Bioleaching of gold and copper from waste mobile phone PCBs by using a cyanogenic bacterium

Chromobacterium violaceum (C. violaceum), a cyanide generating bacterium has been used to leach out
gold and copper from the waste mobile phone printed circuit boards (PCBs) containing 34.5% Cu and
0.025% Au in YP (yeast extract and polypeptone with glycine) medium. The bioleaching was carried
out in an incubator shaker (150 rpm) at 30 C and 15 g/L pulp density in the pH range 8–11. Dissolution
of gold and copper increased from 7.78% (0.225 ppm) to 10.8% (0.46 ppm) and 4.9% (419 ppm) to 11.4%
(879 ppm) in 8 days with increase in pH from 8 to 11 and 8 to 10 respectively. Supplementing oxygen
with 0.004% (v/v) H2O2 increased the copper leaching to 24.6% (1743 ppm) at pH 10 in 8 days whereas
improvement in gold leaching was insignificant with the recovery of 11.31% Au at pH 11.0. The waste
PCBs can thus be recycled in environmental friendly manner.