Scientists from China and Europe say they have discovered a highly efficient, low-cost way of extracting gold from electronic waste . From smartphones and laptops to televisions and washing machines, the world dumps tens of millions of tonnes of e-waste every year. Less than 20 per cent of it is recycled. The team used cheap graphene products to develop a simple process which they said extracted nearly 100 per cent gold – and only gold – from electronic waste. “We hope this technology will increase the economic returns of e-waste recycling, and even build it into a profitable business in the future,” said lead researcher Su Yang from Tsinghua University’s International Graduate School in Shenzhen. In a series of experiments reported in the journal Nature Communications , Su and colleagues from the Chinese Academy of Sciences soaked specially prepared graphene in solutions that contained tiny amounts of ions of various e-waste metals, such as gold, copper and iron. Pure gold appeared on the graphene sheets just a few minutes later. For 1 gram of the graphene material they used, 1.85 grams (0.06 ounce) of gold was extracted, according to their paper published on August 2. China’s giant gold deposit formed by different geological forces: paper The process was not only much faster and more effective than existing practices, which use activated carbon to extract gold, but was also highly selective as coexisting metal ions either remained in the solution, or could be easily stripped off, Su said. “Considering that graphene costs less than US$0.1 per gram and the gold price is around US$55 per gram, our technology seems quite profitable,” he said. They used graphene oxide, an oxidised form of graphene which is cheap and readily available. Unlike graphene, it can be dispersed in water. With ascorbic acid, or vitamin C, the researchers reduced a large part of the graphene oxide to graphene, which was responsible for extracting gold. The rest was intentionally left unreduced to improve extraction efficiency, said the paper’s co-author Andre Geim from the University of Manchester. Geim was awarded a 2010 Nobel Prize for his work on graphene. “They [the graphene oxide areas] serve to repel individual graphene sheets away from each other, disallowing clustering. This increases the total area of graphene accessible for gold ions in solutions,” Geim said. Without the graphene oxide, graphene sheets would coagulate into clumps and the efficiency of the gold extraction would be greatly reduced, he noted. Indeed, when pure graphene was used to retrieve gold ions, Su and his colleagues noticed it would float on top of the solutions or sink to the bottom, cutting the extraction efficiency by an order of magnitude. Breaking down technological hurdles in e-waste recycling is especially meaningful for China, a country that has taken over from the United States to become the world’s largest e-waste producer, according to the Global E-Waste Monitor 2020 report. The research may also help address the global gold sustainability problem. Current underground gold reserves are around 50,000 tons – only about a quarter of the gold that humanity has mined, the US Geological Survey estimated. Gold has been widely applied in electronic devices because it is highly conductive, erosion resistant and relatively soft and easy to work with. However, there is only a tiny amount of gold to be found in each device. To scale up, Su and his colleagues are working to develop mass production of reduced graphene oxide, and expand the extraction to a wider variety of gold ions, including those from mine tailings and electroplating waste water. Su said they were looking for industrial partners who were interested in employing the technology.