Influence of bacterial adhesion on copper extraction from printed circuit boards

• Attachment of A. ferrooxidans influences the Cu extraction from PCBs.
• When the contact mechanism is allowed, 91% of Cu extraction is obtained.
• Disabling the contact mechanism reduces Cu extraction by up to 25%.
• Bacterial attachment of 4.30 × 107 cells/g-PCB occurs for the initial 1 h reaction.

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 12–14 kDa MWCO. A PCB sample of 500–1000 μm particle size was placed inside a partition system for 144 h 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, 1.46 g of Cu was extracted from the initial 1.61 g of Cu (∼91% extraction). When the partition system was used, only 1.10 g of Cu was extracted (∼68% extraction). Bacterial adhesion experiments proved that within the first hour of the experiment, 4.30 × 107 cells 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.

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