New Molecule Lets Electricity Replace Chemicals in Gold Recovery

Researchers at the University of Illinois Urbana-Champaign have designed a new molecule that lets electricity replace most of the chemical reagents typically needed to recover valuable metals, including gold, from electronic waste, mining streams and industrial waste. The findings, led by chemical and biomolecular engineering professor Xiao Su, were published in the journal ACS Energy Letters.

The work builds on a 2024 process from Su's group called electrochemically mediated liquid-liquid extraction, or e-LLE, which used electricity to replace many of the acids and bases needed for liquid-liquid extraction, a common technique for separating and purifying metals. That system still required additional chemical reagents to complete the extraction cycle.

The new molecule removes that remaining step. It is designed to selectively bind metal ions, carry a permanent electrical charge, and stay dissolved in the organic liquid used for extraction. "The new molecule has a permanent built-in charge that acts as electrolyte, letting the liquid conduct electric current," said postdoctoral researcher Deborah Schmitt, a co-author of the paper. "That's what allows the redox reactions to be driven by electricity instead of chemicals." Su said the molecule can now be charged so it binds the metal, carries it into the organic phase, and then releases it again when electricity is applied.

In laboratory tests, the researchers used the molecule to selectively recover gold from electronic-waste leachates, solutions created by dissolving valuable metals out of discarded electronics. Electrifying the process cut chemical consumption by one to two orders of magnitude while also simplifying the extraction cycle.

Gold served as the first demonstration, but graduate student and co-author Aderiyike Aguda said the same electrochemical platform could be adapted to recover other metals, such as platinum-group metals from spent automotive catalysts, by tailoring the extractant chemistry to the target metal. The study was funded by the U.S. Department of Energy's Office of Science, Basic Energy Sciences, and its Separation Science Program.