Electronics dumped in the trash (e-waste) can literally be a gold mine. Gold is valued for use in electronic components beyond its apparent uses in jewelry due to its excellent electrical conductivity and simplicity of processing. But because of the rapid turnover of electronic gadgets, extracting trace amounts of gold and other precious metals is a labor-intensive, inefficient operation that typically requires chemicals or high heat.
Thankfully, scientists have developed a far more straightforward, highly effective approach that doesn’t require additional chemicals or energy to recover gold from electronic waste. Instead, just a little graphene film will do.
Graphene is a remarkable, extremely diverse material. It has been shown to improve solar panels’ efficiency and make them cheaper, make more robust and eco-friendly concrete, enable ultra-high-density hard drives to store 10x more data, prevent mobile batteries from overheating, and prevent repeated rotator cuff injuries. And that only scratches the surface of graphene’s potential.
In the new study, researchers at the Chinese Academy of Sciences, the University of Manchester, and Tsinghua University, first ground up the e-waste, then dissolved it in a solution. Next, a membrane composed of reduced graphene oxide is added to the solution, and within a few minutes, pure gold starts to build up on the membrane surface.
With just 1 gram of commercial graphene oxide, over twice as much gold can be extracted. Even at concentrations as low as 1 part per billion, graphene oxide has a high extraction capacity and precise selectivity when the gold is mixed with other metallic elements. The graphene oxide material attracts more than 95% of the gold in a particular sample. Significantly, it repels other metals from the e-waste mix, and once the graphene membrane has been burnt off, only pure gold is left.
Dr. Yang Su, the study’s lead author, explained:
“This apparent magic is essentially a simple electrochemical process. Unique interactions between graphene and gold ions drive the process and also yield exceptional selectivity. Only gold is extracted with no other ions or salts.”
According to the researchers, the method could help lessen the quantity of gold that is wasted and address the expanding e-waste problem, which is threatening the environment. Other scientists have approached the issue by using solvents composed of mild acids or creating smartwatches that disintegrate in water within 40 hours.
The new study was published on August 2, 2022, in the journal Nature Communications. The team demonstrates the endothermic process in the video below. Watch as gold swiftly forms on the membrane surface.