Enhancement of simultaneous gold and copper extraction from computer printed circuit boards using Bacillus megaterium

• Extraction of Au using Bacillus megaterium was maximized by statistical modeling.
• To maximize simultaneous metals’ extraction four influenced factors were optimized.
• By maximizing both metals’ recovery as optimization target 36.81% gold was extracted.
• By maximizing Au and minimizing Cu as optimization target 14.02% gold was extracted.
• Pretreatment of CPCBs using A. ferrooxidans resulted in the extraction of gold up to 63.8%.

In this research simultaneous gold and copper recovery from computer printed circuit boards (CPCBs) was evaluated using central composite design of response surface methodology (CCD-RSM). To maximize simultaneous metals’ extraction from CPCB waste four factors which affected bioleaching were selected to be optimized. A pure culture of Bacillus megaterium, a cyanogenic bacterium, was used to produce cyanide as a leaching agent. Initial pH 10, pulp density 2 g/l, particle mesh#100 and glycine concentration 0.5 g/l were obtained as optimal conditions. Gold and copper were extracted simultaneously at about 36.81 and 13.26% under optimum conditions, respectively. To decrease the copper effect as an interference agent in the leaching solution, a pretreatment strategy was examined. For this purpose firstly using Acidithiobacillus ferrooxidans copper in the CPCB powder was totally extracted, then the residual sediment was subjected to further experiments for gold recovery by B. megaterium. Using pretreated sample under optimal conditions 63.8% gold was extracted.