Microbial Recovery of Gold Metal From Untreated and Pretreated Electronic Wastes by Wild and Mutated Cyanogenic <i>Bacillus megaterium</i>

Abstract

Technology of biorecovery by Bacillus megaterium to obtain gold as a complex of gold-cyanide from electronic waste material (EWM) was done. The bacteria were subjected to pretreatment and mutation. The exist metals in solution were dissolved via the pretreatment, that way, contest for the cyanide ion from other metals was reduced. The bacteria were subjected to mutation to be able grow at pH 9, 9.5 and 10, where the pKa of HCN is 9.3, thereby, the cyanide ion concentration available for bioleaching was increased by alkaline pH. The new mutated bacteria from the pretreated EWM at 0.5% pulp density obtained gold of 17, 25 and 21% at pH 9, 9.5 and 10, respectively. Whereas the old unmutated bacteria that grow at pH 7, recovered 11%. The outcomes demonstrated that effectiveness of the mutated alkaline bacteria (B. megaterium) in gold biorecovery was more than normal physiological (pH 7).