| Summary: | The rapid advancement of the economy has led to an annual increase in global electronic waste (e-waste) production. As a result, the development of effective recovery technologies becomes increasingly valuable, particularly due to the concentration of precious metals within these sources, which is pivotal for recycling. However, conventional methods such as precious metals leaching using strong acids and cyanide pose significant environmental risks. Hence, this study concentrates on the recovery of metal ingots, specifically gold (Au), from e-waste mobile printed circuit boards (PCBs) through bioleaching and electrowinning processes. Initially, a 2-stage bioleaching process employing the batch stirred tank reactor (BSTR) technique was conducted, with and without aeration at a rate of 0.5 L min-1, while varying the pulp density of e-waste PCBs. The resulting precious metals effluent from the BSTR process was utilised in the subsequent electrowinning step, aiming to yield high-purity metal ingots in crystalline form, thereby eliminating impurities. Aeration at 0.5 L min-1 increased dissolved oxygen (DO) and free cyanide (CN-) concentrations, facilitating metal ingot dissolution. Optimal selection throughout the 2-stage bioleaching process using BSTR led to a higher turnover percentage in metal dissolution. Different concentrations of e-waste PCBs pulp density (0.5%, 1.0%, and 5.0% w/v) resulted in the leaching of gold metal at rates of 59.24%, 37.99%, and 12.81% (w/w), respectively. Lastly, within a 12-hour electrowinning period, the maximum yields of Au, Silver (Ag), and Copper (Cu) reached 97.33%, 81.57%, and 90.35% (w/w) respectively. In conclusion, employing a bio-recovery method involving 2-stage bioleaching and electrowinning proves to be a safe and efficient approach for extracting precious metals from e-waste PCBs. © School of Engineering, Taylor's University.
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