Uranyl ion adsorptivity of N-vinyl 2-pyrrolidone/acrylonitrile copolymeric hydrogels containing amidoxime groups

Summary N-vinyl 2-pyrrolidone (VP) / Acrylonitrile (AN) copolymeric hydrogels were synthesized by using γ-radiation and amidoximated for the purpose of uranyl ion adsorption. Optimum amidoximation time was determined by following the uranyl ion, UO₂ ²⁺, adsorption capacity. The adsorption of amidoximated copolymers was studied from different uranyl ion solutions (1000–1850 ppm). The results of all adsorption studies showed that the interaction between UO₂ ²⁺ and amidoxime groups comply with Langmuir type isotherm. The adsorption capacity was found as 0.54 g UO₂ ²⁺ /g dry amidoximated copolymeric hydrogels. From the stoichiometric calculations, it was found that the bonding between UO₂ ²⁺ and amidoxime groups is 1 to 4. Received: 7 September 1999/Revised version: 21 February 2000/Accepted: 18 March 2000     

Synthesis,characterization, metal sorption,and biological activity of poly(N‐heterocylic acrylamide)

N‐heterocyclic acrylamide monomers were prepared and then transferred to the corresponding polymers to be used as an efficient chelating agent. Polymers reacted with metal nitrate salts (Cu²⁺, Pb²⁺_, Mg²⁺, Cd²⁺, Ni²⁺, Co²⁺_, Fe²⁺) at 150°C to give metal‐polymer complexes. The selectivity of the metal ions using prepared polymers from an aqueous mixture containing different metal ion sreflected that the polymer having thiazolyl moiety more selective than that containing imidazolyl or pyridinyl moieties. Ion selectivity of poly[N‐(benzo[d]thiazol‐2‐yl)acrylamide] showed higher selectivity to many ions e.g. Fe³⁺, Pb²⁺, Cd²⁺, Ni²⁺, and Cu²⁺. While, that of poly[N‐(pyridin‐4‐yl)acrylamide] is found to be high selective to Fe³⁺ and Cu²⁺ only. Energy dispersive spectroscopy measurements, morphology of the polymers and their metallopolymer complexes, thermal analysis and antimicrobial activity were studied. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42712.     

Formation of thermosensitive copolymer beads having phosphinic acid groups and adsorption ability for metal ions

Hydrophilic thermosensitive copolymer beads having phosphinic acid groups were prepared by suspension copolymerization of acryloyloxypropyl n‐octylphosphinic acid (APPO), N‐isopropyl acrylamide (NIPAAm), and tetraethyleneglycol dimethacrylate (4G). The thermosensitivity and the adsorption ability of the copolymer beads for metal ions beads were studied. The APPO‐NIPAAm‐4G copolymer beads were obtained in a good yield by suspension copolymerization of monomers (APPO, NIPAAm, and 4G) dissolved in chloroform, in a saturated Na₂SO₄ aqueous solution in the presence of surfactant and MgCO₃. The APPO‐NIPAAm‐4G copolymer beads had higher adsorption ability for lanthanide metal ions (Eu³⁺, Sm³⁺, Nd³⁺, or La³⁺) than for main transition metal ions (Cu²⁺, Ni²⁺, or Co²⁺). Furthermore, it was also found that the APPO‐NIPAAm‐4G copolymer beads had selective adsorption ability between lanthanide metal ions, and the order of adsorption ability for lanthanide metal ions was as follows: Eu³⁺ > Sm³⁺ > Nd³⁺ > La³⁺. The selective adsorption for these metal ions from their mixed solutions was performed by both a batch method and a column method. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 449–460, 2006     

Stability constants of amidoximated chitosan‐g‐poly(acrylonitrile) copolymer for heavy metal ions

Amidoximated chitosan‐g‐poly(acrylonitrile) (PAN) copolymer was prepared by a reaction between hydroxylamine and cyano group in chitosan‐g‐PAN copolymer prepared by grafting PAN onto crosslinked chitosan with epychlorohydrine. The adsorption and desorption capacities for heavy metal ions were measured under various conditions. The adsorption capacity of amidoximated chitosan‐g‐PAN copolymer increased with increasing pH values, and was increased for Cu²⁺ and Pb²⁺ but a little decreased for Zn²⁺ and Cd²⁺ with increasing PAN grafting percentage in amidoximated chitosan‐g‐PAN copolymer. In addition, desorption capacity for all metal ions was increased with increasing pH values in contrast to the adsorption results. Stability constants of amidoximated chitosan‐g‐PAN copolymer were higher for Cu²⁺ and Pb²⁺ but lower for Zn²⁺ and Cd²⁺ than those of crosslinked chitosan. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 469–476, 1999     

Study of heavy metal ion absorbance by amidoxime group introduced to cellulose‐graft‐polyacrylonitrile

Amidoximated grafted cellulose was obtained by reacting hydroxylamine and cellulose‐graft‐polyacrylonitrile (C‐g‐PAN), prepared by KMnO₄/citric acid redox system, and the resultant amidoximated grafted cellulose was characterized by scanning electron microscope (SEM), solid‐state NMR, FTIR, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and elemental analysis. The highest value of amidoxime content in the grafted sample was 2.42 mmol/g. The adsorption efficiencies of amidoximated grafted cellulose have been evaluated with studying different adsorption conditions. Amidoximated sample with amidoxime content 2.42 mmol/g showed high ability to adsorb the metal ions from the aqueous solutions as high as 1.7 mmol/g, 1.6 mmol/g, and 0.84 mmol/g for Co²⁺, Cu²⁺, Ni²⁺ ions, respectively, at the highest original metal ion concentration. These values are about three times larger than previous studies. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

Competitive removal of heavy metal ions by cellulose graft copolymers

The effect of composition of graft chains of four types cellulose graft copolymers on the competitive removal of Pb²⁺, Cu²⁺, and Cd²⁺ ions from aqueous solution was investigated. The copolymers used were (1) cellulose‐g‐polyacrylic acid (cellulose‐g‐pAA) with grafting percentages of 7, 18, and 30%; (2) cellulose‐g‐p(AA–NMBA) prepared by grafting of AA onto cellulose in the presence of crosslinking agent of N,N′‐methylene bisacrylamide (NMBA); (3) cellulose‐g‐p(AA–AASO₃H) prepared by grafting of a monomer mixture of acrylic acid (AA) and 2‐acrylamido‐2‐methyl propane sulphonic acid (AASO₃H) containing 10% (in mole) AASO₃H; and (4) cellulose‐g‐pAASO₃H obtained by grafting of AASO₃H onto cellulose. The concentrations of ions which were kept constant at 4 mmol/L in an aqueous solution of pH 4.5 were equal. Metal ion removal capacities and removal percentages of the copolymers was determined. Metal ion removal capacity of cellulose‐g‐pAA did not change with the increase in grafting percentages of the copolymer and determined to be 0.27 mmol metal ion/g_copolymer. Although the metal removal rate of cellulose‐g‐p(AA–NMBA) copolymer was lower than that of cellulose‐g‐pAA, removal capacities of both copolymers were the same which was equal to 0.24 mmol metal ion/g_copolymer. Cellulose did not remove any ion under the same conditions. In addition, cellulose‐g‐pAASO₃H removed practically no ion from the aqueous solution (0.02 mmol metal ion/g_copolymer). The presence of AASO₃H in the graft chains of cellulose‐g‐p(AA–AASO₃H) created a synergistic effect with respect to metal removal and led to a slight increase in metal ion adsorption capability in comparison to that of cellulose‐g‐pAA. All types of cellulose copolymers were found to be selective for the removal of Pb²⁺ over Cu²⁺ and Cd²⁺. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2034–2039, 2003     

Kinetic and thermodynamic studies of adsorption of Cu2+ and Pb2+ onto amidoximated bacterial cellulose

Removal of Cu²⁺ and Pb²⁺ from aqueous solutions by adsorption onto amidoximated bacterial cellulose (Am-BC) was investigated. The effects of pH, initial concentration, contact time and temperature were studied in batch experiments. The pseudo-first and pseudo-second orders and intraparticle diffusion equation were used to evaluate the kinetic data and the constants were determined. The experimental data fits well to the pseudo-second order kinetic model, which indicates that the chemical adsorption is the rate-determining step, instead of mass transfer. The equilibrium adsorption data were described by the Langmuir, Freundlich, and Temkin isotherms. The Am-BC showed a better fit to the Langmuir isotherm. The separation factor (R _L ) revealed the favorable nature of the isotherm. The thermodynamic parameters (ΔH _ads⁰, ΔS _ads⁰, ΔG _ads⁰) for Cu²⁺ and Pb²⁺ adsorption onto Am-BC were also determined from the temperature dependence. The values of enthalpy and entropy indicated that this process was spontaneous and exothermic. The experimental studies indicate that Am-BC would be a potential effective adsorbent to remove the metal ions from wastewater.     

Use of amidoximated acrylonitrile/N‐vinyl 2‐pyrrolidone interpenetrating polymer networks for uranyl ion adsorption from aqueous systems

Poly(N‐vinyl 2‐pyrrolidone) (PVP)/acrylonitrile (AN) interpenetrating polymer networks (IPNs) were synthesized and amidoximated for the purpose of uranyl ion adsorption. The adsorption of amidoximated IPNs was studied from different uranyl ion solutions (850, 1000, 1200, 1400, and 1600 ppm). The result of all our adsorption studies showed that the bonding between UO‐amidoxime groups complied with the Langmuir‐type isotherm. The adsorption capacity was found as 0.75 g UO/g dry amidoximated IPN. In order to increase the UO ion adsorption capacity the amidoximated IPN was treated with alkali, but no significant increase could be observed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2324–2329, 2001     

Silica nanoparticles modified with a Schiff base ligand: An efficient adsorbent for Th(IV), U(VI) and Eu(III) ions

Modification of SiO₂ nanoparticles by salicylaldiminepropyl results in efficient adsorbents for removal of Th⁴⁺, UO ₂ ²⁺ and Eu³⁺ ions from aqueous solutions. The effect of parameters influencing the adsorption efficiency such as aqueous phase pH, contact time, initial metal ions concentration, adsorbent dosage and temperature dependency of the process was verified and discussed. Under optimal conditions (pH 5.5, adsorbent dosage 0.05 g, contact time 30 min. and 25 °C), thorium and uranyl ions (initial concentration 20 mg/l) were quantitatively removed from 20 ml of sample solution. Under such conditions 85% of europium ions was removed. Comparison of the adsorption efficiency of the studied modified nano-particles with those unmodified ones shows a shift for uptake of the metal ions vs. pH curves towards lower pH values by applying the modified adsorbents. In addition, a significant improvement of europium ions adsorption was observed by using the modified nanoparticles. Kinetics of the process was studied by considering a pseudo second-order model. This model predicts chemisorption for the adsorption mechanism. Freundlich, Langmuir and Temkin models were suitable for describing the equilibrium data of Th⁴⁺, UO₂ ²⁺ and Eu³⁺ adsorption process, respectively. Thermodynamic investigation reveals the adsorption process of the studied ions is entropy driven.     

Adsorption of Cu2+ ions with poly(N‐isopropylacrylamide‐co‐methacrylic acid) micro/nanoparticles

Chelation efficiency of stimuli‐responsive poly(N‐iospropylacrylamide‐co‐methyacrylic acid) (PNIPAAm‐MAA) nanoparticles with Cu²⁺ ions from CuSO₄·5H₂O solution and from wood treated with copper‐based preservatives was studied. It was shown that particle size played a very important role in the adsorption process. The nano‐scale particles showed much improved Cu ion adsorption efficiency, compared with the micro hydrogels. The amount of Cu ion adsorption increased with increase of MAA ratio in copolymers and adsorption efficiency decreased with increased particle size. Furthermore, the adsorption amount varied with adsorption temperature at temperatures both below and above the corresponding low critical solution temperature (LCST). The high adsorption efficiency of Cu ions by PNIPAAm‐MAA polymer particles provides an effective technique for recovering metal ions (e.g., Cu²⁺) from wood treated with metal‐based preservatives. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Behavior of acrylic acid–itaconic acid hydrogels in swelling,shrinking, and uptakes of some metal ions from aqueous solution

An experimental research of the absorption properties of metal ions onto synthetic hydrogel obtained by solution polymerization of acrylic acid and itaconic acid in presence of N,N′‐methylenebisacrylamide as crosslinking agent was carried out. The swelling behavior in aqueous salt solutions was studied as a function of divalent cation concentration (Cu²⁺, Zn²⁺, Ni²⁺, Co²⁺, Cd²⁺, Pb²⁺, Hg²⁺) in the external solution ranging from 10^?5 to 1M, at 25°C. The ability of these hydrogels to bind cations was measured at different pH values and metal ion concentrations. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 530–536, 2003     

Removal of Cd2+, Cu2+, Ni2+, and Pb2+ ions from aqueous solutions using tururi fibers as an adsorbent

This work investigates the removal of Cd²⁺, Cu²⁺, Ni²⁺, and Pb²⁺ ions from aqueous solutions using tururi fibers as an adsorbent under both batchwise and fixed‐bed conditions. It was found that modification of the tururi fibers with sodium hydroxide increased the adsorption efficiencies of all metal ions studied. The fractional factorial design showed that pH, adsorbent mass, agitation rate, and initial metal concentration influenced each metal adsorption differently. The kinetics showed that multi‐element adsorption equilibria were reached after 15 min following pseudo‐second‐order kinetics. The Langmuir, Freundlich, and Redlich–Peterson models were used to evaluate the adsorption capacities by tururi fibers. The Langmuir model was found to be suitable for all metal ions. Breakthrough curves revealed that saturation of the bed was reached in 160.0 mL with Cd²⁺ and Cu²⁺, and 52.0 mL with Ni²⁺ and Pb²⁺. The Thomas model was applied to the experimental data of breakthrough curves and represented the data well. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40883.     

Synthesis of a polyacrylamidoxime chelating fiber and its efficiency in the retention of palladium ions

A chelating fibrous polymer with metal complexing ability was prepared by partial conversion of the nitrile groups of melana (an acrylonitrile‐based synthetic fiber) into amidoxime groups ? C(NH₂) = NOH using a solution of 3% hydroxylamine in methanol by refluxing at 80°C. The molar ratio of NH₂OH/CN and the reaction time were adjusted to values of 0.9 and 2 h, respectively. The amidoximated polyacrylonitrile fiber with a 2.89 meq/g ion‐exchange capacity functions as an efficient chelating adsorbent for palladium ions. The pH dependence, the contact time, and the temperature of palladium ion retention from a model solution on amidoximated acrylic fiber were studied. The fibrous chelating adsorbent exhibited high affinity for palladium ions in acidic solution (pH = 2–6) at high temperature (50–60°C). The values of parameters q_m and K_L (from the Langmuir equation) determined at different temperatures of adsorption and the thermodynamic quantities ΔG, ΔH, and ΔS were calculated. The adsorbed palladium ions can be quantitatively desorbed by elution with a 0.3% hydrochloric solution of thiourea. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3730–3735, 2004     

Preparation and adsorption properties of poly(N‐vinylformamide/acrylonitrile) chelating fiber for heavy metal ions

In this article we report a new chelating fiber that was prepared from a hydrolyzate of poly(N‐vinylformamide/acrylonitrile) by a wet‐spinning method. This fiber contains chelating groups, such as amidine groups, amino groups, cyano groups, and amide groups, with high densities. We examined the chelating abilities for several metal ions with this fiber, and present the morphological merit of the fibrous product compared with the globular resin. Based on the research results, it is shown that the fiber has higher binding capacities and better adsorption properties for heavy metal ions than the resin. The pH value of the metal ion solution shows strong influences on the adsorption of the metal ions. The maximum adsorption capacities of the fiber for Cu²⁺, Cr³⁺, Co²⁺, Ni²⁺, and Mn²⁺ are 112.23, 88.11, 141.04, 108.06, and 73.51 mg/g, respectively. In mixed metal ions solution, the fiber adsorbs Cr³⁺, Cu²⁺ and Co²⁺ efficiently. The adsorbed metal ions can be quantitatively eluted by hydrochloric acid. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1378–1386, 2002     

ION EXCHANGE BEHAVIOUR OF CHELATING RESIN DOWEX A-1WITH ACTINIDES AND LANTHANIDES

Adsorption studies of several actinides and lanthanides have been carried out by chelating ion exchange resin Dowex A-1. The metal ions studied were Pu⁴⁺, Zr⁴⁺, UO₂ ⁺⁺, Am³⁺, Cm³⁺, Bk³⁺, Cf³⁺, Eu³⁺, and Tm³⁺. The separation factors between consecutive trivalent actinides and between Am(III) and Eu(III) have been evaluated. Mechanism of adsorption of actinides and lanthanides from different aqueous media has been discussed. An ion exchange procedure for the separation of Pu⁴⁺ and UO₂ ⁺⁺ has been developed using this resin.     

Electron Beam Grafted Polymer Adsorbent for Removal of Heavy Metal Ion from Aqueous Solution

Abstract

An electron beam grafted adsorbent was synthesized by post irradiation grafting of acrylonitrile (AN) on to a non‐woven thermally bonded polypropylene (PP) sheet using 2 MeV electron beam accelerator. The grafted poly(acrylonitrile) chains were chemically modified to convert a nitrile group to an amidoxime (AMO) group, a chelating group responsible for metal ion uptake from an aqueous solution. The effect of various experimental variables viz. dose, dose rate, temperature, and solvent composition on the grafting extent was investigated. PP grafted with the amidoxime group (AMO‐g‐PP) was tested for its suitability as an adsorbent for removal of heavy metal ions such as Co²⁺, Ni²⁺, Mn²⁺, and Cd²⁺ from aqueous solution. Langmuir and Freundlich adsorption models were used to investigate the type of adsorption of these ions. The adsorption capacities of the adsorbent for the metal ions were found to follow the order Cd²⁺>Co²⁺>Ni²⁺>Mn²⁺. The kinetics of adsorption of these ions indicated that the rate of adsorption of Cd²⁺ was faster than that of other ions studied.     

Formation of thermosensitive water‐soluble copolymers with phosphinic acid groups and the thermosensitivity of the copolymers and copolymer/metal complexes

Thermosensitive and water‐soluble copolymers were prepared through the copolymerization of acryloyloxypropyl phosphinic acid (APPA) and N‐isopropyl acrylamide (NIPAAm). The thermosensitivity of the copolymers and copolymer/metal complexes was studied. The APPA–NIPAAm copolymers with less than 11 mol % APPA moiety had a lower critical solution temperature (LCST) of approximately 45°C, but the APPA–NIPAAm copolymers with greater than 21 mol % APPA moiety had no LCST from 25 to 55°C. The APPA–NIPAAm copolymers had a higher adsorption capacity for Sm³⁺, Nd³⁺, and La³⁺ than for Cu²⁺, Ni²⁺ and Co²⁺. The APPA–NIPAAm (10:90) copolymer/metal (Sm³⁺, Nd³⁺, or La³⁺) complexes became water‐insoluble above 45°C at pH 6–7, but the APPA–NIPAAm (10:90) copolymer/metal (Cu²⁺,Ni²⁺, or Co²⁺) complexes were water‐soluble from 25 to 55°C at pH 6–7. The temperature at which both the APPA–NIPAAm copolymers and the copolymer/metal complexes became water‐insoluble increased as the pH values of the solutions increased. The APPA–NIPAAm copolymers were able to separate metal ions from their mixed solutions when the temperature of the solutions was changed; this was followed by centrifugation of the copolymer/metal complexes after the copolymers were added to the metal solutions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 116–125, 2004     

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     

Competitive removal of Pb2+, Cd2+, and Zn2+ by poly(acrylamide‐co‐maleic acid) hydrogels/differential pulse polarographic determination

Poly(acrylamide‐co‐maleic acid) [P(AAm/MA)] hydrogels, with various compositions, were prepared from ternary mixtures of acrylamide (AAm)/maleic acid (MA)/water by using ⁶⁰Co γ‐rays. The effect of composition of these hydrogels, on the competitive removal of Pb²⁺, Cd²⁺, and Zn²⁺ ions from aqueous solution, was investigated. The hydrogel compositions and their adsorption behaviors were determined by use of differential pulse polarography, a very sensitive electroanalytical technique. It was observed that the external stimuli of pH, temperature, and ionic strength have an important role on the adsorption. The increments of MA content in P(AAm/MA) hydrogels caused a significant increase in the adsorption these ions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2401–2406, 2004