New poly(N-(hydroxymethyl)methacrylamide-1-allyl-2-thiourea) hydrogels prepared by radiation-induced polymerisation: Selective adsorption, recovery and pre-concentration of Pt(II) and Pd(II)

Poly(N-(hydroxymethyl)methacrylamide-1-allyl-2-thiourea) hydrogels, poly(NHMMA-ATU), which have highly open pore size and high swellability, were synthesized by gamma irradiation using 60Co-γ source at different radiation dose rates and in different 1-allyl-2-thiourea content in the ternary mixture of NHMMA-ATU-H2O. These hydrogels were used for specific platinum and palladium selectivity, recovery and pre-concentration from single and competitive media. It was observed that platinum and palladium adsorption capacities onto the hydrogels were also high at low pHs. Adsorption capacity of the hydrogels for platinum and palladium ions in acidic media around pH 0.5 were found to be about 477 and 407 mg g−1 dry hydrogels for Pt(II) and Pd(II). Adsorption of platinum and palladium ions onto the hydrogels was found to be very fast and also these hydrogels were showed extremely high selectivity to the platinum and palladium ions at pH 0.5 beside the extremely high concentration of the other transition and toxic metal ions. All matrix effects were easily eliminated adsorbing platinum and palladium ions onto the hydrogels at around pH 0.5 and desorbing into 3.0 M HCl solution containing 0.8 M thiourea because of the high specificity of these hydrogels to precious metal ions although the existing of the other metal ions at high concentration and at low pHs. Different amount of platinum spiked geological samples were analyzed for the method validation after discovered method applied and it was found that recovery of platinum was not less than 96.8%.