Integrated methods for gold leaching and recovery from ore and electronic waste

Acutely toxic substances such as cyanide salts and mercury metal are commonly used in gold mining. Mercury amalgamation in artisanal gold mining is especially problematic and the largest source of mercury pollution on Earth. New strategies are needed that do not rely on cyanide and mercury for gold recovery. To address this problem, trichloroisocyanuric acid, activated by a halide catalyst, was used to oxidatively dissolve gold metal. A polysulfide polymer sorbent was then used to selectively bind the gold, even in complex mixtures. The gold can be recovered in high purity by pyrolyzing the sorbent. Alternatively, a recyclable polysulfide sorbent was made that can be depolymerized in its separation from gold. This material was synthesized using a novel photochemical ring-opening polymerization of a cyclic trisulfide. These integrated extraction and recovery methods were validated on ore, electronic waste, and other mixed-metal waste streams. Prospects for uptake are discussed.