shown in Figure 9(d-f), indicating the successful incorporation of these elements into the synthesized PPy/ZnFe₂O₄@Fe₃O₄. This result confirms the successful synthesis of PPy/ZnFe₂O₄@Fe₃O₄ and aligns with the FTIR, XRD, and SEM data.

3.1.4. Pore size distribution BET analysis

Nitrogen adsorption–desorption isotherms were used to calculate the samples’ specific surface areas and porosity characteristics using the BET and BJH techniques, as shown in Figure 10. The surface characteristics of pure ZnFe₂O₄@Fe₃O₄, PPy, and the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite are shown in Table 2. The hysteresis loops for PPy and PPy/ZnFe₂O₄@Fe₃O₄ at relative pressures (P/P₀) were approximately 0.94 and 0.95, respectively, as shown in Figure 10(a). The findings indicate that the structures of PPy and PPy/ZnFe₂O₄@Fe₃O₄ samples exhibit mesoporosity. It was found that pure PPy had mean pore diameters of 24.40 nm, a specific surface area of 26.46 m²/g, and a total pore volume of 0.169 cm³/g. In contrast, the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite exhibited mesoporous behavior, with mean pore diameters of 50.78 nm, a specific surface area of 56.71 m²/g, and a total pore volume of 0.270 cm³/g. A material with pore diameters less than 2 nm is classified as having micropores, those between 2 and 50 nm are classified as having mesopores, and materials with pore diameters greater than 50 nm are classified as having macropores [51].

(a) Nitrogen adsorption–desorption isotherms and (b) Distributions of pore sizes for PPy and PPy/ZnFe2O4@Fe3O4 nanocomposite samples.

Table 2. Pore characteristics of ZnFe₂O₄@Fe₃O₄, PPy, and PPy/ZnFe₂O₄@Fe₃O_4.

Samples	BET surface area (m²/g)	Total pore volume (cm³/g)	Mean pore diameter (nm)
ZnFe₂O₄@Fe₃O₄	38.88	0.102	11.2
PPy	26.46	0.169	24.40
PPy/ZnFe₂O₄@Fe₃O₄	56.71	0.270	50.78

The distribution of pore sizes in the polymer nanocomposite was found to be between 1 and 100 nm, as indicated by the BJH plot (Figure 10b). This indicates the existence of two pore categories: (i) mesopores, predominantly ranging from 2 to 50 nm, and (ii) macropores, spanning from 50 to 100 nm. Compared to the PPy homopolymer, the modification of PPy with ZnFe₂O₄@Fe₃O₄ nanoparticles led to an enhancement in surface area and total pore volume, hence dramatically augmenting porosity and adsorption performance. This can be attributed to the change in the growth orientation and surface morphology of the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite, as corroborated by the SEM data (Figure 9). The enhanced porosity and surface area characteristics of the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite, together with the abundance of functional groups, indicate its significance for drug adsorption.

3.1.5. Magnetic study

The magnetic behavior of the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite and pure ZnFe₂O₄@Fe₃O₄ at 298 K between -15000 and 15000 Oe was characterized using a VSM. Figure 11 shows the magnetization curves for pure ZnFe₂O₄@Fe₃O₄ and the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite. Both samples exhibit magnetic properties as evidenced by their behaviors over conventional hysteresis loops. The corresponding coercivity (Hc), remanent magnetization (Mr), and saturation magnetization (Ms) for ZnFe₂O₄@Fe₃O₄ are 397.12 Oe, 21.96 emu/g, and 44.31 emu/g, respectively. On the other hand, these values are displayed by the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite at 16.12 Oe, 2.41 emu/g, and 12.12 emu/g, respectively. These results are consistent with previous studies [52,53]. The substantial interfacial interaction between ZnFe₂O₄@Fe₃O₄ and PPy diminished the magnetic properties of the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite. This indicates that the nanocomposite possesses certain magnetic characteristics of PPy/ZnFe₂O₄@Fe₃O₄.

PPy/ZnFe2O4@Fe3O4 nanocomposite and ZnFe2O4@Fe3O4 VSM magnetization curves.

3.2. Adsorption studies

3.2.1. Optimization of adsorbent for the adsorption of AZM pharmaceutical

Changes in the Fe/Zn ratio between the ZnFe₂O₄@Fe₃O₄ sample and the PPy/ZnFe₂O₄@Fe₃O₄ composite may be a sign of physical or chemical processes that alter the bulk stoichiometry or surface composition. In particular, if the polymer contains functional groups like amines or carboxylic acids, which PPy has, chemical interactions may change the surface composition and redistribute metal ions. Based on the results shown in Table 3, sample No. 5 was chosen as an adsorbent nanocomposite (PPy: ZnFe₂O₄@Fe₃O₄ (30wt%)) to remove the AZM pharmaceutical pollutant from aqueous solution. Its performance was compared to that of pure PPy to study their kinetic, isothermic, and thermodynamic processes. In addition, temperature, contact time, analyte concentration, adsorbent dosage, and solution pH can all impact the adsorption of AZM pharmaceutical and have been investigated in the following studies.

Table 3. Optimization of PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite for AZM removal (C_i = 50 mg/L), V = 100 mL, time = 120 min, dose = 50 mg, pH = 7) from aqueous solution.

Samples	PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite		AZM removal %
Samples	PPy (mg)	Fe₃O₄@ZnFe₂O₄(mg)	AZM removal %
1	0	50	38
2	50	0	43
3	45	5	50
4	40	10	58
5	35	15	76
6	30	20	71
7	25	25	69

3.2.2. Factors affecting adsorption

3.2.2.1. Impact of initial solution pH

The protonation and deprotonation of the adsorbent surface charge, as well as the speciation of the pharmaceutical contaminants, depend on the pH of the solution. The pH also impacts the adsorbent’s ability by affecting the activity of its functional groups [27,54]. In this study, the adsorption behavior of AZM from water was examined using both PPy and PPy/ZnFe₂O₄@Fe₃O₄ across a wide pH range from 2 to 10, as shown clearly in Figure 12(a). The results indicated that the effectiveness of these adsorbents in removing AZM strongly depended on the pH of the solution. According to the findings in Figure 12(a), both adsorbents’ removal efficiency rose when the pH was raised from 2 to 6; however, effectiveness decreased when the pH was raised above 7. Both adsorbents performed the best adsorption for AZM at pH 6, with the composite (PPy/ZnFe₂O₄@Fe₃O₄) removing almost 85%, which is much better than the pure PPy, which only removed about 48% under the same conditions. This performance enhancement of the PPy/ZnFe₂O₄@Fe₃O₄ compared to the pure PPy is attributed to the combined benefits of the PPy and ZnFe₂O₄@Fe₃O₄ particles. The PPy/ZnFe₂O₄@Fe₃O₄ offers a greater surface area, enhanced porosity, and more active sites for AZM to attach to its surface, thereby boosting electrostatic interactions and overall bonding, particularly at pH 6. Therefore, the ideal pH was determined to be 6.

(a) The percentage of AZM removed by PPy and PPy@ZnFe2O4@Fe3O4 adsorbents at various starting pH solutions (2–10) while maintaining the same values for all other parameters (conditions: beginning Cdrug = 50 mg/L; V= 100 mL; temperature = 298 K, time= 120 min, dosage= 50 mg). (b) the pHpzc analysis of the PPy and PPy@ZnFe2O4@Fe3O4 nanocomposite (PZC- Point of zero charge).

The behavior of these materials in relation to their surface charge is further explained by the point of zero charge (pH_pzc) [55] in Figure 12(b), which shows how the surface charge of PPy and the composite changes with pH. Figure 12(b) indicates that pH_pzc for PPy was 6.66 while for PPy/ZnFe₂O₄@Fe₃O₄ was slightly higher (6.90). At a pH lower than 6, the surface charge of both adsorbents is positive, while at a pH higher than 6, their surfaces are negative, as shown in Figure 12(b). AZM has various functional groups that play an important role in changing the surface charge of the material as pH changes. Under low acidic conditions, AZM has a positive charge, and so do the adsorbents, which enhances the repulsive interaction between the adsorbent and the adsorbate (AZM) and thus reduces adsorption between them. At pH 6 (mildly acidic to neutral pH), AZM has a negative charge, while the adsorbents exhibit a positive charge. This situation increases the attraction between them due to different electric charges, along with other interactions like hydrogen bonding, which helps the adsorbents remove more AZM. When the pH is high, above the pH_pzc, both adsorbents become negatively charged because their functional groups lose protons. Under these conditions, AZM also has a negative charge, leading to repulsive interactions between the adsorbent and AZM and reducing the removal rate. Furthermore, the lower percentage of removal may also be due to H⁺ ions competing for adsorption sites in an acidic environment (protonated drug) and OH^- ions competing in a basic environment (deprotonated drug). Consequently, both adsorbents found that the optimal pH value for AZM to adsorb was 6.

3.2.2.2. Impact of nanocomposite adsorbent dosage

The adsorbent dosage is an important practical factor that greatly affects the removal rate and, thus, the cost-effectiveness of the adsorption method [21]. The impact of the adsorbent dosage was demonstrated using a range of 10 to 140 mg, while maintaining all other variables constant (pH at 6, initial drug concentration = 50 mg/L, volume = 100 mL, temperature = 298 K, treatment time = 120 min). Figure 13(a) depicts the variations in adsorbent dosage concerning the removal efficiency of AZM utilizing the PPy and PPy@ZnFe₂O₄@Fe₃O₄ adsorbents. The data showed that when the amount of PPy adsorbent was raised from 10 mg to 80 mg, the removal percentage of AZM increased from 14.5% to 50.3%. Likewise, increasing the amount of nanocomposite adsorbent from 10 mg to 60 mg resulted in an increase in the removal percentage of AZM from 30.5% to 85.6%. Nevertheless, for both adsorbents, the removal percentage stayed consistent after this. These findings could be explained by the fact that raising the adsorbent’s dosage will increase the number of adsorption sites available, enabling the adsorbent to remove more contaminants overall. This leads to an improvement in the effectiveness of AZM adsorption. From Figure 13(a), it is concluded that both adsorbents demonstrate improved removal efficiencies as the dosage increases. However, the PPy@ZnFe₂O₄@Fe₃O₄ exhibits consistently better efficiency compared to PPy. This is due to the incorporation of ZnFe₂O₄@Fe₃O₄ nanoparticles into the PPy matrix, which increases its surface area and number of active sites, facilitating the entry and binding of AZM molecules into the adsorbent.

Impacts of (a) adsorbent dosage (10-140 mg), (b) initial AZM concentration (20-200 mg/L), (c) sorption time (10-300 min).

3.2.2.3. Impact of initial concentrations of drug

The initial pharmaceutical concentration is crucial for successful adsorption. The result depends on how the surface areas of the adsorbent interact with the pharmaceutical ions. Therefore, adjusting the concentration is important for effective bonding between the active sites of the adsorbent and the concentration of pharmaceutical ions. The efficiency of AZM removal by both adsorbents was evaluated at initial concentrations of the AZM drug between 20 and 200 mg/L, under optimal testing conditions (initial pH = 6, adsorbent dosage = 80 mg for PPy and 60 mg for the composite, duration = 120 min, temperature = 298 K). Figure 13(b) illustrates that the removal efficiencies of AZM by PPy and PPy@ZnFe₂O₄@Fe₃O₄ were consistently 50% and 85.6%, respectively, despite an increase in the initial solution concentration from 20 to 100 mg/L. The observed stability results from the presence of unsaturated active sites in the adsorbent. Thereafter, the removal percentage of AZM decreased from 50.0% to 18.50% with PPy and from 85.6% to 45.40% with PPy@ZnFe₂O₄@Fe₃O₄ as drug concentrations increased from 120 to 200 mg/L. The adsorption effectiveness decreased as the concentration of pharmaceutical ions increased because the adsorption sites on the adsorbent surface were saturated.

3.2.2.4. Impact of reaction time

Contact time is a critical factor in determining the binding speed and effectiveness of an adsorbent for the complete removal of pharmaceutical ions from a solution at a specific equilibrium time. The characterization of the adsorption mechanism is fundamentally reliant on the equilibrium reaction time of the adsorption process and the rate at which equilibrium is attained [56]. The research examined the influence of adsorption duration on the uptake of the AZM drug by the PPy and PPy/ZnFe₂O₄@Fe₃O₄ adsorbents. Adsorption experiments were conducted over a duration of 10 to 300 min, maintaining constant conditions (pH of AZM at 6, initial AZM concentration of 100 mg/L, volume of 100 mL, temperature at 298 K, and adsorbent dosages of 80 mg for PPy and 60 mg for the composite). Figure 13(c) illustrates that the removal rate of AZM medicine with both adsorbents increases with extended sorption time, ultimately achieving a maximum value. The removal rate of AZM increases as the adsorption duration is extended from 10 to 180 min, using both adsorbents. At equilibrium, the adsorption percentages of AZM were 62.3% for PPy and 98.5% for PPy/ZnFe₂O₄@Fe₃O₄. This happens because there are many spots for adsorption at the beginning, but once equilibrium is reached, the available spots decrease, and the repulsive forces between the adsorbent and the adsorbate molecules increase. Therefore, the initial stages produce higher adsorption, while after equilibrium, adsorption remains constant or increases slowly. The sorption duration for the subsequent experiments was established at 180 min for AZM adsorption.

3.3. Adsorption modelling studies

3.3.1. Kinetics modelling study

The adsorption of AZM onto the PPy and PPy/ZnFe₂O₄@Fe₃O₄ adsorbents was evaluated utilizing a range of kinetic models, such as pseudo-first-order, pseudo-second-order, and Elovich models. The linear expression formulas for the different kinetic models are shown in Table 4. The pseudo-first-order model Eq. (4) delineates the adsorption of the adsorbate solely to a singular active, energetically uniform site on the adsorbent’s surface, characterized by physical interactions. The pseudo-second-order model Eq. (5) suggests that the adsorption process is chemical and indicates that an analyte can attach to two active sites with varying binding energies [25]. The Elovich model, defined by Eq. (6), posits that the adsorbent’s surface is heterogeneous, considers chemisorption-type adsorption, and suggests that adsorption occurs in multilayers [21,57].

Table 4. Various kinetics model types.

Model

Linear Equation

Plot

Ref.

Pseudo-first-order

(4)

\ln (q_{e} - q_{t}) = \ln q_{e} - k_{1} t

l n (q_{e} - q_{t}) v s . t

[58]

pseudo-second-order

(5)

\frac{t}{q_{t}} = \frac{1}{k_{2} q_{e}^{2}} + \frac{t}{q_{e}}

\frac{t}{q_{t}} v s . t

[59]

Elovich

(6)

q_{t} = \frac{1}{β} l n (α β) + \frac{1}{β} \ln t

q_{t} v s . \ln t

[60]

Eq. (4): q_e and q_t: the quantities of adsorbate adsorbed by the adsorbent (mg/g) at equilibrium and time t (min), respectively; k₁: the pseudo first order rate constant (min⁻¹).

Eq. (5): k₂: the pseudo-second-order rate constant (g/mg. min)

Eq. (6): α: the initial adsorption rate constant (mg/g. min); β: desorption rate constant (g/mg).

Figures 14 (a-d) demonstrate the application of the kinetic models with an initial drug concentration of 100 mg/L, along with other conditions outlined in the caption. The theoretical and experimental outcomes obtained from the kinetic models are shown in Table 5. Figure 14(a) demonstrates that the equilibrium adsorption of both adsorbents rises with prolonged sorption periods, finally reaching a maximum value at equilibrium. The equilibrium adsorption of AZM by adsorbents rises as the adsorption period extends from 10 to 180 min, after which it stabilizes for both adsorbents. Comparing the experimentally obtained equilibrium adsorption amounts (qe _exp_.) of AZM for both adsorbents with the values of q_e derived from the pseudo-first-order models (Figure 14b) indicates notable discrepancies between these values. The values of AZM adsorbed by PPy are as follows: q_e calculated is 119.69 mg/g and q_m experimental is 77.87 mg/g, while for AZM adsorbed by PPy/ZnFe₂O₄@Fe₃O₄, q_e calculated is 179.68 mg/g and q_m experimental is 165.00 mg/g. The qe values from the pseudo-second-order model were 83.33 mg/g for AZM adsorbed by PPy and 172.12 mg/g for AZM adsorbed by PPy/ZnFe₂O₄@Fe₃O₄, showing a good match with the experimental results. Furthermore, it aligned with the experimental data, exhibiting R² values of 0.9525 and 0.9986 for PPy and PPy/ZnFe₂O₄@Fe₃O₄, respectively (Figure 14c). This model, represented by Eq. (5), recognizes that adsorption involves heterogeneous sites with differing energies and posits chemical adsorption. The Elovich model suggests that the surface of the adsorbent exhibits heterogeneous energy levels and involves a chemical adsorption mechanism. Eq. (6) describes the adsorption kinetics of this model. The incorporation of the Elovich model alongside the pseudo-second-order model enhances its utility by illustrating that the adsorption process may occur in two distinct steps, each represented by two linear segments (see Figure 14d). The initial linear phase occurs when the analyte adheres to the exterior of the adsorbent, primarily on the surfaces of PPy and PPy/ZnFe₂O₄@Fe₃O₄ adsorbents. The second phase is characterized by a prolonged adsorption process, wherein the analyte attaches to specific sites or pores within the adsorbent [61]. Accordingly, the adsorption process phase that most closely matches the experimental data is the most representative. The adsorption of AZM by PPy and PPy/ZnFe₂O₄@Fe₃O₄ demonstrated linear portions with R² values greater than 0.9. According to the kinetic data, the pseudo-second-order kinetic model produced correlation coefficient values that were higher overall (R² > 0.99). Furthermore, the adsorption capacities calculated using the pseudo-second-order model (see Table 5) show a higher degree of agreement with the experimental adsorption capabilities than those obtained from the pseudo-first-order and Elovich models. It can be concluded that the AZM drug is capable of adsorbing both internally and externally to the two adsorbents.

Table 5. Adsorption pseudo-first-order, pseudo-second-order, and Elovich kinetics parameters for AZM drug adsorption by the PPy and PPy@ZnFe₂O₄@Fe₃O₄ adsorbents (conditions: initial pH 6 for AZM; dose = 80 mg for PPy and 60 mg for PPy@ZnFe₂O₄@Fe₃O₄; initial Ci = 100 mg/L; V = 100 mL; T = 298 K).

Kinetic models	Parameter	Adsorbents
Kinetic models	Parameter	PPy	PPy@ZnFe₂O₄@Fe₃O₄
Pseudo-first-order	q_m(exp.) (mg/g)	77.87	165.00
	k₁(min^-1)	-0.0023	-0.0007
	q_ecal.(mg/g)	119.69	179.68
	R²	0.8888	0.9624
Pseudo-second-order	k₂ (g/mg. min)	0.0007	0.0004
	q_ecal.(mg/g)	83.33	172.12
	R²	0.9525	0.9986
Elovich	α (mg/g.min)	0.1318	0.5186
	β (g/mg)	0.04642	0.0292
	R²	0.9243	0.9806

(a) Adsorption time effect: PPy and PPy@ZnFe2O4@Fe3O4 nanocomposite adsorption kinetics plots for adsorption of AZM drug from solutions at different sorption times; (b) pseudo-first-order model; (c) pseudo-second-order model; and (d) Elovich model. Condition: (pH of AZM = 6, initial drug concentration = 100 mg/L, volume = 100 mL, temperature = 298 K, adsorbent dosage = 80 mg for PPy and 60 mg for PPy@ZnFe2O4@Fe3O4.

3.3.2. Isothermal modelling study

Three significant theoretical models, the Langmuir [62], Freundlich [63], and the Temkin [64] were employed to analyze the experimental data regarding the adsorption of AZM pharmaceuticals by PPy and PPy-composite, as well as the adsorbent’s homogeneous and heterogeneous features. Isotherm adsorption tests were performed at starting concentrations of AZM medication between 20 and 200 mg/L at 298 K (Figure 15 (a-d); refer to the caption for further experimental conditions).

(a) Adsorption isotherm studies for the adsorption of AZM drug by the PPy and PPy/ZnFe2O4 @Fe3O4 adsorbents at various drug concentrations (20-200 mg/L), other conditions: initial pH 6; dose = 80 mg for PPy and 60 mg for PPy/ZnFe2O4@Fe3O4; time =180 min; V = 100 mL; T = 298 K), fitted to models of (b) Langmuir, (c) Freundlich, and (d) Temkin.

Adsorption mechanisms, both chemical and physical, have been described using the Langmuir theoretical isotherm model. This model assumes that the drug molecules form a monolayer on the adsorption sites and that the adsorbent’s outer surface is uniform and regular [65]. The Langmuir model’s linear mathematical expression Eq. (7) has been shown in Table 6. Figure 15(a) displays the equilibrium adsorption capacity at various starting concentrations of AZM. The resulting equilibrium adsorption data is then analyzed by fitting it to the Freundlich, Temkin, and Langmuir isotherm models. Figure 15(b) illustrates the linear relationship that results from plotting C_e/q_e against C_e. The values for q_m and k_L were determined using the graph’s gradient and intercepts. Table 7 displays the parameters that were discovered for the AZM drug. The Langmuir separation factor, R_L (R_L = 1/1+K_LC_i), was used to measure the adsorption process isothermally. Its value might be irreversible (R_L = 0), unfavorable (R_L > 1), linear (R_L = 1), or favorable (0 < R_L < 1) [66]. The research determined that the R_L value for AZM was 0.25 when adsorbed by PPy, and 0.88 when adsorbed by PPy/ZnFe₂O₄@Fe₃O₄. This indicates that the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite adsorbent is an effective means of adhering to the AZM medication.

Table 6. Various isotherm model types.

Model

Linear equation

Plot

Ref.

Langmuir

(7)

\frac{C_{e}}{q_{e}} = \frac{C_{e}}{q_{m}} + \frac{1}{q_{m} K_{L}}

\frac{C_{e}}{q_{e}} v s . C_{e}

[62]

Freundlich

(8)

l n q_{e} = l n K_{F} + \frac{1}{n} l n C_{e}

\ln q_{e} v s . \ln C_{e}

[63]

Temkin

(9)

q_{e} = A + B \ln C_{e}

q_{e} v s . \ln C_{e}

[64]

Eq. (7): q_e: the quantity of AZM adsorbed using the adsorbent at equilibrium (mg/g); C_e: the concentration of adsorbate at equilibrium (mg/L); q_max: the maximum adsorption capacity, as calculated from the Langmuir isotherm model (mg/g); K_L: Langmuir constant (L/mg).

Eq. (8): K_F: Freundlich constant (mg/g. (L/mg)^1/n); n: heterogeneity constant.

Eq. (9): B: the heat of sorption constant (J/mol); A: Temkin constant (L/g).

Table 7. Adsorption isotherm parameters of the Langmuir, Freundlich, and Temkin models for the adsorption of AZM by the PPy and PPy/ZnFe₂O₄@Fe₃O₄ adsorbents, other conditions: initial pH 6; dose = 80 mg for PPy and 60 mg for PPy/ZnFe₂O₄@Fe₃O₄; time =180 min; V = 100 mL; T = 298 K).

Isotherm models	Parameter	Adsorbents
Isotherm models	Parameter	PPy	PPy/Fe₃O₄@ZnFe₂O₄
Langmuir	q_m (exp.) (mg/g)	80.13	183.73
	q_m (cal.) (mg/g)	60.60	181.16
	K_L(L/mg)	0.25	0.88
	R_Lrange	0.0057– 0.0602	0.0022 – 0.0217
	R²	0.9203	0.9996
Freundlich	K_F (mg/g (L/mg)^1/n)	520.44	30367.6
	n	3.0215	4.9510
	R²	0.4623	0.5723
Temkin	A (L/g)	2.4319	136.72
	B (J/mol)	12.359	21.144
	R²	0.2742	0.7048

The Freundlich model is characterized by a multilayer process, signifying diverse surfaces. This model is inadequate as it does not predict the saturation of adsorption sites and may not accurately depict the process. Eq. (8) in Table 6 delineates the model in a linear format. Figure 15(c) illustrates a graph of ln q_e vs ln C_e, which facilitates the calculation of both K_f and n. The constant n is frequently employed to indicate the suitability of the adsorption process. The calculated values of n, ranging from 1 to 10, for AZM adsorbed by PPy and the PPy@ZnFe₂O₄@Fe₃O₄ nanocomposite are 3.0215 and 4.9510, respectively (Table 7). The values indicate that drug adsorption on both adsorbents is advantageous. The findings for R_L (refer to Table 7) are in remarkable concordance with this. The Temkin isotherm model describes a linear decrease in adsorption energy with an increase in the adsorbent’s surface area. It also considers the interaction between the adsorbent and the adsorbate. The Temkin model’s linear mathematical formulation Eq. (9) has been shown in Table 6. A plot of q_e against ln C_e (Figure 15d) can be used to determine the constants A and B. The isotherm parameters for the adsorption of AZM medication by both adsorbents are displayed in Table 7.

The derived model factors for all theoretical isotherm models, along with their respective R² values, are displayed in Table 7, indicating the model that provided the best fit. The research indicated that the adsorption capacities predicted by the Langmuir model for AZM (q_m (cal.) = 60.60 mg/g for PPy and 181.16 mg/g for the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite) closely aligned with the experimentally determined adsorption capacities (q_m (exp.) = 80.13 mg/g for PPy and 183.73 mg/g for the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite). This contrasted with the results of the Freundlich and Temkin models. Moreover, the R² values presented in Table 7 indicate that the theoretical Langmuir model provides a superior fit to the data compared to the other models (R² > 0.92 for PPy and R² > 0.99 for PPy/ZnFe₂O₄@Fe₃O₄). Nonetheless, the Temkin and Freundlich models indicated that the R² values for both drugs inadequately aligned with the experimental results. Consequently, it was concluded that, unlike the Freundlich or Temkin models, the theoretical Langmuir model most accurately characterizes the AZM adsorption process by PPy/ZnFe₂O₄@Fe₃O₄.The adsorption mechanism of AZM medication on PPy/ZnFe₂O₄@Fe₃O₄ nanocomposites is characterized as a monolayer adsorption system.

3.4. Comparative analysis of adsorption capacities reported in the literature

The capability of PPy and PPy/ZnFe₂O₄@Fe₃O₄ adsorbents to adsorb AZM is compared to those reported in the literature, utilizing their adsorption capacity (q_m) and other optimal adsorption parameters presented in Table 8. PPy and PPy/ZnFe₂O₄@Fe₃O₄ nanocomposites have high q_m (80.13 mg/g for PPy and 183.73 mg/g for PPy-composite), making them an attractive choice for wastewater treatment. The PPy/ZnFe₂O₄@Fe₃O₄ exhibited a remarkable adsorption capacity for removal of AZM among the others, including Fe₂O₃/Ag/Zn (9.6 mg/g) [54], GO@Fe₃O₄/ZnO/SnO₂ (9.37 mg/g) [67], PAN@Fe₂O₄ (73.49 mg/g) [68], and GO-ZnO (48 mg/g) [69]. However, the current adsorbents have a lower adsorption capacity compared to other adsorbents such as ZnO/Si (213.2 mg/g) [70] and MIL/Cs@Fe₃O₄ NCs (238.55 mg/g) [71]. This may be due to several factors, including surface area, surface composition, reaction time, and adsorbent quantity. The in-situ polymerization of the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite produces unique morphologies with a significantly large specific surface area and mesoporous properties crucial for improved drug adsorption. Moreover, interactions between the AZM molecules and the nanocomposite surface through hydrogen bonding and electrostatic forces are anticipated during the adsorption of AZM. This comparison demonstrates that this research represents a significant advance in the development of highly efficient adsorbents for the removal of pharmaceutical contaminants. This confirms its practical applicability and demonstrates that this work represents a significant contribution to environmental sustainability.

Table 8. A comparison of the capacity and other parameters for removing AZM pharmaceutical contaminants from wastewater, as reported in previous literature.

Adsorbents	Parameters				Best-fitted kinetic model	Best-fitted isotherm model	Adsorption capacities (mg/g)	Reference
Adsorbents	pH	Time (h)	Dose (g/L)	Conc. (mg/L)	Best-fitted kinetic model	Best-fitted isotherm model	Adsorption capacities (mg/g)	Reference
Fe₂O₃/Ag/Zn	5	0.5	1.5	10	----	----	9.6	[54]
GO@Fe₃O₄/ZnO/SnO₂ nanocomposites	3	2	1	30	PSO	Langmuir	9.37	[67]
Graphene/Fe₂O₃	7	0.5	----	150	PSO	Freundlich, Langmuir	9.89	[67]
Polyacrylonitrile (PAN@Fe₂O₃)	7	1.16	0.06	50	PSO	Langmuir	73.49	[68]
GO-ZnO	10	1	1	50	----	----	48	[69]
ZnO/Si	7	0.75	0.02	15	PSO	Langmuir	213.2	[70]
MIL/Cs@Fe₃O₄ NCs	7	1	0.27	10	PSO	Langmuir	238.55	[71]
(CoFe₂O₄ MNP)	6.6	2.5	0.20	60	----	----	17.8	[72]
Prepare activated carbon impregnated magnetite (PAC/Fe/Ag/Zn) nanocomposites	9	120	0.04	40	PFO	Langmuir	14.18	[11]
PPy PPy/ZnFe₂O₄@Fe₃O₄	6	3	0.08 0.06	100	PSO	Langmuir	80.13 183.73	This work

PSO = Pseudo-second order, PFO = Pseudo-first order

3.5. Impact of reaction temperature and thermodynamic studies

The temperature of the reaction is another significant factor that can influence the removal system. The rate of the removal reaction typically increases markedly due to the diffusion of AZM molecules from the solution to the adsorbent surface, as well as the temperature rise associated with the increase in velocity. The reaction temperature was sustained with an adsorbent dosage of 80 mg for PPy and 60 mg for PPy/ZnFe₂O₄@Fe₃O₄ in an AZM drug solution (100 mg/L) at an initial pH of 6, with reaction durations of 180 min, according to optimal conditions established in prior studies. Figure 16(a) demonstrates the influence of temperature on the adsorption capacity of PPy and PPy/ZnFe₂O₄@Fe₃O₄ for the removal of AZM. The removal efficiency (R%) exhibited an increase from 64.4% to 75.6% for PPy and from 98.6% to 99.8% for PPy/ZnFe₂O₄@Fe₃O₄ as the temperature increased from 298 K to 313 K. The findings indicate that the pharmacological reactions observed in this study are endothermic.

(a) Impact of reaction temperature for adsorption of AZM pharmaceutical ions by PPy and PPy/ZnFe2O4@Fe3O4 adsorbents at four different temperatures (298, 303, 308, and 313 K), other conditions: pH 6; dosages = 80 mg for PPy and 60 mg for PPy/ZnFe2O4@Fe3O4; V = 100 mL; time = 180 min). (b) Linear plot of ln KL against 1/T for adsorption of AZM pharmaceutical ions by both adsorbents.

According to this finding, the percentage of adsorption increases with the reaction temperature, peaking at 313 K. This is due to the enhanced mobility of the drug ions and their adequate energy to engage with the accessible locations on the adsorbent surface. The adsorption process is elucidated using thermodynamic analysis. The Van’t Hoff equation Eq. (10) helps calculate the standard Gibbs free energy (ΔG° (kJ/mol)), the standard change in entropy (ΔS° (J/mol K)), and the standard change in enthalpy (ΔH° (kJ/mol)) [30] for the AZM adsorption processes using both adsorbents.

(10)

\ln (K_{L}) = - \frac{Δ H^{°}}{R T} + \frac{Δ S^{°}}{R}

Here, R represents the universal gas constant (8.314 J/mol K), while K_L indicates the Langmuir equilibrium constant (L/mg), and T is the absolute temperature (K). ΔH° and ΔS° were obtained from Figure 16(b), from the slope and intercept of the linear equation of ln K_L versus 1/T. ΔG° was calculated at each of the four designated temperatures (298, 303, 308, and 313 K) using Eq. (11).

(11)

Δ G^{°} = - R T \ln (K_{L})

Table 9 reports the calculated thermodynamic parameters ΔHᵒ, ΔSᵒ, and ΔGᵒ for AZM adsorption onto the PPy and PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite. For the PPy adsorbent, ΔHᵒ and ΔSᵒ are measured at 26.726 kJ/mol and 10.721 J/mol K, respectively, whereas for the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite adsorbent, they are 99.426 kJ/mol and 39.146 J/mol K, respectively. Additionally, ΔGᵒ values were recorded as -2.0212, -2.4355, -2.7655, and -3.5235 kJ/mol for PPy, while for the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite adsorbent, the values were -11.807, -12.738, -14.393, and -17.496 kJ/mol at temperatures of 298, 305, 303, and 313 K, respectively. The results presented in Table 9 demonstrate that the negative ΔGᵒ (ΔGᵒ < 0) and positive ΔHᵒ (ΔHᵒ > 0) values suggest that the adsorption of each pharmaceutical onto the PPy and PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite is characterized as endothermic and spontaneous. The positive entropy value (ΔSᵒ > 0) indicates randomization at the solid-solution interface of the adsorbents during the adsorption of AZM, which acts as the adsorbate.

Table 9. Thermodynamic parameters found for adsorption of AZM pharmaceutical ions by PPy and PPy/ZnFe₂O₄@Fe₃O₄ adsorbents at four different temperatures (298, 303, 308, and 313 K), other conditions: pH 6; dosages = 80 mg for PPy and 60 mg for PPy/ZnFe₂O₄@Fe₃O₄; V = 100 mL; time = 180 min).

Adsorbents	Thermodynamic parameter	Temperatures of reaction (K)
Adsorbents	Thermodynamic parameter	298	303	308	313
PPy	∆G° (kJ/mol)	-2.0212	-2.4355	-2.7655	-3.5235
	∆H° (kJ/mol)	26.726
	∆S° (J/mol K)	10.721
PPy/ZnFe₂O₄@Fe₃O₄	∆G° (kJ/mol)	-11.807	-12.738	-14.393	-17.496
	∆H° (kJ/mol)	99.426
	∆S° (J/mol K)	39.146

The adsorption of AZM pharmaceutical increases at higher temperatures, where rising temperatures promote the spontaneity of adsorption; this is mostly due to chemisorption being the predominant mechanism rather than physisorption, as depicted in Figure 16(a). Furthermore, enthalpy (ΔHᵒ) elucidates the nature of adsorption, indicating the likelihood of chemical/chemisorption (40–800 kJ/mol) vs. physical/physisorption (0-40 kJ/mol) [73]. The elevated ΔHᵒ (99.426 kJ/mol) for AZM adsorbed on PPy/ZnFe₂O₄@Fe₃O₄ indicates chemisorption, whereas the comparatively lower value for AZM adsorbed on PPy (19.848 kJ/mol) suggests physisorption.

3.6. Possible adsorption mechanism

Given the abundance of nitrogen and oxygen-containing functional groups (-OH, -CO, -NH₂) in these materials, the complex mechanisms governing the adsorption of AZM and the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite adsorbent may include hydrogen bonding and electrostatic interactions, as suggested by FTIR analysis. Figures. 17-18 show a possible adsorption mechanism of how the PPy and PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite interact with AZM. Generally, the PPy is protonated (imine and amine groups) in the acidic environment. The protonation of the adsorbent is crucial to the reaction process, resulting in enhanced electrostatic attraction and hydrogen bonding between the adsorbent and adsorbate (AZM). Consequently, the adsorption percentage is increased due to the presence of many protons and electrons in the acidic medium that engage in this process. The adsorption of the polymer with AZM began to diminish in the basic media owing to the deprotonated form of the adsorbent, as seen in Figure 17. Consequently, electron transmission diminishes inside the polymer structure, resulting in a decrease in AZM removal. This results from less electrostatic attraction among components, which restricts their adsorption. In addition, In the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite (Figure 18), PPy exhibits a positive charge at pH levels below the point of zero charge (pH_pzc), whereas AZM carries a negative charge. The interpretation of these tendencies is influenced by the value of pH_pzc, the chemical structure of the adsorbate, the surface chemistry of the adsorbent, and the conditions under which adsorption occurs [74]. However, as was shown in the section above (impact of pH), when pH > pH_pzc, the surface charge of PPy in the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite is negative, which is more favorable to repulsion.

The concept of physisorption for PPy and chemisorption for PPy/ZnFe₂O₄@Fe₃O₄ of AZM adsorption is also supported by the thermodynamic ∆H° data. Therefore, from a thermodynamic standpoint, the following can be used to summarize the likely routes for AZM and their adsorption onto the surface of the nanocomposite:

Reaction strategy for the PPy interacting with AZM in the acidic and basic medium during the adsorption process.

Reaction strategy for the PPy/ZnFe2O4@Fe3O4 nanocomposite interacting with AZM during the adsorption process.

3.6.1. Electrostatic interaction

An electrostatic contact exists between the net positive charge of the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite adsorbent and AZM in solution. The primary element influencing adsorption efficacy is the surface charge of both the adsorbent and adsorbate, as the electrostatic interaction between them can be enhanced by the presence of oppositely charged functional groups on their surfaces. The dissociation constants, solution pH, and point of zero charge (pH_pzc) all influence the ionic charge. Adsorption diminishes when the adsorbate (AZM) and the adsorbent surface possess identical charges due to electrostatic repulsion; conversely, adsorption is augmented when electrostatic attraction occurs as a result of opposing charges [75].

3.6.2. Hydrogen bonds

These are created when an atom from one molecule with a high electronegativity and a hydrogen from another molecule are electrostatically drawn to one another [76,77]. The functional groups in the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite, which include oxygen and nitrogen (–OH, –NH), can establish hydrogen-bonding interactions with nitrogen- and oxygen-containing groups (–OH, –CO, –NH₂) found in the structures of AZM, significantly influencing the mechanism of drug adsorption onto the adsorbent surface.

3.6.3. Hydrophobic interaction

Hydrophobic interactions occur when non-polar molecules or hydrophobic drug moieties engage with the hydrophobic portions of the adsorbent’s surface. This hydrophobic interaction originates from the propensity of non-polar molecules or groups to exhibit hydrophobic characteristics. Pharmaceuticals possessing both hydrophilic and hydrophobic domains, or the application of carbon-based or polymer-based metal oxide composites as adsorbents, predominantly result in hydrophobic interactions during adsorption [78].

3.6.4. Pore-filling interaction

Organic pollutants may infiltrate adsorbent particles via their pores and become trapped inside the adsorbent’s nanometer-scale pores. The dimensions of the particles and their specific surface areas influence the adhesion of organic contaminants to the adsorbent. A reduction in particle size often improves the adsorption rate by increasing the surface area-to-volume ratio [79,80].

3.7. Environmental application

To assess the practical effectiveness of the synthesized PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite adsorbent for the adsorption of AZM in actual water samples, local tap water (Table 10) was employed in various samples (pure AZM, AZM tablet, wastewater drug). The concentrations of AZM were assessed following treatment with the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite adsorbent. Table 11 demonstrates that the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite adsorbent efficiently eliminates AZM medication from tap water samples. The percentage adsorption of these medications in local water markedly diminished due to the presence of additional contaminating ions (see Table 10), which compete with the drugs for adsorption onto the adsorbent’s surface. The adsorbent was unable to eliminate the AZM, particularly in the final sample (wastewater medicine), due to competition from other chemicals in the wastewater. The findings indicate that the PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite adsorbent is effective for the adsorption of AZM and other organic and inorganic pollutants, rendering it suitable for practical applications in wastewater treatment.

Table 10. Concentration of ionic constituents in a tap water sample.

Tap water species	Na⁺	K⁺	Ca²⁺	Mg²⁺	Cl⁻	Zn²⁺	NO₃⁻	SO₄⁻
* Tap water (mM)	0.92	0.08	0.33	0.46	0.93	0.03	-	0.06

* Tap water samples were collected from Koya, Iraq.

Table 11. Adsorption of AZM using a synthetic PPy/ZnFe₂O₄@Fe₃O₄ nanocomposite adsorbent in various wastewater samples. Other conditions: initial pH 6; dose = 60 mg; time = 180 min; V = 100 mL; T = 298 K).

Solutions	Add concentration (mg/L)	Found concentration (mg/L)	Removal (%)
Pure AZM Drug in DW	50	0.75	98.5
AZM Tablet in DW	50	3.88	92.24
Pure AZM in Tap water	50	6.75	86.50
AZM Tablet in Tap water	50	13.7	72.6
AZM Tablet in wastewater medication	50 mg of AZM + 10 mg of (MO, MB, Ni, Cu, Cd)	23.3	53.4

Dyes (MO: Methyl orange, MB: Methylene blue).

3.8. Reusability studies of PPy/ZnFe₂O₄@Fe₃O₄ adsorbent

A key feature for real-world uses is the adsorbent’s reusability, which necessitates careful research. Subsequently, the reusability of PPy/ZnFe₂O₄@Fe₃O₄ was assessed to determine adsorption effectiveness during many usage cycles. Figure 19 demonstrates the reusability of PPy/ZnFe₂O₄@Fe₃O₄ for the adsorption of AZM across five cycles. The PPy/ZnFe₂O₄@Fe₃O₄ adsorbent was isolated by magnetic means, following the initial cycle, and subsequently purified with methanol. Subsequently, it was employed as the adsorbent for further cycles to assess its adsorptive performance after being dried for three hours at 80°C in a vacuum oven. At an initial adsorbate concentration of 100 mg/L, the results in Figure 19 showed a decrease in AZM adsorption from 98.4% to 79.4%; in turn, the desorption test showed a decrease from 94.5% to 72.5%. A continual decline in the adsorption-desorption efficiency of the adsorbent may suggest residual AZM on the adsorbent or the detachment of ZnFe₂O₄@Fe₃O₄ particles from the PPy/ZnFe₂O₄@Fe₃O₄ adsorbent during each adsorption and desorption cycle, thereby diminishing the number of available adsorption sites.

Cycles of adsorption-desorption for AZM loading onto PPy/ZnFe2O4@Fe3O4 adsorbent.

4. Conclusions

This study compares the adsorption of AZM in a batch system onto a novel polymer nanocomposite adsorbent (PPy/ZnFe₂O₄@Fe₃O₄) to pure PPy, both of which are derived from oxaline-DES. Multiple samples of polymer composites were synthesized for drug adsorption applications. The results show that adsorption rises as the weight of ZnFe₂O₄@Fe₃O₄ in the polymer increases, but then adsorption falls because of the excessive weight, which causes clumping or agglomeration in the polymer composite and lessens the interaction between the drug and the adsorbent. Several techniques, including FTIR, XRD, SEM, EDX, BET, and VSM, were employed to characterize the materials. FTIR, XRD, SEM, TEM, and EDX validated the characteristics of the interaction between ZnFe₂O₄@Fe₃O₄ and PPy. The PPy/ZnFe₂O₄@Fe₃O₄ adsorbent nanocomposite has a larger surface area than the PPy polymer, according to the surface area measurements (BET). The experimental batch investigated the effects of temperature, contact time, initial AZM concentration, adsorbent dosage, and initial pH on AZM adsorption. The findings indicate that when the pH of the solution increases, the adsorption of pharmaceuticals onto the PPy and PPy/ZnFe₂O₄@Fe₃O₄ adsorbents also increases, peaking at a pH of 6, which signifies optimal absorption, followed by a decline in efficiency thereafter. The equilibrium duration for the adsorption of AZM was established as 180 min for 80 mg of PPy and 60 min for PPy/ZnFe₂O₄@Fe₃O₄.

The adsorption isotherms for both adsorbents for AZM adsorption showed that the Langmuir isotherm was the best model at 298 K. The highest adsorption capacities of PPy and PPy/ZnFe₂O₄@Fe₃O₄ were 80.13 mg/g and 183.73 mg/g, respectively. The R² values of the Langmuir isotherm for AZM adsorption onto PPy and PPy/ZnFe₂O₄@Fe₃O₄ were 0.9203 and 0.9996, respectively, indicating that AZM was adsorbed uniformly and in a monolayer on both adsorbent surfaces. It was discovered that the pseudo-second-order mechanism best suited the adsorption kinetics of both adsorbents (R² = 0.9525 for PPy and 0.9986 for PPy/ZnFe₂O₄@Fe₃O₄). Additionally, thermodynamic data showed that the adsorption process was endothermic, since the amount of adsorption rose as the temperature rose. Furthermore, the free energy (∆G°) for the adsorption of each drug was negative, indicating a spontaneous response. The enthalpy of PPy was approximately 26 kJ/mol, showing physical adsorption, but for PPy/ZnFe₂O₄@Fe₃O₄, it was around 99 kJ/mol, implying chemical adsorption. The environmental analysis revealed substantial adsorption of AZM by PPy/ZnFe₂O₄@Fe₃O₄, highlighting its potential application in wastewater treatment. The adsorption-desorption analysis of AZM indicated a decrease in the adsorption capacity of the nanocomposite from 98.5% to 72.4% following five cycles.

Acknowledgment

The authors wish to acknowledge Koya and Kashan Universities for providing the required materials and instruments for this work.

CRediT authorship contribution statement

Ahmad F. Hamasdiq: Experiments, resources, characterizations, software, writing the introduction and experimental parts. Hani K. Ismail: writing the results and discussion, formal analysis, project administration, editing and supervision. Rebaz A. Omer: project administration, editing and supervision.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Declaration of Generative AI and AI-assisted technologies in the writing process

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Supplementary data

Supplementary material to this article can be found online at https://dx.doi.org/10.25259/AJC_635_2025.

References

Li W.C.. Occurrence, sources, and fate of pharmaceuticals in aquatic environment and soil. Environmental Pollution. 2014;187:193-201. https://doi.org/10.1016/j.envpol.2014.01.015
[Google Scholar]
Fatta-Kassinos D., Meric S., Nikolaou A.. Pharmaceutical residues in environmental waters and wastewater: Current state of knowledge and future research. Analytical and Bioanalytical Chemistry. 2011;399:251-275. https://doi.org/10.1007/s00216-010-4300-9
[Google Scholar]
Ismail H.K., Qader A.F., Omer R.A., Alesary H.F., Umran H.M., Kareem A.A.. Synthesis of Polypyrrole-Graphene Oxide (PPy/GO) from deep eutectic solvent and its characterization for determination of metronidazole pharmaceutical substance using spectrofluorometric technique. ChemistrySelect. 2025;10:e202405486. https://doi.org/10.1002/slct.202405486
[Google Scholar]
K’oreje K.O., Vergeynst L., Ombaka D., De Wispelaere P., Okoth M., Van Langenhove H., Demeestere K.. Occurrence patterns of pharmaceutical residues in wastewater, surface water and groundwater of Nairobi and Kisumu city, Kenya. Chemosphere. 2016;149:238-244. https://doi.org/10.1016/j.chemosphere.2016.01.095
[Google Scholar]
Tijani J.O., Fatoba O.O., Babajide O.O., Petrik L.F.. Pharmaceuticals, endocrine disruptors, personal care products, nanomaterials and perfluorinated pollutants: A review. Environmental Chemistry Letters. 2016;14:27-49. https://doi.org/10.1007/s10311-015-0537-z
[Google Scholar]
Sdiq A.F.H., Abdulrahman H.H., Ismail H.K., Omer R.A., Alesary H.F., Sultan H.K.I., Barton S.. A review of effective Nanoadsorbents made of carbonaceous, metal oxides, and polymer nanocomposite materials for adsorption of pharmaceutical contaminants in wastewater. International Journal of Environmental Research. 2025;19:159. https://doi.org/10.1007/s41742-025-00825-4
[Google Scholar]
Dular M., Griessler-Bulc T., Gutierrez-Aguirre I., Heath E., Kosjek T., Krivograd Klemenčič A., Oder M., Petkovšek M., Rački N., Ravnikar M., Šarc A., Širok B., Zupanc M., Žitnik M., Kompare B.. Use of hydrodynamic cavitation in (waste)water treatment. Ultrasonics Sonochemistry. 2016;29:577-588. https://doi.org/10.1016/j.ultsonch.2015.10.010
[Google Scholar]
Chen X., Chen G., Yue P.L.. Separation of pollutants from restaurant wastewater by electrocoagulation. Separation and Purification Technology. 2000;19:65-76. https://doi.org/10.1016/s1383-5866(99)00072-6
[Google Scholar]
Gogoi A., Mazumder P., Tyagi V.K., Tushara Chaminda G.G., An A.K., Kumar M.. Occurrence and fate of emerging contaminants in water environment: A review. Groundwater for Sustainable Development. 2018;6:169-180. https://doi.org/10.1016/j.gsd.2017.12.009
[Google Scholar]
Abdulrahman H.H., Sdiq A.F.H., Ismail H.K., Omer R.A., Alesary H.F., Kareem A.A., Barton S.. Polymer nanocomposite adsorbents for the removal of pharmaceutical formulations the aquatic environment: A Review. Water, Air, & Soil Pollution. 2025;236:584. https://doi.org/10.1007/s11270-025-08240-3
[Google Scholar]
Mehrdoost A., Yengejeh R.J., Mohammadi M.K., Haghighatzadeh A., Babaei A.A.. Adsorption removal and photocatalytic degradation of azithromycin from aqueous solution using PAC/Fe/Ag/Zn nanocomposite. Environmental Science and Pollution Research. 2022;29:33514-33527. https://doi.org/10.1007/s11356-021-18158-y
[Google Scholar]
Senta I., Kostanjevecki P., Krizman-Matasic I., Terzic S., Ahel M.. Occurrence and behavior of macrolide antibiotics in municipal wastewater treatment: Possible importance of metabolites, synthesis byproducts, and transformation products. Environmental Science & Technology. 2019;53:7463-7472. https://doi.org/10.1021/acs.est.9b01420
[Google Scholar]
Almeida A.C., Gomes T., Lomba J.A.B., Lillicrap A.. Specific toxicity of azithromycin to the freshwater microalga Raphidocelis subcapitata. Ecotoxicology and Environmental Safety. 2021;222:112553. https://doi.org/10.1016/j.ecoenv.2021.112553
[Google Scholar]
Mohammed A.K., Saadoon S.M., Abd Ali Z.T., Rashid I.M., Hussin AL, Sbani N.. Removal of amoxicillin from contaminated water using modified bentonite as a reactive material. Heliyon. 2024;10:e24916. https://doi.org/10.1016/j.heliyon.2024.e24916
[Google Scholar]
Kasraei R., Malakootian M.. Tetracycline adsorption from aqueous solutions by a magnetic nanoadsorbent modified with ionic liquid. Desalination and Water Treatment. 2021;209:289-301. https://doi.org/10.5004/dwt.2021.26478
[Google Scholar]
Mohammadi Nodeh M.K., Soltani S., Shahabuddin S., Rashidi Nodeh H., Sereshti H.. Equilibrium, kinetic and thermodynamic study of magnetic polyaniline/graphene oxide based nanocomposites for ciprofloxacin removal from water. Journal of Inorganic and Organometallic Polymers and Materials. 2018;28:1226-1234. https://doi.org/10.1007/s10904-018-0782-2
[Google Scholar]
de Andrade J.R., Oliveira M.F., da Silva M.G., Vieira M.G.. Adsorption of pharmaceuticals from water and wastewater using nonconventional low-cost materials: a review. Industrial & Engineering Chemistry Research. 2018;57:3103-3127. https://doi.org/10.1021/acs.iecr.7b05137
[Google Scholar]
Aslam J., Zehra S., Mobin M., Quraishi M.A., Verma C., Aslam R.. Metal/metal oxide-carbohydrate polymers framework for industrial and biological applications: Current advancements and future directions. Carbohydrate Polymers. 2023;314:120936. https://doi.org/10.1016/j.carbpol.2023.120936
[Google Scholar]
Papageorgiou M., Maroulas K.N., Evgenidou E., Bikiaris D.N., Kyzas G.Z., Lambropoulou D.A.. Simultaneous removal of seven pharmaceutical compounds from a water mixture using modified chitosan adsorbent materials. Macromol. 2024;4:304-319. https://doi.org/10.3390/macromol4020018
[Google Scholar]
Taheri N., Alizadeh N.. Vertically grown nanosheets conductive polypyrrole as a sorbent for nanomolar detection of salicylic acid. Journal of Pharmaceutical and Biomedical Analysis. 2020;188:113365. https://doi.org/10.1016/j.jpba.2020.113365
[Google Scholar]
Ismail H.K., Ali L.I.A., Alesary H.F., Nile B.K., Barton S.. Synthesis of a poly(p-aminophenol)/starch/graphene oxide ternary nanocomposite for removal of methylene blue dye from aqueous solution. Journal of Polymer Research. 2022;29 https://doi.org/10.1007/s10965-022-03013-6
[Google Scholar]
Dutta S., Srivastava S.K., Gupta B., Gupta A.K.. Hollow polyaniline microsphere/MnO₂/Fe₃O₄ Nanocomposites in adsorptive removal of toxic dyes from contaminated water. ACS Appl Mater Interfaces. 2021;13:54324-54338. https://doi.org/10.1021/acsami.1c15096
[Google Scholar]
Dutra F.V.A., Pires B.C., Nascimento T.A., Borges K.B.. Functional polyaniline/multiwalled carbon nanotube composite as an efficient adsorbent material for removing pharmaceuticals from aqueous media. Journal of Environmental Management. 2018;221:28-37. https://doi.org/10.1016/j.jenvman.2018.05.051
[Google Scholar]
Saha B., Gayen S., Debnath A.. Sequestration of paracetamol from aqueous solution using zinc oxide/polypyrrole nanocomposite: Cost Analysis, scale-up design, and optimization of process parameters. Journal of Hazardous, Toxic, and Radioactive Waste. 2023;27:e202305101. https://doi.org/10.1002/slct.202305101
[Google Scholar]
Nascimento T.A., Pires B.C., Dutra F.V.A., Borges M.M.C., Borges K.B.. Poly (aniline‐co‐pyrrole) as adsorbent for removal of pharmaceuticals: Preparation, characterization, kinetics, isotherms and application on sample preparation. Chemistry Select. 2024;9:e202305101. https://doi.org/10.1002/slct.202305101
[Google Scholar]
Alesary H.F., Ismail H.K., Mohammed M.Q., Mohammed H.N., Abbas Z.K., Barton S.. A comparative study of the effect of organic dopant ions on the electrochemical and chemical synthesis of the conducting polymers polyaniline, poly(o-toluidine) and poly(o-methoxyaniline) Chemical Papers. 2021;75:5087-5101. https://doi.org/10.1007/s11696-020-01477-8
[Google Scholar]
A. M. Babakir B., Abd Ali L.I., Ismail H.K.. Rapid removal of anionic organic dye from contaminated water using a poly (3-aminobenzoic acid/graphene oxide/cobalt ferrite) nanocomposite low-cost adsorbent via adsorption techniques. Arabian Journal of Chemistry. 2022;15:104318. https://doi.org/10.1016/j.arabjc.2022.104318
[Google Scholar]
Heck J., Goding J., Portillo Lara R., Green R.. The influence of physicochemical properties on the processibility of conducting polymers: A bioelectronics perspective. Acta Biomaterialia. 2022;139:259-279. https://doi.org/10.1016/j.actbio.2021.05.052
[Google Scholar]
Abd Ali L.I., Alesary H.F., Ismail H.K., Hassan W.H., Kareem A.A., Nile B.K.. Polypyrrole-coated zinc/nickel oxide nanocomposites as adsorbents for enhanced removal of Pb(II) in aqueous solution and wastewater: An isothermal, kinetic, and thermodynamic study. Journal of Water Process Engineering. 2024;64:105589. https://doi.org/10.1016/j.jwpe.2024.105589
[Google Scholar]
Alesary H.F., Odda A.H., Ismail H.K., Hassan W.H., Alghanimi G.A., Halbus A.F., Sultan H.K.I., Al-Kinani A.A., Barton S.. Green triiron tetraoxide@Algae (Fe₃O₄@Algae) nanoparticles for highly efficient removal of lead (Pb²⁺), cadmium (Cd²⁺), and aluminum (Al³⁺) from contaminated water: An isothermal, kinetic, and thermodynamic study. Environmental Science and Pollution Research. 2025;32:6817-6838. https://doi.org/10.1007/s11356-025-36169-x
[Google Scholar]
Billah R.E.K., Azoubi Z., López-Maldonado E.A., Majdoubi H., Lgaz H., Lima E.C., Shekhawat A., Tamraoui Y., Agunaou M., Soufiane A., Jugade R.. Multifunctional cross-linked shrimp waste-derived chitosan/MgAl-LDH composite for removal of As(V) from wastewater and antibacterial activity. ACS Omega. 2023;8:10051-10061. https://doi.org/10.1021/acsomega.2c07391
[Google Scholar]
Algethami J.S., Jugade R., Billah El Kaim R., Bahsis L., Achak M., Majdoubi H., Shekhawat A., Korde S., López-Maldonado E.A.. Chitin extraction from crab shells and synthesis of chitin @metakaolin composite for efficient amputation of Cr (VI) ions. Environmental Research. 2024;252:119065. https://doi.org/10.1016/j.envres.2024.119065
[Google Scholar]
Alqarni L.S., Algethami J.S., EL Kaim Billah R., Alorabi A.Q., Alnaam Y.A., Algethami F.K., Bahsis L., Jawad A.H., Wasilewska M., López-Maldonado E.A.. A novel chitosan-alginate@Fe/Mn mixed oxide nanocomposite for highly efficient removal of Cr (VI) from wastewater: Experiment and adsorption mechanism. International Journal of Biological Macromolecules. 2024;263:129989. https://doi.org/10.1016/j.ijbiomac.2024.129989
[Google Scholar]
Keshta B.E., Gemeay A.H., Kumar Sinha D., Elsharkawy S., Hassan F., Rai N., Arora C.. State of the art on the magnetic iron oxide nanoparticles: Synthesis, functionalization, and applications in wastewater treatment. Results in Chemistry. 2024;7:101388. https://doi.org/10.1016/j.rechem.2024.101388
[Google Scholar]
Fatimah I., Yanti I., Wijayanti H.K., Ramanda G.D., Sagadevan S., Tamyiz M., Doong R.-an. One-pot synthesis of Fe₃O₄/NiFe₂O₄ nanocomposite from iron rust waste as reusable catalyst for methyl violet oxidation. Case Studies in Chemical and Environmental Engineering. 2023;8:100369. https://doi.org/10.1016/j.cscee.2023.100369
[Google Scholar]
Alabdullah S.S.M., Ismail H.K., Ryder K.S., Abbott A.P.. Evidence supporting an emulsion polymerisation mechanism for the formation of polyaniline. Electrochimica Acta. 2020;354:136737. https://doi.org/10.1016/j.electacta.2020.136737
[Google Scholar]
V. Gayathri V.G., R. Balan R.B.. Synthesis and characterisation of inorganic acid doped conducting polymer. Journal of Environmental Nanotechnology. 2019;8:20-23. https://doi.org/10.13074/jent.2019.06.192367
[Google Scholar]
Alesary H.F., Noori D.Y., Al‐Yasari A., Hassan W.H., Taj‐Aldeen R.A., Ismail H.K., Athab Z.H., Halbus A.F., Barton S.. Manganese electrochemistry in a deep eutectic solvent: The effects of KBr. ChemistrySelect. 2024;9 https://doi.org/10.1002/slct.202401407
[Google Scholar]
Abbott A.P., Capper G., Davies D.L., Rasheed R.K., Tambyrajah V.. Novel solvent properties of choline chloride/urea mixtures. Chemical Communications 2003:70-71. https://doi.org/10.1039/B210714G
[Google Scholar]
Husin N.A., Muhamad M., Yahaya N., Miskam M., Syazni Nik Mohamed Kamal N.N., Asman S., Raoov M., Mohamad Zain N.N.. Application of a new choline-imidazole based deep eutectic solvents in hybrid magnetic molecularly imprinted polymer for efficient and selective removal of naproxen from aqueous samples. Materials Chemistry and Physics. 2021;261:124228. https://doi.org/10.1016/j.matchemphys.2021.124228
[Google Scholar]
Omer R.A., Ismail H.K., Sultan H.K.I., Alesary H.F., Kareem A.A., Azeeza Y.H., Kareem R.O.. Synthesis of polyaniline, polypyrrole, and poly(aniline-co-pyrrole) in deep eutectic solvent: A comparative experimental and computational investigation of their structural, spectral, thermal, and morphological characteristics. Chemistry of Heterocyclic Compounds. 2024;60:463-472. https://doi.org/10.1007/s10593-024-03364-6
[Google Scholar]
Ghayem F., Miraninezhad S., Hosseini S., Pourmousavi S.A.. ZnFe₂O₄@Fe₃O₄ Nanocatalyst for the synthesis of the 1,8-dioxooctahydroxanthene: Antioxidant and antimicrobial studies. Materials Chemistry Horizons. 2023;2:207-224. https://doi.org/10.22128/mch.2023.704.1046
[Google Scholar]
Hillman A.R., Ryder K.S., Ismail H.K., Unal A., Voorhaar A.. Fundamental aspects of electrochemically controlled wetting of nanoscale composite materials. Faraday Discussions. 2017;199:75-99. https://doi.org/10.1039/c7fd00060j
[Google Scholar]
Ismail H.K., Qader I.B., Alesary H.F., Kareem J.H., Ballantyne A.D.. Effect of graphene oxide and temperature on electrochemical polymerization of pyrrole and its stability performance in a novel eutectic solvent (Choline Chloride–Phenol) for supercapacitor applications. ACS Omega. 2022;7:34326-34340. https://doi.org/10.1021/acsomega.2c03882
[Google Scholar]
Sobika M., Paul Raj E., Krishnamoorthy S., Dash S.. Development and evaluation of azithromycin dihydrate in single and binary micellar mediums. Chemical Physics Impact. 2023;6:100229. https://doi.org/10.1016/j.chphi.2023.100229
[Google Scholar]
Nguyen T.T., Rembert K., Conboy J.C.. Label-free detection of drug-membrane association using ultraviolet−Visible sum-frequency generation. Journal of the American Chemical Society. 2009;131:1401-1403. https://doi.org/10.1021/ja8070607
[Google Scholar]
Li J., Xiao Q., Li L., Shen J., Hu D.. Novel ternary composites: Preparation, performance and application of ZnFe₂O₄/TiO₂/polyaniline. Applied Surface Science. 2015;331:108-114. https://doi.org/10.1016/j.apsusc.2015.01.001
[Google Scholar]
Wei W., Yang S., Hu H., Li H., Jiang Z.. Hierarchically grown ZnFe₂O₄-decorated polyaniline-coupled-graphene nanosheets as a novel electrocatalyst for selective detecting p-nitrophenol. Microchemical Journal. 2021;160:105777. https://doi.org/10.1016/j.microc.2020.105777
[Google Scholar]
Nejat R.. Nano-Ferrite ZnFe₂O₄: as Efficient and re-usable catalyst for the synthesis of 4H-chromenes and 4H-Pyrano[2,3-c]pyrazoles. Inorganic Chemistry Research. 2022;6:10-16. https://doi.org/10.22036/icr.2021.304989.1118
[Google Scholar]
Qader I.B., Ismail H.K., Alesary H.F., Kareem J.H., Maaroof Y.T., Barton S.. Electrochemical sensor based on polypyrrole/triiron tetraoxide (PPY/Fe₃O₄) nanocomposite deposited from a deep eutectic solvent for voltammetric determination of procaine hydrochloride in pharmaceutical formulations. Journal of Electroanalytical Chemistry. 2023;951:117943. https://doi.org/10.1016/j.jelechem.2023.117943
[Google Scholar]
Kim K.N., Jung H.-R., Lee W.-J.. Hollow cobalt ferrite–polyaniline nanofibers as magnetically separable visible-light photocatalyst for photodegradation of methyl orange. Journal of Photochemistry and Photobiology A: Chemistry. 2016;321:257-265. https://doi.org/10.1016/j.jphotochem.2016.02.007
[Google Scholar]
Hafeez H.Y., Lakhera S.K., Narayanan N., Harish S., Hayakawa Y., Lee B.K., Neppolian B.. Environmentally sustainable synthesis of a CoFe₂O₄–TiO₂/rGO ternary photocatalyst: a highly efficient and stable photocatalyst for high production of hydrogen (solar fuel) ACS Omega. 2019;4:880-891. https://doi.org/10.1021/acsomega.8b03221
[Google Scholar]
Chandel N., Sharma K., Sudhaik A., Raizada P., Hosseini-Bandegharaei A., Thakur V.K., Singh P.. Magnetically separable ZnO/ZnFe₂O₄ and ZnO/CoFe₂O₄ photocatalysts supported onto nitrogen doped graphene for photocatalytic degradation of toxic dyes. Arabian Journal of Chemistry. 2020;13:4324-4340. https://doi.org/10.1016/j.arabjc.2019.08.005
[Google Scholar]
Hosseini R., Keshavarzi F., Haghnazari N., Karami C.. Removal of azithromycin from aqueous solutions using Fe₂O₃/Ag/Zn nanocomposites. Desalination and Water Treatment. 2023;291:163-169. https://doi.org/10.5004/dwt.2023.29485
[Google Scholar]
Carneiro Pires B., Avelar Dutra F.V., Aparecida Nascimento T., Bastos Borges K.. Removal of pharmaceuticals from aqueous samples by adsorption using pristine polypyrrole as adsorbent: Kinetic, isothermal and thermodynamic studies. International Journal of Environmental Analytical Chemistry. 2023;103:5337-5354. https://doi.org/10.1080/03067319.2021.1938019
[Google Scholar]
Jadoun S., Fuentes J.P., Urbano B.F., Yáñez J.. A review on adsorption of heavy metals from wastewater using conducting polymer-based materials. Journal of Environmental Chemical Engineering. 2023;11:109226. https://doi.org/10.1016/j.jece.2022.109226
[Google Scholar]
Ali L.A., Ismail H.K., Alesary H.F., Aboul-Enein H.. A nanocomposite based on polyaniline, nickel and manganese oxides for dye removal from aqueous solutions. International Journal of Environmental Science and Technology. 2021;18:2031-2050. https://doi.org/10.1007/s13762-020-02961-0
[Google Scholar]
Al-Ghouti M.A., Da’ana D.A.. Guidelines for the use and interpretation of adsorption isotherm models: A review. Journal of hazardous materials. 2020;393:122383. https://doi.org/10.1016/j.jhazmat.2020.122383
[Google Scholar]
McKay G., Ho Y., Ng J.. Biosorption of copper from waste waters: A review. Separation and Purification Methods. 1999;28:87-125. https://doi.org/10.1080/03602549909351645
[Google Scholar]
Elovich S.Y., Larionov O.G.. Theory of adsorption from nonelectrolyte solutions on solid adsorbents. Russ Chem Bull. 1962;11:198-203. https://doi.org/10.1007/BF00908017
[Google Scholar]
Rudzinski W., Plazinski W.. Theoretical description of the kinetics of solute adsorption at heterogeneous solid/solution interfaces. Applied Surface Science. 2007;253:5827-5840. https://doi.org/10.1016/j.apsusc.2006.12.038
[Google Scholar]
Langmuir I.. The constitution and fundamental properties of solids and liquids. Journal of the Franklin Institute. 1917;183:102-105. https://doi.org/10.1016/s0016-0032(17)90938-x
[Google Scholar]
Freundlich H.. Über die Adsorption in Lösungen. Zeitschrift für Physikalische Chemie. 1907;57U:385-470. https://doi.org/10.1515/zpch-1907-5723
[Google Scholar]
Lu L., Na C.. Gibbsian interpretation of Langmuir, Freundlich and Temkin isotherms for adsorption in solution. Philosophical Magazine Letters. 2022;102:239-253. https://doi.org/10.1080/09500839.2022.2084571
[Google Scholar]
Yu K.L., Lee X.J., Ong H.C., Chen W.H., Chang J.S., Lin C.S., Show P.L., Ling T.C.. Adsorptive removal of cationic methylene blue and anionic Congo red dyes using wet-torrefied microalgal biochar: Equilibrium, kinetic and mechanism modeling. Environmental Pollution. 2021;272:115986. https://doi.org/10.1016/j.envpol.2020.115986
[Google Scholar]
Foroutan R., Mohammadi R., Ramavandi B.. Elimination performance of methylene blue, methyl violet, and Nile blue from aqueous media using AC/CoFe₂O₄ as a recyclable magnetic composite. Environmental Science and Pollution Research. 2019;26:19523-19539. https://doi.org/10.1007/s11356-019-05282-z
[Google Scholar]
Sayadi M.H., Sobhani S., Shekari H.. Photocatalytic degradation of azithromycin using GO@Fe₃O₄/ZnO/SnO₂ nanocomposites. Journal of Cleaner Production. 2019;232:127-136. https://doi.org/10.1016/j.jclepro.2019.05.338
[Google Scholar]
Raut S., Behera A.K., Sahoo S.K.. Electrospun polyacrylonitrile reinforced greenly synthesized iron oxide nanocomposite fibers sheet for remediation of azithromycin from water. Materials Today Communications. 2024;40:110113. https://doi.org/10.1016/j.mtcomm.2024.110113
[Google Scholar]
Singh V., Samanta S.K.. Magnetic graphene oxide-zinc oxide nanocomposite for enhanced photocatalytic degradation of azithromycin under normal sunlight. Journal of Environmental Management. 2024;370:122571. https://doi.org/10.1016/j.jenvman.2024.122571
[Google Scholar]
Sobhan Ardakani S., Cheraghi M., Jafari A., Zandipak R.. PECVD synthesis of ZnO/Si thin film as a novel adsorbent for removal of azithromycin from water samples. International Journal of Environmental Analytical Chemistry. 2022;102:5229-5246. https://doi.org/10.1080/03067319.2020.1793973
[Google Scholar]
Azari A., Malakoutian M., Yaghmaeain K., Jaafarzadeh N., Shariatifar N., Mohammadi G., Masoudi M.R., Sadeghi R., Hamzeh S., Kamani H.. Magnetic NH2-MIL-101(Al)/Chitosan nanocomposite as a novel adsorbent for the removal of azithromycin: modeling and process optimization. Scientific Reports. 2022;12:18990. https://doi.org/10.1038/s41598-022-21551-3
[Google Scholar]
Modabberasl A., Pirhoushyaran T., Esmaeili-Faraj S.H.. Synthesis of CoFe₂O₄ magnetic nanoparticles for application in photocatalytic removal of azithromycin from wastewater. Scientific Reports. 2022;12:19171. https://doi.org/10.1038/s41598-022-21231-2
[Google Scholar]
Kul A.R., Aldemir A., Koyuncu H.. An investigation of natural and modified diatomite performance for adsorption of basic blue 41: Isotherm, kinetic, and thermodynamic studies. Desalination and Water Treatment. 2021;229:384-394. https://doi.org/10.5004/dwt.2021.27381
[Google Scholar]
Doan V.D., Tran T.K.N., Nguyen A.-T., Tran V.A., Nguyen T.D., Le V.T.. Comparative study on adsorption of cationic and anionic dyes by nanomagnetite supported on biochar derived from Eichhornia crassipes and Phragmites australis stems. Environmental Nanotechnology, Monitoring & Management. 2021;16:100569. https://doi.org/10.1016/j.enmm.2021.100569
[Google Scholar]
Rasoulzadeh H., Mohseni-Bandpei A., Hosseini M., Safari M.. Mechanistic investigation of ciprofloxacin recovery by magnetite–imprinted chitosan nanocomposite: Isotherm, kinetic, thermodynamic and reusability studies. International Journal of Biological Macromolecules. 2019;133:712-721. https://doi.org/10.1016/j.ijbiomac.2019.04.139
[Google Scholar]
Tang Y., Chen Q., Li W., Xie X., Zhang W., Zhang X., Chai H., Huang Y.. Engineering magnetic N-doped porous carbon with super-high ciprofloxacin adsorption capacity and wide pH adaptability. Journal of Hazardous Materials. 2020;388:122059. https://doi.org/10.1016/j.jhazmat.2020.122059
[Google Scholar]
Mangla D., Annu, Sharma A., Ikram S.. Critical review on adsorptive removal of antibiotics: Present situation, challenges and future perspective. Journal of Hazardous Materials. 2022;425:127946. https://doi.org/10.1016/j.jhazmat.2021.127946
[Google Scholar]
Igwegbe C.A., Oba S.N., Aniagor C.O., Adeniyi A.G., Ighalo J.O.. Adsorption of ciprofloxacin from water: A comprehensive review. Journal of Industrial and Engineering Chemistry. 2021;93:57-77. https://doi.org/10.1016/j.jiec.2020.09.023
[Google Scholar]
Yu Y., Mo W.Y., Luukkonen T.. Adsorption behaviour and interaction of organic micropollutants with nano and microplastics – A review. Science of The Total Environment. 2021;797:149140. https://doi.org/10.1016/j.scitotenv.2021.149140
[Google Scholar]
Aziz K., Mamouni R., Kaya S., Aziz F.. Low-cost materials as vehicles for pesticides in aquatic media: A review of the current status of different biosorbents employed, optimization by RSM approach. Environmental Science and Pollution Research. 2024;31:39907-39944. https://doi.org/10.1007/s11356-023-27640-8
[Google Scholar]

1. Introduction

2. Materials and Methods

2.1. Chemicals and reagents
2.2. Preparation of Fe3O4 nanoparticles
2.3. Preparation of ZnFe2O4 nanoparticles
2.4. Preparation of ZnFe2O4@Fe3O4 nanoparticles
2.5. Preparation based DES
2.6. Chemical polymerization
2.7. Preparation of AZM pharmaceutical stock solution
2.8. Ultraviolet-visible spectroscopy
2.9. pH points of zero charges (pHpzc)
2.10. Adsorption study
2.11. Adsorption modelling studies
2.12. Regeneration of PPy/ZnFe2O4@Fe3O4 adsorbent
2.13. Environmental application
2.14. Instrumental

3. Results and Discussion

3.1. Characterization of polymeric samples
3.2. Adsorption studies
3.3. Adsorption modelling studies
3.4. Comparative analysis of adsorption capacities reported in the literature
3.5. Impact of reaction temperature and thermodynamic studies
3.6. Possible adsorption mechanism
3.7. Environmental application
3.8. Reusability studies of PPy/ZnFe2O4@Fe3O4 adsorbent

4. Conclusions

Fulltext Views
754

PDF downloads
4,002

View/Download PDF
Download Citations

BibTeX
RIS

Show Sections

[1] Li W.C.. Occurrence, sources, and fate of pharmaceuticals in aquatic environment and soil. Environmental Pollution. 2014;187:193-201. https://doi.org/10.1016/j.envpol.2014.01.015
[Google Scholar]

[2] Fatta-Kassinos D., Meric S., Nikolaou A.. Pharmaceutical residues in environmental waters and wastewater: Current state of knowledge and future research. Analytical and Bioanalytical Chemistry. 2011;399:251-275. https://doi.org/10.1007/s00216-010-4300-9
[Google Scholar]

[3] Ismail H.K., Qader A.F., Omer R.A., Alesary H.F., Umran H.M., Kareem A.A.. Synthesis of Polypyrrole-Graphene Oxide (PPy/GO) from deep eutectic solvent and its characterization for determination of metronidazole pharmaceutical substance using spectrofluorometric technique. ChemistrySelect. 2025;10:e202405486. https://doi.org/10.1002/slct.202405486
[Google Scholar]

[4] K’oreje K.O., Vergeynst L., Ombaka D., De Wispelaere P., Okoth M., Van Langenhove H., Demeestere K.. Occurrence patterns of pharmaceutical residues in wastewater, surface water and groundwater of Nairobi and Kisumu city, Kenya. Chemosphere. 2016;149:238-244. https://doi.org/10.1016/j.chemosphere.2016.01.095
[Google Scholar]

[5] Tijani J.O., Fatoba O.O., Babajide O.O., Petrik L.F.. Pharmaceuticals, endocrine disruptors, personal care products, nanomaterials and perfluorinated pollutants: A review. Environmental Chemistry Letters. 2016;14:27-49. https://doi.org/10.1007/s10311-015-0537-z
[Google Scholar]

[6] Sdiq A.F.H., Abdulrahman H.H., Ismail H.K., Omer R.A., Alesary H.F., Sultan H.K.I., Barton S.. A review of effective Nanoadsorbents made of carbonaceous, metal oxides, and polymer nanocomposite materials for adsorption of pharmaceutical contaminants in wastewater. International Journal of Environmental Research. 2025;19:159. https://doi.org/10.1007/s41742-025-00825-4
[Google Scholar]

[7] Dular M., Griessler-Bulc T., Gutierrez-Aguirre I., Heath E., Kosjek T., Krivograd Klemenčič A., Oder M., Petkovšek M., Rački N., Ravnikar M., Šarc A., Širok B., Zupanc M., Žitnik M., Kompare B.. Use of hydrodynamic cavitation in (waste)water treatment. Ultrasonics Sonochemistry. 2016;29:577-588. https://doi.org/10.1016/j.ultsonch.2015.10.010
[Google Scholar]

[8] Chen X., Chen G., Yue P.L.. Separation of pollutants from restaurant wastewater by electrocoagulation. Separation and Purification Technology. 2000;19:65-76. https://doi.org/10.1016/s1383-5866(99)00072-6
[Google Scholar]

[9] Gogoi A., Mazumder P., Tyagi V.K., Tushara Chaminda G.G., An A.K., Kumar M.. Occurrence and fate of emerging contaminants in water environment: A review. Groundwater for Sustainable Development. 2018;6:169-180. https://doi.org/10.1016/j.gsd.2017.12.009
[Google Scholar]

[10] Abdulrahman H.H., Sdiq A.F.H., Ismail H.K., Omer R.A., Alesary H.F., Kareem A.A., Barton S.. Polymer nanocomposite adsorbents for the removal of pharmaceutical formulations the aquatic environment: A Review. Water, Air, & Soil Pollution. 2025;236:584. https://doi.org/10.1007/s11270-025-08240-3
[Google Scholar]

[11] Mehrdoost A., Yengejeh R.J., Mohammadi M.K., Haghighatzadeh A., Babaei A.A.. Adsorption removal and photocatalytic degradation of azithromycin from aqueous solution using PAC/Fe/Ag/Zn nanocomposite. Environmental Science and Pollution Research. 2022;29:33514-33527. https://doi.org/10.1007/s11356-021-18158-y
[Google Scholar]

[12] Senta I., Kostanjevecki P., Krizman-Matasic I., Terzic S., Ahel M.. Occurrence and behavior of macrolide antibiotics in municipal wastewater treatment: Possible importance of metabolites, synthesis byproducts, and transformation products. Environmental Science & Technology. 2019;53:7463-7472. https://doi.org/10.1021/acs.est.9b01420
[Google Scholar]

[13] Almeida A.C., Gomes T., Lomba J.A.B., Lillicrap A.. Specific toxicity of azithromycin to the freshwater microalga Raphidocelis subcapitata. Ecotoxicology and Environmental Safety. 2021;222:112553. https://doi.org/10.1016/j.ecoenv.2021.112553
[Google Scholar]

[14] Mohammed A.K., Saadoon S.M., Abd Ali Z.T., Rashid I.M., Hussin AL, Sbani N.. Removal of amoxicillin from contaminated water using modified bentonite as a reactive material. Heliyon. 2024;10:e24916. https://doi.org/10.1016/j.heliyon.2024.e24916
[Google Scholar]

[15] Kasraei R., Malakootian M.. Tetracycline adsorption from aqueous solutions by a magnetic nanoadsorbent modified with ionic liquid. Desalination and Water Treatment. 2021;209:289-301. https://doi.org/10.5004/dwt.2021.26478
[Google Scholar]

[16] Mohammadi Nodeh M.K., Soltani S., Shahabuddin S., Rashidi Nodeh H., Sereshti H.. Equilibrium, kinetic and thermodynamic study of magnetic polyaniline/graphene oxide based nanocomposites for ciprofloxacin removal from water. Journal of Inorganic and Organometallic Polymers and Materials. 2018;28:1226-1234. https://doi.org/10.1007/s10904-018-0782-2
[Google Scholar]

[17] de Andrade J.R., Oliveira M.F., da Silva M.G., Vieira M.G.. Adsorption of pharmaceuticals from water and wastewater using nonconventional low-cost materials: a review. Industrial & Engineering Chemistry Research. 2018;57:3103-3127. https://doi.org/10.1021/acs.iecr.7b05137
[Google Scholar]

[18] Aslam J., Zehra S., Mobin M., Quraishi M.A., Verma C., Aslam R.. Metal/metal oxide-carbohydrate polymers framework for industrial and biological applications: Current advancements and future directions. Carbohydrate Polymers. 2023;314:120936. https://doi.org/10.1016/j.carbpol.2023.120936
[Google Scholar]

[19] Papageorgiou M., Maroulas K.N., Evgenidou E., Bikiaris D.N., Kyzas G.Z., Lambropoulou D.A.. Simultaneous removal of seven pharmaceutical compounds from a water mixture using modified chitosan adsorbent materials. Macromol. 2024;4:304-319. https://doi.org/10.3390/macromol4020018
[Google Scholar]

[20] Taheri N., Alizadeh N.. Vertically grown nanosheets conductive polypyrrole as a sorbent for nanomolar detection of salicylic acid. Journal of Pharmaceutical and Biomedical Analysis. 2020;188:113365. https://doi.org/10.1016/j.jpba.2020.113365
[Google Scholar]

[21] Ismail H.K., Ali L.I.A., Alesary H.F., Nile B.K., Barton S.. Synthesis of a poly(p-aminophenol)/starch/graphene oxide ternary nanocomposite for removal of methylene blue dye from aqueous solution. Journal of Polymer Research. 2022;29 https://doi.org/10.1007/s10965-022-03013-6
[Google Scholar]

[22] Dutta S., Srivastava S.K., Gupta B., Gupta A.K.. Hollow polyaniline microsphere/MnO₂/Fe₃O₄ Nanocomposites in adsorptive removal of toxic dyes from contaminated water. ACS Appl Mater Interfaces. 2021;13:54324-54338. https://doi.org/10.1021/acsami.1c15096
[Google Scholar]

[23] Dutra F.V.A., Pires B.C., Nascimento T.A., Borges K.B.. Functional polyaniline/multiwalled carbon nanotube composite as an efficient adsorbent material for removing pharmaceuticals from aqueous media. Journal of Environmental Management. 2018;221:28-37. https://doi.org/10.1016/j.jenvman.2018.05.051
[Google Scholar]

[24] Saha B., Gayen S., Debnath A.. Sequestration of paracetamol from aqueous solution using zinc oxide/polypyrrole nanocomposite: Cost Analysis, scale-up design, and optimization of process parameters. Journal of Hazardous, Toxic, and Radioactive Waste. 2023;27:e202305101. https://doi.org/10.1002/slct.202305101
[Google Scholar]

[25] Nascimento T.A., Pires B.C., Dutra F.V.A., Borges M.M.C., Borges K.B.. Poly (aniline‐co‐pyrrole) as adsorbent for removal of pharmaceuticals: Preparation, characterization, kinetics, isotherms and application on sample preparation. Chemistry Select. 2024;9:e202305101. https://doi.org/10.1002/slct.202305101
[Google Scholar]

[26] Alesary H.F., Ismail H.K., Mohammed M.Q., Mohammed H.N., Abbas Z.K., Barton S.. A comparative study of the effect of organic dopant ions on the electrochemical and chemical synthesis of the conducting polymers polyaniline, poly(o-toluidine) and poly(o-methoxyaniline) Chemical Papers. 2021;75:5087-5101. https://doi.org/10.1007/s11696-020-01477-8
[Google Scholar]

[27] A. M. Babakir B., Abd Ali L.I., Ismail H.K.. Rapid removal of anionic organic dye from contaminated water using a poly (3-aminobenzoic acid/graphene oxide/cobalt ferrite) nanocomposite low-cost adsorbent via adsorption techniques. Arabian Journal of Chemistry. 2022;15:104318. https://doi.org/10.1016/j.arabjc.2022.104318
[Google Scholar]

[28] Heck J., Goding J., Portillo Lara R., Green R.. The influence of physicochemical properties on the processibility of conducting polymers: A bioelectronics perspective. Acta Biomaterialia. 2022;139:259-279. https://doi.org/10.1016/j.actbio.2021.05.052
[Google Scholar]

[29] Abd Ali L.I., Alesary H.F., Ismail H.K., Hassan W.H., Kareem A.A., Nile B.K.. Polypyrrole-coated zinc/nickel oxide nanocomposites as adsorbents for enhanced removal of Pb(II) in aqueous solution and wastewater: An isothermal, kinetic, and thermodynamic study. Journal of Water Process Engineering. 2024;64:105589. https://doi.org/10.1016/j.jwpe.2024.105589
[Google Scholar]

[30] Alesary H.F., Odda A.H., Ismail H.K., Hassan W.H., Alghanimi G.A., Halbus A.F., Sultan H.K.I., Al-Kinani A.A., Barton S.. Green triiron tetraoxide@Algae (Fe₃O₄@Algae) nanoparticles for highly efficient removal of lead (Pb²⁺), cadmium (Cd²⁺), and aluminum (Al³⁺) from contaminated water: An isothermal, kinetic, and thermodynamic study. Environmental Science and Pollution Research. 2025;32:6817-6838. https://doi.org/10.1007/s11356-025-36169-x
[Google Scholar]

[31] Billah R.E.K., Azoubi Z., López-Maldonado E.A., Majdoubi H., Lgaz H., Lima E.C., Shekhawat A., Tamraoui Y., Agunaou M., Soufiane A., Jugade R.. Multifunctional cross-linked shrimp waste-derived chitosan/MgAl-LDH composite for removal of As(V) from wastewater and antibacterial activity. ACS Omega. 2023;8:10051-10061. https://doi.org/10.1021/acsomega.2c07391
[Google Scholar]

[32] Algethami J.S., Jugade R., Billah El Kaim R., Bahsis L., Achak M., Majdoubi H., Shekhawat A., Korde S., López-Maldonado E.A.. Chitin extraction from crab shells and synthesis of chitin @metakaolin composite for efficient amputation of Cr (VI) ions. Environmental Research. 2024;252:119065. https://doi.org/10.1016/j.envres.2024.119065
[Google Scholar]

[33] Alqarni L.S., Algethami J.S., EL Kaim Billah R., Alorabi A.Q., Alnaam Y.A., Algethami F.K., Bahsis L., Jawad A.H., Wasilewska M., López-Maldonado E.A.. A novel chitosan-alginate@Fe/Mn mixed oxide nanocomposite for highly efficient removal of Cr (VI) from wastewater: Experiment and adsorption mechanism. International Journal of Biological Macromolecules. 2024;263:129989. https://doi.org/10.1016/j.ijbiomac.2024.129989
[Google Scholar]

[34] Keshta B.E., Gemeay A.H., Kumar Sinha D., Elsharkawy S., Hassan F., Rai N., Arora C.. State of the art on the magnetic iron oxide nanoparticles: Synthesis, functionalization, and applications in wastewater treatment. Results in Chemistry. 2024;7:101388. https://doi.org/10.1016/j.rechem.2024.101388
[Google Scholar]

[35] Fatimah I., Yanti I., Wijayanti H.K., Ramanda G.D., Sagadevan S., Tamyiz M., Doong R.-an. One-pot synthesis of Fe₃O₄/NiFe₂O₄ nanocomposite from iron rust waste as reusable catalyst for methyl violet oxidation. Case Studies in Chemical and Environmental Engineering. 2023;8:100369. https://doi.org/10.1016/j.cscee.2023.100369
[Google Scholar]

[36] Alabdullah S.S.M., Ismail H.K., Ryder K.S., Abbott A.P.. Evidence supporting an emulsion polymerisation mechanism for the formation of polyaniline. Electrochimica Acta. 2020;354:136737. https://doi.org/10.1016/j.electacta.2020.136737
[Google Scholar]

[37] V. Gayathri V.G., R. Balan R.B.. Synthesis and characterisation of inorganic acid doped conducting polymer. Journal of Environmental Nanotechnology. 2019;8:20-23. https://doi.org/10.13074/jent.2019.06.192367
[Google Scholar]

[38] Alesary H.F., Noori D.Y., Al‐Yasari A., Hassan W.H., Taj‐Aldeen R.A., Ismail H.K., Athab Z.H., Halbus A.F., Barton S.. Manganese electrochemistry in a deep eutectic solvent: The effects of KBr. ChemistrySelect. 2024;9 https://doi.org/10.1002/slct.202401407
[Google Scholar]

[39] Abbott A.P., Capper G., Davies D.L., Rasheed R.K., Tambyrajah V.. Novel solvent properties of choline chloride/urea mixtures. Chemical Communications 2003:70-71. https://doi.org/10.1039/B210714G
[Google Scholar]

[40] Husin N.A., Muhamad M., Yahaya N., Miskam M., Syazni Nik Mohamed Kamal N.N., Asman S., Raoov M., Mohamad Zain N.N.. Application of a new choline-imidazole based deep eutectic solvents in hybrid magnetic molecularly imprinted polymer for efficient and selective removal of naproxen from aqueous samples. Materials Chemistry and Physics. 2021;261:124228. https://doi.org/10.1016/j.matchemphys.2021.124228
[Google Scholar]

[41] Omer R.A., Ismail H.K., Sultan H.K.I., Alesary H.F., Kareem A.A., Azeeza Y.H., Kareem R.O.. Synthesis of polyaniline, polypyrrole, and poly(aniline-co-pyrrole) in deep eutectic solvent: A comparative experimental and computational investigation of their structural, spectral, thermal, and morphological characteristics. Chemistry of Heterocyclic Compounds. 2024;60:463-472. https://doi.org/10.1007/s10593-024-03364-6
[Google Scholar]

[42] Ghayem F., Miraninezhad S., Hosseini S., Pourmousavi S.A.. ZnFe₂O₄@Fe₃O₄ Nanocatalyst for the synthesis of the 1,8-dioxooctahydroxanthene: Antioxidant and antimicrobial studies. Materials Chemistry Horizons. 2023;2:207-224. https://doi.org/10.22128/mch.2023.704.1046
[Google Scholar]

[43] Hillman A.R., Ryder K.S., Ismail H.K., Unal A., Voorhaar A.. Fundamental aspects of electrochemically controlled wetting of nanoscale composite materials. Faraday Discussions. 2017;199:75-99. https://doi.org/10.1039/c7fd00060j
[Google Scholar]

[44] Ismail H.K., Qader I.B., Alesary H.F., Kareem J.H., Ballantyne A.D.. Effect of graphene oxide and temperature on electrochemical polymerization of pyrrole and its stability performance in a novel eutectic solvent (Choline Chloride–Phenol) for supercapacitor applications. ACS Omega. 2022;7:34326-34340. https://doi.org/10.1021/acsomega.2c03882
[Google Scholar]

[45] Sobika M., Paul Raj E., Krishnamoorthy S., Dash S.. Development and evaluation of azithromycin dihydrate in single and binary micellar mediums. Chemical Physics Impact. 2023;6:100229. https://doi.org/10.1016/j.chphi.2023.100229
[Google Scholar]

[46] Nguyen T.T., Rembert K., Conboy J.C.. Label-free detection of drug-membrane association using ultraviolet−Visible sum-frequency generation. Journal of the American Chemical Society. 2009;131:1401-1403. https://doi.org/10.1021/ja8070607
[Google Scholar]

[47] Li J., Xiao Q., Li L., Shen J., Hu D.. Novel ternary composites: Preparation, performance and application of ZnFe₂O₄/TiO₂/polyaniline. Applied Surface Science. 2015;331:108-114. https://doi.org/10.1016/j.apsusc.2015.01.001
[Google Scholar]

[48] Wei W., Yang S., Hu H., Li H., Jiang Z.. Hierarchically grown ZnFe₂O₄-decorated polyaniline-coupled-graphene nanosheets as a novel electrocatalyst for selective detecting p-nitrophenol. Microchemical Journal. 2021;160:105777. https://doi.org/10.1016/j.microc.2020.105777
[Google Scholar]

[49] Nejat R.. Nano-Ferrite ZnFe₂O₄: as Efficient and re-usable catalyst for the synthesis of 4H-chromenes and 4H-Pyrano[2,3-c]pyrazoles. Inorganic Chemistry Research. 2022;6:10-16. https://doi.org/10.22036/icr.2021.304989.1118
[Google Scholar]

[50] Qader I.B., Ismail H.K., Alesary H.F., Kareem J.H., Maaroof Y.T., Barton S.. Electrochemical sensor based on polypyrrole/triiron tetraoxide (PPY/Fe₃O₄) nanocomposite deposited from a deep eutectic solvent for voltammetric determination of procaine hydrochloride in pharmaceutical formulations. Journal of Electroanalytical Chemistry. 2023;951:117943. https://doi.org/10.1016/j.jelechem.2023.117943
[Google Scholar]

[51] Kim K.N., Jung H.-R., Lee W.-J.. Hollow cobalt ferrite–polyaniline nanofibers as magnetically separable visible-light photocatalyst for photodegradation of methyl orange. Journal of Photochemistry and Photobiology A: Chemistry. 2016;321:257-265. https://doi.org/10.1016/j.jphotochem.2016.02.007
[Google Scholar]

[52] Hafeez H.Y., Lakhera S.K., Narayanan N., Harish S., Hayakawa Y., Lee B.K., Neppolian B.. Environmentally sustainable synthesis of a CoFe₂O₄–TiO₂/rGO ternary photocatalyst: a highly efficient and stable photocatalyst for high production of hydrogen (solar fuel) ACS Omega. 2019;4:880-891. https://doi.org/10.1021/acsomega.8b03221
[Google Scholar]

[53] Chandel N., Sharma K., Sudhaik A., Raizada P., Hosseini-Bandegharaei A., Thakur V.K., Singh P.. Magnetically separable ZnO/ZnFe₂O₄ and ZnO/CoFe₂O₄ photocatalysts supported onto nitrogen doped graphene for photocatalytic degradation of toxic dyes. Arabian Journal of Chemistry. 2020;13:4324-4340. https://doi.org/10.1016/j.arabjc.2019.08.005
[Google Scholar]

[54] Hosseini R., Keshavarzi F., Haghnazari N., Karami C.. Removal of azithromycin from aqueous solutions using Fe₂O₃/Ag/Zn nanocomposites. Desalination and Water Treatment. 2023;291:163-169. https://doi.org/10.5004/dwt.2023.29485
[Google Scholar]

[55] Carneiro Pires B., Avelar Dutra F.V., Aparecida Nascimento T., Bastos Borges K.. Removal of pharmaceuticals from aqueous samples by adsorption using pristine polypyrrole as adsorbent: Kinetic, isothermal and thermodynamic studies. International Journal of Environmental Analytical Chemistry. 2023;103:5337-5354. https://doi.org/10.1080/03067319.2021.1938019
[Google Scholar]

[56] Jadoun S., Fuentes J.P., Urbano B.F., Yáñez J.. A review on adsorption of heavy metals from wastewater using conducting polymer-based materials. Journal of Environmental Chemical Engineering. 2023;11:109226. https://doi.org/10.1016/j.jece.2022.109226
[Google Scholar]

[57] Ali L.A., Ismail H.K., Alesary H.F., Aboul-Enein H.. A nanocomposite based on polyaniline, nickel and manganese oxides for dye removal from aqueous solutions. International Journal of Environmental Science and Technology. 2021;18:2031-2050. https://doi.org/10.1007/s13762-020-02961-0
[Google Scholar]

[58] Al-Ghouti M.A., Da’ana D.A.. Guidelines for the use and interpretation of adsorption isotherm models: A review. Journal of hazardous materials. 2020;393:122383. https://doi.org/10.1016/j.jhazmat.2020.122383
[Google Scholar]

[59] McKay G., Ho Y., Ng J.. Biosorption of copper from waste waters: A review. Separation and Purification Methods. 1999;28:87-125. https://doi.org/10.1080/03602549909351645
[Google Scholar]

[60] Elovich S.Y., Larionov O.G.. Theory of adsorption from nonelectrolyte solutions on solid adsorbents. Russ Chem Bull. 1962;11:198-203. https://doi.org/10.1007/BF00908017
[Google Scholar]

[61] Rudzinski W., Plazinski W.. Theoretical description of the kinetics of solute adsorption at heterogeneous solid/solution interfaces. Applied Surface Science. 2007;253:5827-5840. https://doi.org/10.1016/j.apsusc.2006.12.038
[Google Scholar]

[62] Langmuir I.. The constitution and fundamental properties of solids and liquids. Journal of the Franklin Institute. 1917;183:102-105. https://doi.org/10.1016/s0016-0032(17)90938-x
[Google Scholar]

[63] Freundlich H.. Über die Adsorption in Lösungen. Zeitschrift für Physikalische Chemie. 1907;57U:385-470. https://doi.org/10.1515/zpch-1907-5723
[Google Scholar]

[64] Lu L., Na C.. Gibbsian interpretation of Langmuir, Freundlich and Temkin isotherms for adsorption in solution. Philosophical Magazine Letters. 2022;102:239-253. https://doi.org/10.1080/09500839.2022.2084571
[Google Scholar]

[65] Yu K.L., Lee X.J., Ong H.C., Chen W.H., Chang J.S., Lin C.S., Show P.L., Ling T.C.. Adsorptive removal of cationic methylene blue and anionic Congo red dyes using wet-torrefied microalgal biochar: Equilibrium, kinetic and mechanism modeling. Environmental Pollution. 2021;272:115986. https://doi.org/10.1016/j.envpol.2020.115986
[Google Scholar]

[66] Foroutan R., Mohammadi R., Ramavandi B.. Elimination performance of methylene blue, methyl violet, and Nile blue from aqueous media using AC/CoFe₂O₄ as a recyclable magnetic composite. Environmental Science and Pollution Research. 2019;26:19523-19539. https://doi.org/10.1007/s11356-019-05282-z
[Google Scholar]

[67] Sayadi M.H., Sobhani S., Shekari H.. Photocatalytic degradation of azithromycin using GO@Fe₃O₄/ZnO/SnO₂ nanocomposites. Journal of Cleaner Production. 2019;232:127-136. https://doi.org/10.1016/j.jclepro.2019.05.338
[Google Scholar]

[68] Raut S., Behera A.K., Sahoo S.K.. Electrospun polyacrylonitrile reinforced greenly synthesized iron oxide nanocomposite fibers sheet for remediation of azithromycin from water. Materials Today Communications. 2024;40:110113. https://doi.org/10.1016/j.mtcomm.2024.110113
[Google Scholar]

[69] Singh V., Samanta S.K.. Magnetic graphene oxide-zinc oxide nanocomposite for enhanced photocatalytic degradation of azithromycin under normal sunlight. Journal of Environmental Management. 2024;370:122571. https://doi.org/10.1016/j.jenvman.2024.122571
[Google Scholar]

[70] Sobhan Ardakani S., Cheraghi M., Jafari A., Zandipak R.. PECVD synthesis of ZnO/Si thin film as a novel adsorbent for removal of azithromycin from water samples. International Journal of Environmental Analytical Chemistry. 2022;102:5229-5246. https://doi.org/10.1080/03067319.2020.1793973
[Google Scholar]

[71] Azari A., Malakoutian M., Yaghmaeain K., Jaafarzadeh N., Shariatifar N., Mohammadi G., Masoudi M.R., Sadeghi R., Hamzeh S., Kamani H.. Magnetic NH2-MIL-101(Al)/Chitosan nanocomposite as a novel adsorbent for the removal of azithromycin: modeling and process optimization. Scientific Reports. 2022;12:18990. https://doi.org/10.1038/s41598-022-21551-3
[Google Scholar]

[72] Modabberasl A., Pirhoushyaran T., Esmaeili-Faraj S.H.. Synthesis of CoFe₂O₄ magnetic nanoparticles for application in photocatalytic removal of azithromycin from wastewater. Scientific Reports. 2022;12:19171. https://doi.org/10.1038/s41598-022-21231-2
[Google Scholar]

[73] Kul A.R., Aldemir A., Koyuncu H.. An investigation of natural and modified diatomite performance for adsorption of basic blue 41: Isotherm, kinetic, and thermodynamic studies. Desalination and Water Treatment. 2021;229:384-394. https://doi.org/10.5004/dwt.2021.27381
[Google Scholar]

[74] Doan V.D., Tran T.K.N., Nguyen A.-T., Tran V.A., Nguyen T.D., Le V.T.. Comparative study on adsorption of cationic and anionic dyes by nanomagnetite supported on biochar derived from Eichhornia crassipes and Phragmites australis stems. Environmental Nanotechnology, Monitoring & Management. 2021;16:100569. https://doi.org/10.1016/j.enmm.2021.100569
[Google Scholar]

[75] Rasoulzadeh H., Mohseni-Bandpei A., Hosseini M., Safari M.. Mechanistic investigation of ciprofloxacin recovery by magnetite–imprinted chitosan nanocomposite: Isotherm, kinetic, thermodynamic and reusability studies. International Journal of Biological Macromolecules. 2019;133:712-721. https://doi.org/10.1016/j.ijbiomac.2019.04.139
[Google Scholar]

[76] Tang Y., Chen Q., Li W., Xie X., Zhang W., Zhang X., Chai H., Huang Y.. Engineering magnetic N-doped porous carbon with super-high ciprofloxacin adsorption capacity and wide pH adaptability. Journal of Hazardous Materials. 2020;388:122059. https://doi.org/10.1016/j.jhazmat.2020.122059
[Google Scholar]

[77] Mangla D., Annu, Sharma A., Ikram S.. Critical review on adsorptive removal of antibiotics: Present situation, challenges and future perspective. Journal of Hazardous Materials. 2022;425:127946. https://doi.org/10.1016/j.jhazmat.2021.127946
[Google Scholar]

[78] Igwegbe C.A., Oba S.N., Aniagor C.O., Adeniyi A.G., Ighalo J.O.. Adsorption of ciprofloxacin from water: A comprehensive review. Journal of Industrial and Engineering Chemistry. 2021;93:57-77. https://doi.org/10.1016/j.jiec.2020.09.023
[Google Scholar]

[79] Yu Y., Mo W.Y., Luukkonen T.. Adsorption behaviour and interaction of organic micropollutants with nano and microplastics – A review. Science of The Total Environment. 2021;797:149140. https://doi.org/10.1016/j.scitotenv.2021.149140
[Google Scholar]

[80] Aziz K., Mamouni R., Kaya S., Aziz F.. Low-cost materials as vehicles for pesticides in aquatic media: A review of the current status of different biosorbents employed, optimization by RSM approach. Environmental Science and Pollution Research. 2024;31:39907-39944. https://doi.org/10.1007/s11356-023-27640-8
[Google Scholar]

Adsorption of azithromycin pharmaceutical by polypyrrole and polypyrrole/zinc ferrite@magnetite (PPy/ZnFe2O4@Fe3O4) adsorbents synthesized from deep eutectic solvent: Kinetic, isothermic, and thermodynamic studies

Abstract

Keywords

Adsorption

Azithromycin

Conducting polymer composite

Deep eutectic solvents

Kinetic and isotherms

Polypyrrole

1. Introduction

2. Materials and Methods

2.1. Chemicals and reagents

2.2. Preparation of Fe3O4 nanoparticles

2.3. Preparation of ZnFe2O4 nanoparticles

2.4. Preparation of ZnFe2O4@Fe3O4 nanoparticles

2.5. Preparation based DES

2.6. Chemical polymerization

2.6.1. Synthesis of PPy

2.6.2. Synthesis of PPy/ZnFe2O4@Fe3O4 composite

2.7. Preparation of AZM pharmaceutical stock solution

2.8. Ultraviolet-visible spectroscopy

2.9. pH points of zero charges (pHpzc)

2.10. Adsorption study

2.11. Adsorption modelling studies

2.12. Regeneration of PPy/ZnFe2O4@Fe3O4 adsorbent

2.13. Environmental application

2.14. Instrumental

3. Results and Discussion

3.1. Characterization of polymeric samples

3.1.1. FTIR study

3.1.2. XRD study

3.1.3. Surface morphology study

3.1.4. Pore size distribution BET analysis

3.1.5. Magnetic study

3.2. Adsorption studies

3.2.1. Optimization of adsorbent for the adsorption of AZM pharmaceutical

3.2.2. Factors affecting adsorption

3.2.2.1. Impact of initial solution pH

3.2.2.2. Impact of nanocomposite adsorbent dosage

3.2.2.3. Impact of initial concentrations of drug

3.2.2.4. Impact of reaction time

3.3. Adsorption modelling studies

3.3.1. Kinetics modelling study

3.3.2. Isothermal modelling study

3.4. Comparative analysis of adsorption capacities reported in the literature

3.5. Impact of reaction temperature and thermodynamic studies

3.6. Possible adsorption mechanism

3.6.1. Electrostatic interaction

3.6.2. Hydrogen bonds

3.6.3. Hydrophobic interaction

3.6.4. Pore-filling interaction

3.7. Environmental application

3.8. Reusability studies of PPy/ZnFe2O4@Fe3O4 adsorbent

4. Conclusions

Acknowledgment

CRediT authorship contribution statement

Declaration of competing interest

Declaration of Generative AI and AI-assisted technologies in the writing process

Supplementary data

References

Suggested read for related articles:

Adsorption of azithromycin pharmaceutical by polypyrrole and polypyrrole/zinc ferrite@magnetite (PPy/ZnFe₂O₄@Fe₃O₄) adsorbents synthesized from deep eutectic solvent: Kinetic, isothermic, and thermodynamic studies

2.2. Preparation of Fe₃O₄ nanoparticles

2.3. Preparation of ZnFe₂O₄ nanoparticles

2.4. Preparation of ZnFe₂O₄@Fe₃O₄ nanoparticles

2.6.2. Synthesis of PPy/ZnFe₂O₄@Fe₃O₄ composite

2.9. pH points of zero charges (pH_pzc)

2.12. Regeneration of PPy/ZnFe₂O₄@Fe₃O₄ adsorbent

3.8. Reusability studies of PPy/ZnFe₂O₄@Fe₃O₄ adsorbent