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 0.1–0.2 M CuCl₂ and 0–0.3 M 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 14.8 mg cm⁻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 “raspberry-like” or “confeito-like” gold microspheres under the condition of less than 1.5 M of Cl⁻ ion and over 0.013 M 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.