GREEN CHEMISTRY EXTRACTION METHOD FOR RECOVERY OF GOLD IONS FROM CYANIDE WASTEWATERS

Abstract

In this study, the possibility of Au(III) ions recovery from cyanide solution by extraction in aqueous two-phase systems formed from polyethylene glycol (PEG) and (NH4)2SO4 inorganic salt, in presence of chloride ions as extracting agent, was analyzed in batch systems. Due to the non-toxic character of the components of extraction system, the Au(III) ions extraction in aqueous two-phase systems can be included in the category of green chemistry methods. The Au(III) extraction efficiency was examined as a function of several experimental parameters, such as molecular weight of PEG, salt solution pH and chloride ions extractant concentration, in order to find the optimal conditions. The experimental results have shown that the maximum extraction of Au(III) ions (> 89%) is obtained in aqueous two-phase systems prepared by PEG-6000, salt solution with pH of 3.15 and chloride ions concentration higher than 0.1 mol.L-1. These conditions were then used in case of Au(III) extraction from cyanide wastewater, when the experimental data have indicated that the Au(III) ions extraction is more efficient in presence of 0.1 mol Cl-.L-1 (> 85%), than in their absence (< 17%). The obtained results indicate that the aqueous two-phase systems have potential for the recovery of Au(III) ions from cyanide wastewaters, both due to its extraction performances, and green chemistry characteristics.