Heterogeneous Fenton oxidation of aniline aerofloat catalyzed by Fe/Mn binary oxides supported on activated carbon: performance and mechanism

The Fe/Mn binary oxides supported on activated carbon (Fe/Mn-AC) was prepared and employed for the catalytic Fenton degradation of aniline aerofloat (DDA). Preparation parameters were optimized by response surface methodology (RSM). Doping Mn optimized the crystalline structure of Fe oxides (mainly Fe₃O₄) and alleviated agglomeration of Fe/Mn oxides on Fe/Mn-AC, endowing it with more active catalytic sites and promoting the cycling of Fe(II)/Fe(III) and electron transfer. Various versatile functional groups on Fe/Mn-AC enhanced the binding with H₂O₂ and DDA, shorten the mass transfer distance, giving rapid DDA mineralization and high H₂O₂ utilization. Heterogeneous Fenton catalyzed by Fe/Mn-AC exerted high DDA mineralization with TOC removal efficiency of 84.83 %. The synergistic functions of Fe and Mn catalytic components enriched the generation approaches of multiple radicals in H₂O₂ catalytic decomposition. The dominant ·OH and other radicals such as ·OOH and ·O₂- were the reactive oxygen species (ROS) produced from the decomposition of H₂O₂ catalyzed by Fe/Mn-AC in well-timed way. ·OH was likely produced through alternative pathways catalyzed by Fe/Mn binary components with the mediation of Mn in the later period. The well-timed generation of multiple radicals and coordinated catalytic activity allowed the overall processes in an orderly way, performing high DDA removal and promoting H₂O₂ utilization. Moreover, the degradation pathway of DDA was analyzed through Density Function Theory (DFT) calculations and intermediates detection. The prepared catalyst presented exceptional stability. This study provided insights for the preparation and optimization of binary oxides catalyst with environment friendly application.