Insights into periodate oxidation of antibiotics mediated by visible-light-induced polymeric carbon nitride: Performance and mechanism

Abstract

Periodate (PI)-based advanced oxidation processes (AOPs) have drawn growing attention in an effort to alleviate pollutants issues in the aqueous environment. Different from previous use of ultraviolet light or metal catalysts, this study proposes a novel system for the visible-light-assisted activation of PI via metal-free polymeric carbon nitride (CN). The best catalytic effect was achieved by CN synthesized from urea (UCN). Effective charge separation predominately caused kinetic increase in photocatalytic degradation, where interfacial electron transfer in UCN/PI/Vis system occurred in the synergistic process. UCN generated photogenerated electrons-hole under visible light irradiation. The organic pollutant acted as an electron donor. PI could effectively act as an electron capture agent and inhibit the complexation of charge carriers. The combination of PI-based AOP and photocatalysis greatly increased the degradation of pollutants through photocatalysis, achieving the effect of 1 + 1 > 2. The tetracycline (TC) effectively underwent nearly 100 % removal within 10 min and the corresponding kobs attained 0.40839 min−1. Besides, outstanding catalytic performance in a broad range of pH (2.99–11.01) was confirmed. Meanwhile, the UCN/PI/Vis system demonstrated favorable immunity to common wastewater components, good stability, and reusability. The prominent active species for TC degradation were singlet oxygen (1O2) and iodate radical (IO3·, IO4·), followed by superoxide radicals (O2−). This study establishes a precedent for visible-light-induced activation of PI by UCN, interfacial electron transfer occurs in a synergistic process, and greatly accelerated photocatalytic oxidation is accomplished with PI acting as an electron scavenger.