Screening of Non-cyanide Leaching Reagents for Gold Recovery from Waste Electric and Electronic Equipment

Abstract

The importance of gold recycling from waste electronic and electrical equipment (WEEE) is continuously increasing due to raising gold demand and the need for new recycling methods for this complex waste. In state-of-the art processes gold is recovered in the copper route. In necessary pre-treatment steps, a significant loss of gold occurs. Furthermore, in this process the gold is bound for a longer time period in a copper phase and is separated in a mixture with other noble metals, which needs further treatment. A direct gold extraction from WEEE by selective leaching and precipitation would have many advantages. Due to raising social awareness of the ecological impacts of cyanidic gold extraction and environmental specifications, cyanide cannot be used as gold extractant in modern processes. Therefore, over the course of this study, two experimental sets have been conducted on each of six non-cyanide leaching reagents to test their feasibility and compare them against each other. Aqua regia and iodine/iodide leaching systems were the most successful reagents, yielding 100% of gold while showing very fast leaching rates. A comparison between the two successful reagents was carried out, with the results favoring iodine leaching due to its high selectivity for precious metals and reduced environmental impact.