Recovery of Gold and Other Precious Metal Resources from Environmental Polluted E-waste Printed Circuit Board by Bioleaching Frankia

The physicochemical profiling of e-waste was done by AAS, XRD, and SEM with EDX that reveals the composition of valuable metals like Au-, Ag-, Zn-, and Cu-. Thus, the present findings provide the important resource of precious metal in the e-waste (PCBs) as pollutant in the environment and human impact. The native isolates Frankia sp. DDNSF-01 and Frankia casuarinae DDNSF-02 were subjected for bioleaching of gold and precious elements bearing e-waste under one and two-step leaching methods. The two-step bioleaching protocol was found effectual in expression with high level of metal leaching within the culture medium of Frankia metabolites and organic acids which were obtained by the leaching of metals. The presence of organic acids functional groups was determined by FT-IR spectrum and by low pH of growth medium. The AAS analysis quantified the initial concentration of metals and their significant increase brought by the leaching. The initial concentration of precious metal elements was found in the e-waste like Au-, Ag-, Cu-, and Zn- (0.04, 0.05, 0.35, 0.1 mg/g) respectively. Frankia sp. leached out precious metals like Au-, Ag-, Cu-, and Zn- (0.2, 0.14, 0.68, 0.2 mg/g) respectively. Frankia casuarinae leached out precious metals like Au-, Ag-, Cu-, and Zn- (0.25, 0.15, 0.55, and 0.2 mg/g) respectively. The precious metal gold was highly leached out by F. casuarinae than Frankia sp.. The valuable metal copper was significantly increased by Frankia sp. than F. casuarinae. Higher gold recovery, at 75%, was obtained for F. casuarinae and copper 94% recovery by Frankia sp. bioleaching of the biooxidised e-waste at 0.2% low pulp densities. The results were confirmed by XRD and SEM with EDX analysis. Graphic abstract