Electronic waste—including old cell phones, televisions and computers—is thought to contain as much as 7% of the world’s gold. However, current methods for extracting the metal from the printed circuit boards found inside such devices are inefficient and can be hazardous to health, as they often use toxic chemicals such as cyanide.

Current methods for extracting gold from the printed circuit boards found inside electronic devices are inefficient and can be hazardous to health. Image credit: Pixabay.A University of Edinburgh study authored by, among others, Jason Love, professor of molecular inorganic chemistry, now says that vast quantities of gold could be salvaged from old cell phones using a simple chemical method. The extraction process does not use toxic chemicals and recovers gold more effectively than current methods, according to the researchers. The finding could help salvage some of the estimated 300 metric tons of gold used in electronics each year.

Printed circuit boards are first placed in a mild acid to dissolve all of their metal parts. An oily toulene liquid containing the team’s chemical compound—a simple primary amide—is then added, which extracts gold selectively from the complex mixture of other metals. Unlike current processes, reverse-phase transfer is achieved simply using water.

According to the researchers, the recovery of metals using solvent extraction can offer significant environmental advantages over energy- and capital-intensive pyrometallurgical methods, particularly where a single metal—in this case gold—is targeted. The research team believes their findings could aid the development of methods for large-scale recovery of gold and other precious metals from waste electronics.