Technique to recover trace gold from electronics

New Materials Asia, Oct, 2006

A research team at Japan's Tokyo Institute of Technology has developed a cost-effective way to recover the trace amounts of gold that remain after discarded cell phones and other electronic devices have been recycled.

Small amounts of precious metals like gold and palladium are used in the electronic components that go into products like cell phones, and these metals can be recovered to a certain extent using chemical processes. The solution that remains after this processing still contains gold in amounts of around 10 parts per million, but because recovery is so expensive the solution is simply thrown away.

In the new recovery process, this solution is placed in a container with an organic solvent that contains an azo compound. The solution and the solvent do not mix, but the gold, in the form of gold ions, migrates into the solvent.

The container is then exposed to ultraviolet light, which causes the azo compound to alter molecular structure, taking on a C-shape that traps the gold ions, the researchers say.

The solvent is then transferred to another container with weak acidic water and exposed to visible light. This causes the azo compound to change structure again, releasing the gold ions, which migrate into the water. From there the gold can be recovered using conventional techniques.

For further information, contact: Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan; tel: 81-3-5734-3027; fax: 81-3-5734-3677; Internet: www.titech.ac.jp