Researchers extract gold from e-waste using cheesemaking byproduct
Whey to go
Researchers at the Swiss Federal Institute of Technology (ETH Zurich) have developed an innovative and sustainable method to recover gold from electronic waste.
In a paper published in Advanced Materials, scientists at ETH Zurich used a protein fibril sponge derived from whey, a byproduct of the cheese industry.
Extracting gold from electronic waste is a complex and often hazardous process that uses harmful chemicals such as nitric and hydrochloric acids and cyanide solutions to strip away the plastic and other non-metal components from the shredded electronic waste and then isolate and recover the gold.
The Swiss researchers, led by Professor Raffaele Mezzenga, created a sponge by denaturing whey proteins causing them to aggregate into nanofibrils.
Gold ions in a solution of mixed metals adhered to the protein fibres much more efficiently than ions of other metals.
The sponge was then heated, reducing the gold ions into flakes, which were melted down into almost pure gold.
The process is not only more environmentally friendly (although acid is still required to dissolve the metals) but also cost-effective.
From 20 old computer motherboards, the researchers were able to extract a 22-carat gold nugget weighing 450 milligrams.
Efficient recovery of precious metals from electronic waste is a priority given the rising demand for gold and the energy-intensive, toxic methods employed in its extraction from e-waste.
The whey-based technology is already commercially viable, with procurement and energy costs amounting to a fraction of the value of the gold recovered, the researchers claim.
They now plan to refine the process further and explore other potential sources of gold, including industrial waste from microchip and gold-plating processes, as well as looking at alternative materials to create the protein fibril sponge.
"The fact I love the most is that we're using a food industry byproduct to obtain gold from electronic waste," Mezzenga said in a blog post. The method transforms two waste products into gold, he added. "You can't get much more sustainable than that."