Golden solution

A new and simple way to extract gold from electronic waste

YOU KNOW those old cell phones rattling around at the back of your desk drawer? It turns out they’re not worthless after all. Like most electronic waste, they contain a small amount of gold, which conducts electricity well and doesn’t oxidize — properties that make it perfect f or covering copper and nickel connections on circuit boards. The problem is that extracting gold from e-waste hasn’t been cost-effective or environmentally friendly — until now. University of Saskatchewan chemists have found that dipping e-waste in 99 per cent acetic acid — basically concentrated vinegar — and then adding zinc to the resulting solution yields gold that’s 90 per cent pure. Stephen Foley, who led the research, says only 100 litres of acetic acid, which costs about $70, is needed to dispose of five to six tonnes of e-waste and recover about one kilogram of gold, worth about $51,000. What’s more, the acid only needs to be neutralized before being poured down the drain. In North America and Europe, the main methods of recovering gold from e-waste are pyrometallurgy, where waste is crushed and burned and 60 per cent of the gold is retrieved, or hydrometallurgy, where waste is bathed in aqua regia, a toxic soup of hydrochloric and nitric acid, and anywhere between 60 and 99 per cent of the gold is retrieved. The biggest drawback of using acetic acid? The stink. “You know what vinegar smells like,” says Foley. “Imagine having 100 litres of the pure stuff.” Still, he cautions that acetic acid isn’t a solution to the growing and global e-waste problem. “We’re stripping the gold off, but you still have the circuit board left,” he says, “so we’re just one step in a process.”