Dynamics of adsorption of Ni(II), Co(II) and Cu(II) from aqueous solution onto newly synthesized poly[N-(4-[4-(aminophenyl)methylphenylmethacrylamide])]

Atul Kumar Kushwaha; Neha Gupta; M.C. Chattopadhyaya

doi:10.1016/j.arabjc.2013.06.007

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Original article

10 (

2_suppl

); S1645-S1653

doi:

10.1016/j.arabjc.2013.06.007

Dynamics of adsorption of Ni(II), Co(II) and Cu(II) from aqueous solution onto newly synthesized poly[N-(4-[4-(aminophenyl)methylphenylmethacrylamide])]

Atul Kumar Kushwaha^{^a,^b,⁎}, Neha Gupta^{^b}, M.C. Chattopadhyaya^{^b}

a Department of Chemistry, Lovely Professional University, Phagwara, Punjab, India

b Department of Chemistry, University of Allahabad, Allahabad, UP 211002, India

⁎Corresponding author at: Department of Chemistry, Lovely Professional University, Phagwara, Punjab, India. Tel.: +91 532 2462393. atulkk2008@gmail.com (Atul Kumar Kushwaha),

Received: 2012-7-27, Accepted: 2013-6-9, Published: 2013-05-01

Disclaimer:
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 work poly[N-(4-[4-(aminophenyl)methylphenylmethacrylamide])] (PAMMAm) was synthesized and characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), elemental analysis and proton nuclear magnetic resonance (¹H NMR). The synthesized material was tested for the removal of nickel, cobalt and copper from aqueous solution by adsorption. Effect of various parameters such as pH, adsorbent dose, initial metal ion concentration, contact time and temperature on adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm was investigated. The equilibrium data were analysed using Langmuir and Freundlich isotherm models. The adsorption kinetics was evaluated by the pseudo-first order, pseudo-second order and intraparticle diffusion models. Kinetic studies showed that the adsorption followed pseudo-second order kinetics and intraparticle diffusion model. Negative values of Gibb’s free energy change (ΔG°) showed that the adsorption was feasible and spontaneous and negative values of enthalpy change (ΔH°) confirmed exothermic adsorption.

Keywords

Adsorption

Equilibrium

Copper

Cobalt

Nickel

Poly-methyl methacrylamide

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1 Introduction

The discharge of toxic heavy metal ions from many industrial processes leads to an increase in the heavy metal concentration in aquatic system, creating a major global concern because of their high toxicity. In fact, the presence of heavy metals in water supplies may cause serious environmental problems. Among the different heavy metals, Ni(II), Co(II) and Cu(II) are commonly used and released into the natural waters from various industrial activities such as mining, metal plating, battery manufacturing, welding and alloy manufacturing. Heavy metals are non-biodegradable and they can be accumulated in living tissues, causing various diseases and disorders. Nickel can cause acute adverse effects on the lungs, kidney and reproductive system, mucous membranes and nervous system (Argun, 2008). However, higher concentration of cobalt may cause paralysis, diarrhoea, lung irritation, dermatitis, hair loss, respiratory hypersensitivity and even death (Egila et al., 2010) and higher concentration of copper leads to severe mucosal irritation and corrosion, widespread capillary damage, hepatic and renal damage and central nervous system irritation followed by depression (Ajmal et al., 1998). Therefore, these metals must be removed from wastewaters before discharge.

Several physico-chemical treatments are employed for the removal of heavy metals from aqueous solution such as coagulation (Samrani et al., 2008), ion exchange (Browski et al., 2004), electroflocculation (Bratskaya et al., 2009), ultrafiltration (Barakat and Schmidt, 2010), electro-chemical precipitation (Kongsricharoern and Polprasert, 1996), and reverse osmosis (Mohsen-Nia et al., 2007). A comparative account of all these processes was studied and reported by (Barakat (2011). All these procedures have significant disadvantages, which are for instance incomplete removal, high-energy requirements, and production of toxic sludge or waste products that also require disposal (Gad and El-Sayed, 2009). However, adsorption is one of the treatment processes found to be quite suitable, cheap and effective for the removal of heavy metals from aqueous solution.

Synthetic polymer is a choice of great interest due to its mechanical strength, high selectively, stability and sensitivity to the high concentration of ions which makes it a promising adsorbent for metal removal from aqueous solutions (Ahamed et al., 2008). Poly-methyl methacrylate (PMMA) is a transparent thermoplastic and synthetic polymer of methyl methacrylate. It is a low cost material used for several purposes such as in medical, optics, semiconductor, and paints. Most adsorbents developed nowadays for the removal of heavy metal ions rely on their interactions with the functional groups on the surfaces of the adsorbents, and hence, the functional groups have important effects on the effectiveness, capacity and reusability of the adsorbents. In the present work, the surface of PMMA was functionalized with amino groups in order to get active adsorption sites on its surface. The resulting material, poly[N-(4-[4-(aminophenyl)methylphenylmethacrylamide])] (PAMMAm) was tested for the removal of Ni(II), Co(II) and Cu(II) from aqueous solutions by the batch adsorption method.

2 Materials and methods

2.1

2.1 Synthesis of adsorbent (PAMMAm)

Poly-methyl methacrylate (PMMA) (average Mol.wt. 15,000, powder) and 4,4′-diaminodiphenylmethane were obtained from Sigma Aldrich, India. 5 g PMMA was dissolved in 50 mL of toluene followed by the addition of 50 mmol of 4,4′-diaminodiphenylmethane. Resulting mixture was stirred for 8 h at 90 °C. After that the reaction mixture was allowed to cool. By cooling the reaction mixture, microsolids of poly[N-(4-[4-(aminophenyl)methylphenylmethacrylamide])] (Fig. 1) come out of the solution leaving the solvent behind. Microsolids of material (PAMMAm) were filtered, dried and kept in dessicator for its use as an adsorbent.

Poly[N-(4-[4-(aminophenyl)methylphenylmethacrylamide])] (PAMMAm).

2.2

2.2 Adsorption experiments

Stock solution (1000 mg/L) of each metal ion was prepared by dissolving required amount of nitrate salt of metal (Ni(NO₃)₂·6H₂O, Co(NO₃)₂·6H₂O and Cu(NO₃)₂·5H₂O obtained from Merck) into double distilled water. The experimental solution of desired concentration was prepared by successive dilution of stock solution. The initial pH of each metal ion solution was maintained by adding 0.1 M HNO₃ or 0.1 M NaOH. The batch experiments were performed in a 150 mL conical flask by adding pre-weighed amount of adsorbent in 50 mL of metal ion solution. The mixture was stirred on magnetic stirrer (Remi) at the speed of 200 rpm. The adsorption was monitored by determining the concentration of metal ion in solution by atomic absorption spectrophotometer (ECIL-4141).

Percentage removal of metal ion and quantity of metal ion adsorbed on adsorbent at the equilibrium time (q_e) were calculated using Eqs. (1) and (2), respectively.

(1)

% adsorption = (C_{0} - C_{e}) / C_{0} \times 100

(2)

q_{e} = (C_{0} - C_{e}) V / W

where C₀ and C_e are the initial and the equilibrium concentrations (mg/L) of metal ion in solution, respectively. q_e is the quantity of metal ion adsorbed on the adsorbent at the time of equilibrium (mg/g), V is the volume (L) of solution and W is the mass of adsorbent (g) taken for experiment.Batch experiments were carried out to determine the effects of pH, adsorbent dose, initial metal ion concentration, contact time and temperature on adsorption by varying the parameter under study and keeping other parameters constant. All adsorption experiments were performed in triplicate and the mean values were used in data analysis.

3 Results and discussion

3.1

3.1 Characterization of PAMMAm

The FT-IR spectrum of PMMA and PAMMAm was recorded on a FTLA2000 spectrophotometer using the KBr disc method in the range of 4000–500 cm⁻¹ (Fig. 2). Spectrum of PMMA shows a band at 1739 cm⁻¹ is due to C⚌O stretching of the ester group. Appearance of band at 3440 cm⁻¹ appears to be an overtone band having frequency twice that of C⚌O stretching frequency. A band at 1242 cm⁻¹ is due to C–O–C stretching. Bands at 2951 and 2994 cm⁻¹ are due to C–H stretching. The corresponding bending peak occurs at 1449 cm⁻¹. Spectrum of PAMMAm shows a band around 3500 cm⁻¹ is due to stretching of the N–H group. The bands at 2996 and 2951 cm⁻¹ are due to C–H stretching and the corresponding bending peak occurred at 1435 cm⁻¹. The band at 1730 cm⁻¹ is due to C⚌O stretching in PAMMAm. ¹H NMR (300 MHz, CDCl₃) is used to ascertain the molecular structure of PAMMAm. ¹H NMR of PMMA presents peak at 3.59 ppm which represents three protons of OCH₃, at 1.8 ppm represents two protons of CH₂ and at 1.2 ppm represents three protons of CH₃. ¹H NMR spectrum of PAMMAm (Fig. 3) was obtained as expected. Peak at 3.8 ppm represents 2 protons of NH₂, peak at 3.59 ppm corresponds to two protons of CH₂ and peak at 1.2 ppm corresponds to three protons of CH₃. Spectrum shows two doublet peaks at 6.65 and 6.93 ppm, each of this corresponds to four protons of benzene rings’ confirmed formation of PAMMAm. SEM micrograph (Fig. 4) revealed the surface morphology of the PAMMAm which was investigated by SUPRA 40VP scanning electron microscope operated at 10 kV accelerating voltage. The particles of polymer are round in shape and 10–50 μm in size. The surface of polymer is homogenous, porous and rough in nature. EDX analysis shows the presence of three elements C, N and O and their elemental ratio which is further confirmed by elemental analysis. Elemental analysis of PAMMAm was done by Elementar Vario EL III and wt% of C, H, N and O in PAMMAm was found to be 76.51%, 7.62%, 9.95% and 5.92%, respectively.

SEM micrograph and EDX spectrum of PAMMAm.

3.2

3.2 Influence of pH

The pH is one of the most important factors controlling the adsorption of metal ion onto PAMMAm. The influence of pH on adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm was studied over the pH range of 2–6. Fig. 5 shows that the adsorption of Cu(II) was increased from 21% to 82% with increasing pH from 2 to 5.5 and the adsorption of Ni(II) and Co(II) was increased from 5% to 45% and 6% to 51%, respectively, with increasing pH from 2 to 6. At lower pH values, hydrogen ion competes with metal ions which reduce the adsorption of metal ion. At higher pH values there is a reduced competition between hydrogen ion and metal ion, enhances the adsorption capacity of adsorbent for metal ion. Further increase in pH may cause precipitation of metal ions due to formation of hydroxide (Bhattacharyya and Gupta, 2006) therefore, the pH higher than 5.5 for Cu(II) and 6 for Ni(II) and Co(II) was avoided.

Effect of pH on adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm.

3.3

3.3 Effect of adsorbent dose

The effect of adsorbent dose on adsorption of Ni(II), Co(II) and Cu(II) was studied using different PAMMAm dosages in the range of 0.5–3 g/L for 10 mg/L of initial metal ion concentration. Fig. 6 shows that on increasing adsorbent dose from 0.5 to 2 g/L the adsorption of Ni(II), Co(II) and Cu(II) on PAMMAm increased from 10% to 45%, 12% to 51% and 22% to 82%, respectively. Such a trend is mainly attributed to an increase in the adsorptive surface area and the availability of more adsorption sites (El-Sayed, 2011). There was no significant change observed as the adsorbent dose was further increased. This was due to the concentration of metal ions that reached at equilibrium status between solid and solution phase.

Effect of adsorbent dose on adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm.

3.4

3.4 Effect of initial metal ion concentration

To observe the effect of initial metal ion concentration on adsorption, the experiments were conducted over the range of 5–25 mg/L for each metal ion (Fig.7). The amount of Ni(II), Co(II) and Cu(II) adsorbed at equilibrium (q_e) increased from 1.3 to 4 mg/g, 1.45 to 4.65 mg/g and 2.15 to 8.7 mg/g, respectively, as the concentration was increased from 5 to 25 mg/L. The initial concentration provides an important driving force to overcome all mass transfer resistances of the metal ion between the aqueous and solid phases (Ahmad et al., 2009). Hence a higher initial concentration of metal ion will enhance the adsorption amount of metal ions. However, the % removal of Ni(II), Co(II) and Cu(II) decreased from 52% to 32%, 58% to 37% and 86% to 69.6%, respectively, as initial metal ion concentration increased from 5 to 25 mg/L.

Effect of initial metal ion concentration on adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm.

3.5

3.5 Adsorption isotherm

The analysis of the adsorption process requires the relevant adsorption equilibrium for better understanding the adsorption process. Adsorption equilibrium describes the nature of adsorbate–adsorbent interaction. In the present study the equilibrium data were analysed using the Langmuir and Freundlich isotherms.

3.5.1

3.5.1 Langmuir isotherm model

The Langmuir model is valid for monolayer adsorption onto a surface with a finite number of identical sites which are homogeneously distributed over the adsorbent surface. The well known expression of the Langmuir model (Hui et al., 2005) is given as:

(3)

q_{e} = Q_{m} {bC}_{e} / (1 + {bC}_{e})

The linearized forms of Eq. (3) can be written as follows:

(4)

C_{e} / q_{e} = 1 / {bQ}_{m} + C_{e} / Q_{m}

where q_e is the adsorption density (mg/g) at equilibrium of metal ion, C_e is the equilibrium concentration (mg/L) of the metal ion in solution, Q_m is the monolayer adsorption capacity (mg/g) and b is the Langmuir constant (L/mg) related to the free energy of adsorption. The values of Q_m and b were calculated from the slopes (1/Q_m) and intercepts (1/bQ_m) of the plots of C_e/q_e vs. C_e (Fig. 8) and are presented in Table 1. Linear plots of C_e/q_e vs. C_e showed that the adsorption of all the three metal ions onto PAMMAm followed the Langmuir isotherm model. Experimental results showed that monolayer adsorption capacity of PAMMAm for metal ions increased in the order Ni(II) < Co(II) < Cu(II).

The Langmuir plots for the adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm.

Table 1 Isotherm parameters adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm.

Metal ion	Langmuir isotherm parameters			Freundlich isotherm parameters
Metal ion	Q_max	b	R²	K_f	n	R²
Ni(II)	6.13	0.107	0.996	0.80	1.76	0.994
Co(II)	7.19	0.117	0.998	0.97	1.70	0.990
Cu(II)	12.8	0.269	0.994	2.76	1.70	0.993

3.5.2

3.5.2 Freundlich isotherm model

The Freundlich model (Uddin et al., 2009) is an empirical equation based on adsorption onto a heterogeneous surface given below by Eq. (5)

(5)

q_{e} = K_{f} C_{e}^{1 / n}

The logarithmic forms of Eq. (5) can be written as follows:

(6)

ln q_{e} = ln K_{f} + (1 / n) ln C_{e}

where K_f and n are Freundlich constants related to adsorption capacity [mg g⁻¹ (mg L⁻¹)^−1/ⁿ] and adsorption intensity of adsorbents. The values of the K_f and n were calculated from the intercepts (lnK_f) and slopes (1/n) of the plots ln q_e vs. ln C_e (Fig. 9) and are presented in Table 1. Linear plots of ln q_e vs. ln C_e showed that the adsorption isotherm of Ni(II), Co(II) and Cu(II) on PAMMAm also fitted well in the Freundlich isotherm model and the K_f values showed that the adsorption capacity increased in the order Ni(II) < Co(II) < Cu(II). The values of n > 1 indicate favourable adsorption conditions (Hameed et al., 2008; Hameed, 2009).

The Freundlich plots for the adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm.

3.6

3.6 Adsorption kinetics

Fig. 10 shows the adsorption kinetics of Ni(II), Co(II) and Cu(II) onto PAMMAm. It can be seen that the adsorption rate of metal ions was rapid in the initial stages and gradually decreased with the progress of adsorption until the equilibrium was reached. The equilibrium point was reached within 30 min of contact time for all the three metal ions. As the contact time increased after 30 min, no change was observed in adsorption.

Adsorption kinetics of the adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm.

To investigate the adsorption kinetics of heavy metals onto the PAMMAm, two kinetic models (i) A pseudo-first order kinetic model of Lagergren (ii) a pseudo-second order kinetic model of Ho, were employed to simulate the experimental data. The best-fit model was selected based on both linear regression correlation coefficient (R²) and the calculated q_e values.

The rate constant of adsorption was determined from the pseudo-first order rate expression (Lagergren, 1898) Eq. (7):

(7)

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

where q_e and q_t are the amount of metal ion adsorbed at equilibrium and at time t (mg/g), respectively and k₁ (min⁻¹) is the rate constant of adsorption. The values of k₁ and q_e^cal were calculated from the slopes (−k₁) and intercepts (lnq_e) of the plots of ln (q_e−q_t) vs. t (Fig. 11), respectively and are presented in Table 2. Table 2 shows a good agreement between experimental and calculated q_e values for Ni(II) and Co(II). The correlation coefficients for the pseudo-first order kinetic model were 0.962 and 0.981 for Ni(II) and Co(II), respectively, indicated the applicability of the pseudo-first order equation for the adsorption of Ni(II) and Co(II) on PAMMAm. Although the correlation coefficient value for Cu(II) was 0.935, the experimental q_e values did not agree with the calculated ones, obtained from the linear plots. This showed that the adsorption of Cu(II) onto PAMMAm was not of pseudo-first order.

Pseudo-first order kinetics plots for the adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm.

Table 2 Kinetic parameters adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm.

Metal ions	q_e^exp	Pseudo-first order			Pseudo-second order			Intraparticle diffusion
Metal ions	q_e^exp	q_e^exp	K₁	R²	q_e^exp	k₂	R²	k_i	C	R²
Ni(II)	2.25	2.23	0.112	0.962	2.39	0.116	0.961	0.332	0.458	0.997
Co(II)	2.55	2.51	0.124	0.981	2.71	0.116	0.972	0.360	0.646	0.986
Cu(II)	4.1	2.98	0.127	0.935	4.18	0.164	0.992	0.315	2.387	0.992

The pseudo second order sorption kinetics (Ho and McKay, 1999) may be written as follows:

(8)

t / q_{t} = 1 / k_{2} q_{e}^{2} + t / q_{e}

where k₂ is the rate constant of adsorption (g/mg min), q_e and q_t are the amount of metal ion adsorbed at equilibrium and at time t (mg/g) respectively. The values of k₂ and q_e^cal were calculated from the intercepts (1/k₂ q_e²) and slopes (1/q_e) of the plots of t/q_t vs. t. (Fig. 12), respectively and are presented in Table 2. Table 2 shows that the correlation coefficient of adsorption of Cu(II) for the pseudo-second order kinetic model was 0.992 and a good agreement between experimental and calculated q_e values, indicated the applicability of pseudo-second order kinetic model for the adsorption of Cu(II) onto PAMMAm.

Pseudo-second order kinetics plots for the adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm.

The mechanism of adsorption can be explained by the intraparticle diffusion model (Weber and Morris, 1963) which can be expressed as follows:

(9)

Q_{t} = k_{i} t^{0.5} + C

where k_i is the intraparticle diffusion constant (mg/g min^0.5) and the intercept (C) reflects the boundary layer effect. The values of k_i were calculated from slopes (k_i) of the plots of q_t vs. t^0.5 (Fig. 13) and are presented in Table 2. Results showed that the rate constant for intraparticle diffusion (k_i) decreased in the order Co(II) > Ni(II) > Cu(II), indicated higher diffusion rate of Co(II) in aqueous solution. This can be explained on the basis of its better mobility due to smaller radius of its hydrated ion as compared to Ni(II) and Cu(II). Fig. 13 shows that the lines of plots are not passing through the origin. Adsorption of Cu(II) showed higher value of C than the Co(II) and Ni(II). The larger the value of C, the greater is the contribution of the surface sorption in the rate-limiting step. Results confirmed the presence of both surface adsorption and intraparticle diffusion (Kumar and Porkodi, 2007).

Intraparticle diffusion plots for the adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm.

3.7

3.7 Thermodynamic study

To observe the effect of temperature on the adsorption of metal ions on PAMMAm, experiments were conducted at three different temperatures 303, 313 and 323 K. It was observed that the adsorption decreased with increasing temperature, which indicated a low temperature favours metal ion removal by adsorption onto the PAMMAm. This may be due to a tendency of metal ions to escape from the solid phase to the bulk phase with an increase in temperature of the solution. A similar observation was also reported in the study on the sorption of Pb onto modified and unmodified kaolinite clay (Jiang et al., 2009)

Thermodynamic parameters such as enthalpy (ΔH°), entropy (ΔS°) and Gibb’s free energy (ΔG°) were determined by Eq. (10) (Nandi et al., 2009) and Eq. (11).

(10)

ln (q_{e} m / C_{e}) = Δ S^{°} / R - Δ H ° / RT

(11)

Δ G^{°} = Δ H ° - TS °

where m is the adsorbent dose (mg/L), C_e is the equilibrium concentration (mg/L) of the metal ion in solution and q_em is the solid-phase concentration (mg/L) at equilibrium. R is the gas constant (8.314 J/mol/K) and T is the temperature (K). ΔH°, ΔS° and ΔG° are changes in enthalpy (J/mol), entropy (J/mol/K) and Gibb’s free energy (J/mol), respectively.

The values of ΔH° and ΔS° were determined from the slope (−ΔH°/R) and the intercept (ΔS°/R) of the plots of ln (q_em/C_e) vs. 1/T (Fig. 14). The ΔG° values were calculated using Eq. (11). The values of thermodynamic parameters are presented in Table 3. Negative values of ΔH° suggested the adsorption process was exothermic in nature. The values of ΔH° were in the range of −9.4 to −18.4, revealed that the adsorption process was physical in nature (Ahmad and Kumar, 2010). Negative values of ΔG° for the adsorption of Cu at all three temperatures indicated that the adsorption process was feasible and spontaneous in nature. The ΔG° value was negative for the adsorption of Co(II) at 303 K and as the temperature was further increased it became slightly positive, showed that at higher temperature desorption was more dominant than adsorption. The ΔG° value was slightly positive for the adsorption of Ni(II) showing lower affinity of PAMMAm for Ni(II). Negative value of ΔS° described the decrease in randomness at the adsorbent-solution interface during the adsorption. The value of ΔS° for Cu(II) was the smallest, indicated that Cu(II) ion would be more stable on the adsorption site.

The plots of ln (qem/Ce) vs. 1/T for the adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm.

Table 3 Thermodynamic parameters adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm.

Metal ions	ΔH° (kJ/mol)	ΔS° (J/mol/K)	ΔG° (kJ/mol)
Metal ions	ΔH° (kJ/mol)	ΔS° (J/mol/K)	303 K	313 K	323 K
Cu(II)	−18.415	−48.08	−3.847	−3.366	−2.886
Co(II)	−9.403	−30.58	−0.136	0.168	0.474
Ni(II)	−11.481	−39.47	0.479	0.873	1.267

3.8

3.8 Regeneration of the PAMMAm

The adsorbent regeneration is necessary to make the adsorption process economical. Each metal ion-loaded PAMMAm was stirred with 0.1 M HNO₃ solution at room temperature to desorb the metal ion. The adsorption–desorption cycle was repeated three times by using the same adsorbent. After three cycles the adsorption capacity of PAMMAm for Ni, Co and Cu, decreased from 45% to 42%, 51% to 48.5% and 82% to 79.7%, respectively. Very small change was observed in adsorption capacity of PAMMAm after three cycles confirmed the reusability of PAMMAm as an adsorbent.

4 Conclusion

The results of the study clearly demonstrated that PAMMAm can be used as an adsorbent for the removal of Ni(II), Co(II) and Cu(II) ions from aqueous medium. The adsorption was found to be drastically dependent on pH, adsorbent dosage, and contact time. The optimum pH for the adsorption was found to be 6 for Ni(II) and Co(II) ions and 5.5 for Cu(II) ion. Monolayer adsorption capacity of PAMMAm for metal ions was found in the order Ni(II) < Co(II) < Cu(II). Adsorption processes followed pseudo-second order kinetics, surface adsorption and intraparticle diffusion mechanism. Thermodynamic study revealed that the adsorption was favoured at lower temperature. Thermodynamic parameters suggested that the adsorption of Ni(II), Co(II) and Cu(II) onto PAMMAm was a thermodynamically feasible, spontaneous and exothermic process. Regeneration experiments showed that the PAMMAm can be reused.

Acknowledgement

The authors thank the SAIF-CDRI Lucknow for recording ¹H NMR and elemental analysis; Dr. Dinesh Deva of Nanoscience, IIT Kanpur for recording SEM–EDX; and Council of Scientific and Industrial Research (CSIR), New Delhi, India, for the financial support.

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Introduction

Materials and methods

Synthesis of adsorbent (PAMMAm)
Adsorption experiments

Results and discussion

Characterization of PAMMAm
Influence of pH
Effect of adsorbent dose
Effect of initial metal ion concentration
Adsorption isotherm
Adsorption kinetics
Thermodynamic study
Regeneration of the PAMMAm

Conclusion

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[Google Scholar]

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[Google Scholar]

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[Google Scholar]

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[Google Scholar]

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[Google Scholar]

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Dynamics of adsorption of Ni(II), Co(II) and Cu(II) from aqueous solution onto newly synthesized poly[N-(4-[4-(aminophenyl)methylphenylmethacrylamide])]

Abstract

Keywords

Adsorption

Equilibrium

Copper

Cobalt

Nickel

Poly-methyl methacrylamide

1 Introduction

2 Materials and methods

2.1 Synthesis of adsorbent (PAMMAm)

2.2 Adsorption experiments

3 Results and discussion

3.1 Characterization of PAMMAm

3.2 Influence of pH

3.3 Effect of adsorbent dose

3.4 Effect of initial metal ion concentration

3.5 Adsorption isotherm

3.5.1 Langmuir isotherm model

3.5.2 Freundlich isotherm model

3.6 Adsorption kinetics

3.7 Thermodynamic study

3.8 Regeneration of the PAMMAm

4 Conclusion

Acknowledgement

References

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