The standard way today to recover precious metals from electronic equipment is close to being an environmental disaster with most illegally dumped, according to a UN report.

Each year around 40 million tons of electronic waste is produced, which is the fastest-growing component of solid wastes due to the rapid upgrade of personal electrical and electronic equipment.

 Many western consumers believe that the old computer or mobile phone they drop off at a recycling centre will be reused by students in African countries or will be recycled in a green manner.

Unfortunately, as reports from Al Jazeera and other news programmes have shown, very little of this e-waste is reused. Instead, it is illegally shipped and dumped into huge fields in western African and Southeast Asian countries and burnt. People working these fields – often young children – breath in the toxic smoke while recovering precious metals from the burning plastic.

However, in a paper published by Nature Communications, Bing Deng, Duy Xuan Luong, Zhe Wang and others from the Department of Chemistry, Rice University, Houston, Texas, believe they have a better solution in a method they call “urban mining”.

In “Urban mining by flash Joule heating” the researchers outline a method using flash Joule heating which not only recovers the precious metals from e-waste, but also removes toxic heavy metals.

“Precious metal recovery from electronic waste, termed urban mining, is important for a circular economy. Present methods for urban mining, mainly smelting and leaching, suffer from lengthy purification processes and negative environmental impacts. Here, a solvent-free and sustainable process by flash Joule heating is disclosed to recover precious metals and remove hazardous heavy metals in electronic waste within one second.

“The sample temperature ramps to ~3400 K in milliseconds by the ultrafast electrical thermal process. Such a high temperature enables the evaporative separation of precious metals from the supporting matrices, with the recovery yields >80% for Rh, Pd, Ag, and >60% for Au. The heavy metals in electronic waste, some of which are highly toxic including Cr, As, Cd, Hg, and Pb, are also removed, leaving a final waste with minimal metal content, acceptable even for agriculture soil levels. Urban mining by flash Joule heating would be 80× to 500× less energy consumptive than using traditional smelting furnaces for metal-component recovery and more environmentally friendly.”