Catalytic role of biogenic gold nanoparticles in improving Cr(VI) removal efficiency of biocathode microbial fuel cells

BACKGROUND: Biogenic metal nanoparticle-modified electrodes have a promising prospect for improving the efficiency of microbial fuel cells (MFCs) for hexavalent chromium (Cr(VI))-containing wastewater treatment. In this study, a graphene (GO) electrode was modified with chemical gold nanoparticles (ChemAu) and biogenic gold nanoparticles (BioAu), respectively, and the two modified electrodes were then used as MFC biocathode electrodes to treat Cr(VI)-containing wastewater. RESULTS: The results demonstrated that the BioAu/GO biocathode-based MFC obtained the highest power density (95.78 ± 1.11 mW m⁻²) and Cr(VI) removal rate (2.17 ± 0.51 mg L⁻¹ h), which were 13.19 and 1.03 times higher than those of the graphite paper biocathode-based MFC, respectively. The Cr(VI) removal efficiency of the BioAu/GO biocathode-based MFC under close-circuit condition reached 87.61 ± 0.19%, which was 3.74 times higher than that recorded under open-circuit conditions, indicating the critical role of the bioelectrochemical reduction reaction mediated by the BioAu/GO biocathode on Cr(VI) removal. CONCLUSION: The BioAu/GO electrode first confirmed its superior performance to the ChemAu/GO electrode in Cr(VI)-reducing MFCs due to its excellent material properties. This study provides a technical reference for the exploration of efficient bioelectrode materials based on biogenic metal nanoparticles for MFCs to treat recalcitrant pollutant-containing wastewater.