Efficient activation of periodate for sulfamethoxazole degradation by modulating charge density in single-atom Mn regions via carbon vacancies in carbon nitride

Abstract

The advanced oxidation system involving periodate (PI) has demonstrated effective degradation capabilities for certain organic pollutants in water. A critical aspect of this process is the efficient activation of periodate. In this experiment, carbon vacancy-containing graphitic carbon nitride (C_v-CN) was prepared through a simple high-temperature calcination method, and Mn atoms were uniformly dispersed on its surface, forming Mn-C_v-CN. The presence of carbon vacancies modulated the electron density around the single-atom Mn, significantly enhancing the activation efficiency of PI. Surface-anchored Mn atoms with carbon vacancies in carbon nitride/periodate (Mn-C_v-CN/PI) system degraded 99% of sulfamethoxazole (SMX) within 25 min. Various degradation factors for SMX, including O₂⁻, ¹O₂, IO₃, OH, and electron transfer processes, were detected, with O₂⁻ identified as the primary reactive oxygen species (ROS). PI was activated by acquiring electrons from active sites, generating a substantial amount of O₂⁻ to catalytically transform the pollutants. Liquid chromatography-mass spectrometry was used to analyze the possible degradation pathways and intermediates of SMX. Multiple experiments demonstrated that the Mn-C_v-CN/PI system showed promising potential in treating water containing recalcitrant antibiotics. The findings provided a novel strategy for efficiently activating PI with single-atom catalysts to remove refractory pollutants from water.