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Porous acrylonitrile (AN)/methyl acrylate (MA) copolymer beads were prepared by suspended emulsion polymerization. The cyano groups in AN/MA copolymer beads were converted to amidoxime (AO) groups by reaction with hydroxylamine hydrochloride (NH(2)OH.HCl) to remove metal ions in aqueous solution. The untreated AN/MA and amidoximated AN/MA (AO AN/MA) copolymer beads were characterized by FTIR spectroscopy, SEM, and porous structural analysis. Both mesopores and macropores were presented in AN/MA and AO AN/MA copolymer beads. Qualitative experiments of adsorption were conducted to evaluate modified and unmodified resins on fixing Hg(2+), Ag(+), Cu(2+), Fe(3+) and Pb(2+) from aqueous solution using batch extractions. It was found that AO AN/MA copolymer beads have excellent adsorption capacities for Hg(2+), Ag(+) and Cu(2+), especially for Hg(2+), and it have good selectivity for Hg(2+). The equilibrium was established in 10h through adsorption kinetics study. The Langmuir model was much better than the Freundlich model to describe the isothermal process., ((c) 2009 Elsevier B.V. All rights reserved.)

Porous a crylonitrile (AN)/methyl acrylate (MA) copolymer beads were synthesized by suspended emulsion polymerization and amidoximated for the purpose of Ag+ adsorption. Optimum amidoximation temperature and time were determined by following the adsorption capacity for Ag+. The results showed that amidoximated AN/MA (AO AN/MA) with the amidoximation temperature 70°C and amidoximation time 20 hr had a relatively higher adsorption capacity for Ag+. The effect of pH on adsorption for Ag+ was studied; the highest adsorption capacity presented at pH 5.0. Adsorption kinetics and isotherms of AO AN/MA copolymer beads for Ag+ were also investigated. The kinetics data indicated that the adsorption process was governed by the film diffusion and followed both pseudo-first-order and pseudo-second-order rate model. The isotherms indicated that adsorption capacities increased with equilibrium concentration and temperature. The Langmuir model and Sips model could describe the isothermal process. Thermodynamic analysis revealed that the adsorption behaviors of Ag+ ions on AO AN/MA could be considered as endothermic and physical sorption process. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Polyacrylonitrile (PAN) was grafted from surfaces of chloro-modified silica-gel with their surface chlorines as initiation sites, using an iron (III)-mediated surface-initiated atom transfer radical polymerization (ATRP) with activators regenerated by electron transfer (SI-ARGET ATRP) method. The graft reaction exhibits first-order kinetics with respect to the polymerization time in the low-monomer-conversion stage. The conversion of monomer ( C%) and the percentage of grafting (PG%) increased with increasing of the polymerizing time and reached 23 and 730% after a polymerizing time of 24 hr, respectively. Hydroxylamine (NH2OH·HCl) was used to modify the cyano groups of SG-g-PAN to obtain amidoxime (AO) groups. The AO SG-g-PAN was used to remove Hg2+. The adsorption kinetics indicated that the pseudo-second-order model was more suitable to describe the adsorption kinetics of AO SG-g-PAN for Hg2+. The adsorption isotherms demonstrated that Langmuir model was much better than Freundlich model to describe the isothermal process. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Differences between adsorption properties for Hg(II) and Au(III) on polystyrene-supported bis-8-oxyquinoline-terminated open-chain crown ether (PS-DB) were studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and the density functional theory (DFT) method. The comparison studies included kinetics, equilibriums and thermodynamics of the adsorption process. Pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data. The pseudo-second-order kinetic model provided a better correlation with the experimental data for Hg(II) in comparison with the pseudo-first-order model. While for Au(III), the conclusion was the reverse. Both the adsorption rate and adsorption amount at equilibrium for Hg(II) were greater than those for Au(III) ions, which was probably caused by the differences in form and volume between the two kinds of absorbed ions. Langmuir, Freundlich and Tempkin isotherm models were applied in the adsorption isotherm study. The results showed that the Langmuir and Tempkin isotherm models were more applicable in describing the processes. The thermodynamic parameters for the adsorption process such as free energy of adsorption (ΔG), enthalpy of adsorption (ΔH) and entropy of adsorption (ΔS) were calculated. The density functional theory (DFT) method was used to investigate the coordination geometries and the interactions between the metal ions with PS-DB. These results showed that the adsorption for Hg(II) was physisorption while that for Au(III) was chemisorption, which was also consistent with the data obtained from the Dubinin–Radushkevich (D–R) isotherm model and ΔH values. [Copyright &y& Elsevier]

Abstract: The adsorption properties of silica-gel supported hyperbranched polyamidoamine dendrimers (SiO2-G0–SiO2-G4.0) have been investigated by batch method. The effect of pH of the solution, contact time, initial Pb(II) ion concentration, temperature and coexisting metal ions have been demonstrated. The results indicated that the optimum pH value was 5. Adsorption kinetics was found to follow the pseudo-second-order model and controlled by film diffusion. The adsorption isotherms were fitted by Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models. Langmuir isotherm model was found to be more suitable to describe the equilibrium data, suggesting the uptake of Pb(II) ions by monolayer adsorption. From D–R isotherm model, the calculated mean free energy E demonstrated the adsorption processes occurred by chemical ion-exchange mechanism. FTIR analysis revealed that amine groups were mainly responsible for the adsorption of Pb(II) by amino-terminated adsorbents, while Cr groups also participated in the adsorption process of ester-terminated ones. The adsorbents can selectively adsorb Pb(II) from binary ion systems in the presence of Mn(II), Cu(II), Co(II), and Ni(II). Based on the results, it is concluded that SiO2-G0–SiO2-G4.0 had great potential for the removal of Pb(II) from aqueous solution. [Copyright &y& Elsevier]

Abstract: Using waste poly(p-phenylene terephthalamide) fibers (PPTA) as a starting material and novel Schiff base-containing adsorbent for metal ions, PPTA-Sal and its basification product PPTA-Sal(Na) were prepared via a series of chemical modification reactions. The structures of the modified fibers were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TG). Metal ions, such as Pb2+, Cu2+ and Ni2+, were chosen as representatives to determine the adsorption capacities of the modified fibers in aqueous solutions. The experimental results showed that the adsorption capacities for Pb2+ of PPTA-Sal and PPTA-Sal(Na) can reach 15.12 and 19.06mg/g respectively, which are much higher than the 10.56mg/g of the intermediate product amination PPTA (PPTA-NH2). The adsorption of Pb2+ on PPTA-Sal and PPTA-Sa(Na) followed well the pseudo second-order model. Langmuir and Freundlich models were employed to fit the isotherm adsorption of Pb2+ on PPTA-Sal and PPTA-Sal(Na), and the results revealed that both models were able to closely predict the experimental data. The Freundlich isotherm was slightly better than the Langmuir isotherm in describing the Pb2+ adsorption onto PPTA-Sal(Na), while the latter model was more suitable for fitting the data of Pb2+ adsorption onto PPTA-Sal. The adsorption capacities of PPTA-Sal and PPTA-Sal(Na) were compared using various adsorbents. [Copyright &y& Elsevier]

Abstract: A novel method of surface modification was developed via iron (III)-mediated atom transfer radical polymerization, with activators regenerated by electron transfer (ARGET ATRP) on the surfaces of polystyrene resin-supported N-chlorosulfonamide groups. The well-defined polyacrylonitrile (PAN) was grafted onto the surfaces of the polystyrene (PS). The graft reaction exhibited first-order kinetics with respect to the polymerization time in the low-monomer-conversion stage. The cyano group of PAN-g-PS was modified by NH2OH·HCl to yield amidoxime (AO) groups. The AO groups had been demonstrated to be an efficient Hg-specific sorbent, which can remove Hg2+ from solutions. No interference arose from common metal ions, such as Pd2+, Ag+, and Cu2+. Three adsorption–desorption cycles demonstrated that this resin is suitable for reuse without any considerable change in adsorption capacity. [Copyright &y& Elsevier]

Abstract: Two novel chelating resins, denoted as PS-DEG-3-AP and PS-TEG-3-AP, were obtained by inserting spacer ethylene oxide and ethylene sulfide, respectively, with 3-aminopyridine (3-AP) into polystyrene-co-divinylbenzene. Fourier transform-infrared spectra (FTIR) and elemental analysis were employed to characterize their structures. The adsorption properties of the resins for Hg(II), Ag(I), Fe(III), Pb(II), Co(II), Cu(II), Ni(II), Cd(II) and Zn(II) had been studied, and the results revealed that the resins had higher adsorption capacities and adsorption selectivity for Hg(II). The adsorption kinetics and adsorption isotherms of the resins for Hg(II) were also investigated. The adsorption data of Hg(II) on the resins were fitted well by the pseudo second-order kinetics. Langmuir and Freundlich models were used to describe Hg(II) adsorption isotherms on both resins. The adsorption mechanisms of PS-DEG-3-AP and PS-TEG-3-AP for Hg(II) were confirmed by X-ray photoelectron spectroscopy (XPS). Furthermore, five consecutive sorption–desorption cycles demonstrated that the resins were suitable for repeated use without considerable change in adsorption capacity. [ABSTRACT FROM AUTHOR]

Abstract: A novel inorganic–organic hybrid material silica gel chemically modified by triethylenetetraminomethylenephosphonic acid (denoted as GH-T-P) has been synthesized and characterized. Its adsorption properties GH-T-P for Au(III), Hg(II), Cu(II), Pb(II), Co(II), Zn(II), Ni(II), Cr(III) and Cd(II) have been investigated, and the research results revealed that GH-T-P has the best adsorption capacity for Au(III). Furthermore, the adsorption selectivity results of GH-T-P for Au(III) displayed that GH-T-P had excellent adsorption for Au(III) in binary ions systems, especially in the systems of Au(III)–Zn(II), Au(III)–Ni(II) and Au(III)–Cr(III). Langmuir and Freundlich isotherm models were applied to analyze the experimental data, and the best interpretation for the experimental data was given by the Langmuir isotherm equation. GH-T-P could reach to the saturation adsorption capacity within 2h, and its excellent adsorption capacity for Au(III) was 266.49mg/g when the initial solution concentration was 2.0mmol/L at 35°C. Moreover, the research revealed that its adsorption kinetics can be modeled by pseudo-second-order rate equation wonderfully, and the thermodynamic parameters ΔG, ΔH and ΔS were −20.79kJmol−1, 5.17kJmol−1, and 84.37JK−1 mol−1, respectively. Thus, this novel hybrid material silica gel chemically modified by triethylenetetraminomethylenephosphonic acid GH-T-P is favorable and useful for the uptake of Au(III), and the high adsorption capacity and good reproducibility make it a good promising candidate material for the precious metal uptake. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption behaviors of Hg(II) on adsorbents, chitosan functionalized by generation 1.0–3.0 of amino-terminated hyperbranched polyamidoamine polymers (denoted as CTS-1.0, CTS-2.0 and CTS-3.0, respectively), were studied. The optimum pH corresponding to the maximum adsorption capacities was found to be 5.0 for the three adsorbents. The experimental equilibrium data of Hg(II) on the three adsorbents were fitted to the Freundlich and the Langmuir models, and it is found that the Langmuir isotherm was the best fitting model to describe the equilibrium adsorption. The kinetics data indicated that the adsorption process of Hg(II) ions on CTS-1.0, CTS-2.0 and CTS-3.0 were governed by the film diffusion and followed pseudo-second-order rate model. Thermodynamic analysis and FTIR analysis revealed that the adsorption behaviors of Hg(II) ions on the three adsorbents could be considered as spontaneous, endothermic and chemical sorption process, resulting in their higher adsorption capacities at higher temperature. [Copyright &y& Elsevier]

Four kinds of silica-gel (SG)-supported diethylenetriamine (DETA) chelating resins SG-DETA-1, SG-DETA-2, SG-DETA-3, and SG-DETA-4 were prepared by functionalization of silica-gel via so-called “heterogeneous-direct-amination” (hetero-DA), “homogeneous-direct-amination” (homo-DA), “heterogeneous end-group protection” (hetero-EGP), and “homogeneous end-group protection” (homo-EGP) routes, respectively. These functionalized reactions on silica-gel were confirmed through elemental analysis, infrared spectroscopy, X-ray diffractometry, porous analysis, and thermogravimetry. Element analysis revealed that the direct-amination routes and homogeneous condition were more beneficial than the corresponding end-group protection routes and heterogeneous condition to the syntheses of chelating resins with high N content. Several metal ions, such as Ag+, Cu2+, Ni2+, Hg2+, Zn2+ and Pb2+, were chosen as representatives to investigate the relationship between adsorption capacities and N content of ligands onto the surface of silica-gel. The experiments results showed that all resins, SG-DETA-1, SG-DETA-2, SG-DETA-3 and SG-DETA-4, had a better adsorption for Hg2+ and Cu2+ than others. One conclusion should be drawn from the above compared experiments, that is, higher N content of silica-gel resins does not ensure a higher utilization ratio of N. [Copyright &y& Elsevier]

Abstract: Four kinds of silica-gel supported diethylenetriamine adsorbents with different structures, were prepared by so-called “heterogeneous-direct-amination” (hetero-DA), “homogeneous-direct-amination” (homo-DA), “heterogeneous end-group protection” (hetero-EGP), and “homogeneous end-group protection” (homo-EGP) methods, respectively. The obtained products were named SG-HE-dD, SG-HO-dD, SG-HE-pD and SG-HO-pD, respectively (where SG means silica-gel; HE means heterogeneous, HO means homogeneous, d means direct, p means protected and D means diethylenetriamine). Their structures were characterized by FT-IR, elemental analysis, porous structure analysis and thermogravimetric analysis. The adsorption capabilities of such adsorbents towards Hg(II) were studied and evaluated by static method. SG-HE-pD and SG-HO-pD showed higher performance towards Hg(II) adsorption than corresponding counterparts SG-HE-dD and SG-HO-dD, even though the former two possessed lower contents of diethylenetriamine (DETA). The kinetics data indicated that the adsorption process was governed by the film diffusion and followed pseudo-first-order rate model for SG-HE-dD, SG-HO-dD and SG-HE-pD and pseudo-second-order model for SG-HO-pD. The Langmuir model was applied to fit the experimental equilibrium data for all adsorbents. The end-group protection method exhibited its advantage in preparation of effective adsorbent for metal ions uptake compared to the direct-amination method. [Copyright &y& Elsevier]

Abstract: A series of insoluble chitosan (CTS) derivatives were prepared by grafting ester- and amino-terminated dendrimer-like polyamidoamine (PAMAM) into CTS using a divergent method by repeating two processes: (1) Michael addition of methyl acrylate (MA) to surface amino groups, and (2) amidation of the resulting esters with ethylenediamine (EDA). Their structures were characterized by infrared spectra (IR) and wide-angle X-ray diffraction (WAXD). The adsorption capabilities of the products for Au3+, Pd2+, Pt4+, Ag+, Cu2+, Zn2+, Hg2+, Ni2+, and Cd2+ were studied. The results showed that the products exhibited better adsorption capabilities for Au3+ and Hg2+ than for other metal ions, and the adsorption capabilities of amino-terminated products were higher than those of ester-terminated ones. Also it was observed that a high percentage of grafting of PAMAM into CTS does not ensure a high adsorption capacity. [Copyright &y& Elsevier]

Abstract: Two novel chelating resins were prepared by anchoring ethylenediamine to crosslinked polystyrene via a spacer containing sulfide. Their structures were characterized by Fourier transform-infrared spectra (FTIR) and scanning electron microscopy (SEM). Porous structure parameters of the resins were measured by ASAP 2020 using BET and BJH methods. Their adsorption capacities for several heavy metal ions especially Hg2+ were investigated. The results showed that for the two resins, the more N contents did not mean the better adsorption capacity and the saturated adsorption capacity of poly(2-ethylenediamidomercaptomethylstyrene) (PSM-EDA) for Hg2+ could reach to 3.0mmol/g at room temperature. Isothermal adsorptions of the resins for Hg2+ could be described by Langmuir formula. The adsorption mechanism of the resins for Hg2+, Cu2+ and Ag+ was confirmed by X-ray photoelectron spectroscopy (XPS) and FTIR. [Copyright &y& Elsevier]

Abstract: A series of ester- and amino-terminated dendrimer-like polyamidoamine (PAMAM) grafted silica-gel (SiO2-G0–SiO2-G4.0) was prepared with a divergent method by repeating two processes: (1) Michael addition of methyl acrylate (MA) to surface amino groups; and (2) amidation of the resulting esters with ethylenediamine (EDA) from γ-aminopropyl silica gel core. Their structures were characterized by FTIR, XRD, TG, porous analysis, and SEM. FTIR method was employed to monitor amidation reaction in order to judge the optimum reaction time. The results indicated it needed at least 5, 7, 8, and 9days for SiO2-G0.5, SiO2-G1.5, SiO2-G2.5, and SiO2-G3.5 to be converted into SiO2-G1.0, SiO2-G2.0, SiO2-G3.0 and SiO2-G4.0, respectively at 25°C. The porous structure analysis showed the BET surface area, BJH desorption average pore diameter and BJH desorption cumulative volume of pores for the products decreased after the series of grafting reactions. Au3+, Pd2+, Pt4+, Ag+, Cu2+, Zn2+, Hg2+, and Cd2+ were chosen as representatives to investigate the relationship between adsorption capacities and percentage of grafting of polymer onto the surface of silica-gel. The experiments showed that both ester- and amino-terminated dendrimer-like polyamidoamine (PAMAM) grafted silica-gel exhibited better adsorption capabilities for Au3+ and Pd2+ than for base metal ions Cu2+, Zn2+, Hg2+, and Cd2+ and noble metal ions Pt4+ and Ag+. One interesting conclusion could be drawn from the above investigation, that is, a high percentage of grafting of polymer onto the surface of silica-gel did not mean a high adsorption capacity. [Copyright &y& Elsevier]

Abstract: Two novel chelating resins, polystyrene supported G1.0 diethanolamine-typed dendrimer (PS-DEA) and G2.0 diethanolamine-typed dendrimer (PS-(DEA)2), were prepared by anchoring low-generations diethanolamine-typed dendrimer into crosslinked polystyrene in this paper. Fourier transform-infrared spectra (FTIR), scanning electron microscopy (SEM) and elemental analysis were employed to character their structures. The results of adsorption for metal ions showed that the resins had good adsorption capacities for Cu2+, Ag+ and Hg2+, especially PS-DEA for Cu2+. The adsorption kinetics and adsorption isotherms of PS-DEA for Cu2+ and PS-(DEA)2 for Hg2+ were studied. The results showed that the adsorption kinetics of the two resins can be modeled by pseudo second-order rate equation wonderfully and Langmuir and Freundlich equations could well interpret the adsorption of PS-(DEA)2 for Hg2+ and PS-DEA for Cu2+, respectively. The adsorption mechanism of the resins for Cu2+ was confirmed by X-ray photoelectron spectroscopy (XPS). [Copyright &y& Elsevier]

Abstract: A novel chelating resin containing S, N and O atoms (PSME–EDA) was synthesized by using poly(2-hydroxyethylmercaptomethylstyrene) (PSME) and diethanolamine (EDA) as materials. Its structure was characterized by elemental analysis, Fourier transform-infrared spectra (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The adsorption of the resin for Hg2+ was investigated. The saturated adsorption capacity of PSME–EDA for Hg2+ could reach to about 1.1mmol/g at 25°C when the initial Hg2+ concentration was 0.02mol/l. Some factors affecting the adsorption such as temperature, reaction time and ion concentration were also studied. The results showed that adsorption was controlled by liquid film diffusion. The increasing of temperature was beneficial to adsorption. The Langmuir model was better than the Freundlich model to describe the isothermal process. The values of ΔG, ΔH, and ΔS calculated at 25°C were −7.99kJmol−1, 22.5kJmol−1 and 34.4Jmol−1 K−1, respectively. The adsorption mechanism of PSME–EDA resin for Hg(II) was confirmed by X-ray photoelectron spectroscopy (XPS). [Copyright &y& Elsevier]