Elevating Tetracycline Removal in Microbial Electrochemical Systems: Insights from Extracellular Electron Transfer and Rational Aggregation of Microbial Consortia.

In microbial electrochemical systems (MESs), the anode electroactive biofilm is crucial for mitigating the threat of tetracycline (TC) residue, a typical broad-spectrum antibiotic frequently found in the environment, to public health security. In this work, the Co3O4@PEDOT-CC anode was rationally designed and fabricated by poly(3,4-ethylenedioxythiophene) (PEDOT) coating Co3O4 nanowires grown on carbon cloth, featuring it with hierarchical architecture and interfacial properties of excellent conductivity and biocompatibility. The Co3O4@PEDOT-CC exhibited a minimal charge-transfer resistance of 6.5 Ω, which is 27.3 times lower than that of bare carbon cloth (CC) and achieves a maximum power density of 3.33 W/m2, significantly surpassing those of previously reported Co-based nanomaterial-modified anodes. Based on the superior power generation capability of Co3O4@PEDOT-CC, it has been innovatively applied to TC treatment, revealing pioneering insights that the combination of extracellular electron-transfer process and functional microbial consortia regulation contribute to TC degradation. At a TC concentration of 4 mg/L, the MES with Co3O4@PEDOT-CC maintained a power output comparable to that in the absence of TC along with 80% TC removal, whereas the CC exhibited significant declines in both electricity output and TC elimination. For this interesting phenomenon, the underlying mechanism has been uncovered: Co3O4@PEDOT-CC facilitates the enrichment and survival of exoelectrogens. Under dual selective pressures, it enables the rational aggregation of exoelectrogens with TC-degrading bacteria; extracellular-electron-transfer-mediated optimized functional microbial consortia balance the TC-induced reactive oxygen species stress and the power generation capability. This provides wisdom for advancing the design of high-performance anodes purifying water with refractory organic compounds.