Metal‐chelating properties of poly(2‐hydroxyethyl methacrylate–methacryloylamidohistidine) membranes

Metal‐chelating membranes have advantages as adsorbents in comparison with conventional beads because they are not compressible and they eliminate internal diffusion limitations. The aim of this study was to explore in detail the performance of poly(2‐hydroxyethyl methacrylate–methacryloylamidohistidine) [poly(HEMA–MAH)] membranes for the removal of three toxic heavy‐metal ions—Cd(II), Pb(II), and Hg(II)—from aquatic systems. The poly(HEMA–MAH) membranes were characterized with scanning electron microscopy and ¹H‐NMR spectroscopy. The adsorption capacity of the poly(HEMA–MAH) membranes for the selected heavy‐metal ions from aqueous media containing different amounts of these ions (30–500 mg/L) and at different pH values (3.0–7.0) was investigated. The adsorption capacity of the membranes increased with time during the first 60 min and then leveled off toward the equilibrium adsorption. The maximum amounts of the heavy‐metal ions adsorbed were 8.2, 31.5, and 23.2 mg/g for Cd(II), Pb(II), and Hg(II), respectively. The competitive adsorption of the metal ions was also studied. When the metal ions competed, the adsorbed amounts were 2.9 mg of Cd(II)/g, 14.8 mg of Pb(II)/g, and 9.4 mg of Hg(II)/g. The poly(HEMA–MAH) membranes could be regenerated via washing with a solution of nitric acid (0.01M). The desorption ratio was as high as 97%. These membranes were suitable for repeated use for more than three adsorption/desorption cycles with negligible loss in the adsorption capacity. The stability constants for the metal‐ion/2‐methacryloylamidohistidine complexes were calculated to be 3.47 × 10⁶, 7.75 × 10⁷, and 2.01 × 10⁷ L/mol for Cd(II), Pb(II), and Hg(II) ions, respectively, with the Ruzic method. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1213–1219, 2005     

Sorption properties of poly(styrene‐co‐divinylbenzene) amine functionalized weak resin

The poly(styrene‐co‐divinylbenzene) amine functionalized weak resin was studied as adsorbent of heavy metal ions from an aqueous solution by using the Batch equilibrium procedure. The resin adsorbed Hg(II) 56% (0.56 mEq/g) at pH 2, and 45% (1.13 mEq/g) of U(VI), 38% (0.36 mEq/g) of Pb(II) at pH 5 from an aqueous solution containing 1 g/L of each metal ion. It did not adsorb Cd(II), Zn(II). The equilibrium time was achieved during the first hour. The maximum load capacity for Hg(II) was 0.8 mEq/g (75 mg)/g dry resin. It is possible to recover around 60% of the resin after the treatment with 1–4 M HClO₄ and HNO₃ of the loaded Hg(II) resin. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2123–2127, 2001     

Preparation and characterization of magnetic polymethylmethacrylate microbeads carrying ethylene diamine for removal of Cu(II), Cd(II), Pb(II), and Hg(II) from aqueous solutions

Magnetic polymethylmethacrylate (mPMMA) microbeads carrying ethylene diamine (EDA) were prepared for the removal of heavy metal ions (i.e., copper, lead, cadmium, and mercury) from aqueous solutions containing different amount of these ions (5–700 mg/L) and at different pH values (2.0–8.0). Adsorption of heavy metal ions on the unmodified mPMMA microbeads was very low (3.6 μmol/g for Cu(II), 4.2 μmol/g for Pb(II), 4.6 μmol/g for Cd(II), and 2.9 μmol/g for Hg(II)). EDA‐incorporation significantly increased the heavy metal adsorption (201 μmol/g for Cu(II), 186 μmol/g for Pb(II), 162 μmol/g for Cd(II), and 150 μmol/g for Hg(II)). Competitive adsorption capacities (in the case of adsorption from mixture) were determined to be 79.8 μmol/g for Cu(II), 58.7 μmol/g for Pb(II), 52.4 μmol/g for Cd(II), and 45.3 μmol/g for Hg(II). The observed affinity order in adsorption was found to be Cu(II) > Pb(II) > Cd(II) > Hg(II) for both under noncompetitive and competitive conditions. The adsorption of heavy metal ions increased with increasing pH and reached a plateau value at around pH 5.0. The optimal pH range for heavy‐metal removal was shown to be from 5.0 to 8.0. Desorption of heavy‐metal ions was achieved using 0.1 M HNO₃. The maximum elution value was as high as 98%. These microbeads are suitable for repeated use for more than five adsorption‐desorption cycles without considerable loss of adsorption capacity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 81–89, 2000     

Adsorption characterization of lead(II) and cadmium(II) on crosslinked carboxymethyl starch

The adsorption of Pb(II) and Cd(II) ions with crosslinked carboxymethyl starch (CCS) was investigated as function of the solution pH, contact time, initial metal‐ion concentration, and temperature. Isotherm studies revealed that the adsorption of metal ions onto CCS better followed the Langmuir isotherm and the Dubinin–Radushkevich isotherm with adsorption maximum capacities of about 80.0 and 47.0 mg/g for Pb(II) and Cd(II) ions, respectively. The mean free energies of adsorption were found to be between 8 and 16 kJ/mol for Pb(II) and Cd(II) ions; this suggested that the adsorption of Pb(II) and Cd(II) ions onto CCS occurred with an ion‐exchange process. For two‐target heavy‐metal ion adsorption, a pseudo‐second‐order model and intraparticle diffusion seem significant in the rate‐controlling step, but the pseudo‐second‐order chemical reaction kinetics provide the best correlation for the experimental data. The enthalpy change for the process was found to be exothermic, and the ΔS^θ values were calculated to be negative for the adsorption of Pb(II) and Cd(II) ions onto CCS. Negative free enthalpy change values indicated that the adsorption process was feasible. The studies of the kinetics, isotherm, and thermodynamics indicated that the adsorption of CCS was more effective for Pb(II) ions than for Cd(II) ions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Batch and fixed‐bed column adsorption of Cu(II), Pb(II) and Cd(II) from aqueous solution onto functionalised SBA‐15 mesoporous silica

Functionalised SBA‐15 mesoporous silica with polyamidoamine groups (PAMAM‐SBA‐15) was successfully prepared with the structure characterised by X‐ray diffraction, nitrogen adsorption–desorption, Fourier transform infrared spectra and thermogravimetric analysis. PAMAM‐SBA‐15 was applied as adsorbent for Cu(II), Pb(II) and Cd(II) ions removal from aqueous solution. The effects of the solution pH, adsorbent dosage and metal ion concentration were studied under the batch mode. The Langmuir model was fitted favourably to the experimental data. The maximum sorptive capacities were determined to be 1.74 mmol g^?1 for Cu(II), 1.16 mmol g^?1 for Pb(II) and 0.97 mmol g^?1 for Cd(II). The overall sorption process was fast and its kinetics was fitted well to a pseudo‐first‐order kinetic model. The mean free energy of sorption, calculated from the Dubinin–Radushkevich isotherm, indicated that the sorption of lead and copper, with E > 16 kJ mol^?1, followed the sorption mechanism by particle diffusion. The adsorbent could be regenerated three times without significant varying its sorption capacity. A series of column tests were performed to determine the breakthrough curves with varying bed heights and flow rates. The breakthrough data gave a good fit to the Thomas model. Maximum sorption capacity of 1.6, 1.3 and 1.0 mmol g^?1 were found for Cu(II), Pb(II) and Cd(II), respectively, at flow rate of 0.4 mL min^?1 and bed height of 8 cm, which corresponds to 83%, 75% and 73% of metallic ion removal, respectively, which very close to the value determined in the batch process. Bed depth service time model could describe the breakthrough data from the column experiments properly. © 2012 Canadian Society for Chemical Engineering     

The effect of gel composition on the uranyl ions adsorption capacity of poly(N‐vinyl 2‐pyrrolidone‐g‐citric acid) hydrogels prepared by gamma rays

Poly(N‐vinyl 2‐pyrrolidone‐g‐citric acid) (PVP‐g‐CA) hydrogels with varying compositions were prepared from ternary mixtures of N‐vinyl 2‐pyrrolidone–citric acid–water by using ⁶⁰Co γ‐rays. The effect of gel composition on the uranyl ions adsorption capacity of PVP‐g‐CA hydrogels was investigated. Uranyl adsorption capacity of these hydrogels were found to be in the range of 18–144 mg [UO]/g dry gel from the aqueous solution of uranyl nitrate and 22–156 mg [UO]/g dry gel from the aqueous solution of uranyl acetate, depending on the content of citric acid in the hydrogel, while poly(N‐vinyl 2‐pyrrolidone) hydrogel did not sorb any uranyl ion. The swelling of PVP‐g‐CA hydrogel containing 2.7 mol % CA was observed in water (1620%), in uranyl acetate solution (1450%) and in uranyl nitrate solution (1360%), as compared to 700% swelling of pure PVP hydrogels. The diffusion coefficients were varied from 12.57 up to 4.04 • 10⁻⁸ m² s⁻¹. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1037–1043, 2000     

Synthesis and characterization of poly(ethylene glycol dimethacrylate–1‐vinyl‐1,2,4‐triazole) copolymer beads for heavy‐metal removal

We prepared poly(ethylene glycol dimethacrylate–1‐vinyl‐1,2,4‐triazole) [poly(EGDMA–VTAZ)] beads (average diameter = 150–200 μm) by copolymerizing ethylene glycol dimethacrylate (EGDMA) with 1‐vinyl‐1,2,4‐triazole (VTAZ). The copolymer composition was characterized by elemental analysis and found to contain five EGDMA monomer units for each VTAZ monomer unit. The poly(EGDMA–VTAZ) beads had a specific surface area of 65.8 m²/g. Poly(EGDMA–VTAZ) beads were characterized by Fourier transform infrared spectroscopy, elemental analysis, surface area measurements, swelling studies, and scanning electron microscopy. Poly(EGDMA–VTAZ) beads with a swelling ratio of 84% were used for the heavy‐metal removal studies. The adsorption capacities of the beads for Cd(II), Hg(II), and Pb(II) were investigated in aqueous media containing different amounts of these ions (5–750 mg/L) and at different pH values (3.0–7.0). The maximum adsorption capacities of the poly(EGDMA–VTAZ) beads were 85.7 mg/g (0.76 mmol/g) for Cd(II), 134.9 mg/g (0.65 mmol/g) for Pb(II), and 186.5 mg/g (0.93 mmol/g) for Hg(II). The affinity order toward triazole groups on a molar basis was observed as follows: Hg(II) > Cd(II) > Pb(II). pH significantly affected the adsorption capacity of the VTAZ‐incorporated beads. The equilibrium data were well fitted to the Redlich–Peterson isotherm. Consideration of the kinetic data suggested that chemisorption processes could have been the rate‐limiting step in the adsorption process. Regeneration of the chelating‐beads was easily performed with 0.1M HNO₃. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4276–4283, 2006     

Polymer‐grafted banana (Musa paradisiaca) stalk as an adsorbent for the removal of lead(II) and cadmium(II) ions from aqueous solutions: kinetic and equilibrium studies

This study examined the effectiveness of a new adsorbent prepared from banana (Musa paradisiaca) stalk, one of the abundantly available lignocellulosic agrowastes, in removing Pb(II) and Cd(II) ions from aqueous solutions. The adsorbent (PGBS‐COOH) having a carboxylate functional group at its chain end was synthesized by graft copolymerization of acrylamide on to banana stalk, followed by functionalization. Batch adsorption experiments were carried out as a function of solution pH, ionic strength, contact time, metal concentration, adsorbent dose and temperature. A pH range of 5.5–8.0 was found to be effective for the maximum removal for both Pb(II) and Cd(II). Metal uptake was found to decrease with increase in ionic strength due to the expansion of the diffuse double layer and, more importantly, the formation of some chloro complexes (since NaCl was used in the adjustment of ionic strength), which do not appear to be adsorbed to the same extent as cations [M²⁺ and M(OH)⁺]. The kinetic studies showed that an equilibrium time of 3 h was needed for the adsorption of Pb(II) and Cd(II) on PGBS‐COOH and adsorption processes followed a pseudo‐second‐order equation. The Langmuir isotherm model fitted the experimental equilibrium data well. The maximum sorption capacity for Pb(II) and Cd(II) ions was 185.34 and 65.88 mg g^?1, respectively, at 30 °C. The thermodynamic parameters such as changes in free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were derived to predict the nature of adsorption. The isosteric heat of adsorption was found to be independent of surface coverage. Adsorption experiments were also conducted using a commercial cation exchanger, Ceralite IRC‐50, for comparison. Synthetic wastewater samples were treated with the adsorbent to demonstrate its efficiency in removing Pb(II) and Cd(II) ions from industrial wastewaters. Acid regeneration was tried for several cycles with a view to recovering the sorbed metal ions and also restoring the sorbent to its original state. Copyright © 2005 Society of Chemical Industry     

Facile preparation of a silica‐sphere–poly(catechol hexamethylenediamine) composite for the competitive removal of cadmium(II), lead(II), and copper(II) ions

A silica‐sphere–poly(catechol hexamethylenediamine) (PCHA–SiO₂) composite was prepared via the one‐step facile polymerization of catechol and hexamethylenediamine; this method uses a silica sphere as a hard template. The chemical structures and morphologies of this composite were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and transmission electron microscopy. The adsorption experiments indicated that the PCHA–SiO₂ composite served as a very attractive adsorbent for Pb(II)‐, Cu(II)‐, and Cd(II)‐ion removal at lower concentrations and had very good selective adsorption abilities for Pb(II) and Cu(II) ions in a solution contaminated with these three ions at higher concentrations. These interesting results may have been due to the reversible H⁺ adsorption–desorption properties of the characteristic phenol amine structure of the PCHA–SiO₂ composite. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45839.     

Adsorption of heavy‐metal ions on poly(ethylene imine)‐immobilized poly(methyl methacrylate) microspheres

Poly(methyl methacrylate) (PMMA) microspheres carrying poly(ethylene imine) (PEI) were prepared for the removal of heavy‐metal ions (copper, cadmium, and lead) from aqueous solutions with different amounts of these ions (50–600 mg/L) and different pH values (3.0–7.0). Ester groups in the PMMA structures were converted to imine groups in a reaction with PEI as a metal‐chelating ligand in the presence of NaH. The adsorption of heavy‐metal ions on the unmodified PMMA microspheres was very low [3.6 μmol/g for Cu(II), 4.6 μmol/g for Cd(II), and 4.2 μmol/g for Pb(II)]. PEI immobilization significantly increased the heavy‐metal adsorption [0.224 mmol/g for Cu(II), 0.276 mmol/g for Cd(II), and 0.126 mmol/g for Pb(II)]. The affinity order of adsorption (in moles) was Cd(II) > Cu(II) > Pb(II). The adsorption of heavy‐metal ions increased with increasing pH and reached a plateau value around pH 5.5. Their adsorption behavior was approximately described with the Langmuir equation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 197–205, 2001     

Removal of Cd(II), Hg(II), and Pb(II) ions from aqueous solution using p(HEMA/chitosan) membranes

An interpenetration network (IPN) was synthesized from 2‐hydroxyethyl methacrylate (HEMA) and chitosan, p(HEMA/chitosan) via UV‐initiated photo‐polymerization. The selectivity to different heavy metal ions viz Cd(II), Pb(II), and Hg(II) to the IPN membrane has been investigated from aqueous solution using bare pHEMA membrane as a control system. Removal efficiency of metal ions from aqueous solution using the IPN membranes increased with increasing chitosan content and initial metal ions concentrations, and the equilibrium time was reached within 60 min. Adsorption of all the tested heavy metal ions on the IPN membranes was found to be pH dependent and maximum adsorption was obtained at pH 5.0. The maximum adsorption capacities of the IPN membrane for Cd(II), Pb(II), and Hg(II) were 0.063, 0.179, and 0.197 mmol/g membrane, respectively. The adsorption of the Cd(II), Hg(II), and Pb(II) metal ions on the bare pHEMA membrane was not significant. When the heavy metal ions were in competition, the amounts of adsorbed metal ions were found to be 0.035 mmol/g for Cd(II), 0.074 mmol/g for Hg(II), and 0.153 mmol/g for Pb(II), the IPN membrane is significantly selective for Pb(II) ions. The stability constants of IPN membrane–metal ions complexes were calculated by the method of Ruzic. The results obtained from the kinetics and isotherm studies showed that the experimental data for the removal of heavy metal ions were well described with the second‐order kinetic equations and the Langmuir isotherm model. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and application of cotton‐based chelate fibers grafted with poly(1‐vinyl‐1,2,4‐triazole) side chains

Cotton‐based chelate fibers grafted with poly(1‐vinyl‐1,2,4‐triazole) (PVTAZ) side chains were synthesized facilely by ozone‐induced graft polymerization of 1‐vinyl‐1,2,4‐triazole (VTAZ) monomer onto cotton fibers. The synthesis conditions were optimized to improve the yield and mechanical strength of the products. The obtained cotton‐g‐PVTAZ fibers were characterized and evaluated for batch adsorption of heavy metal ions from aqueous solutions. The maximum adsorption capacity of Ag(I), Pb(II), and Cu(II) on the fibers at pH 6.8 was 522, 330, and 184 mg/g, respectively. At 30% graft yield, the Young's modulus of cotton fiber increased about 26.5%, and its adsorption capacities of Ag(I), Pb(II), and Cu(II) increased about 2.6, 1.9, and 1.4 times, respectively. After washed with 0.1 mol/L HNO₃ solutions, the adsorbed metal ions were eluted, and the regenerated cotton‐g‐PVTAZ fibers could be used repeatedly for water treatment. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41617.     

Preparation and Characterization of the Newly Synthesized Metal‐Complexing‐Ligand N‐Methacryloylhistidine Having PHEMA Beads for Heavy Metal Removal from Aqueous Solutions

The aim of this study was to investigate in detail the performance for removal of heavy metal ions of beads composed of poly(2‐hydroxyethyl methacrylate) (pHEMA) to which N‐methacryloylhistidine (MAH) was copolymerized. The metal‐complexing ligand MAH was synthesized by using methacryloyl chloride and histidine. Spherical beads with an average size of 150–200 μm were obtained by the radical suspension polymerization of MAH and HEMA conducted in an aqueous dispersion medium. Owing to the reasonably rough character of the bead surface, p(HEMA‐MAH) beads had a specific surface area of 17.6 m²/g. The synthesized MAH monomer was characterized by NMR; p(HEMA‐MAH) beads were characterized by swelling studies, FTIR and elemental analysis. The p(HEMA‐MAH) beads with a swelling ratio of 65%, and containing 1.6 mmol MAH/g, were used in the adsorption/desorption experiments. Adsorption capacity of the beads for the selected metal ions, i. e., Cu(II), Cd(II), Cr(III), Hg(II) and Pb(II), were investigated in aqueous media containing different amounts of these ions (10–750 mg/L) and at different pH values (3.0–7.0). Adsorption equilibria were established in about 20 min. The maximum adsorption capacities of the p(HEMA‐MAH) beads were 122.7 mg/g for Cu(II), 468.8 mg/g for Cr(III), 639.4 mg/g for Cd(II), 714.1 mg/g for Pb(II) and 1 234.4 mg/g for Hg(II). pH significantly affected the adsorption capacity of MAH incorporated beads. The chelating beads can be easily regenerated by 0.1 M HNO₃ with high effectiveness. These features make p(HEMA‐MAH) beads a potential candidate for heavy metal removal at high capacity.     

Selective separation and concentration of Pd(II) from Fe(III), Co(II), Ni(II), and Cu(II) ions using thiourea‐formaldehyde resin

Thiourea‐formaldehyde (TUF), a well‐known chelating resin, has been synthesized and it was used in the adsorption, selective separation, and concentration of Pd(II) ions from Fe(III), Co(II) Ni(II), and Cu(II) base metal ions. The composition of the synthesized resin was determined by elemental analysis. The effect of initial acidity/pH and the adsorption capacity for Pd(II) ions were studied by batch technique. The adsorption and separation of Pd(II) were then examined by column technique. FTIR spectra and SEM/EDS analysis were also recorded before and after the adsorption of Pd(II). The optimum pH was found to be 4 for the adsorption. The adsorption data fitted well to the Langmuir isotherm. The maximum adsorption capacity of the TUF resin for Pd(II) ions was found to be 31.85 mg g⁻¹ (0.300 mmol g⁻¹). Chelating mechanism was effective in the adsorption. Pd(II) ions could be separated efficiently from Fe(III), Cu(II), Ni(II), and Co(II) ions using TUF resin. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Pyromellitic dianhydride‐modified β‐cyclodextrin microspheres for Pb(II) and Cd(II) adsorption

In this work, the pyromellitic dianhydride (PMDA)‐grafted β‐cyclodextrin (β‐CD) microspheres have been prepared for the removal of lead and cadmium metal ions in aqueous solution by a batch‐equilibration technique. The effects of the pH of the solution, contact time, and initial metal concentration were studied. The adsorption capacities for the two metal ions increase significantly as a large number of carboxyl groups are present on the microspheres surface. The equilibrium process is better described by the Langmuir isotherm than the Freundlich isotherm. The maximum adsorption capacities are 135.69 and 92.85 mg g^?1 for Pb(II) and Cd(II), respectively. Kinetic studies show good correlation coefficients for a pseudosecond‐order kinetic model, confirming that the sorption rate is controlled by chemical adsorption. The regeneration of the adsorbent can be carried out by treating the loaded microspheres with 0.2 (mol L^?1) HCl obtaining high desorption rate for the two metal ions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Removal of phosphate by using copper‐loaded poly(N‐vinylimidazole) hydrogels as polymeric ligand exchanger

Polymeric ligand exchangers (PLE) are generally composed of a crosslinked hosting resin that can firmly hold a transition metal ion which can act as terminal functional groups. In this study, poly(N‐vinylimidazole) (PVIm) hydrogels were synthesized by free radical polymerization/crosslinking of N‐vinylimidazole in aqueous solution. Swelling behavior of PVIm hydrogels was investigated and the gel with minimum amount of crosslinking agent, hence showing maximum swelling was selected as the optimum gel system for further studies. To prepare the corresponding PLE for the removal of phosphate, PVIm hydrogels were loaded with Cu(II) ions. Copper loading capacity of PLE was determined to be 5 mmol of Cu(II)/g of dry gel. For removal of phosphate, adsorption experiments were performed in batch mode at different pH (3–9) and phosphate concentrations. It was found that phosphate adsorption capacity did not change significantly within this pH range. The effect of initial concentration of phosphate on the adsorption behavior of PLE was determined for 10 different phosphate concentrations (0.1–1000 mg/L) at pH 7. NaCl solution was used for regeneration of phosphate adsorbed Cu(II) loaded PVIm hydrogels with 100% regeneration efficiency. The new PLE showed high affinity for phosphate; the highest uptake was found to be 218 mg/g dry PLE from 1000 mg/L phosphate solution. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Metal chelating properties of Cibacron Blue F3GA‐derived poly(EGDMA‐HEMA) microbeads

Metal chelating properties of Cibacron Blue F3GA‐derived poly(EGDMA‐HEMA) microbeads have been studied. Poly(EGDMA‐HEMA) microbeads were prepared by suspension copolymerization of ethylene glycol dimethacrylate (EGDMA) and hydroxy‐ethyl methacrylate (HEMA) by using poly(vinyl alcohol), benzoyl peroxide, and toluene as the stabilizer, the initiator, and the pore‐former, respectively. Cibacron Blue F3GA was covalently attached to the microbeads via the nucleophilic substitution reaction between the chloride of its triazine ring and the hydroxyl groups of the HEMA, under alkaline conditions. Microbeads (150–200 μm in diameter) with a swelling ratio of 55%, and carrying 16.5 μmol Cibacron Blue F3GA/g polymer were used in the adsorption/desorption studies. Adsorption capacity of the microbeads for the selected metal ions, i.e., Cu(II), Zn(II), Cd(II), Fe(III), and Pb(II) were investigated in aqueous media containing different amounts of these ions (5–200 ppm) and at different pH values (2.0–7.0). The maximum adsorptions of metal ions onto the Cibacron Blue F3GA‐derived microbeads were 0.19 mmol/g for Cu(II), 0.34 mmol/g for Zn(II), 0.40 mmol/g for Cd(II), 0.91 mmol/g for Fe(III), and 1.05 mmol/g for Pb(II). Desorption of metal ions were studied by using 0.1 M HNO₃. High desorption ratios (up to 97%) were observed in all cases. Repeated adsorption/desorption operations showed the feasibility of repeated use of this novel sorbent system. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1397–1403, 1999     

Adsorption of Cd(II), Pb(II), and Ag(I) in aqueous solution on hollow chitosan microspheres

Cross‐linked chitosans synthesized by the inverse emulsion cross‐link method were used to investigate adsorption of three metal ions [Cd(II), Pb(II), and Ag(I)] in an aqueous solution. The chitosan microsphere, was characterized by FTIR and SEM, and adsorption of Cd(II), Pb(II), and Ag(I) ions onto a cross‐linked chitosan was examined through analysis of pH, agitation time, temperature, and initial concentration of the metal. The order of adsorption capacity for the three metal ions was Cd²⁺ > Pb²⁺ > Ag⁺. This method showed that adsorption of the three metal ions in an aqueous solution followed the monolayer coverage of the adsorbents through physical adsorption phenomena and coordination because the amino (? NH₂) and/or hydroxy (? OH) groups on chitosan chains serve as coordination sites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Modelling Individual and Competitive Adsorption of Cadmium(II) and Zinc(II) Metal Ions from Aqueous Solution onto Bagasse Fly Ash

Abstract

The present study deals with the competitive adsorption of cadmium (Cd(II)) and zinc (Zn(II)) ions onto bagasse fly ash (BFA) from binary systems. BFA is a waste obtained from the bagasse‐fired boilers of sugar mills. The initial pH≈6.0 is found to be the optimum for the individual removal of Cd(II) and Zn(II) ions by BFA. The equilibrium adsorption data were obtained at different initial concentrations (C ₀ = 10–100 mg/l), 5 h contact time, 30°C temperature, BFA dosage of 10 mg/l at pH ₀ = 6. The Redlich–Peterson (R–P) and the Freundlich models represent the single ion equilibrium adsorption data better than the Langmuir model. The adsorption capacities in the binary‐metal mixtures are in the order Zn(II)>Cd(II) and is in agreement with the single‐component adsorption data. The equilibrium metal removal decreases with increasing concentrations of the other metal ion and the combined action of Cd(II) and Zn(II) ions on BFA is found to be antagonistic. Equilibrium isotherms for the binary adsorption of Cd(II) and Zn(II) ions on BFA have been analyzed by non‐modified Langmuir, modified Langmuir, extended‐Langmuir, Sheindorf–Rebuhn–Sheintuch (SRS), non‐modified R–P and modified R–P adsorption models. The isotherm model fitting has been done by minimizing the Marquardt's percent standard deviation (MPSD) error function using MS Excel. The SRS model satisfactory fits for most of the adsorption equilibrium data of Cd(II) and Zn(II) ions onto BFA.     

Determination of the competitive adsorption of heavy metal ions on poly(n‐vinyl‐2‐pyrrolidone/acrylic acid) hydrogels by differential pulse polarography

Poly(N‐vinyl‐2‐pyrrolidone) and poly(N‐vinyl‐2‐pyrrolidone/acrylic acid) hydrogels were prepared by gamma irradiation for the removal of heavy metal ions (i.e., lead, copper, zinc, and cadmium) from aqueous solutions containing different amounts of these ions (2.5–10 mg/L) and at different pH values (1–13). The observed affinity order in adsorption of these metal ions on the hydrogels was Zn(II) > Pb(II) > Cu(II) > Cd(II) under competitive conditions. The optimal pH range for the heavy metal ions was from 7 to 9. The adsorption of the heavy metal ions decreased with increasing temperature in both water and synthetic seawater conditions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2013–2018, 2003