METAL LEACHING FROM ELECTRONIC SCRAP BY FUNGI

The present work was initiated to evaluate the use of the fungus Aspergillus niger for bioleaching of metals from electronic scrap and then to determine the effect of process steps, the scrap concentration and type of substrate. A sucrose and mineral salts medium was initially used to produce citric and gluconic acids by A. niger at various concentrations of scrap (1, 5, 10 and 15% w/v). Maximal removal of up to 60% of the copper was obtained for the 5% scraps when the organic acid supernatant was added to the scraps. In a single step process, A. niger was then grown in the presence of scraps at various concentrations. Maximum copper solubilization (63%) occurred with 10% scraps using sucrose as the substrate. Other substrates were then evaluated including molasses, corn cobs and brewery waste (10% scraps). Sucrose gave the best results for copper removal, followed by molasses, corn cobs and brewery waste. Other experiments using ultrasound as a pretreatment showed that 80% removal of the copper could be obtained for a 5% scraps concentration.