Microalgae fuel cells enhanced biodegradation of imidacloprid by Chlorella sp.

The widespread use of neonicotinoid pesticides has caused environmental threat that has attracted scientific concern. This study developed a microalgae fuel cells (MFCs) with Chlorella sp. as the cathode synergistically enhanced the removal of imidacloprid (IMI). The MFCs were operated at open-circuit and closed-circuit. Under closed-circuit condition (with an external load), 57.20–61.66% of IMI (10–50 mg/L) was removed within 12 days. However, only 39.66–42.66% was removed in the open-circuit (without an external load). Additionally, a voltage of 200 mV was also detected in the closed-circuit MFCs, indicating the green bioenergy was produced during the degradation of IMI. Cyclic voltammetry revealed that the cathodic electroactivity was higher with the addition of IMI. Biomass accumulation (indicated by chlorophyll and dry cell weight) were significantly enhanced by IMI. On the 12th day, there was no difference in MDA content between the different IMI concentration (10–50 mg/L), while a significantly upregulated superoxide dismutase (SOD) of each group was also found at the same time. Six intermediates were detected and five major degradation pathways were proposed. Based on the identified products and microalgae growth, the degradation products of IMI were less toxic /non-toxic than IMI. Considering the efficient removal of IMI and energy production, the MFCs could be a promising technique for controlling IMI contamination by effective detoxification.