Low Environmentally Impact Recovery of Gold using Cyanide Producing Bacteria

In the electronic assembly, Au is frequently used for surface plating and a bonding wire material. To recover gold from waste electronics, the dissolution process using cyan is a popular method, however, the solution is highly toxic. Accordingly, the environmentally conscious substitute process is preferable. Chromobacterium violaceum having ability of cyanide formation and decomposition were used to dissolve Au and decompose cyanide after Au dissolution. In this study the effects of dissolved oxygen on Au dissolution was investigate as a factor of Au bioleaching and continuous and repeated batch cultures were performed for the continuous Au dissolution as a reproducing cyanide process. Dissolved oxygen concentration decreased by the bacterial respiration but the aeration could recover it and activate Au dissolution. By replacing the medium C.violaceum can produce cyanide repeatedly then 60% of Au was dissolved from Au powder after 300h immersion.