Solar-initiated continuous electron injection to promote Fe3+/Fe2+ catalytic cycle in tourmaline/g-C3N4 composite system for enhanced PMS activation

Abstract

It is of great significance for improving the electron transmission performance of graphite phase carbon nitride (g-C3N4) by an economical method. Herein, urea was mixed with tourmaline (TM) and calcined to obtain g-C3N4/TM composite photocatalyst. Under solar light, g-C3N4/TM activated peroxymonosulfate (PMS) to degrade carbamazepine (CBZ) entirely within 25 ​min. g-C3N4/TM had a superior photocatalytic oxidation performance under solar light than g-C3N4. Photogenerated electron-hole pairs of g-C3N4 were efficaciously suppressed, originating from the more excellent electronic transfer to TM. Four active species, including SO4•-, •OH, 1O2, and O2•-, were identified for the degradation of CBZ. Ten intermediates of CBZ and six intermediates of sulfaquinoxaline sodium (SQXNa) were determined by using ultra-performance liquid chromatography coupled with a high definition mass spectrometer (UPLC-HDMS), and a degradation pathway was proposed. As the reaction progressed, all aromatic nuclear intermediates were mineralized. The degradation of other organic pollutants by the g-C3N4/TM/PMS system validated the universal adaptability in practical applications. This research provided an effective way to improve the g-C3N4 photocatalytic activity in wastewater treatment.