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

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

Automated summary

The use of Mn-CNH co-catalyst in constructing a solid-liquid interfacial Fenton reaction has shown promising results in efficiently removing pollutants at lower pH levels. This method accelerates the Fe-III/Fe-II redox cycle, achieving high regeneration rate of FeII and significantly improving pollutant degradation efficiency.