Accelerating FeIII-Aqua Complex Reduction in an Efficient Solid-Liquid-Interfacial Fenton Reaction over the Mn-CNH Co-catalyst at Near-Neutral pH.

Abstract

The sluggish regeneration rate of FeII and low operating pH still restrict the wider application of classical Fenton process (FeII/H2O2) for practical water treatment. To overcome these challenges, we exploit the Mn-CNH co-catalyst to construct a solid-liquid interfacial Fenton reaction and accelerate the FeIII/FeII redox cycle at the interface for sustainably generating •OH from H2O2 activation. The Mn-CNH co-catalyst exhibits an excellent regeneration rate of FeII (∼65%) and a high tetracycline removal rate (Kobs) of 0.0541 min-1, which is 19.0 times higher than that of the FeII/H2O2 system (0.0027 min-1) at a near-neutral pH (pH ≈ 5.8), and it also attains 100% degradation of sulfamethoxazole, rhodamine B, and methyl orange. The cyclic mechanism of FeIII/FeII is further elucidated in an atomic scale by combining characterizations and density functional theory calculations, including FeaqIII specific adsorption and the electron-transfer process. Mn active sites can accumulate electrons from the matrix and adsorb FeaqIII to form Mn-Fe bonds at the solid-liquid interface, which accelerate electron transfer from Mn-CNH to FeaqIII and promote the regeneration of FeII at a wide pH range with a lower energy barrier. The regeneration rate of FeII in the Mn-CNH/FeII/H2O2 system outperforms the benchmark Fenton system and other typical metal nanomaterials, which has great potential to be widely applied in actual environment remediation.