Preparation And Performance Of Themo-sensitive Hydrogel For Ranium Adsorption

Absorption of uranium from aqueous solutions with environmentically friendly andeconomic methods has great scientific value and realistic significance. Thermosensitivesmart gel, which could control the process of adsorption and desorption of uranium, wasprepared by introducing chitosan (CS) as adsorption component and N_-Isopropylacrylamide (NIPAAm) as thermosensitive component with IPN、porous techniques andion-imprinted techniques (IIT). The prepared gels were characterized by FTIR and SEManalysis. The kinetic, thermodynamic adsorption and adsorption isotherms of U(VI) ionswere studied in a batch adsorption experiments.Thermo-sensitive semi-inter-penetrating network (semi-IPN) hydrogels were preparedby introducing CS as a metal ion receptor into the poly(N_-isopropylacrylamide)(PNIPAAm) hydrogels with an IPN technique. The swelling behavior of the semi-IPNhydrogels under different temperatures was studied. Feasibility of U(VI) sorption usingthe prepared hydrogels were investigated at different optimized conditions. The kineticstudy demonstrated that the pseudo-first-order model correlated with the experimentaldata better than the pseudo-second-order model examined. To discuss the mechanism ofadsorption of uranium(VI) ions on the semi-IPN hydrogels at temperature above andbelow the lower critical solution temperature (LCST), Langmuir and Freundlichadsorption models were applied to describe the isotherms at293and323K. Theadsorption results at different temperature showed that the PNIPAAm/CS hydrogelsadsorbed UO22+ions at lower temperature. Thermodynamic parameters such as enthalpychange (ΔH), entropy change (ΔS), free energy change (ΔG) were determined. Thenegative values of ΔH and ΔS indicated that the spontaneous nature and exothermicprocess of the U(VI) adsorption. The increase in the value of ΔG with a rise intemperature showed that the sorption was more favorable to low temperature.Porous poly(N_-isopropylacrylamide)/chitosan IPN were prepared by suspendedemulsion polymerization to improve the adsorption ability of uranium. The porous IPN hydrogels were characterized by FTIR and SEM analysis. The swelling behavior,temperature sensitivity, pH sensitivity were investigated. The results indicated that theporous IPN hydrogels exhibited pH and temperature-sensitivity. And the uraniumadsorption onto porous PNIPAAm/CS increased obviously. At303K,2h, the maximunadsorption amount was115mg/g. The behavior of the porous hydrogels towardUranium(VI) at different temperatures were studied, the result showed that the uraniumadsorption amount decreased as temperature increased.And at LCST, the hydrogel hadmaximum adsorption amount.Ion imprinted technology was applied widely in industrial analysis, ion imprintedpolymer has high adsorption capacity and selectivity. Therefore, uranium imprintedPNIPAAm/CS semi-IPN hydrogels were prepared by IIT．The adsorption capacity for theuranium(VI) ions of the hydrogels were systematically studied in this paper. The resultsshowed that the sorption equilibrium was achieved in6h and the maximum sorption ofuranium(VI) imprinted polymer was about89mg/g.