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

Abstract

The present investigation articulates the application of a MIL-53(Fe) metal-organic framework (MOF)-derived Fe₃O₄ and multi-walled carbon nanotubes (cFe@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 (H₂O₂), further turning into hydroxyl radical (˙OH) to degrade the acridine orange (ACO) dye. The k value for the degradation of ACO in BEF-cFe@MWCNT was 0.0075 min⁻¹, which was 17.3-fold lower than the k value attained by the BEP-cFe@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-cFe@MWCNT and BEP-cFe@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-cFe@MWCNT system towards emerging contaminant degradation in a shorter reaction time and affirmed its practical feasibility in wastewater treatment.