Peroxymonosulfate activation by boron doped C3N5 metal-free materials with n → π* electronic transitions for tetracycline degradation under visible light: Insights into the generation of reactive species

Heterogeneous photocatalysis coupled with peroxymonosulfate (PMS) activation is regarded as an advanced water treatment technology for emerging contaminates degradation. We introduce a novel coupling system that integrates PMS with metal-free visible light-driven photocatalysis, utilizing boron doped C3N5 (BCNs), with the objective of swiftly eliminating tetracycline (TC) from wastewater. With commendable traits including a robust response to visible light, n → π* electronic transitions and a narrow bandgap, 3BCN optimized from BCNs, exhibited superior catalytic activity in photocatalysis and PMS activation. In 3BCN/PMS/vis system, the degradation efficiency of TC reached 88.6 % in 120 min, with an observed rate constant (kobs) of 0.0222 min−1 for TC removal. Moreover, in real water matrices including tap water, landscape water and secondary effluent, the 3BCN/PMS/vis system consistently maintained high and stable pollutant removal efficiency. To elucidate the underlying mechanisms, the origins of reactive species (h+, SO4−•, •OH and 1O2) were identified and the enhanced pathways in the PMS-based photocatalytic system were systematically investigated. Based on theoretical calculations, generation pathway of reactive oxygen species involving PMS oxidation and reduction over the region of boron atom neighboring N in BCN was unraveled. The BCN catalyst was employed in a flow-through device to explore its potential in practical application. The results showed that continuous and impressive efficient removal of TC was achieved with over 93 % removal rate during 32 h operation. Our findings underscore the substantial promise of chemical-photocatalysis synergy for environment remediation, offering a feasible approach to optimize the performance of metal-free materials in photo-catalytic oxidation of antibiotics.