Chalmers University of Technology researchers using gold scrap to purify biodiesel

In Sweden, researchers at Chalmers University of Technology in Sweden have developed an environmentally friendly method for recycling and purifying metals. Using gold earrings from a pawnshop in Gothenburg and biodiesel from the nearest filling station, the discovery could change an industry that is currently dependent on large amounts of fossil oil.

In the researchers’ method, gold scrap − usually in the form of small earrings bought a local pawn shop − is dissolved in a mixture of hydrochloric acid and nitric acid (aqua regia). The gold found in jewelry is an alloy with other metals, including silver, and this leads to the silver depositing in solid form as silver chloride. In just two more steps, pure gold is then extracted from the solution. Firstly, HVO100 and the chemical malonamide are added, and secondly the entire mixture is shaken with ordinary salt water. The method used by the Chalmers researchers is even more ‘green’, since the malanomide was made from renewable biomass, which replaces more toxic and carcinogenic chemicals that are traditionally used to purify gold scrap.

The same method can be used to purify and recycle many other socially important metals, such as platinum, which is used in catalysts; nickel and cobalt in batteries; uranium and plutonium for the nuclear industry; and rare earth elements. The latter are a prerequisite for the rapid development of everyday electronics such as smartphones and tablets, and are important for modern green technology, such as in wind turbines and electric vehicles.