Bioleaching of Gold from Sulfidic Gold Ore Concentrate and Electronic Waste by Roseovarius tolerans and Roseovarius mucosus

Abstract

Gold bioleaching mediated by iodide oxidizing bacteria (IOB) has been proposed as a sustainable alternative to conventional technologies such as cyanidation. This study evaluated the ability of two IOB sourced from a commercial culture collection, <i>Roseovarius</i> (<i>R.</i>) <i>tolerans</i> DSM 11457^T and <i>R. mucosus</i> DSM 17069^T, to bioleach gold from electronic waste (e-waste) (1030 ppm gold) and sulfidic gold ore concentrate (45 ppm gold) using one-step, two-step and spent medium leaching at 1% pulp density over 10 days. Two-step bioleaching of ore concentrate resulted in the highest gold leaching yields (approximately ~100% and 34% for <i>R. tolerans</i> and <i>R. mucosus</i>, respectively), followed by spent medium leaching and one-step leaching. The yields remained low for e-waste with both strains (maximum 0.93% and 1.6% for <i>R. tolerans</i> and <i>R. mucosus</i>, respectively) and decreased over time, likely due to the instability of the solubilized gold at relatively low redox potentials (<300 mV vs. Ag/AgCl). Another limiting factor may be the partial inhibition of bacterial growth in the presence of the ore concentrate and e-waste. Therefore, future studies should evaluate the pre-treatment of the ore concentrate and e-waste to remove inhibitory and oxidant consuming compounds before bioleaching with IOB to optimize leaching yields.