A novel process for the production of gold micrometer-sized particles from secondary sources

Abstract

A novel method for the production of gold micrometer-sized particles from secondary sources is presented. The method consists of the leaching of gold using dimethyl sulfoxide (DMSO, (CH3)2SO) solutions containing copper chloride (CuCl2) followed by the precipitation of gold with hydrochloric acid (HCl). Gold was dissolved in a DMSO solution with 0.10.2M CuCl2 and 00.3M sodium chloride (NaCl) at 343 K. The precipitation of dissolved gold was performed by the addition of HCl, during which the effects of the concentration of the Cl- ion was investigated. It was found that the initial gold dissolution rate in DMSO solutions with CuCl2 was up to 14.8mgcm-2 h-1, which was larger than the rates obtained with other leaching methods, but smaller than the author's previous research using copper bromide (CuBr2) and potassium bromide (KBr). A gold recovery efficiency of up to 92.6% was obtained by precipitation with HCl solution. We obtained "raspberrylike" or "confeito-like" gold microspheres under the condition of less than 1.5M of Cl- ion and over 0.013M of dissolved gold. Our results demonstrated that a circulating system for gold leaching and recovery and production of functional material could be developed, which would offer a number of advantages, including eco-friendliness, easy operation, low costs, and minimization of chemical sludge production.