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Removal of pharmaceutical compounds from urine via chemical coagulation by green synthesized ZnO-nanoparticles followed by microfiltration for safe reuse
⁎Corresponding author. waterbiotech@yahoo.com (Hussein I. Abdel-Shafy) hshafywater@yahoo.com (Hussein I. Abdel-Shafy)
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Received: ,
Accepted: ,
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.
Peer review under responsibility of King Saud University.
Abstract
In the present study green chemistry was employed for synthesizing ZnO nanoparticles using the extract of black tea solid waste and Zn acetate dihydrate. The characterization of the green synthesized ZnO was conducted by XRD, SEM, HR-TEM, DLS and EDAX. Urine samples from donors under medication with Ibuprofen, Ephedrine and Propranolol were separated and collected through a diversion toilet. A batch experiment was conducted in order to determine the optimum dose of green synthesized ZnO nanoparticles for the removal of the pharmaceutical compounds from human urine. The determined optimum dose of the ZnO nanoparticles was 1.5 g/l. ZnO nanoparticle possess the ability to adsorb the Pharmaceutical active compounds (PACs) on the surface. In addition, it binds such adsorbed particles and facilitates their precipitation. Coagulant reagents react with some of the suspended and colloidal particles in water/wastewater to enhance their binding together, thus, allowing their removal in the subsequent treatment processes. The mechanism of aggregation consists of the combination of charge neutralization, entrapment, adsorption and/or complexion with the coagulant ions to form insoluble precipitate. Thus, the particles and colloids can be removed. A semi-pilot plant consisted of mixing tank for chemical coagulation using the predetermined ZnO nanoparticles followed by microfiltration unit, was designed and operated continuously for the treatment of the separated urine. The overall results of the semi-pilot study showed that the concentration of Ibuprofen, Ephedrine and Propranolol decreased from 5.0, 10.15 and 15.2 mg/l to 0.01, 0.10 and 0.03 mg/l respectively. The overall removal rate exceeded 99%. Meanwhile, the treatment system succeeded to improve the physical and chemical characteristics of the contaminated human urine. The treated urine could be safely used for agriculture purposes without any environmental threat.
Keywords
ZnO nanoparticles
Green synthesis
Pharmaceutical removal
Chemical coagulation
Urine safe reuse
Membrane microfiltration
1 Introduction
Pharmaceutical active compounds (PACs) have, presently, been classified as emerging pollutants of concern because of their detection in aquatic environment and surface waters. High consumption of PACs of more than $250 billion (Khetan and Collins, 2007) in the USA during 2006, provides a continuous input of the PACs into the environment. Such PACs can enter wastewater treatment plants via excretion (Kummerer, 2004), industrial facilities (Larsson et al., 2007), or even disposal of unused or expired drugs (Abdel-Shafy and Mansour, 2013a). The removal efficiency of the PACs in treatment plants varies widely, often ended by their discharge into receiving streams and natural bodies of water (Beausse, 2004; Martyn et al., 2011; Camacho-Mũnoz et al., 2010; Abdel-Shafy and Mansour, 2013b).
These PACs can end up onto soils when sewage sludge is employed as fertilizer (Beausse, 2004; Camacho-Mũnoz et al., 2010). Their occurrence in surface water has been documented by several investigators (Ashton et al., 2004; Fatta-Kassinos et al., 2011; Spongberg et al., 2011; Abdel-Shafy and Mansour, 2013c). The most important source of pharmaceuticals in the environment and water cycle is via human metabolism. These compounds are partially metabolized by the human body. Therefore, they enter the environment either as parent compounds (unchanged), or as a mixture of metabolites and/or conjugated compounds (Jjemba, 2006; Lienert et al., 2007). Generally, PACs are excreted largely through urine (generally 55–80% of the total with an average of 70%, with few exceptions) and partially in the feces (Abdel-Shafy and Mansour, 2013a).
In the 1990s and beyond, various researchers worked on the same concept by separating urine at source for the purpose of promoting the sustainability of wastewater management (Larsen and Gujer, 1996; Regelsberger et al., 2007; Masi et al., 2010). All these researches are based on the fact that urine contains most of chemical nutrient elements in domestic wastewater. However, it makes up less than 1% of the total wastewater volume. Adequate separation of urine at source would, therefore, allow nutrient recycling. Meanwhile, it would minimize advanced nutrient removal, including nitrification, denitrification and phosphorus elimination (Wilsenach and Van Loosdrecht, 2004). Separation of urine presents several advantages. Besides the above mentioned advantages, it offers better ways of removing organic micro-pollutants resulted from the human metabolism (Wilsenach and Van Loosdrecht, 2004; Abdel-Shafy and Mansour, 2013b). This leads to more efficient wastewater management (Larsen and Gujer, 2001).
Recently, several investigators studied the elimination of PACs from contaminated urine using Fenton’s reagents. The overall conclusion is that Fenton’s treatment can be rated as uneconomical method for larger volumes of urine (Abdel-Shafy and Mansour, 2013b). However, this Fenton’s oxidation is considered an effective pre-treatment method for the non-biodegradable portions, which could render them to be ready for biodegradation by the following biological processes. If the Fenton’s oxidation is employed as a pre-treatment method, lower dose of such reagents can be used. Thus, purified urine can be used safely for agricultural purpose without any hazard of pharmaceutical contamination (Abdel-Shafy and Mansour, 2013a).
On the other hand, membrane technology proved to be effective for the separation of pharmaceutical compounds from urine (Abdel-Shafy and Mansour, 2016; Abdel-Shafy and Mohamed-Mansour, 2014). Nanofiltration was employed for pharmaceutical and estrogenic removal with the aim of producing urine free of any micro pollutant that can be used as fertilizer (Pronk et al., 2006; Abdel-Shafy, Al-Sulaiman, et al., 2015; Abdel-Shafy, Schories, et al., 2015).
Meanwhile, chemical coagulation and flocculation for water/wastewater treatment proved to be efficient for altering some of the dissolved and suspended matters into precipitate. Thus, it facilitates their removal by sedimentation (Matilainen et al., 2010; Abdel-Shafy, 2015; Abdel-Shafy and Al-Sulaiman, 2014). Coagulant reagents react with some of the suspended and colloidal particles in water/wastewater to enhance binding them together, thus, allowing their removal in the subsequent treatment processes (Lia et al., 2006). The mechanism of aggregation consists of the combination of charge neutralization, entrapment, adsorption and/or complexion with the coagulant ions to form insoluble precipitate. Thus, the particles and colloids can be removed (Matilainen et al., 2010; Verma et al., 2012). Coagulation process forms an integral part of the conventional water/wastewater treatment and has been employed to decrease turbidity, color and to remove pathogens (Matilainen et al., 2010; Verma et al., 2012).
On the other hand, nanoparticles possess the unique size property. Such property depends on what is known as high ‘aspect ratio’, which is the ratio between the surface areas to the volume. The smaller the particle size the greater will be the aspect ratio (i.e., greater surface area compared to their volume). Thus, the higher ‘aspect ratio’ enhances the reactivity of the nanoparticles with the surrounding molecules. Synthesizing the nanoparticles by conventional methods has some adverse effects (i.e. the critical conditions of temperature and pressure cost of chemicals, long refluxing time of reaction, toxicity of the byproducts, etc.). Chemical synthesis of ZnO is reported by several investigators (Omri et al., 2014). On the contrary, synthesizing the nanoparticles via green methods has gained recently significant importance and it became one of the most adequate and preferred methods. The advantages of green synthesis procedures include simple, good stability of the nanoparticles, inexpensive, non-toxic byproducts, less time consuming and large-scale synthesis (Awad et al., 2013; Moritz and Geszka-Moritz, 2013; Hassan et al., 2015).
More recently, several studies have been reported on the synthesizing of green nanoparticles of the noble metals including silver (Ag) and gold (Au) in terms of their antimicrobial activities (Awad et al., 2013). Meanwhile, few studies were carried out on the green synthesis of some metal oxide nanoparticles including AlO, CuO, FeO2, MgO, TiO2 and ZnO (Awad et al., 2013; Moritz and Geszka-Moritz, 2013). Further extensive work has been done to study the plant assisted reduction of metal nanoparticles along with the respective role of phytochemicals. The most important water soluble phytochemicals are flavones, quinones and organic acids. They are responsible for the immediate reduction. In addition, protocatechualdehyde and catechol were reported in the hydrophyte studies together with other phytochemicals. It was confirmed that catechol in the alkaline conditions is transformed into protocatechaldehyde then into protocatechuic acid in the final stage. These two processes liberated hydrogen. It was reported by Jha and Prasad (2009) that these processes play role in the synthesis of the nanoparticles. It is worth mentioning that the main phytochemicals present in the leaves of black tea consist of water soluble Catechins, Theaflavins and Thearubigins. They are oligomers of catechins of unknown structure. It was, therefore, suggested that water soluble phytochemicals of tea may be able to play a major role in the overall reduction reactions (Larsen and Gujer, 1996).
The main concern of the present study is to investigate the removal of the pharmaceutical active compounds (PACs) from urine for safe reuse. The purpose of this study was to remove the pharmaceutical contaminants from urine. Therefore the purified urine can be used for agriculture purpose as environmental friendly source of nutrient elements. The investigation includes two successive steps. The first step is to examine green synthesized ZnO nanoparticles and to examine the efficiency of this ZnO for the elimination of PACs. The second step is to investigate the efficiency of microfiltration for the removal of the pharmaceutical compounds from urine. The ZnO nanoparticles were synthesized by a green chemistry method. The present investigation was examined by both bench laboratory scale and semi-pilot continuous systems.
2 Materials and methods
2.1 Chemicals
Zinc acetate dihydrate (99% purity) and sodium hydroxide (pellet, purity 99%) were purchased from Sigma–Aldrich (St. Louis, MO). Ibuprofen (purity 99%), Ephedrine (purity 99%) and Propranolol (purity ⩾ 99%) standards were also purchased from Sigma–Aldrich (St. Louis, MO).
2.2 Synthesization and characterization of zinc oxide nanoparticles
2.2.1 Preparation of the extract
The extract was prepared by weighing 2.0 g of dried black tea solid waste, this amount was placed in 200 ml glass beaker and 100 ml of deionizer water was added. The mixture was placed on a hot plate and was heated gently until boiling. The gentle boiling was continued until the color of the aqueous solution changes to dark red. The extract was cooled to room temperature and filtered using Whatman (No. 40) filter paper. A qualitative analysis of the black tea solid waste extract was carried out according to Trease and Evans, (1989)
2.2.2 Green synthesization of ZnO nanoparticles
A weight of 0.2 g zinc acetate dihydrate was added to 50 ml of distilled water. The mixture was stirred vigorously for 10 min. A volume of 1.0 ml of the black tea extract was added to the Zn acetate solution. NaOH (2.0 M) was added dropwise until the pH increased to 12. At this moment a pale white aqueous solution was gained. The mixture was stirred slowly to allow the precipitation of ZnO nanoparticles. The obtained pale white precipitate was collected and washed several times with double distilled water, followed by ethanol. The centrifuge was employed for collecting the ZnO nanoparticles after each step of washing. The collected powder was dried at 70 °C for overnight period.
2.2.3 Characterization of green synthesized ZnO nanoparticles
The pale white powder of ZnO nanoparticles was carefully collected and characterized using XRD, SEM, HR-TEM, DLS and EDAX before conducting any experimental investigation. Furthermore, the antibacterial activity of green synthesized ZnO nanoparticles was also examined according to Moritz and Geszka-Moritz, (2013).
2.3 Raw urine sources
Urine diversion toilet was installed at the semi-pilot plant in the National Research Center (NRC), Cairo, Egypt (Fig. 1). Through piping system, the separated urine was directed to the semi-pilot plant and finally to a collection tank in the NRC. The toilet users were under medication with Ibuprofen, Ephedrine and Propranolol.
Urine diversion toilet.
2.4 Laboratory batch experiment
Jar test was employed to determine the optimum dose of green synthesized ZnO nanoparticles for the removal of pharmaceutical active compounds from the collected contaminated urine. Different doses of ZnO nanoparticles (namely: 0.5, 0.7, 1.0, 1.3, 1.5 and 1.7 g/l) were examined. The addition of the green ZnO nanoparticles was under flash mixing for 5 min at 350 rpm, followed by flocculation for 30 min at 80 rpm and finally sedimentation for 60 min.
2.5 Semi-pilot plant
A semi-pilot plant as continuous system was designed for the treatment of the contaminated urine (Fig. 2). This semi-pilot plant consists of collection, coagulation/flocculation and sedimentation tanks followed by membrane microfiltration system (Fig. 2). The study was carried out at room temperature.
Schematic diagram of the treatment system (where UDT, C.T., CCFT, ST and MF are the urine diversion toilet, the collection tank, the chemical coagulation/flocculation tank, the settling tank and microfiltration unit respectively).
2.5.1 Coagulation, flocculation and sedimentation tanks
Two baffled tanks were used. The first baffled tank with an effective dimension of 0.4 m × 0.4 m × 0.8 m was used for chemical coagulation/flocculation. The second baffled tank was used for sedimentation with an effective dimension of 0.5 m × 0.5 m × 0.5 m. The predetermined optimum dose of green synthesized ZnO nanoparticles was added to the coagulation tank along with the urine pathway using dosing pump. Both liquids namely the contaminated urine and the ZnO solution were mixed together before reaching the tank by passing them together through circled tube to allow a complete mixing. The liquid was then slowly flown to allow the formation of the flocks. Finally the effluent was flown gradually to the sedimentation tank for settling all the particles.
2.5.2 Membrane microfiltration laboratory scale unit
The effluent of the sedimentation tank was directed by a dosing pump to the membrane microfiltration (MF) system for further treatment (Fig. 2). The feeding to the membrane system was from the top of the MF unit.
The MF membrane unit was especially designed in 2014 as a treatment system for water and wastewater. The microfiltration pore size was 0.378 μm to guarantee and provide reliable separation of bacteria and all particulate matters. Up-flow aeration from the bottom of the MF reactor was supplied by a compressor of 116 psi (pounds per square inch) pressure capacity. The aeration was daily supplied to facilitate aerobic environment of the system as well as minimizing any possible fouling or clogging of the membrane reactor. In addition, fouling on the surface of the plate and frame module (KUBOTA) is controlled through tangential flow along the MF membrane surface. In order to avoid any fouling problem, the backwashing of the membrane was carried out monthly during the entire experimental work (Judd, 2004). The necessary trans-membrane pressure difference is applied by the water head (1.4 m height) above the membrane to allow the gravity flow. Thus the system was operated without any energy input (Strathmann et al., 2006; Abdel-Shafy, Al-Sulaiman, et al., 2015; Abdel-Shafy, Schories, et al., 2015). In this respect, the aeration system of MF-membrane could save about 40% of the total required energy (i.e. the energy consumption was about 60% of the total required energy). A rough estimation of the present study reveals that applying the water head (1.1 m height) for gravity flow of wastewater could save between 30% and 40% of the total required energy. The small pore sizes of the MF-membrane guarantee retaining any possible nitrifying bacteria and other microorganisms in the reactor. Furthermore, the separation by MF-membranes was able to allow mixed liquor suspended solid concentrations that by far exceed the usual 2–4 g/L in conventional treatment systems. The main purpose was to obtain an effluent free of any germs and particles. The experiments were carried out in the MF-reactor that was operated under aerobic conditions (oxygen concentration in the tank ranged between 1 and 4 mgO2/L). Meanwhile, the continuous aeration provided for MF limited membrane fouling and could successfully maintain the aerobic condition of the reactor. The specifications of the pilot MF-membrane unit are given in Table 1.
Item
Specificationa
The material of the membrane
Polyelectrolyte complex (PEC)
Surface area of the Membrane
0.6 m2
Number of the membranes
8
Resistance/temperature WC
<50
Resistance/pH range
between 1.5 and 10
Resistance/H2O2 (NaOCl)
between, ppm 3000 and 5000 (normal 500)
Resistance/pressure, as (mWS)
Max. 1–3 (1.02 mWS¼ 10 kPa)
2.5.3 Schematic operation of the Semi Pilot plant treatment system
The ZnO treated effluent was pumped from the sedimentation tank to the top of the MF reactor (Fig. 2). The urine flew in the aerobic MF by gravity. The final effluent was reused for agriculture purposes. The schematic diagram of the treatment system is shown in Fig. 2.
2.6 Analytical measurement
XRD [PANalytical-Empyrean] was used in order to investigate the purity of synthesized ZnO nanoparticles under the following condition: Scan Axis: Gonio, Start Position [°2Th.]: 5.0129, End Position [°2Th.]: 79.9709, Step Size [°2Th.]: 0.0260, Scan Step Time [s]: 18.8700, Scan Type: Continuous, PSD Length [°2Th.]: 3.35, Measurement Temperature [°C]: 25.00, Anode Material: Cu, K-Alpha1 [Å]: 1.54060, K-Alpha2 [Å]: 1.54443, K-Beta [Å]: 1.39225, K-A2/K-A1 Ratio: 0.50000, Generator Settings: 30 mA, 45 kV.
SEM [quanta FEG 250] gives illustration on the surface morphology of synthesized ZnO nanoparticles. HR-TEM [JEOL JEM – 2100 electron microscope] was used to gain the actual particle size of synthesized ZnO nanoparticles. EDAX [AMETEK material analysis device] was also used for ZnO nanoparticles characterization. DLS [Malvern instruments, Zetasizer Nano-ZS] at wavelength 633 nm and the source of the laser that is He-Ne was used for zeta potential measurement.
The concentration of pharmaceutical active compounds in the raw contaminated urine as well as through all the study periods was determined using Water 2795 HPLC equipped with Quattro Ultima® MS/MS detector and a column: water X Terra® C18, 3.5 μm, 10 cm, 2.1 mm. Ionization: Electro-spray positive (ES+). Acquisition: MRM mode, unit resolution. The mobile phase consisted of (A) 0.3% formic acid and 0.1% Ammonium format, and (B) 1:1 acetonitrile:methanol. The solvent program was Gradient; the injection volume was 5 μL.
The physical and chemical characteristics of the studied urine including COD (total and dissolved), BOD, nitrates, nitrites, ammonia, total phosphates, K, Na and Ca were determined according to the Standard Methods for Examination of Water and Wastewater (APHA, 2005).
3 Results and discussions
3.1 Qualitative analysis of the extract
Results of the qualitative analysis of the black-tea solid waste extract showed that the phytochemical compounds are flavonoid, catechin and theaflavins. The phytochemical constituents of black-tea solid waste are responsible for the reduction activity in the reaction.
3.2 Characterization of green synthesized ZnO nanoparticles
The use of black-tea solid waste extract leads to the reduction of Zn acetate dihydrate to pure ZnO nanoparticles directly at pH 12 without any need to calcination. The green synthesized ZnO nanoparticles were characterized as follows.
The formation of ZnO was confirmed by using XRD. Fig. 3 is the XRD spectra of the synthesized ZnO nanoparticles. The obtained diffraction peak positions were 31.731°, 34.371°, 36.219°, 47.49°, 56.539°, 62.79°, 64.879°, 66.272°, 67.87° and 69.09°. These data confirm that there are no impurities in the synthesized ZnO nanoparticles. It also confirms hexagonal phase of ZnO (Singh et al., 2011). The hexagonal structure has a point group 6 mm (Hermann–Mauguin notation) or C6v (Schoenflies notation), and the space group is P63mc or C6v4. The lattice constants are a = 3.25 Å and c = 5.2 Å; their ratio c/a ∼ 1.60 is close to the ideal value for hexagonal cell c/a = 1.633. As in most group II–VI materials, the bonding in ZnO is largely ionic (Zn2+O2−). These properties are responsible for the preferential formation of wurtzite rather than zinc blended structure including the strong piezoelectricity property of ZnO. Due to the polar Zn–O bonds, oxygen and zinc planes are electrically charged. The surfaces of ZnO are stable, atomically flat and exhibit no reconstruction (Baruah and Dutta, 2016).
X-ray spectra of green synthesized ZnO nanoparticles.
Fig. 4 represents the EDAXS pattern of green synthesized ZnO nanoparticles. This EDAXS elemental analysis shows that only Zn and O atoms exist at the atomic ratio of 44% O:56% Zn.
EDAX of green synthesized ZnO nanoparticles.
The surface morphology of green synthesized ZnO nanoparticles was gained using SEM (Fig 5). It presents the SEM image of the synthesized ZnO nanoparticles at different magnification. It is worth mentioning that this image shows rod shape of the nanoparticles.
SEM image of green synthesized ZnO nanoparticles at different magnification.
Furthermore, HR-TEM gives the actual particle size. In addition, Fig. 6 shows HR-TEM image of the green synthesized ZnO nanoparticles, as the average particle size is 19.5 nm.
HR-TEM image of ZnO nanoparticles synthesized by using black tea solid waste.
On the other hand, DLS instrument was employed to measure the Zeta potential of the green synthesized ZnO nanoparticles. In this respect, Zeta potential is the electric potential in the interfacial double layer (DL) at the location of the slipping plane versus a point in the bulk fluid away from the interface. It is, therefore, the potential difference between the dispersion medium and the stationary layer of fluid that is attached to the dispersed particle. The positive or negative value of 25 mV can be taken as the arbitrary value that separates low-charged surfaces from highly-charged surfaces. The significance of zeta potential, in the liquid, is that its value can be related to the stability of colloidal dispersions. Therefore, zeta potential indicates the degree of repulsion between adjacent, similarly charged particles in dispersion. In case of the molecules and particles that are small enough, the high zeta potential will confer stability. In other words, the solution or dispersion will resist aggregation. When the potential is low, the attraction exceeds the repulsion; thus, the dispersion will break and flocculate. Zeta potential (i.e. Surface potential) has a direct relation with the stability of a form and/or structure. The obtained zeta potential (Fig. 7) of green synthesized ZnO nanoparticles was (−41.3) mV which indicates a good stability.
DLS Zeta potential distribution of green synthesized ZnO nanoparticles.
DLS is employed to study stability of the particles. In addition, it shows whether the particles aggregate over time by observing whether the hydrodynamic radius of the particle increases. When the particles aggregate, there will be a larger population of these particles with a larger radius. DLS size distribution by number: Fig. 8 indicates that the particles are mono-dispersed. This means that one size range of particles was formed (i.e. the population of the particle size within the range of 54 nm was the most population ones).
DLS size distribution by number of green synthesized ZnO nanoparticles.
The role of black tea waste extract on the synthesis of ZnO Nanoparticles can be explained as follows: Biosynthesis of the present nanoparticles is considered a type of bottom up approach in which the main occurring reaction is reduction/oxidation. In this respect, the microbial enzymes and/or the plant phytochemical with antioxidant or reducing properties are generally responsible for the reduction of the metal compounds into their corresponding nanoparticles. The three main steps for the preparation of nanoparticles that should be evaluated from a green chemistry perspective are as follows: (a) the choice of the solvent medium used for the synthesizing, (b) the choice of an environmentally benign reducing agent and (c) the choice of a non-toxic material for the stabilization of the nanoparticles (Raveendran et al., 2003). In green nanoparticle synthesis, water is commonly used as an environmentally benign solvent (i.e. water here replaces the toxic organic solvents). Recently, biological entities have been reported to serve as both surface stabilizing and reducing agents for green synthesis of metallic nanoparticles. The advantage of using natural plants or their solid waste for the synthesis of nanoparticles is that they are inexpensive, available, can be handled safely and possess a broad variability of metabolites which is effective in reduction.
3.3 Characterization of raw urine sample
Table 2 represents the main characteristics of raw urine in terms of pH, turbidity, CODT, CODD, BOD, T.P., NO3, NO2, NH3 K, Na, Ca, Mg and the concentrations of the pharmaceutical active compounds (namely, Ibuprofen, Ephedrine and Propranolol). The given results indicate that the urine was collected from patients who were under medication with the Ibuprofen, Ephedrine and Propranolol. N∗ = Number of samples, CODT = Total Chemical Oxygen Demand, CODD = Dissolved Chemical Oxygen Demand, BOD5 = Biological Oxygen Demands, T.P. = Total Phosphates, NO3 = Nitrates, NO2 = Nitrites, NH3 = ammonia, K = Potassium, Na = Sodium, Ca = calcium, Mg = Magnesium.
Parameter
Unit
N
Minimum
Maximum
Average
pH
…
6
4.5
5.3
5.1 ± 0.22
Turbidity
NTU
6
190
250
201 ± 0.19
CODT
mg l−1
6
19,700
19,950
19,820 ± 86
CODD
mg l−1
6
11,800
11,200
11,892 ± 73
BOD5
mg l−1
6
2450
2600
2552 ± 63
BOD5/COD
…
6
0.09
0.15
0.13
T.P.
mg l−1
6
180
260
200 ± 31
NO3
mg l−1
6
5
15
10 ± 0.27
NO2
mg l−1
6
34.9
49.8
44.7 ± 0.81
NH3
mg l−1
6
364.2
523.5
491.2 ± 0.56
K
mg l−1
6
800
900
866 ± 92
Na
mg l−1
6
500
600
556 ± 78
Ca
mg l−1
6
1300
1400
1344 ± 69
Mg
mg l−1
6
40
70
53.5 ± 11
SAR
…
6
3. 5
6
4.1
Ibuprofen (mg/l)
mg l−1
6
4.2
5.5
5 ± 0.46
Ephedrine (mg/l)
mg l−1
6
8
11
10.15 ± 0.69
Propranolol (mg/l)
mg l−1
6
11
18
15.2 ± 0.89
3.4 Jar-Test batch experiments
The results (Table 3) showed that increasing the dose of ZnO nanoparticles increases the removal rate of the examined parameters. However, increasing the ZnO dose up to 1.7 g/l did not exhibit remarkable removal percentage. The optimum dose of the ZnO nanoparticles was found to be 1.5 g/l at which the concentration of Ibuprofen, Ephedrine and Propranolol decreased from 5.00, 10.15 and 15.20 to 0.08, 0.90 and 0.20 respectively (Table 3). N∗ = Number of samples, CODT = Total Chemical Oxygen Demand, CODD = Dissolved Chemical Oxygen Demand, BOD5 = Biological Oxygen Demands, T.P. = Total Phosphates, NO3 = Nitrates, NO2 = Nitrites, NH3 = ammonia, K = Potassium, Na = Sodium, Ca = calcium, Mg = Magnesium.
Parameter
N
Raw contaminated human urine
ZnO nanoparticles dose (g/l)
0.5
0.7
1
1.3
1.5
1.7
pH
7
5.1(±0.22)
7.6
7.8
8.0
8.2
8.6
8.8
Turbidity (NTU)
7
201(±0.15)
47
41
37
36
35
34
CODT (mg/l)
7
19,820(±86)
6400
6080
1200
680
500
489
CODD (mg/l)
7
11,892(±73)
4032
3769.6
732
421.6
310
299
BOD5 (mg/l)
7
2552(±66)
1243.3
974.6
471.6
207.9
100.8
89.9
BOD5/COD
7
0.13
0.19
0.16
0.39
0.31
0.20
0.18
T.P (mg/l)
7
200(±45)
106
96.4
94.4
91.8
91.6
88.3
NO3 (mg/l)
7
10(±0.26)
6.96
5.0
4.7
4.55
4.2
4.0
NO2 (mg/l)
7
44.7(±0.52)
31.7
22.9
20.9
20.3
19.0
17.9
NH3 (mg/l)
7
491.2(±21)
343.0
245.8
228.8
213.5
203.2
197.6
K (mg/l)
7
866(±30)
356
340
320
296
206
199
Na (mg/l)
7
556(±48)
238
198
76
46
25
21
Ca (mg/l)
7
1344(±39)
600
454
292
264
220
209
Mg (mg/l)
7
53.5(±11)
30.1
19.4
15.4
10.1
6.2
5.9
SAR
4.1
2.6
2.4
1.2
0.7
0.45
0.41
Ibuprofen (mg/l)
7
5.0 (±0.88)
3.5
2
1.2
0.9
0.08
0.08
Ephedrine (mg/l)
7
10.15 (±0.95)
5.2
3.2
2
1.4
0.90
0.88
Propranolol (mg/l)
7
15.2 (±0.82)
9.6
6.3
4
1.3
0.20
0.18
Coagulation and flocculation process for the removal of pharmaceutical compounds depends mostly on the compounds propensity to be sorbet on the surface of ZnO nanoparticles. As a result, hydrophobic compounds with high octanol–water partition coefficient (log Kow) can potentially be removed by coagulation/flocculation (Lia et al., 2006; Matilainen et al., 2010; Verma et al., 2012). The high removal of Ibuprofen, Ephedrine and Propranolol by chemical ZnO coagulation, in the present investigation, is due to the octanol–water partition coefficient (log Kow) which is equal to 3.97, 1.65 and 3.48 of Ibuprofen, Ephedrine and Propranolol respectively at 20 °C.
The sorption of micro-pollutants including: pharmaceuticals, personal care products (PPCPs) and endocrine (EDCs) by solids, depends mainly on their physical/chemical properties, such as lipophilicity or acidity. Meanwhile, the sorption of these micro-pollutants depends also on their behavior during the physical/chemical treatment (such as flocculation and/or adsorption). There are two types of coefficients namely: (Ko: organic carbon partition coefficient) and (Kow: octanol–water partition coefficient). Usually, they are used to determine the sorption effectiveness as well as the affinity of a given compound or substance to effluent organic matter (EfOM). In this respect, the physical/chemical properties of the EDCs/PPCPs can be partitioned into three main groups namely: neutral (nonionic), lipophilic (with high Kow values) and acidic (hydrophilic and ionic) compounds (carballa et al., 2005).
By adding the optimum dose of ZnO remarkable removal of the pollution parameters was observed (Table 2). The concentration of CODT, CODD and BOD decreased from 19,820 to 500 mg/l, 11,892 to 310 mg/l and from 2552 to 100.8 mg/l respectively (Table 2). Meanwhile, T.P., NO3, NO2, NH3, K, Na, Ca, and Mg decreased from 200, 10, 44.7, 491.2, 866, 556, 1344 and 53.5 mg/l to 91.6, 4.2, 19.0, 203.2, 206, 25, 220 and 6.2 mg/l successively. Turbidity also decreased from 201 NTU and 4.1 NTU.
3.5 Semi-pilot plant continuous system
In the continuous semi-pilot plant (Fig. 2) the predetermined optimum dose of ZnO nanoparticles namely 1.5 g/l, was added to the coagulation tank. The obtained results Table 3 indicated that the concentration of Ibuprofen, Ephedrine and Propranolol decreased from 5.0, 10.15 and 15.2 mg/l to 0.2, 1.1 and 0.4 mg/l respectively. The concentration of COD and BOD decreased from 19,820 to 500 mg/l and from 2552 to 110 successively. In addition, T.P., NO3, NO2, NH3, K, Na, Ca and Mg decreased from 200, 10, 44.7, 491.2, 866, 556, 1344 and 53.5 mg/l to 92.8, 4.9, 20.8, 144.1, 215, 28, 230 and 7 mg/l respectively (Table 3). Meanwhile, the turbidity decreased from 201 to 37 NTU. It is worth to notice that the ZnO nanoparticles were able to remove more than 95% of the Ibuprofen, Propranolol, CODT, CODD, BOD and Na. However, 89% removal of the Ephedrine was achieved. On the other hand, the recorded removal rate of K, Ca and Mg was between 75% and 86% (Table 3). The removal of NH3 was higher than that of the other nitrogen compounds namely, NO3 and NO2. This is attributed to the conversion of NH3 by oxidation to NO2 and NO3.
The ZnO treated effluent was submitted directly to the microfiltration semi-pilot plant for further treatment. Results (Table 4) exhibit further decrease in the concentration of all the studied parameters. The final concentration of Ibuprofen, Ephedrine and Propranolol reached 0.01, 0.10 and 0.03 mg/l respectively. This decrease is corresponding to 99.8, 99.0 and 99.8% removal rate successively. The concentration of CODT, CODD and BOD decreased to 79.5, 68.0 and 19.8 mg/l respectively. The T.P., NO3, NO2, NH3, K, Na, Ca and Mg also decreased to 9.0, 0.6, 1.06, 2.8, 26, 3.6, 8.0 and 0.7 mg/l successively (Table 3). In addition, turbidity decreased down to 0.6 NTU. N∗ = Number of samples, CODT = Total Chemical Oxygen Demand, CODD = Dissolved Chemical Oxygen Demand, BOD5 = Biological Oxygen Demands, T.P. = Total Phosphates, NO3 = Nitrates, NO2 = Nitrites, NH3 = ammonia, K = Potassium, Na = Sodium, Ca = calcium, Mg = Magnesium.
Parameter
N
Raw contaminated human urine
Effluent of ZnO treatment
Effluent of microfiltration
Total % Removal
Conc.
% Removal
Conc.
% Removal
pH
9
5.1(±0.22)
8.4
–
8.7
–
–
Turbidity (NTU)
9
201(±0.15)
37
81.6
0.6
98.4
99.7
CODT (mg/l)
9
19,820(±86)
500
97.4
79.5
85
99.5
CODD (mg/l)
9
11,892(±73)
340
97.1
68.0
80
99.3
BOD5 (mg/l)
9
2552(±66)
110
95
19.8
82
99.2
BOD5/COD
9
0.13
0.61
0.25
–
T.P (mg/l)
9
200(±45)
92.8
53.6
80.2
13.6
59.9
NO3 (mg/l)
9
10(±0.26)
4.9
51.0
0.6
87.7
94
NO2 (mg/l)
9
44.7(±0.52)
20.8
53.5
1.06
94.9
97.6
NH3 (mg/l)
9
491.2(±21)
144.1
70.7
2.8
98.1
99.4
K (mg/l)
9
866(±30)
215
75
26
87.9
91.3
Na (mg/l)
9
556(±48)
28
94.9
3.6
87.1
99.3
Ca (mg/l)
9
1344(±39)
230
82.8
8.0
96.5
99.4
Mg (mg/l)
9
53.5(±11)
7
86.9
0.7
90
98.7
SAR
4.1
0.6
0.3
–
Ibuprofen (mg/l)
9
5.0 (±0.88)
0.20
96
0.01
95
99.8
Ephedrine (mg/l)
9
10.15 (±0.95)
1.10
89.2
0.10
90.9
99
Propranolol (mg/l)
9
15.2 (±0.82)
0.40
97.4
0.03
92.5
99.8
The overall removal of Ibuprofen, Ephedrine and Propranolol via this continuous treatment system reached 99.8, 99.0 and 99.8 respectively. The corresponding overall removal rates of COD, BOD, T.P., NO3, NO2, NH3, K, Na, Ca, Mg and turbidity were 99.5, 99.2, 95.5, 94, 97.6, 99.4, 91.3, 99.3, 99.4, 98.7 and 99.7% successively.
3.6 Conclusions
-
ZnO nanoparticles could be green synthesized by using Zn acetate dihydrate and the extract of black tea solid waste. The average particle size was 19.5 nm as defined by HR-TEM. XRD, EDAX, SEM, and DLS. Zeta potential was used for the characterization of green synthesized ZnO nanoparticles.
-
Employing such ZnO nanoparticles at the optimum dose in a semi-pilot plant was able to remove the studied pharmaceutical contaminants from urine at a rate ranged from 89% to 97%. The studied pharmaceutical contaminants are Ibuprofen, Ephedrine and Propranolol.
-
By using ZnO nanoparticles, the pollution parameters namely CODT, CODD and BOD were removed at a rate ranged from 95% to 97%. On the other hand, the removal rate of T.P., NO3, NO2, NH3, K, Na, Ca, Mg and turbidity ranged between 51% and 94%.
-
By submitting the ZnO treated urine to the membrane micro-filtration (MF) in the semi-pilot plant study, the selected PACs were successfully removed from the contaminated urine at the range from 99.0% to 99.8%.
-
By employing the designed semi-pilot plant, the overall removal rate of the pharmaceutical compounds exceeded 99%. Meanwhile, such treatment system was successful in improving the physical and chemical characteristics of the contaminated urine. The overall removal of COD, BOD, NO3, NH3, K, Na, Ca and Mg and turbidity ranged from 91% to 99.7%. It is worth mentioning that the removal of TP was the lowest namely 59.9% which is an advantage of using the treated urine as a source of nutrient elements.
-
Finally, the treated urine could then safely be used for agriculture purposes without any environmental threat.
Acknowledgment
The authors wish to express their deep appreciation and gratitude to the facilities provided by the project titled “Sustainable Development for Wastewater Treatment and Reuse via Constructed Wetlands in Sinai (SWWTR)” that is funded by STDF of Egypt.
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