Selective recovery of gold from acidic solutions using resins with methylenediphosphonate and carboxymethylphosphonate ligands

The polymeric resins with methylenediphosphonate and carboxy-methylphosphonate ligands in the ethyl ester form have been synthesized characterized and used in the removal of Au(III) from hydrochloric acid solutions. It has been found that they are able to adsorb as much as 130-166 mg Au/g of the resin at high concentration of the external solutions. At low concentrations affinity of resins towards gold is very good and the obtained distribution coefficient logarithm is in the range of 4.0-4.4 for the 1 x 10(-4) M Au(III) in 0.25-6.0 M hydrochloric acid solutions. Other metals chlorocomplexes such as Fe(III), Pd(II), Pt(II) and Ag(I) are removed to a lesser extent and the resins do not recognize Cu(II) chlorocomplexes. This allows for the use of the synthesized resins in the selective removal of Au(III) from the concentrated copper solution typically obtained in the processing of the electronic scrap. It has been possible to treat more than 1900 bed volumes of such solution (1 x 10(-4) M Au(III) and 1 x 10(-2) M Cu(II) in 3M HCl) obtaining sorption of 70 mg Au(III) on resin 1 with diphosphonate ligands. This resin has been effectively regenerated using 5 wt.% solution of thiourea in 0.5 M HCl.