Integrating plant microbial fuel cells and permeable O2-releasing rods to enhance copper removal and electricity generation in sediment

Abstract

The high mass transfer resistance of the sediment limits the migration of copper (Cu) ions generated from the operation of a sediment microbial fuel cell (SMFC), causing difficulty in obtaining high removal efficiencies of Cu ions through the SMFC. Therefore, approaches are required to reduce the internal resistance of the system and to increase the power generation of the SMFC. In this study, the anode zone of SMFCs was planted with water spinach, which produces root exudates to activate the microorganisms. A permeable oxygen release rod (POR) was installed in the cathode zone of the SMFC to slowly release a small amount of oxygen to enhance power generation, prompting copper ions to migrate to the cathode for a reduction reaction to remove copper. Under the condition of growing water spinach and setting POR simultaneously, the power density (94.9 mW/m3) of SMFC was increased by 14.1 times, significantly increasing the removal efficiency of Cu ions (from 20.9 % to 84.9 %). The abundance of electro-producing bacteria (e.g., Clostridium, Bacillus, and Thiobacillus) was increased when the anode zone of the SMFC was planted with water spinach. This suggests that the root exudates of water spinach and trace oxygen from POR promoted the electricity production of SMFC and accelerated the migration of Cu ions.