Composite many times more effective at capturing gold than existing materials
A self-assembled composite of graphene oxide and chitosan can capture gold from electronic waste many times more efficiently and selectively than existing materials, researchers in Singapore have shown. The material could potentially eliminate several purification steps and make industrial recycling more economically competitive. Because of the inertness of gold, its mining has a significant environmental footprint, usually requiring toxic chemicals such as mercury or cyanide to extract it from other components of the ore. This stability, together with its high electrical conductivity and ductility, makes it useful in electronics. Recycling gold to reduce mining faces the same extraction problems. Unwanted components are decomposed using one of several possible processes such as immersion in aqua regia (a concentrated mixture of hydrochloric acid and nitric acid). This yields a mixture of gold(I) and gold(III) ions mixed with copper, nickel, zinc and many others. 'Now electrolysis is used,' says Daria Andreeva at the National University of Singapore; 'Electrolysis is a very long process that can take days or even weeks, so it's a very interesting approach to…