Enhancement in Iron Oxidation and Multi-metal Extraction from Waste Television Printed Circuit Boards by Iron Oxidizing Leptospirillum feriphillum Isolated from Coal Sample

Purpose of this study was to analyse the ability of isolated Leptospirillum to extract the metals from television printed circuit boards (TV-PCBs). Activation of iron oxidizer enriched from coal sample resulted in 8.5-fold enhancement in iron oxidation rate. The television printed circuit board (TV-PCBs) adapted culture showed 1.2-, 1.3- and 1.6-fold higher Cu, Zn and Ni leaching, respectively, from 10g/L TV-PCBs waste pulp density compared to unadapted culture. It also showed 24-h reduction in leaching time. The two-step process showed 1.3-fold higher metal extractions compared to one-step process with both adapted and unadapted culture. Additionally, there was a 1.3-fold reduction in reaction time in the two-step leaching process as compared to the one-step process. The effect of change in leaching process parameters such as pH, Fe (III) concentrations, and particle size were investigated. The maximum metal leaching occurred at a pH of 2.0, Fe (III) concentration of 8.2g/L, and at particle size less than 0.044mm. Under the above-stated optimum conditions, all the three metal extractions namely Cu, Zn and Ni were greater than 95%.