S-scheme heterojunction g-C3N4/Ag/AgNCO for efficient tetracycline removal in a photo-assisted peroxymonosulfate system

Photo-assisted peroxymonosulfate (PMS) activation process is emerging as an effective and eco-friendly technology for sewage purification. Herein, a g-C3N4-based S-scheme heterostructure (g-C3N4/Ag/AgNCO) was fabricated by a facile chemical-deposition and photo-reduction method. Because of intensive hetero-interface contact and synergistic effect between g-C3N4 and Ag/AgNCO, the assembled heterojunction exhibits enhanced light absorption, rapid charge separation/transport and impressive catalytic performance. Tetracycline (TC) degradation efficiency of 98% with a rate constant of 0.2995 min(-1) can be accomplished over 40%-g-C3N4/Ag/AgNCO/PMS/light system within 12 min, 3.05 and 4.86 times better than that obtained over g-C3N4/PMS/light and AgNCO/PMS/light system, respectively. The quenching/ESR investigation suggested that the active species function syngenetically in TC degradation and the significance follows the order of h(+) > SO4 & BULL;- ~ O-& BULL;(2)- > O-1(2) > (OH)-O-& BULL;. The cyclic test proved the excellent stability of the current catalyst system. The involved degradation routes, intermediates, and toxicity assessment have been studied in detail. The current research may serve as a versatile tactic for designing the g-C3N4-based functionalized catalytic material for wastewater purification through the photocatalysis/sulfate-mediated advanced treatment process.