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     

Radiation synthesis and characterization of poly(N‐vinyl‐2‐pyrrolidone/acrylic acid) and poly(N‐vinyl‐2‐pyrrolidone/acrylamide) hydrogels for some metal‐ion separation

Two different hydrogels, prepared from N‐vinyl‐2‐pyrrolidone/acrylic acid (NVP/AAc) and N‐vinyl‐2‐pyrrolidone/acrylamide (NVP/AAm), were studied for the separation and extraction of some heavy‐metal ions from wastewater. The hydrogels were prepared by the γ‐radiation‐induced copolymerization of the aforementioned binary monomer mixtures. Further modification was carried out for the NVP/AAc copolymer through an alkaline treatment to improve the swelling behavior by the conversion of the carboxylic acid groups into its sodium salts. The thermal stability and swelling properties were also investigated as functions of the N‐vinyl‐2‐pyrrolidone content. The characterization and some selected properties of the prepared hydrogels were studied, and the possibility of their practical use in wastewater treatment for heavy metals such as Cu, Ni, Co, and Cr was investigated. The maximum uptake for a given metal was higher for a treated NVP/AAc hydrogel than for an untreated NVP/AAc hydrogel and was higher for an untreated NVP/AAc hydrogel than for an NVP/AAm hydrogel. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2642–2652, 2004     

Water‐soluble copolymers of 1‐vinyl‐2‐pyrrolidone and acrylamide derivatives: synthesis,characterization, and metal binding capability studied by liquid‐phase polymer‐based retention technique

Radical copolymerizations of 1‐vinyl‐2‐pyrrolidone with acrylamide and N,N′‐dimethylacrylamide at different feed ratios were investigated. The copolymers were characterized by Fourier transform infrared spectroscopy, ¹H NMR, and ¹³C NMR spectroscopy. The copolymer composition was determined from the ¹H NMR spectra and found to be statistical. The metal complexation of poly(acrylamide‐co‐1‐vinyl‐2‐pyrrolidone) and poly(N,N′‐dimethylacrylamide‐co‐1‐vinyl‐2‐pyrrolidone) for the metal ions Cu(II), Co(II), Ni(II), Cd(II), Zn(II), Pb(II), Fe(III), and Cr(III) were investigated in an aqueous phase. The liquid‐phase polymer‐based retention method is based on the retention of inorganic ions by soluble polymers in a membrane filtration cell and subsequent separation of low‐molecular compounds from the polymer complex formed. The metal ion interaction with the hydrophilic polymers was determined as a function of the pH and the filtration factor. Poly(N,N‐dimethylacrylamide‐co‐1‐vinyl‐2‐pyrrolidone) showed a higher affinity for the metal ions than poly(acrylamide‐co‐1‐vinyl‐2‐pyrrolidone). According to the interaction pattern obtained, Cr(III) and Cu(II) formed the most stable complexes at pH 7. Pb(II) and Zn(II) were not retained. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 741–750, 1999     

Synthesis of poly(acrylamide‐co‐4‐vinylpyridine) hydrogels and their application in heavy metal removal

A series of poly(acrylamide‐co‐4‐vinylpyridine) hydrogels having varied acrylamide/4‐vinylpyridine content and different crosslink ratios of N,N′‐methylene‐bisacrylamide was prepared by using solution polymerization. The prepared hydrogel polymers were characterized by their elemental analysis, infrared spectroscopy, and equilibrium water content. The polymers were investigated toward metal ion uptake of Mn(II), Co(II), Ni(II), Cu(II), and Zn(II). The polymers were more sensitive to Cu(II) and Ni(II) and the order of metal ion binding was Ni(II), Cu(II) > Zn(II) > Co(II) > Mn(II). Metal ion uptake by the polymers was reduced as the pH of the medium decreased. Recycling of the resins resulted in high recovery of the metal ions from their aqueous solutions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2522–2526, 2003     

Effect of pH,ionic strength,and temperature on uranyl ion adsorption by poly(N‐vinyl 2‐pyrrolidone‐g‐tartaric acid) hydrogels

Poly‐electrolyte N‐vinyl 2‐pyrrolidone‐g‐tartaric acid (PVP‐g‐TA) hydrogels with varying compositions were prepared in the form of rods from ternary mixtures of N‐vinyl 2‐pyrrolidone/tartaric acid/water. The effect of external stimuli, such as the solution pH, ionic strength, and temperature, on uranyl adsorption by these hydrogels was investigated. Uranyl adsorption capacities of the hydrogels were determined to be 53.2–72.2 (mg UO/g dry gel) at pH 1.8, and 35.3–60.7 (mg UO/g dry gel) at pH 3.8, depending on the amount of TA in the hydrogel. The adsorption studies have shown that the temperature and the ionic strength of the swelling solution also influence uranyl ion adsorption by PVP‐g‐TA hydrogels. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2219–2226, 2000     

Metal‐ion‐retention properties of the poly(2‐acrylamido‐2‐methyl‐1‐propanosulfonic acid‐co‐4‐vinyl pyridine) resin

The water‐insoluble resin poly(2‐acrylamido‐2‐methyl‐1‐propanosulfonic acid‐co‐4‐vinyl pyridine), through a radical polymerization solution, was synthesized with ammonium persulfate as an initiator and N,N‐methylene bisacrylamide as a crosslinking reagent. The metal‐ion‐retention properties were studied by batch and column equilibrium procedures for the following metal ions: Hg(II), Cu(II), Cd(II), Zn(II), Pb(II), and Cr(III). These properties were investigated under competitive and noncompetitive conditions. The effects of the pH, maximum retention capacity, and regeneration capacity were studied. The resin showed a high retention ability for Hg(II) ions at pH 2.0. The retention of Hg(II) ions from a mixture of ions was greater than 90%. The resin showed a high selectivity for Hg(II) with respect to other metal ions. The Hg(II)‐loaded resin was able to be recovered with 4M HClO₄. The retention capacity was kept after four cycles of adsorption and desorption. The retention properties for Hg(II) were very similar with the batch and column methods. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3556–3562, 2003     

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     

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     

Strontium(II) ion uptake on poly(N‐vinyl imidazole)‐based hydrogels

In this article, we report on the extraction of Sr(II) ions from aqueous solution with a series of poly(N‐vinyl imidazole)‐based hydrogels. The hydrogels were synthesized by the crosslinking of N‐vinyl imidazole with four different crosslinkers with γ rays as initiators. The well‐characterized hydrogels were used as Sr(II) sorbents. Sr(II) uptake was determined with a colorimetric method with Rose Bengal anionic dye. Scanning electron microscopy–energy‐dispersive spectroscopy analysis of the Sr(II)‐loaded polymers was recorded to ascertain the uptake of Sr(II) ions. The experimental adsorption values were analyzed with the Freundlich and Temkin equations, and the kinetics of adsorption were investigated with a pseudo‐second‐order sorption kinetic model. The results show that the equilibrium data fit well in the Freundlich isotherm and followed a pseudo‐second‐order kinetic model. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Application of anionic acrylamide‐based hydrogels in the removal of heavy metals from waste water

Crosslinked acrylamide (AM) and 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) homopolymers and copolymers were prepared by free radical solution polymerization using N,N′‐methylenebisacrylamide as the crosslinker. The chemical structures of hydrogels were characterized by FTIR analysis and the results were consistent with the expected structures. These hydrogels were used for the separation of Cd(II), Cu(II), and Fe(III) ions from their aqueous solutions. The influence of the uptake conditions such as pH, time and initial feed concentration on the metal ion binding capacity of hydrogel was also tested. The selectivity of the hydrogel towards the different metal ions tested was Cd(II) > Cu(II) > Fe(III). It was observed that the specific interaction between metal ions and ionic comonomers in the hydrogel affected the metal binding capacity of the hydrogel. The recovery of metal ions was also investigated in acid media. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Hexafunctional poly(propylene glycol) based hydrogels for the removal of heavy metal ions

Two types of degradable poly(propylene glycol) (PPG) hydrogels that are suitable for the absorption of heavy metals have been presented. The PPG‐O‐P(O)Cl₂ fragments obtained by treating hexafunctional PPG with phosphorous oxychloride (POCl₃) react with 1,3‐propanediamine (PDA; Gel‐1 ) or PDA together with 1,2‐ethanedithiol ( Gel‐2 ), to yield cross‐linked and water‐swellable hydrogels in a one‐pot method. This protocol for the fabrication of PPG hydrogels exhibits promising advantages over prior methods including a short reaction time, mass‐production, easy separation, and high yield. A series of heavy metal ions were employed to test the adsorptive properties of the hydrogels. Gel‐2 shows better adsorption capacity than Gel‐1 for all the metal ions and the metal ions adsorption efficiency of the two types of hydrogels is in the order of Fe(III) > Pb(II) > Cd(II) > Zn(II) > Cu(II) > Ni(II) > Co(II) > Hg(II). The amounts of metal ions adsorbed increases with metal ion concentration and hydrogel dosage, but decreases with temperature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40610.     

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 some hazardous materials from their solutions using active carbon‐filled poly vinyl alcohol/N‐vinyl pyrrolidone membrane subjected to freeze–thawing and gamma irradiation

Carbon membrane consisting of a mixture of powdered activated carbon and poly vinyl alcohol/N‐vinyl pyrrolidone was made by single freezing and thawing followed by gamma‐ray irradiation. The prepared membrane was characterized by X‐ray diffraction, scanning electron microscopy, and gel content. The membrane was applied for adsorption of some hazardous wastes (acid dye, basic dye, heavy metal ions such as Co and Ni, dichromate anion, and phenols) from their solutions. From the results, it was found that the prepared membrane possesses greater efficiency toward removal of heavy metal ions than powdered activated carbon, whereas their adsorption capacity toward dyes and phenol is almost the same as active carbon. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nonionic water‐soluble polymer: Preparation,characterization, and application of poly(1‐vinyl‐2‐pyrrolidone‐co‐hydroxyethylmethacrylate) as a polychelatogen

The free‐radical copolymerization of water‐soluble poly(1‐vinyl‐2‐pyrrolidone‐co‐hydroxyethylmethacrylate) was carried out with a feed monomer ratio of 75:25 mol %, and the total monomer concentration was 2.67M. The synthesis of the copolymer was carried out in dioxane at 70°C with benzoyl peroxide as the initiator. The copolymer composition was obtained with elemental analysis and ¹H‐NMR spectroscopy. The water‐soluble polymer was characterized with elemental analysis, Fourier transform infrared, ¹H‐ and ¹³C‐NMR spectroscopy, and thermal analysis. Additionally, viscosimetric measurements of the copolymer were performed. The thermal behavior of the copolymer and its complexes were investigated with differential scanning calorimetry (DSC) and thermogravimetry techniques under a nitrogen atmosphere. The copolymer showed high thermal stability and a glass transition in the DSC curves. The separation of various metal ions by the water‐soluble poly(1‐vinyl‐2‐pyrrolidone‐co‐hydroxyethylmethacrylate) reagent in the aqueous phase with liquid‐phase polymer‐based retention was investigated. The method was based on the retention of inorganic ions by this polymer in a membrane filtration cell and subsequent separation of low‐molar‐mass species from the polymer/metal‐ion complex formed. Poly(1‐vinyl‐2‐pyrrolidone‐co‐hydroxyethylmethacrylate) could bind metal ions such as Cr(III), Co(II), Zn(II), Ni(II), Cu(II), Cd(II), and Fe(III) in aqueous solutions at pHs 3, 5, and 7. The retention percentage for all the metal ions in the polymer was increased at pH 7, at which the maximum retention capacity could be observed. The interaction of inorganic ions with the hydrophilic polymer was determined as a function of the pH and filtration factor. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 178–185, 2006     

Spectroscopic and thermal studies of poly[(N‐vinylimidazole)‐co‐(maleic acid)] hydrogel and its quaternized form

BACKGROUND: In this study, poly[(N‐vinylimidazole)‐co‐(maleic acid)] (poly(VIm/MA)) hydrogels were prepared by γ‐irradiation of ternary mixtures of N‐vinylimidazole–maleic acid–water using a ⁶⁰Co γ‐source. Spectroscopic and thermal analyses of these hydrogels as a function of protonation showed that the results are consistent with the existence of an H‐bridged complex when the imidazole rings are partially protonated. Finally, the efficiency and binding trends of Cu²⁺, Co²⁺, Cd²⁺ and Pb²⁺ ions with both protonated and unprotonated poly(VIm/MA) hydrogels were determined. RESULTS: Gelation of 90% was reached at around 180 kGy dose at the end of irradiation. The poly(VIm/MA) hydrogels synthesized were further protonated in HCl solutions with different concentrations. Hydrogels originally showed 450% volumetric swelling; this ratio reached 1900% after protonation at pH = 5.0. Fourier transform infrared spectral changes in the ⁺N? H stretching region (3200–3600 and 1173 cm^?1) and the ring mode deformation at 915 cm^?1 are consistent with the formation of an H‐bridged complex between the protonated and unprotonated imidazole rings upon partial protonation. Similar changes were obtained from NMR spectra of both the protonated and unprotonated forms of the hydrogels. CONCLUSION: Protonated and unprotonated hydrogels have been used in heavy metal ion adsorption studies for environmental purposes. Adsorption decreased with decreasing pH value due to the protonation of the VIm ring. The adsorption of Me²⁺ ions decreased in the order Cu²⁺ > Co²⁺ > Cd²⁺ > Pb²⁺, which is related to the complexation stability as well as the ionic radius of the metal ions. These results show that P(VIm/MA) hydrogels can be used efficiently to remove heavy metal ions from aqueous solutions. However, the protonated form is a bad choice for heavy metal ion adsorption due to electrostatic repulsion forces; it can nevertheless be assumed to be a good choice for anion adsorption from environmental waste water systems. Copyright © 2007 Society of Chemical Industry     

Study on the synthesis,characterization, and sorption of some metal ions on gelatin‐ and acrylamide‐based hydrogels

Graft copolymers and networks of gelatin were synthesized with three acrylamides (acrylamide, 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid, and N‐iso‐propylacrylamide) by using a redox initiator system consisting of ammonium peroxysulfate–ferrous ammonium sulfate in either the absence or the presence of a crosslinker (N,N‐methylene bisacrylamide) at two temperatures. Characterization of synthesized polymers was studied by FTIR and thermal studies to investigate evidence of grafting or interpenetrating network formation and to investigate the effect of reaction conditions and crosslinker concentration on the properties of synthesized polymers. Detailed investigation into water‐uptake properties of these hydrogels was carried out as a function of time, temperature, and pH. The inherent properties of the monomer incorporated onto gelatin collectively act as determinant of the water‐absorption behavior of the hydrogels. Sorption of Fe⁺², Cr⁺⁶, and Cu⁺² ions from their aqueous solutions was also studied on select hydrogels, where it was observed that metal ions are sorbed by effective partitioning between hydrogels and solution phase and apart from the nature of metal ions, and structural aspects of hydrogels also determine the quantum of metal ion uptake. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3856–3871, 2003     

Acrylonitrile/acrylamidoxime/2‐acrylamido‐2‐ methylpropane sulfonic acid‐based hydrogels: Synthesis,characterization and their application in the removal of heavy metals

Crosslinked acrylonitrile/acrylamidoxime/2‐acrylamido‐2‐methylpropane sulfonic acid (AN/AAx/AMPS)‐based hydrogels were prepared by free radical crosslinking solution polymerization technique. The chemical structures of the hydrogels were characterized by FT‐IR analysis. The morphology of the dry hydrogel sample was examined by scanning electron microscope (SEM). These hydrogels were used for the removal of Cd(II), Cu(II), and Fe(III) ions from their aqueous solutions. The influence of the uptake conditions such as pH, time and initial feed concentration on the metal ion binding capacity of hydrogel was also tested. The selectivity of the hydrogel towards the different metal ions tested was arranged in the order of Cd(II) > Fe(III) > Cu(II). It was observed that the specific interaction between metal ions and ionic comonomer in the hydrogel affected the metal binding capacity of the hydrogel. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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 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     

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