Effects of pH, concentration and temperature on radionuclides sorption onto polyhydroxyethyl methacrylate-expanded perlite composite

Poly (hydroxyethylmethacrylate-expanded perlite) [P(HEMA-EP)], was synthesized and its adsorptive features were investigated for natural radionuclides (TI+, Ra2+, Bi3+, Ac3+ and Pb2+) in aqueous media at differing initial pH, initial radionuclides concentration and adsorption thermodynamics. The amounts of natural radionuclides at equilibrium were determined by gamma spectrometry. The Langmuir adsorption capacities (X-L) were found to be in the order of Pb-212 (0.4 MBq kg(-1)) > Ac-228 and Tl-208 (0.3 MBq kg(-1)) > Ra-226 and Bi-212 (0.2 MBq kg(-1)). These findings indicated that P(HEMA-EP) adsorbed natural radionuclides with high affinity. It was also demonstrated that the adsorption mechanism was spontaneous (Delta G < 0), the process was exothermic (Delta H < 0) thus increasing entropy (Delta S > 0). The composite was reused for four more times after regeneration without any detectable changes either in its structure or adsorptive capability.