E-waste valorisation by recovering valuable metals with microorganisms

Abstract

The effectiveness of bioleaching in copper recovery from printed circuit boards by Acidithiobacillus ferrooxidans has been evaluated under a wide range of conditions demonstrating the suitability of the technology and their limits. The process has been tested using a column reactor simulating conditions found at industrial scale and operating in continuous mode. Moreover, new strategies have been adapted to increase the efficiency of the operation and to reduce the time required for this purpose. Taking into account the complex composition of electronic waste, the limitations of applicability, for instance due to the accumulation of toxic metals in the solution, have been also identified by microrespirometric measurements. Experiments carried out at laboratory scale verifies the proof of concept of the biotechnology for this application, recovering 37% of copper using flasks with a concentration of 7.5 g/L of e-waste in 6 hours. This efficiency was improved in the case of the packed column, where 50% of copper was recovered using the same amount of e-waste at the same period time. New strategy was developed to increase the kinetic of reaction and overcome transport limitations for the leaching solution, achieving copper recoveries up to 80% in the same period than previously reported. Regarding toxicity assays, the methodology used allows to identify that, depending on the concentration and the time exposed, nickel, copper and aluminium affected the microorganisms’ activity, inactivating them. It was concluded that aluminium resulted more toxic than copper, which in turn was more toxic than nickel, at the conditions tested.Peer Reviewe