Bioelectricity enhanced tetracycline degradation by iron‑carbon activated persulfate: Performance, mechanism and toxicity assessment

The broad-spectrum antibiotic tetracycline widely used in medical treatment and livestock farming, has become an emerging pollutant in natural water bodies due to its extensive misuse. In this study, a bioelectricity/Fe-C/peroxydisulfate (BET/Fe-C/PDS) system was constructed and used to degrade TC. For this system, a novel microbial desalination fuel cell (MDC) was utilized to generate bioelectricity and enhance persulfate (PDS) activation by Fe C materials. The results showed the MDC achieved a maximum voltage of 1.43 V and a power density of 45.63 W/m 3 . Compared with Fe-C/PDS system, BET/Fe-C/PDS system exhibited a higher reaction rate constant (k obs ) and achieved 98.62 % TC removal in 40 min. With the increase of PDS concentration and Fe C dosage, the removal of TC showed a trend of initially increases and then decreases. The k obs for TC degradation reached maximum value at pH = 5 and the BET/Fe-C/PDS system displayed excellent performance in a wide range of pH (3−10). Both coexisting anions and natural organic matter inhibited degradation of TC. Quenching experiments and EPR results identified ·SO 4 − , ·OH, ·O 2 − , and 1 O 2 as the primary active species. The possible attack sites and degradation pathways of TC were systematically elucidated according to the analysis results of UPLC-MS, DFT and HOMO-LUMO. The main degradation mechanism involves multi-step reactions including C N bond breaking, demethylation, decarbonylation, deamidation, ring opening, dehydration condensation and addition. The toxicity variation of tetracycline by BET/Fe-C/PDS system was confirmed based on quantitative structure-activity relationship predictions. Future research should focus on enhancing MDC power generation, elucidating in depth reactive species formation and TC degradation mechanisms, and expanding the system's application to diverse antibiotics and multi-component pollutant removal.