Modulating the redox couples of graphene-like NBC-TiO2@FeMn through forming photo-Fenton system for boosting persulfate activation to accelerate the contaminant degradation

The sluggish cycling of redox couples hampers the practical application of catalysts in contaminant degradation. Herein, a novel strategy was introduced by constructing a photo-Fenton system onto the graphene-like NBC to realize the ultrafast modulating of redox couples during the contaminant degradation. The constructed NBC-TiO2@FeMn (NBTF) exhibits a higher proportion of reductive redox couples (Fe (II)/Mn (II)) after the degradation, which is attributable to the photo-Fenton system and the graphene-like NBC with high electron transfer efficiency. Density functional theory (DFT) calculations also confirm that constructing the photo-Fenton system on graphene-like NBC greatly enhances electron transfer, enabling the modulation of redox couples during the degradation process. During activation, various reactive oxygen species (including •OH, SO4•-, high-valent metal oxides, and non-radical pathways) are generated, effectively degrading pulp wastewater Tetrachloroguaiacol (TeCG) with a degradation efficiency of 98.8 % within 14 min. Quenching experiments and EPR spectroscopic analysis indicate that the degradation of TeCG is mainly mediated by hydroxyl radicals (•OH) and sulfate radicals (SO4•-) as predominant pathways, while high-valent metal oxides, 1O2 and direct electron transfer mechanisms act in a cooperative manner. Substitution reaction on active sites reveal that both FeMn LDH and graphene-like NBC are identified as the main active sites, with Mn exhibiting superior PMS activation compared to Fe. A possible degradation pathway of TeCG is proposed, and a decrease in the toxicity of intermediates is observed. This study provides a new perspective on the modulation of redox couples in SR-AOPs to realize sustainable pollutants degradation.