Visual detection of the toxicity of wastewater containing heavy metal ions using a microbial fuel cell biosensor with a Prussian blue cathode

A self-powered microbial fuel cell (MFC) biosensor containing a bioanode and Prussian blue (PB) cathode was successfully developed to assay the toxicity of wastewater. Factors such as the oxidation of Prussian white (PW), external resistor and reduction time were studied and optimized. The electrochromic PB cathode facilitated the process of monitoring the electrocatalytic performance of the bioanode using colorimetric detection. Thus, the toxicities of heavy metal ions, such as Co2+, Cd2+, Pb2+ and Cu2+, were sensitively detected by the MFC-based biosensor without an extra power supply. The inhibition absorbances values (IA) were 28.4%, 11.0%, 33.8% and 66.6% for the samples with 1 mg/L Cd2+, 1 mg/L Co2+, 1 mg/L Pb2+ and 1 mg/L Cu2+, respectively, and the toxicity was in the order of Co2+ < Cd2+ < Pb2+ < Cu2+. The intensity toxicity was correlated with the decoloration of PB distinguished using colorimetric detection. The results of this work indicate that the self-powered biosensor could be applied to the acute toxicity assessment of heavy metal ions samples with excellent performance as recoverable and visual detection, which may provide a novel and reasonable way for the toxicity detection of wastewater. Furthermore, the biosensor is expected to serve as future technique for in situ wastewater monitoring.