Distinct voltage signals of sediment microbial fuel cell sensors in sensing various contaminants

Abstract

AbstractThe sediment microbial fuel cell (SMFC) sensors using cathode as sensing element exhibited attractive prospects for online and in‐situ monitoring. However, the sensing performance of SMFC sensors to different types of contaminants was seldom reported. In this study, SMFCs were constructed in stimulated wetland to sense five types of contaminants, including oxidative heavy metals (Cu2+ and Cr6+), non‐oxidative heavy metals (Ni2+ and Zn2+), salt (NaCl), acid (HCl), and alkali (NaOH). The addition of Cu2+, Cr6+ or H+ triggered voltage peaks whereas the voltage dropped immediately following the addition of OH−. The addition of Ni2+ and Zn2+ did not trigger any obvious peaks. The NaCl solutions caused slight voltage peaks which were not increased with increasing concentrations. X‐ray photoelectron spectroscopy (XPS) illustrated the reduction of Cu2+ and Cr6+ to elemental Cu and Cr3+ on the cathodic surface, indicating the contaminants that promote or inhibit electron consumption on cathode would cause voltage peaks or drops. The addition of heavy metals, OH− and NaCl significantly increased Simpson's diversity whereas Cu2+, Cr6+ and OH− significantly decreased the abundance of exoelectrogenic bacteria‐associated genera in the top‐layer soil. However, the influence of the contaminants on the abundance and diversity was attenuated in the middle and bottom layers, indicating that the exoelectrogenic bacteria could to some extent withstand these contaminants and guarantee the operation of the SMFC sensors.