Influence of bacterial adhesion on copper extraction from printed circuit boards

Abstract

In order to analyze the influence of the contact mechanism in the bioleaching process, bacterial attachment on the Printed Circuit Boards (PCB) surface was avoided using a partition system. The partition system was obtained with a semi-permeable membrane of 12–14kDa MWCO. A PCB sample of 500–1000μm particle size was placed inside a partition system for 144h to compare the copper (Cu) extraction rate by Acidithiobacillus ferrooxidans, with the Cu extraction of a system without partition. The results demonstrated that when the contact mechanism was avoided, there was a decrease of 25% in the Cu extraction. When the contact bioleaching was enabled, 1.46g of Cu was extracted from the initial 1.61g of Cu (∼91% extraction). When the partition system was used, only 1.10g of Cu was extracted (∼68% extraction). Bacterial adhesion experiments proved that within the first hour of the experiment, 4.30×107cells were attached per gram of PCB, supporting that bacterial adhesion was responsible for the higher Cu extraction rate. The results for bacterial adhesion tests were consistent with Derjaguin–Landau–Verwey–Overbeek theory.