Photoinduced g-C3N4-promoted Mn2+/Mn3+/Mn4+ redox cycles for activation of peroxymonosulfate

In this work, a novel g-C3N4 modified Mn3O4 composite was synthesized and applied to activate peroxymonosulfate (PMS) for phenol degradation under simulated sunlight. We investigated the effect of solution initial pH and reaction temperature, meanwhile ascertaining the optimal molar ratio of Mn3O4 and g-C3N4 and the stability and reusability of the materials. The g-C3N4/Mn3O4 exhibited superior activity for PMS activation under simulated sunlight, 87.3% phenol degradation and 47.3% phenol mineralization at 60 min were achieved. The combination of Mn3O4 nanoparticles and g-C3N4 sheets results in a higher catalytic activity than pure Mn3O4 and g-C3N4. Furthermore, quenching experiments and electron spin resonance measurements (ESR) prove that phenol degradation by g-C3N4/Mn3O4/PMS system is primarily attributed to the generation of sulfate radicals, hydroxyl radicals, and superoxide radicals. A possible mechanism was proposed for phenol removal by g-C3N4/Mn3O4/PMS system under simulated sunlight. This work is intent to arise more interest about solar light for PMS activation and future research on water treatment.