Cysteine-metal affinity chromatography: determination of heavy metal adsorption properties

Various adsorbent materials have been reported in the literature for heavy metal removal. We have developed a novel approach to obtain high metal sorption capacity utilising cysteine containing adsorbent. Metal complexing aminoacid-ligand cysteine was immobilised onto poly(hydroxyethylmethacrylate) (PHEMA) microbeads. PHEMA-cysteine affinity microbeads containing 0.318 mmol cysteine/g were used in the removal of heavy metal ions (i.e. copper, lead and cadmium) from aqueous media containing different amounts of these ions (50–400 mg/l for Pb(II) and Cd(II), 25–60 mg/l for Cu(II)) and at different pH values (4.0–7.0). The maximum adsorption capacity of heavy metal ions onto the cysteine-containing microbeads under non-competitive conditions were 0.259 mmol/g for Pb(II), 0.330 mmol/g for Cd(II) and 0.229 mmol/g for Cu(II). The affinity order was observed as follows: Cd(II)>Pb(II)>Cu(II). The competitive adsorption capacities of the heavy metals were 0.260 mmol/g for Cd(II) and 0.120 mmol/g for Cu(II). Pb(II) adsorption onto cysteine-immobilised microbeads was zero under competitive conditions. The affinity order was as follows: Cd(II)>Cu(II)>Pb(II). The formation constants of cysteine–metal ion complexes have been investigated applying the method of Ruzic. The calculated value of stability constants were 1.75×10⁴ l/mol for Pb(II)–cysteine complex and 4.35×10⁴ l/mol for Cd(II)–cysteine complex and 1.39×10⁴ l/mol for Cu(II)–cysteine complex. PHEMA microbeads carrying cysteine can be regenerated by washing with a solution of hydrochloric acid (0.05 M). The maximum desorption ratio was greater than 99%. These PHEMA microbeads are suitable for repeated use for more than three adsorption–desorption cycles without considerable loss in adsorption capacity.     

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     

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     

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     

Investigation of Heavy Metal Ion Adsorption Characteristics of Poly(N,N Dimethylamino Ethylmethacrylate) Hydrogels

Abstract

In this study, Poly(N,N dimethyl‐amino ethylmethacrylate) (Poly(DMAEMA)) hydrogels with varying compositions were prepared in the form of rods by irradiating ternary mixtures of N,N‐dimethylamino ethylmethacrylate/ethyleneglycoldimethacrylate/water with gamma rays at ambient temperature. Swelling studies of poly (DMAEMA) hydrogels were performed at different pH values and maximum swelling values reached at pH 2. The adsorption characteristics of Pb(II), Cd(II), Ni(II), Zn(II), Cu(II), and Co(II) ions to poly(N,N dimethylamino ethylmethacrylate) hydrogels were investigated by a batch process. The order of affinity based on amount of metal ion uptake was found as follows: Cu(II)>Zn(II)?Co(II)>Pb(II) >> Ni(II)>Cd(II). In the adsorption studies of Cu(II), Zn(II), Co(II), Pb(II), Ni(II), and Cd(II) ions the Langmuir type adsorption isotherms were observed for all gel systems.     

Metal ion retention properties of water‐insoluble polymers containing carboxylic acid groups

Crosslinked poly(acrylic acid), PAA, and poly(2‐acrylamidoglycolic acid), PAAG, were synthesized by radical polymerization. Both resins contain carboxylic acid groups. PAA at basic pH exists basically as an acrylate anion and PAAG shows three atoms or groups, carboxylic acid, hydroxyl, and amide groups, that can act as ion exchanger or chelating groups. Both resins are studied as adsorbents to trace metal ions from saline aqueous solutions and natural sea water and their properties by Batch equilibrium procedure are compared. The metal ions studied under competitive and noncompetitive conditions were Cu(II), Pb(II), Cd(II), and Ni(II). The effects of pH, time of contact, amount of resin, temperature, and salinity were studied. Resin PAA shows a high affinity (>80%) for Cu(II) and Cd(II) and resin PAAG shows also a high affinity for Ni(II), Pb(II), and Cd(II). By treatment of the metal ion‐loaded resin with 4M HNO₃ it is possible to recover completely the Cu(II) ions from resin PAA and Ni(II) and Pb(II) from resin PAAG. The metal ion retention properties were studied with natural sea water. For those natural sea waters containing Cu(II) and Cd(II), the resins showed a high affinity for Cd(II) ions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 697–705, 2006     

Adsorption properties of poly(acrylaminophosphonic-carboxyl-hydrazide)type chelating fiber for heavy metal ions

In this article, the adsorption properties of poly(acrylaminophosphonic-carboxyl-hydrazide) chelating fibers for Cu(II), Cd(II), Co(II), Mn(II), Pb(II), Zn(II), Ni(II), and Cr(III) are investigated by a batch technique. Based on the research results of binding capacity, adsorption isotherm, effect of pH value on sorption, and adsorption kinetics experiments, it is shown that the poly(acrylaminophosphonic-carboxyl-hydrazide) chelating fibers have higher binding capacities and good adsorption kinetic properties for heavy metal ions. The sorption of the metal ions on the chelating fibers is strongly dependent on the equilibrium pH value of the solution. The adsorption isotherms of Cu(II) and Cd(II) on the chelating fiber exhibit a Langmuir-type equation. The adsorbed Cu(II), Cd(II), Zn(II), and Pb(II) could be eluted by diluted nitric acid. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 7–14, 1998     

Adsorption Behavior of Iminodiacetic Acid Type of Chelating Gel Prepared from Waste Paper

Abstract

Adsorption gel was prepared from waste recycled paper by immobilizing iminodiacetic acid (IDA) functional group by chemical modification. The gel exhibited good adsorption behavior for a number of metal ions viz. Cu(II), Pb(II), Fe(III), Ni(II), Cd(II), and Co(II) at acidic pH. The order of selectivity was found to be as follows: Cu(II)>Pb(II)>Fe(III)>Ni(II)～Cd(II)～Co(II). From the adsorption isotherms, the maximum adsorption capacity of the gel for both Cu(II) and Pb(II) was found to be 0.47 mol/kg whereas that for Cd(II) was 0.24 mol/kg. A continuous flow experiment for Cd(II) showed that the gel can be useful for pre‐concentration and complete removal of Cd(II) from aqueous solution.     

Preparation of amidoximated polyester fiber and competitive adsorption of some heavy metal ions from aqueous solution onto this fiber

In this study, a fibrous adsorbent containing amidoxime groups was prepared by graft copolymerization of acrylonitrile (AN) onto poly(ethylene terephthalate) (PET) fibers using benzoyl peroxide (Bz₂O₂) as initiator in aqueous solution, and subsequent chemical modification of cyano groups by reaction with hydroxylamine hydrochloride in methanol. The grafted and modified fibers were characterized by FTIR, TGA, SEM, and XRD analysis. The crystallinity increased, but thermal stability decreased with grafting and amidoximation. The removal of Cu(II), Ni(II), Co(II), Pb(II), and Cd(II) ions from aqueous solution onto chelating fibers were studied using batch adsorption method. These properties were investigated under competitive conditions. The effects of the pH, contact time, and initial ion concentration on the removal percentage of ions were studied. The results show that the adsorption rate of metal ions followed the given order Co(II) > Pb(II) > Cd(II) > Ni(II) > Cu(II). The percentage removal of ions increased with initial ion concentration, shaking time, and pH of the medium. Total metal ion removal capacity was 49.75 mg/g fiber on amidoximated fiber. It was observed that amidoximated fibers can be regenerated by acid without losing their activity, and it is more selective for Pb(II) ions in the mixed solution of Pb‐Cu‐Ni–Co‐Cd at pH 4. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Adsorption of some heavy metal ions from aqueous solutions on Nafion 117 membrane

Nafion 117 membrane was investigated for the removal of Ni(II), Co(II), Pb(II), Cu(II) and Ag(I) metal ions from their synthesized aqueous solutions. The different variables affecting the adsorption capacity of the membrane such as contact time, initial metal ion concentration in the feed solution, pH of the sorption medium and temperature of the solution were investigated on a batch sorption basis. The affinity of Nafion 117 membrane towards heavy metal ions was found to increase in the sequence of Cu(II), Ni(II), Co(II), Pb(II), and Ag(I) with adsorption equilibrium achieved after 30 min for all metal ions. Among all parameters, pH has the most significant effect on the adsorption capacity, particularly in the range of 3.1-5.9. The variation of temperature in the range of 25-65 °C was found to have no significant effect on the adsorption capacity. Nafion 117 membrane was found to have high stability combined with repeated regeneration ability and can be suggested for effective removal of heavy metal ions such as Cu(II), Ni(II) and Co(II) from aqueous solutions.     

Synthesis,Characterization, and Applications of a New Chelating Resin Containing 4-2-(Thiazolylazo) Resorcinol (TAR)

A new phenol–formaldehyde based chelating resin containing 4-(2-thiazolylazo) resorcinol (TAR) functional groups has been synthesized and characterized by Fourier transform infrared spectroscopy and elemental analysis. Its adsorption behavior for Cu(II), Pb(II), Ni(II), Co(II), Cd(II), and Mn(II) has been investigated by batch and column experiments. The chelating resin is highly selective for Cu(II) in the pH range 2 ～ 3, whereas alkali metal and alkaline earth metal ions such as Na(I), Mg(II), and Ca(II) are not adsorbed even at pH 6. Quantitative recovery of most metal ions studied in this work except Co(II) is achieved by elution with 2M HNO₃ at a flow rate of 0.2 mL min^?1. A similar trend is observed for distribution coefficient values. The quantitative separations achieved on a mini-column of chelating resin include Cd(II) – Cu(II), Mn(II) – Pb(II), Co(II) – Cu(II), Mn(II) – Ni(II), and Mn(II) – Co(II) – Cu(II). The recovery of copper(II) is quantitative (98.0–99.0%) from test solutions (10–50 mg/L) by 1 mol/L HNO₃-0.01 mol/L EDTA. The chelating resin is stable in acidic solutions below 2.5 M HNO₃ or HCl as well as in alkaline solution below pH 11. The adsorption behavior of the resin towards Cu(II) was found to follow Langmuir isotherm and second order rate.     

A new metal chelate sorbent for glucose oxidase: Cu(II)- and Co(II)-chelated poly(N-vinylimidazole) gels

Poly(N-vinylimidazole) (PVIm) gels were prepared by irradiating a binary mixture of N-vinylimidazole (VIm)–water in a ⁶⁰Co-γ source having 4.5 kGy/h dose rate. In the glucose oxidase (GOx) adsorption studies, affinity gels with a swelling ratio of 1100% for PVIm and 40 and 55% for Cu(II)- and Co(II)-chelated PVIm gels, respectively, at pH 6.5 in phosphate buffer were used. FTIR spectra were taken for PVIm and Cu(II)- and Co(II)-chelated PVIm, and glucose oxidase adsorption on these gels, to characterize the nature of the interactions in each species. The results show that PVIm–glucose oxidase interaction is mainly electrostatic and metal ion–chelated PVIm gel–glucose oxidase interaction is of coordinate covalent nature. Cu(II) and Co(II) ions were chelated within the gels via amine groups on the imidazole ring of the gel. Different amounts of Cu(II) and Co(II) ions [maximum 3.64 mmol/g dry gel for Cu(II) and 1.72 mmol/g dry gel for Co(II)] were loaded on the gels by changing the initial concentration of Cu(II) and Co(II) ions at pH 7.0. GOx adsorption on these gels from aqueous solutions containing different amounts of GOx at different pH was investigated in batch reactors. GOx adsorption capacity was further increased when Cu(II) and Co(II) ions were attached [up to 0.53 g GOx/g dry Co(II)-chelated PVIm gels]. More than 90% of the adsorbed GOx was desorbed in 5 h in desorption medium containing 1.0M KSCN at pH 7.0 for plain gel and 0.05M EDTA at pH 4.9 for metal-chelated gel. Nonspecific glucose oxidase adsorption on/in the metal ion–chelated PVIm gel was investigated using 0.02M of phosphate buffer solution. The nonspecific GOx adsorption was determined to be about 18% for PVIm and 8% for the metal ion–chelated PVIm gels. The ionic strength effect was investigated both on PVIm and on the metal ion–chelated PVIm gels for the glucose oxidase adsorption. It was found that ionic strength was more effective on the PVIm gel because of the electrostatic interaction between protonated gel and the deprotonated glucose oxidase side chain. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 446–453, 2001     

Metal sorption on macroporous poly(GMA-co-EGDMA) modified with ethylene diamine

Two samples of macroporous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate), poly(GMA-co-EGDMA), with different porosity parameters were synthesized by suspension copolymerization and modified by ring-opening reaction of the pendant epoxy groups with ethylene diamine (EDA). The samples were characterized by mercury porosimetry, FT-IR spectroscopy and elemental analysis. The sorption rate of the modified copolymer, poly(GMA-co-EGDMA)-en for Cu(II) ions determined under non-competitive conditions was relatively rapid, i.e. the maximum capacity was reached within 30 min. Batch sorption capacities for Cu(II), Fe(II), Mn(II), Cd(II), Zn(II), Pb(II), Cr(III) and Pt(IV) ions were determined under non-competitive conditions in the pH range 1.25–5.5 at room temperature. The maximum sorption capacities of poly(GMA-co-EGDMA)-en under non-competitive conditions were 1.30 mmol/g for Pt(IV) at pH 5.5, 1.10 mmol/g for Cu(II) at pH 5.5, 1.06 mmol/g for Pb(II) at pH 1.25 and 0.67 mmol/g for Cd(II) ions at pH 5.5. The selectivity of poly(GMA-co-EGDMA)-en towards Cu(II), Co(II), Ni(II), Pb(II) and Pt(IV) ions was investigated under competitive conditions. Poly(GMA-co-EGDMA)-en showed high selectivity for Pt(IV) over Cu(II), Co(II), Ni(II) and Pb(II) ions at pH 2.1. At pH 5.5, the metal sorption capacities of poly(GMA-co-EGDMA)-en decreased in the order: Cu(II) > Co(II) > Pt(IV) ≈ Ni(II) > Pb(II). Regeneration of the Cu(II), Ni(II) and Pb(II) loaded poly(GMA-co-EGDMA)-en with 2 M H₂SO₄ showed that the polymer can be reused in several sorption/desorption cycles.     

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     

Adsorption properties of a chelating resin containing hydroxy group and iminodiacetic acid for copper ions

A chelating resin, PSGI, was synthesized by the radical polymerization of GMA‐IDA, DVB, and styrene for the removal of Cu(II), Co(II), and Cd(II) from an aqueous solution. The characteristic functional groups and chemical composition of PSGI were analyzed by Fourier transform infrared spectroscopy and elemental analysis of C, H, and N. The equilibrium adsorption capacities of PSGI from their single‐metal ion solutions were 1.46 mmol/g for Cu(II), 1.02 mmol/g for Co(II), and 1.10 mmol/g for Cd(II). The adsorption isothermal of Cu(II) by PSGI followed the Langmuir isotherm. Increasing the concentration (0–0.1 M) of KCl in Cu(II) solution affected the adsorption behavior slightly. Within the pH range of 2–5.5, decreasing the pH of the Cu(II) solution did not produce remarkable changes in the equilibrium adsorption capacities. The adsorption capacities of PSGI for Cu(II) did not cause significant change during the repeated adsorption–desorption operations. The competitive adsorption tests verified that this resin had good adsorption selectivity for Cu(II) with the coexistence of Co(II) and Cd(II). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2123–2130, 2004     

Polyelectrolyte‐assisted removal of metal ions with ultrafiltration

The water‐soluble polymers poly(styrene sulfonic acid‐co‐maleic acid) and poly(acrylic acid‐co‐maleic acid) were investigated with respect to their metal‐ion‐binding ability with ultrafiltration. The studied metal ions included Ag(I), Cu(II), Ni(II), Co(II), Ca(II), Mg(II), Pb(II), Cd(II), Zn(II), Al(III), and Cr(III) ions. The retention properties of the polyelectrolytes for the metal ions depended strongly on the ligand type. As for the carboxylate ligands, with increasing concentration and pH, the metal‐binding affinity increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1091–1099, 2005     

Preparation of cibacron blue F3GA‐attached polyamide hollow fibers for heavy metal removal

Dye‐affinity adsorption has been used increasingly for heavy metal removal. Synthetic hollow fibers have advantages as support matrices in comparison to conventional bead supports because they are not compressible and they eliminate internal diffusion limitations. The goal of this study was to investigate in detail the performance of hollow fibers composed of modified polyamide to which Cibacron Blue F3GA was attached for the removal of heavy metal ions. The Cibacron Blue F3GA loading was 1.2 mmol/g. The internal matrix was characterized by scanning electron microscopy. No significant changes in the hollow fiber cross‐section or outer layer morphology were observed after dye modification. The effect of the initial concentration of heavy metal ions and medium pH on the adsorption efficiency were studied in a batch reactor. The adsorption capacity of the hollow fibers for the selected metal ions [i.e., Cu(II), Zn(II) and Ni(II)] were investigated in aqueous media with different amounts of these ions (10–400 ppm) and at different pH values (3.0–7.0). The maximum adsorptions of metal ions onto the Cibacron Blue F3GA‐attached hollow fibers were 246.2 mg/g for Cu(II), 133.6 mg/g for Zn(II), and 332.7 mg/g for Ni(II). Furthermore, a Langmuir expression was calculated to extend the adsorption equilibrium. Nitric acid (0.1M) was chosen as the desorption solution. High desorption ratios (up to 97%) were observed in all cases. Consecutive adsorption/desorption operations showed the feasibility of repeated use of this novel sorbent system. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3089–3098, 2002; DOI 10.1002/app.2338     

Mono- and multi-component biosorption of lead(II), cadmium(II), copper(II) and nickel(II) ions onto coco-peat biomass

The potential of using coco-peat biomass (CPB) has been assessed for the removal of Pb(II), Cd(II), Cu(II) and Ni(II) ions from single and quaternary solutions. According to Langmuir isotherm, the maximum biosorption capacity of CPB was 0.484, 0.151, 0.383 and 0.181 mmol/g for Pb(II), Cd(II), Cu(II) and Ni(II) ions, respectively. Scanning electron microscopy along with energy-dispersive X-ray spectroscopy and Fourier-transform IR spectroscopy confirmed changes in the biosorbent functionality after metal sorption. Through quaternary isotherm experiments, 16.1%, 48.2%, 32.3% and 46.5% decrease in experimental uptakes were observed for Pb(II), Cd(II), Cu(II) and Ni(II), respectively, in the presence of other metal ions.     

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.     

Metal ion retention properties of poly(acrylic acid) and poly[N‐3‐(dimethylamino)propyl acrylamide‐co‐acrylic acid]

The crosslinked resins poly(acrylic acid) (PAA) and poly[N‐3‐(dimethylamino)propyl acrylamide‐co‐acrylic acid] [P(NDAPA‐co‐AA)] are obtained by radical polymerization and characterized by FTIR spectroscopy. PAA at basic pH exists basically as an acrylate anion that may contain end carboxylate groups or form bridges acting as mono‐ or bidentate ligands. P(NDAPA‐co‐AA) presents three potential ligand groups in its structure: carboxylic acid, amide, and amine. The trace metal ion retention properties of these two resins is compared by using the batch equilibrium procedure. The metal ions are contained in saline aqueous solutions and are found in natural seawater. The retention of Cu(II), Pb(II), Cd(II), and Ni(II) metal ions is studied under competitive and noncompetitive conditions. The effects on the pH, contact time, amount of adsorbent, temperature, and salinity are investigated. The PAA resin presents a high affinity (>80%) for Cu(II) and Cd(II) ions. The P(NDAPA‐co‐AA) resin shows a high affinity for Pb(II) and Cd(II) ions. With 4M HNO₃ it is possible to completely recover the PAA resin charged with Cu(II) ions and the P(NDAPA‐co‐AA) resin charged with Pb(II) ions. The two resins show a high affinity for Cd(II) ions from the seawater containing Cu(II) and Cd(II) ions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1385–1394, 2005