N-doped coal-based carbon membrane coupling peroxymonosulfate activation for bisphenol A degradation: The role of micro-carbon structure and nitrogen species

Herein, a novel N-doped coal-based carbon membrane (N-CCM) was prepared by using melamine as N source with high-temperature pyrolysis assistance. Through reasonable regulation of membrane micro-carbon structure and N species by varying pyrolysis temperature, the N-CCM integrated with peroxymonosulfate (PMS) activation under membrane filtration (MFPA) process showed excellent bisphenol A (BPA) removal of 98.3%. The excellent performance of N-CCM MFPA process was mainly owing to the following reason: For one thing, the more orderly micro-carbon structure of N-CCM possessed high defect density and boundary active sites under suitable pyrolysis temperature (700 degrees C), contributing to PMS activation (enhanced generation of reactive oxygen species (ROS) and electron transfer). For another, pyrrolic N, pyridinic N and C=C were beneficial to PMS adsorption and facilitate the electrons transfer from BPA to PMS. While C-O and graphitic N were responsible for the generation of ROS (SO4 center dot-, center dot OH and O-1(2)). Theoretical calculations showed that the bond length of O-O, O-H and O-S in PMS adsorbed on C atom near N sites was significantly lengthened, corresponding to the generated ROS. Overall, the co-effect of radical process (SO4 center dot- and center dot OH) and non-radical process (O-1(2) and electron transfer) achieved efficient BPA degradation in system.