After it was announced that Apple had been able to source £28 million in gold from old iPhones in 2015, scientists and organisations have been clambering at the scenes to try and find more efficient ways of extracting precious metals from old hardware.
Researchers at the University of Edinburgh have discovered a simple extraction method using non-toxic compounds that recovers gold from circuits more effectively than current inefficient methods.
What’s more, chemicals such as cyanide are often used to extract materials from old components, which are hazardous to human health.
The method involves printed circuit boards being placed in a mild acid, dissolving the metal parts before an oily toluene solvent containing primary amide is added.
This then extracts the gold selectively from the mixture of other metals.
Prof Jason Love, from the Edinburgh School of Chemistry in conversation with The Engineer, said that, “After separation of the oily phase from the acid phase, washing the oily phase with water transfers the gold into the water phase for electrowinning.”
He continued, “We have to do this a couple of times to ensure complete phase transfer, but each wash step is very quick.”
It is estimated that printed circuit boards contain as much as 7 per cent of the world’s gold, which amounts to around 300 tonnes.
It is estimated that the new extraction method could help curb the environmental impact of gold mining, therefore reducing the carbon dioxide emissions as a result.
A report published earlier in the year by the United Nations University (UNU) revealed that electronic waste is increasing at a global rate of two million tonnes a year.
The amount of gold being thrown away is thought to total around £7 billion.
