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     

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     

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     

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     

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.     

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     

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 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     

Polarographic determination of the competitive adsorption of U(VI), Pb(II), and Cd(II) ions on poly(N‐vinyl‐2‐pyrrolidone‐g‐citric acid) hydrogels

Poly(N‐vinyl‐2‐pyrrolidone‐g‐citric acid) [P(VP‐g‐CA)] hydrogels were prepared for the removal of U(VI), Pb(II), and Cd(II) from aqueous solutions containing different amounts of these ions (2.5–10 mg/L). Different pHs (1–13), temperatures (20–40°C), and ionic strengths (0.5M) were also tried for the adsorption behavior of these ions. The competitive adsorption values of U(VI), Pb(II), and Cd(II) ions on pure poly(N‐vinyl‐2‐pyrrolidone) were low [0.71–2.03 mg of U(VI)/g of dry gel, 0.15–1.58 mg of Pb(II)/g of dry gel, and 0.10–0.68 mg of Cd(II)/g of dry gel]. The incorporation of citric acid significantly increased the adsorption of these ions [0.67–2.12 mg of U(VI)/g of dry gel, 0.44–1.88 mg of Pb(II)/g of dry gel, and 0.04–0.92 mg of Cd(II)/g of dry gel for P(VP‐g‐CA)‐1; 0.71–2.36 mg of U(VI)/g of dry gel, 0.60–2.16 mg of Pb(II)/g of dry gel, and 0.14–0.80 mg of Cd(II)/g of dry gel for P(VP‐g‐CA)‐2; and 0.79–2.47 mg of U(VI)/g of dry gel, 0.70–2.30 mg of Pb(II)/g of dry gel, and 0.20–0.86 mg of Cd(II)/g of dry gel for P(VP‐g‐CA)‐3]. The observed affinity order of adsorption was U(VI) > Pb(II) > Cd(II) for competitive conditions. The optimal pH range for the removal of these ions was 5–9. Competitive adsorption studies showed that other stimuli, such as the temperature and ionic strength of the solution, also influenced the U(VI), Pb(II), and Cd(II) adsorption capacity of P(VP‐g‐CA) hydrogels. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2019–2024, 2003     

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     

Water‐soluble amine and imine polymers with the ability to bind metal ions in conjunction with membrane filtration

The commercial polymers poly(ethylene imine) (PEI), poly(ethylene imine epichlorohydrin), and poly(dimethylamine‐co‐epichlorohydrin) were purified and fractionated by ultrafiltration. Their metal‐ion‐binding properties with respect to different ligand groups and the effect of the concentration on the retention properties were investigated. The amine ligands of the polymers formed the most stable complexes with the metal ions. In general, there was an effect of the pH and polymer fraction size on the retention properties. As the pH and polymer fraction size increased, the affinity to bind metal ions also increased. PEI had the highest metal‐retention values, particularly at higher pHs, at which the amine groups were nonprotonated and could coordinate easily with the metal ions. Only Pb(II) was poorly retained. The affinity for all the metal ions, except Pb(II), increased significantly at pH 5. The metal‐ion retention decreased quickly as the filtration factor increased, except for Cu(II), Co(II), Ni(II), Cd(II), and Zn(II) ions, which were retained by over 40% at a filtration factor of 4. For other metal ions such as Pb(II), Ca(II), and Mg(II), only 10% remained bound to the polymer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 222–231, 2005     

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     

Synthesis of 1,4,8,11‐tetraazacyclotetradecane monomer by addition of acryloyl chloride and its polymer for specific transition metal binding

1,4,8,11‐Tetraazacyclotetradecane (cyclam) was reacted with acryloyl chloride in a 1 : 2 molar ratio in dichloromethane in the presence of pyridine at 0°C. The modified cyclam was polymerized by adding an azobisisobutyronitrile initiator and irradiated with a UV lamp under reflux for 6 h. Precipitated cyclam containing polymer in the bulk structure was removed from the suspension by filtration. After washing and drying the final polymeric materials were used for transition metal ion adsorption and desorption studies. A Fourier transform IR spectrophotometer and thermogravimetric analyzer were used to characterize the polymeric structure. The affinity of the polymeric material for transition metal ions was used to test the adsorption–desorption of selected ions [Cu(II), Ni(II), Co(II), Cd(II), Pb(II)] from aqueous media containing different amounts of these metal ions (5–800 ppm) at different pH values (2.0–8.0). It was found that the adsorption rates were high and the adsorption equilibrium was reached in about 30 min. The uptake of the transition metal ions onto the polymer from solutions containing a single metal ion was 3.17 mmol/g for Cu(II), 0.98 mmol/g for Cd(II), 0.79 mmol/g for Co(II), 0.78 mmol/g for Ni(II), and 0.32 mmol/g for Pb(II). This polymer showed high affinity for Cu(II) compared to the other metal ions in the single ion solution and in the mixture of transition metal ions. The affinity order of the transition metal ions was Cu(II) ? Ni(II) > Cd(II) > Co(II) > Pb(II) for competitive adsorption. More than 95% of the adsorbed transition metal ions were desorbed in 2 h in a desorption medium containing 1.0M HNO₃. Poly(cyclam) was found to be suitable for repeated use of more than five cycles without a noticeable loss of adsorption capacity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1406–1414, 2002     

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     

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.     

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     

Reactive green HE‐4BD functionalized supermacroporous poly(hydroxyethyl methacrylate) cryogel for heavy metal removal

The aim of this study was to investigate the heavy metal adsorption performance of supermacroporous poly(hydroxyethyl methacrylate) [PHEMA] cryogel. The PHEMA cryogel was produced by cryo‐polymerization. The PHEMA cryogel was characterized by scanning electron microscopy (SEM). The PHEMA cryogel containing 385 μmol Reactive Green HE‐4BD/g were used in the adsorption studies. Adsorption capacity of the PHEMA cryogel for the metal ions, i.e., Cu²⁺, Cd²⁺, and Pb²⁺ were investigated in aqueous media containing different amounts of the ions (5–600 mg/L) and at different pH values (3.2–6.9). The maximum adsorption capacities of the PHEMA cryogel were 11.6 mg/g (56 μmol/g) for Pb²⁺, 24.5 mg/g (385 μmol/g) for Cu²⁺ and 29.1 mg/g (256 μmol/g) for Cd²⁺. The competitive adsorption capacities were 10.9 mg/g (52 μmol/g) for Pb²⁺, 22.1 mg/g for Cd²⁺ (196 μmol/g) and 23.2 mg/g (365 μmol/g) for Cu²⁺. The PHEMA/Reactive Green HE‐4BD cryogel exhibited the following metal ion affinity sequence on molar basis: Cu²⁺ > Cd²⁺ > Pb²⁺. The PHEMA/Reactive Green HE‐4BD cryogel can be easily regenerated by 50 mM EDTA with higher effectiveness. These features make the PHEMA/Reactive Green HE‐4BD cryogel a potential adsorbent for heavy metal removal. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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     

Removal of heavy metal ions using the chelating polymers derived by the condensation of poly(3‐hydroxy‐4‐acetylphenyl methacrylate) with different diamines

A series of methacrylate‐based chelating polymers was synthesized by the reaction of 3‐hydroxy‐4‐acetylphenyl methacrylate with amines (e.g., ethylenediamine, propylenediamine, and phenylenediamine) in tetrahydrofuran. The chelating polymers were characterized by infrared (IR) and carbon‐13 nuclear magnetic resonance (¹³C–NMR) spectroscopic techniques. The thermal stabilities of these polymers were investigated by thermogravimetric (TG) and differential thermal analyses (DTA). Heavy metal ions [viz., Pb(II), Hg(II), Cd(II), and Cr(VI)] were removed with these chelating polymers, and metal ion uptake efficiency, reusability of the resins, and effects of pH and time on the metal removal were also studied. The chelating polymers possess appreciable selectivity for Pb(II) and Hg(II) compared with Cd(II) and Cr(VI). The chelating ability of the polymers towards the heavy metal ions is a sensitive function of the nature of the substituent on the nitrogen atom. The amount of metal uptake by the chelating polymer was determined by atomic absorption spectrophotometry (AAS). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 414–421, 2003