Environmentally-friendly process for recovering gold from Waste from Electrical and Electronic Equipment (WEEE or e-waste) [Technology Offer]

A gold leaching solution using environmentally-friendly chemistry, easy to implement and allowing an easy recovery of dissolved gold downstream of the process.

Gold extraction from waste electrical and electronic equipment (WEEE or e-waste) or from ores requires a leaching step in which metallic gold is solubilized in an oxidized form. Traditional hydrometallurgical processes use large amounts of water and toxic, hazardous or aggressive substances (cyanides, concentrated inorganic acids, aqua regia, etc.), posing risks to human health and the environment.       

This invention relates to gold leaching using a solution containing dissolved Au(III) in a deep eutectic solvent (DES) based on choline chloride (ChCl). DES are an emerging class of solvents compatible with green chemistry objectives, potentially made from non-toxic, biodegradable substances, possibly sourced from biomass. Although the leaching agent is expensive due to its gold content, one equivalent of injected Au(III) allows for the recovery of three equivalents of Au(I) in a reaction with excellent atomic efficiency and conversion. The invention can be easily adapted to other solvents.

   

• Environmentally-friendly & green process
• No use of harmful solvents (cyanide, mercury...)
• Rational use of water
• Excellent atomic efficiency & conversion and E factor

Due to the high market value of gold and public policies promoting metal recycling and recovery, the invention has significant economic potential. The proposed chemistry should be applicable for both WEEE and ores.

The inventors are members of the Laboratoire de Chimie des Surfaces, Interfaces et Nanomatériaux (ChemSIN) of the Université libre de Bruxelles (ULB) and of the Laboratoire de Chimie Analytique, de Physique Spatiale et Energétique (L@CAPSE) of the Université Norbert Zongo (UNZ) in Burkina Faso:

• ChemSIN has strong expertise in electrochemistry. Professor Claudine Buess-Herman, internationally recognized for her scientific contributions in interfacial electrochemistry, has led the laboratory for many years and developed innovative research themes on electrochemistry in non-conventional media (deep eutectic solvents, ionic liquids). Professor Thomas Doneux leads the interfacial electrochemistry unit at ChemSIN, developing research in bioelectrochemistry and electrodeposition.
• L@CAPSE conducts research in analytical chemistry and environmental chemistry to meet societal needs in Burkina Faso. Professor Moussa Bougouma, specializing in the synthesis and characterization of semiconductor materials, directs the Center for Metal Recovery and Valorization (CERVAM). Dr. Fousséni Soma completed a Ph.D. on the recovery of precious metals (Ag, Pd, Au) using environmentally-friendly chemistries.

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