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Abstract: Poly((N-(Hydroxymethyl)methacrylamide)–1-allyl-2-thiourea) hydrogels, Poly(NHMMA–ATU), were synthesized by gamma radiation using 60Co γ source at different irradiation doses and different ATU content in the irradiated monomer mixture. The swellability of the synthesized hydrogels was changed by irradiation doses and by the content of ATU in the irradiated mixture. These hydrogels were used for the specific gold recovery and pre-concentration from single gold ion solutions and from different natural samples. It has been observed that gold adsorption capacity onto the hydrogels was high at low pHs and reached maximum value at pH=0.5. Adsorption capacity of the hydrogels for gold at pH=0.5 was found to be about 698 mg g−1 dry hydrogels. Adsorption equilibrium time of gold ions onto the hydrogels was found to be very short and also these hydrogels were showed extremely high selectivity to the gold ions in acidic media when the concentration of the other metal ions were extremely higher than gold. Because of the high specificity of these hydrogels to gold beside the other metal ions at low pHs, all matrix effects were easily eliminated adsorbing gold onto the hydrogels and desorbing into 3 M HCl solution containing 0.8 M thiourea. These hydrogels were found to be highly open pore size. This property of the hydrogels make them attractive due to high adsorption capacity of gold ions on/in the hydrogels penetrating inside and react to all functional groups in the interior surface of the hydrogels. [Copyright &y& Elsevier]

Abstract: 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 407mgg−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 3.0M HCl solution containing 0.8M 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%. [Copyright &y& Elsevier]

Abstract: Poly(N-(hydroxymethyl)methacrylamide)-1-allyl-2-thiourea) hydrogels, poly(NHMMA-ATU), were synthesized by gamma radiation using 60Co γ source in the ternary mixture of NHMMA-ATU-H2O. These hydrogels were used for the specific gold, silver, platinum and palladium recovery, pre-concentration and matrix elimination from the solutions containing trace amounts of precious metal ions. Elimination of inorganic matrices such as different transition and heavy metal ions, and anions was performed by adjusting the solution pH to 0.5 that was the selective adsorption pH of the precious metal ions. Desorption of the precious metal ions was performed by using 0.8M thiourea in 3M HCl as the most efficient desorbing agent with recovery values more than 95%. In the desorption medium, thiourea effect on the atomic signal was eliminated by selecting proper pyrolysis and atomization temperatures for all precious metal ions. Precision and the accuracy of the results were improved in the graphite furnace-atomic absorption spectrometer (GFAAS) measurements by applying the developed matrix elimination method performing the adsorption at pH 0.5. Pre-concentration factors of the studied precious metal ions were found to be at least 1000-fold. Detection limits of the precious metal ions were found to be less than 10ngL−1 of the all studied precious metal ions by using the proposed pre-concentration method. Determination of trace levels of the precious metals in the sea-water, anode slime, geological samples and photographic fixer solutions were performed using GFAAS clearly after applying the adsorption–desorption cycle onto the poly(NHMMA-UTU) hydrogels. [Copyright &y& Elsevier]