MnO2/tourmaline composites as efficient cathodic catalysts enhance bioelectroremediation of contaminated river sediment and shape biofilm microbiomes in sediment microbial fuel cells

Abstract

The efficient degradation of pollutants in river sediments is essential for the bioremediation of contaminated rivers. In the present study, sediment microbial fuel cells (SMFCs) with manganese dioxide/tourmaline composite modified cathodes (MnO2/T-SMFCs) were developed to simultaneously produce electricity and degrade organic matter in contaminated river sediment and water. The MnO2/T-SMFCs exhibited a higher power density of 368.99 mW/m3, which was 1.26 and 2.06 times that of SMFCs with MnO2 cathode and open-circuit SMFCs (OC-SMFCs), respectively. Moreover, MnO2/T-SMFCs exhibited the highest total organic carbon (TOC) removal of 55.7 %, which was 1.76 times that of the OC-SMFCs. It also obtained the highest NH4+-N removal of 93.7 %, 40 % higher than OC-SMFCs. The high oxidation reduction reaction (ORR) associated with the MnO2/T cathode is partly attributed to the synergetic effect between MnO2 and tourmaline to change the electronic structure of MnO2 electrode and modify its adsorption/desorption behaviors. PacBio sequencing of 16S rRNA gene amplicons showed that volatile fatty acid- and alcohol-oxidizing Syntrophus and Smithella, and electroactive Geobacter dominated the anode biofilms in the MnO2/T-SMFCs. These results indicated that MnO2/T-SMFCs are effective for sediment bioelectroremediation in contaminated rivers.