Metal Recovery from Printed Circuit Boards through Biotechnology

Abstract

The increase of e-waste generated through electrical and electronic equipment has led to vast exploitation in recent years as they have increased the risk of destruction of both life and the environment. The end-of-life PCBs represent one of the most significant wastes in this category. PCBs contain a high amount of Cu and Zn with concentrations around 25% and 2% respectively. Pyrometallurgical treatments and hydrometallurgical treatments are the most common methods used for PCB recycling at present. Bio-hydrometallurgical strategies have been identified as a successful alternative for the existing methods as they reduce the economic costs and are more environmentally friendly. The poster introduces a sustainable bioleaching process by using two bacteria Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans. This developed technology allows to obtain a high PCB concentration and to reduce the metal toxicity on the bacteria metabolism. Ferric iron was used as the oxidant to leach Cu and Zn. The best conditions were when At. ferrooxidans was used at 30ºC, with a solid concentration of 5% (w/v) with 10g/L of Fe2+ for 9 days. The carbon footprint assessment proved the environmental advantage of the process. The bioleaching treatment which was the most efficient method according to the analyzation explained that the amount of raw material reduction that results in decreasing the bioreactor size and lowering the energy requirement could be facilitated by increasing the PCB concentration. Through this process, the environmental impact could be decreased up to 4 times compared to the existing bioleaching processes.