Gold Recovery Revolutionized by New Sponge Technology

A team of scientists from the National University of Singapore, collaborating with colleagues from Manchester University in the U.K. and Guangdong University of Technology in China, has engineered a novel sponge composed of graphene oxide and chitosan. This sponge is designed specifically for extracting gold from electronic waste.

Their findings, published in the Proceedings of the National Academy of Sciences, outline the development process and effectiveness of the sponge. Historically, the recovery of metals such as gold and silver from obsolete electronic devices has proven to be both challenging and environmentally harmful, often leading to low recovery rates and toxic byproducts.

The sponge represents a more cost-effective and environmentally friendly alternative to conventional extraction techniques, achieving much greater efficiency. The selected materials were chosen strategically; both have been previously utilized for metal recovery. Graphene is effective at absorbing ions, while chitosan, a natural biopolymer, acts as a strong reducing agent, aiding in the transformation of gold ions into solid gold.

To fabricate the composite, chitosan was allowed to self-assemble onto two-dimensional graphene flakes, creating binding sites for gold ions. After these ions were absorbed by the graphene, chitosan facilitated their conversion to solid gold, making the collection process both simple and efficient.

The research team evaluated their sponge with actual electronic waste sourced from a recycling company. This waste had been processed into a solution containing various materials, with an initial gold concentration of 3 ppm. Impressively, the sponge extracted around 17g/g of Au³⁺ ions and slightly more than 6 g/g of Au⁺, making it about ten times more effective than any existing extraction method.