Spin-states-assistance peroxymonosulfate absorption via Mn doped catalyst with/without light for BPA oxidation: The negative contribution of electrons transfer by light

• Low spin state of Mn-N motifs strengthened the adsorption between PMS and MCN. • Nonradical theories were both occurred in the PMS dark and light activation by MCN. • Due to special theory, light was a passive role for BPA removal in MCN/PMS-L system. • The light restriction of BPA removal was emerged with attenuated electrons transfer. • In situ spectra and DFT revealed the courses of PMS activation and light-suppression. Adsorption is the initial and critical step in peroxymonosulfate (PMS) activation, the favorable adsorption can accelerate the activation rate between PMS and materials. Low spin states of transition metals can enhance binding strength between metal sites and oxygen-containing species. Herein, a low spin-state of Mn doped C 3 N 4 composite (MCN) could further strengthen PMS adsorption in bisphenol A (BPA) oxidation, and showed remarkable the removal capacity of BPA with and without light irradiation. Interestingly, unlike previous studies, the contribution of light in MCN/PMS systems was decreasing for BPA degradation as the Mn increases in this study. When the amount of Mn was 11 wt%, the BPA degradation rate of 11MCN/PMS-light was less than that of 11MCN/PMS-dark, however 11MCN still had wonderful ability in photocatalysis and PMS activation. Subsequently, the catalytic mechanisms of electrons-transfer processes were manifested in the MCN/PMS systems with/without light via the in-situ spectra and density functional theory (DFT). Due to the unique mechanism of electrons transfer, the cause of negative influence for BPA degradation in light was the opposite direction of electrons transfer to that of PMS activation. In this study, our findings could provide a novel insight into the catalytic mechanisms of the photo-Fenton process for selecting more suitable external assistance.