Separation of uranium and thorium in aqueous solution using polyhydroxyethylmethacrylate-hydroxyapatite novel composite
Poly(hydroxyethylmethacrylate-hydroxyapatite) [P(HEMA-Hap)] composite was synthesized by free radical polymerization in aqueous solution. The adsorptive features of P(HEMA-Hap) composite were investigated for UO22+ and Th4+ using a range of pH, concentration, time, temperature, and ionic strength values. It was observed that P(HEMA-Hap) composite had high affinity to uranium and thorium ions and that the adsorption capacity of the composite increased in proportion to the amount of Hap content. Adsorption data obtained fitted well into the classical Lagmuir, Freundlich, and Dubinin-Radushkevich sorption models. Changes in the enthalpy and entropy values showed that the overall adsorption process was endothermic and spontaneous (Delta G < 0), as expected. The adsorption kinetics following the pseudo-second order model indicated that the rate-controlling step was chemical adsorption that occurred by ion exchange process. Reusability of the composite was also investigated, and it was found that the composite could be used at least five times.