Accelerating Fe<sup>III</sup>-Aqua Complex Reduction in an Efficient Solid–Liquid-Interfacial Fenton Reaction over the Mn–CNH Co-catalyst at Near-Neutral pH
Yueshuang Mao, Pengfei Wang, Dongpeng Zhang, Yuguo Xia, Yi Li, Wenlu Zeng, Sihui Zhan, John C. Crittenden
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.