Enhancement of chromium (VI) removal and power generation by adding biochar to a single-medium sediment-based microbial fuel cell

A single-medium membrane-less sediment microbial fuel cell (SMFC) was developed to remove Cr6+ from sediment by embedding its cathode and anode in the sediment, so that the electrons that are generated by the degradation of organic matter at the anode are received by Cr6+ at the cathode, reducing the competition for oxygen. The best power density and Cr6+ removal efficiency of the SMFC were found to be 8.8 mW/m(3) and 60.9 %, respectively, for a system in a high Cr6+ concentration (600 mg/kg). Biochar has a high specific surface area and adsorption capacity, facilitating electron transfer. As an electron mediator, peanut husk biochar that was sintered at 800 degrees C had an electron transfer capacity of 0.295 mmol e(-)/g biochar. This biochar was added to the SMFC system to improve its performance by exploiting the electron transfer ability of the biochar, increasing the electricity production and Cr6+ removal efficiency of the SMFC. The power density and Cr6+ removal efficiency of the biochar-added system were 55.1 mW/m3 and 97.74 %, or 6.26 times and 1.6 times those of the system without biochar, respectively, indicating the improvement that is provided by adding biochar.