Electronic Recovery of Scrap Gold

Used electronic devices are a major source of scrap gold.

Scrap computers, cell phones and other electronic devices are good sources of gold, silver and other valuable metals. During recycling, components are dissolved in baths of acid or cyanide. An electrochemical process -- electrolysis -- extracts the gold by depositing it onto electrodes.

Process

Soaking in nitric acid, hydrochloric acid or cyanide solution dissolves precious metals from electrical components. Gold is extracted from this solution -- known as the electrolyte -- using a pair of electrodes attached to a battery. The electrolyte conducts electricity between the electrodes. Gaining a positive charge, metal ions in the solution are attracted to the negative electrode (cathode) and deposited there. Gold deposited on the cathode can be scraped or melted off. Cathodes with larger surface area speed gold deposition.

Limitations

Electrolyte solutions obtained from electronic scrap contain copper, silver, lead and other metals as well as gold. High silver or copper content can inhibit gold deposition. The gold deposited may be impure -- blended with these metals. As today's electronic devices get smaller, the amount of gold they contain is shrinking.

Warning

Lead, mercury, cadmium and other elements found in scrap electronics are toxic. Both dissolution in acid and dissolution with dilute cyanide carry health risks. Toxic gases may be given off during the extraction process. This should not be undertaken by amateurs. Safer methods are being developed.

References

• "Metallurgist"; Improving a Technology Used for the Electro-Refining of Gold; Y. Voronin , V. Kondaurov et al.; 2003
• Gold Avenue: Electrolysis/Electrorefining/Electrowinnowing
• "Journal of the Minerals, Metals and Materials Society" ; The Aquaeus Recovery of Gold from Electronic Scrap; S. Kulandaisamy, J. Prabhakar Rethinaraj, et. al.; August 2003
• Toxics Link: Computer Myths: The Story of Scrap
• Tennessee Department of Environment and Conservation: Facing the Challenge of Electronic Scrap
• Best Netsale: Gold Bullion: Scrap Gold Recovery Question

Resources

• CNN: Gold Recycling Plant Outside of Tokyo
• Gold N Scrap
• The Metal Casting: Electronic Scrap Recycling
• "Gold Bulletin": Gold Recovery From Used Electrical Contactors; John Niederkorn and Steve Huszar; 1984
• Geology.com: The Many Uses of Gold
• Gold Recovery From Computer CPUs, Pins and Edge Connectors