Degradation of acridine orange using sustainable bio-electro-Fenton and bio-electro-peroxone systems with MIL-53(Fe)-derived Fe3O4 and MWCNT composite: A comparative assessment

• MIL-53(Fe)-derived Fe 3 O 4 /MWCNT ( c Fe@MWCNT) found an excellent cathode catalyst. • A comparison between Bio-electro-Fenton (BEF) and Bio-electro-Peroxone (BEP). • BEP- c Fe@MWCNT outperformed BEF- c Fe@MWCNT in acridine orange (ACO) degradation. • ACO degradation and concurrent power generation were accomplished by both systems. • Potential pathways for the degradation of ACO were identified. The present investigation articulates the application of a MIL-53(Fe) metal-organic framework (MOF)-derived Fe 3 O 4 and multi-walled carbon nanotubes ( c Fe@MWCNT) composite as cathode catalyst in bio-electro-Fenton (BEF) and bio-electro-peroxone (BEP) systems. Both the systems were comparatively inspected for the in-situ production of hydrogen peroxide (H 2 O 2 ), further turning into hydroxyl radical ( ˙ OH) to degrade the acridine orange (ACO) dye. The k value for the degradation of ACO in BEF- c Fe@MWCNT was 0.0075 min −1 , which was 17.3-fold lower than the k value attained by the BEP- c Fe@MWCNT system (0.1298 min −1 ). Interestingly, the baffling in the BEP system increased the degradation rate from 0.0575 to 0.1298 min −1 . Further, the ACO degradation in the secondary treated sewage was determined to be 78.51 ± 3.02 % (240 min) and 83.2 ± 2.7 % (50 min) in BEF- c Fe@MWCNT and BEP- c Fe@MWCNT, respectively. The demethylation reaction, initiated by the ˙ OH attack, was identified as the primary pathway for ACO degradation in both systems. Simultaneously, the intrinsic microbial activity in the anodic chamber was capable of generating power of 120.0 ± 2.2 and 103.6 ± 4.7 mW m −2 in BEF and BEP, respectively. A comprehensive comparative assessment of both systems was conducted based on pollutant degradation, power generation, and operational cost. Overall, results indicated the superiority of the baffled BEP- c Fe@MWCNT system towards emerging contaminant degradation in a shorter reaction time and affirmed its practical feasibility in wastewater treatment.