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ABSTRACT:The sorption behavior of Th(IV) and U(VI) species on two batch molds of radiation-induced polymerized unsaturated polyester beads containing 40 wt % styrene was investigated. The distribution coefficients of both ions on the polymeric sorbents were evaluated at 30°C using 10 Ϫ4M solution and found to be 271.9 and 469.8 mL/g on the first mold and 296 and 1189.2 mL/g on the second mold for Th(VI) and U(IV), respectively. Testing the sorption data using different theories provided evidence that the sorption data accurately fit the Langmuir, Freundlich, and D-R isotherms, indicating chemisorption occurred and that E, the mean sorption energy of thorium and uranium on the different molds of unsaturated polyester-styrene, was between 8.304 and 13.92 kJ/mol, reflecting the nature of the ion exchange. The thermodynamics of sorption were considered in order to evaluate ⌬H, ⌬S, and ⌬G. The data showed that the sorption process was spontaneous and exothermic.

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Removal of cesium, cobalt, and europium ions from radioactive waste solutions using poly-acrylamide based Ce(IV) phosphate material was investigated using both batch and fixed bed column techniques. The effect of pH, initial metal ion concentration, and temperature had been studied. Simple kinetic and thermodynamic models had been applied from which the mechanism of the process and the thermodynamic parameters were determined. The positive values of enthalpy change, DH, obtained for the three metal ions confirmed the endothermic nature of the sorption process and suggested that chemisorption is the predominant sorption mechanism. The high positive values found for the entropy change, DS, show the increased randomness at the solid/solution interface. The obtained negative values of free energy change, DG, indicating the feasibility and the spontaneous nature of the sorption processes. Breakthrough data were investigated in a fixed bed column at room temperature (298 K) under the effect of various process parameters like bed depth, flow rate, and initial ion concentration. The results showed that the overall bed capacity decreased with increasing flow rate and increased with increasing initial metal ion concentrations and bed depth.

Functionalized membranes were obtained by radiation-induced graft copolymerization (RIGP) of acrylamide-acrylic acid (AAm-AAc) and acrylamide-4-vinyl pyridine (AAm-4VP) binary monomers on both low-density polyethylene and polypropylene films. The supporting conditions as inhibitor concentration, irradiation dose comonomer compositions and concentrations were studied and optimized. The prepared membranes were characterized using SEM, DTA-TG, and FTIR. They proved that supporting the selected hydrogels on the base films have modified their structure and enhanced their thermal and mechanical characteristics. The sorption characteristics of Th(IV) and U(VI) on the different membranes were studied. The amount of ions sorbed at equilibrium was found to increase with increase in the degree of graft at certain conditions. The kinetics of sorption was also studied and found to obey the Lagergren and Morris-Weber kinetic models.

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