Recovery and pre-concentration of gold onto poly((N-(Hydroxymethyl)methacrylamide)-1-allyl-2-thiourea) hydrogels synthesized by gamma radiation

Poly((N-(Hydroxymethyl)methacrylamide)-1-allyl-2-thiourea) hydrogels, Poly(NHMMA-ATU), were synthesized by gamma radiation using Co-60 gamma 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. (c) 2006 Elsevier B.V. All rights reserved.