Preferable utilization of in-situ produced H2O2 rather than externally added for efficient deposition of tungsten and molybdenum in microbial fuel cells

•W and Mo were deposited on the cathodes of microbial fuel cells (MFCs).•In-situ produced H2O2 in MFCs improved W and Mo deposition.•In-situ produced H2O2 rather than externally added for efficient W and Mo deposition.•Supply of oxygen, initial pH and external resistance affected system performance.

In-situ H2O2 production at the cathode in microbial fuel cells (MFCs) has been well documented to be useful for removal of recalcitrant pollutants based on its reductive and oxidative characteristics. However, the advantages of in-situ produced H2O2, rather than using an exogenous source of this chemical has not been previously examined for removal and cathodic deposition of metals. Greater percentages of W and Mo were deposited on the cathodes of MFCs with in-situ produced H2O2 compared to that achieved with chemical addition to the solution through either intermittent multiple-time or one-time modes. A high oxygen supply with in-situ produced H2O2 reached deposition of 67.2 ± 3.1% of W and 86.4 ± 1.9% of Mo, and a coulombic efficiency of 66.4% ± 3.1%, which were 2.4, 1.3 and 3.1 times, respectively as those in the no oxygen control. These metals removals were appreciably higher than the maximum achieved with chemical H2O2 of 80 mg/L externally added through either intermittent multiple-time or one-time modes for W deposition, although there was a negligible difference for Mo deposition. More acidic pHs and a lower external resistance were favorable for W and Mo deposition. This study provides a new approach for efficient W and Mo deposition, where in-situ produced H2O2 resulted in more complete metal removal than that obtained with an externally intermittent multiple-time or one-time added source of this oxidizer.

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