Mechanistic Insights into Biphasic Effects of Ce(III) on Anode Biofilms in Bioelectrochemical Systems during Industrial Wastewater Treatment
摘要
Although abundant research has demonstrated the hazardous nature of Cerium (Ce(III)), the mechanisms behind its removal from anodes and subsequent effects on bacteria in bioelectrochemical systems (BES), as well as extracellular electron transfer (EET) in electroactive biofilms (EAB), remain unclear. Hence, this study investigated Ce(III) removal and its influence on EAB in the anodic chamber of a BES to elucidate its impact. (1) Ce(III) enhanced the power output from 233.89 ± 3.98 mW/m2 at 0 mg/L to 347.24 ± 8.07 mW/m2 at 10 mg/L, and it declined to 143.99 ± 1.33 mW/m2 at 40 mg/L. (2) Ce(III) removal efficiency was greater than 99% at sub-toxic levels of 2, 5, and 10 mg/L, whereas, at 20, 30, and 40 mg/L, it declined owing to reduced biofilm viability as indicated by scanning electron microscopy (SEM) and confocal lens scan microscopy (CLSM). (3) Fourier transform infrared (FTIR) showed that functional groups had a role in Ce(III) absorption. (4) The availability of Ce(III) in the anode biofilms was demonstrated through XPS and SEM–EDS analysis. (5) Cyclic voltammetry (CV) results showed that 2, 5, and 10 mg/L Ce(III) enhanced charge transfer capacitance and the electrochemical impedance spectrum (EIS) confirmed a reduced internal resistance at these levels. (6) Results from high-throughput sequencing showed that at a high Ce(III) amount, i.e., 40 mg/L, Desulfovibrio was the most abundant, while Geobacter was the least. (7) EET-related genes were enriched at 2, 5, and 10 mg/L Ce(III) but diminished at 20, 30, and 40 mg/L. These results provide a new and feasible way to treat Ce(III) wastewater and chemical oxygen demand (COD) degradation and enhance our knowledge of the effects of Ce(III) on EABs at the anode.