Electricity generation and enhanced thiacloprid biodegradation in microbial fuel cells using microalgae biocathode

Thiacloprid (THI), as a commonly used neonicotinoid, is frequently detected in environmental media, posing a potential threat to the environment and organisms. In this study, microalgae fuel cells (MFCs) with Chlorella sp. as cathode and wastewater (with sludge) as anode were constructed to remove THI (10, 20 and 50 mg/L) while generating bioelectricity. The results showed that, comparing with the open-circuit condition, the generation of bioelectricity (closed-circuit) significant enhanced the removal of THI by 13.14–32.47%. The presence of low concentration of THI (10–20 mg/L) did not significantly affect the accumulation of Chlorella sp. biomass, while high concentration THI (50 mg/L) strongly depressed its biomass. It was also found that high concentration THI caused obvious oxidative damages (MDA) to Chlorella sp., although SOD activity was upregulated. Both the highest THI removal efficiency (%) and stable bioelectricity voltage (202 mV) occurred at the low THI concentration (10 mg/L). Seven degradation products of THI were identified and the oxidation of the thiazole ring was the main detoxification way of THI. Additionally, toxicity evaluation also showed that the toxicity of degradation products were lower than THI. This study implies that MFCs could be a promising application, coupling pollutants removal, bioenergy generation and biomass production.