Removal of P-arsanilic acid using a gas diffusion cathode prepared from CoFe-MOF-C-700 to construct a three-dimensional electro-Fenton system: Reaction kinetics and mechanism

P-arsanilic acid (P-ASA), an antimicrobial and growth-promoting agent widely used in animal husbandry, has become a focal point of environmental concern due to its resistance to degradation and potential for water contamination. This study investigates the efficacy of a three-dimensional electro-Fenton (TD-EF) system for the removal of P-ASA from aqueous solutions. The TD-EF reactor was configured with a gas diffusion electrode (GDE) fabricated from ZIF-67-derived CoFe-MOF-C-700 and carbon black, paired with graphite as the anode and granular activated carbon impregnated with FeSO4 & sdot;7H2O as the particle electrode. The experimental findings indicated that the TD-EF system achieved a remarkable 97.4 % removal rate of P-ASA and a 51.2 % reduction in total organic carbon (TOC) within 100 min. Characterization and electrochemical analyses confirmed that the CoFe-MOF-C-700 composite exhibited a high density of active sites and superior catalytic efficiency in the oxygen reduction reaction. Notably, hydrogen peroxide generation was optimized, with an accumulation up to 67.5 mM after 60 min. The degradation process was significantly influenced by hydroxyl radicals and singlet oxygen, as evidenced by reactive oxygen species trapping and electron paramagnetic resonance experiments. Additionally, LC-MS analysis and DFT calculations provided insights into the degradation pathways of P-ASA, while EPI software evaluations and toxicity tests confirmed the environmentally friendly nature of the treated effluent. This research not only provides critical insights into the design and application of bimetallic metal-organic frameworks (MOFs) with enhanced catalytic performance but also underscores the potential of the TD-EF system as a sustainable technology for arsenic remediation.