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 (XL) were found to be in the order of 212Pb (0.4 MBq kg-1) > 228Ac and 208Tl (0.3 MBq kg-1) > 226Ra and 212Bi (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 (ΔG < 0), the process was exothermic (ΔH < 0) thus increasing entropy (ΔS > 0). The composite was reused for four more times after regeneration without any detectable changes either in its structure or adsorptive capability. (author)