Sea-Urchin carbon nitride with carbon vacancies (C-v) and oxygen substitution (O-s) for photodegradation of Tetracycline: Performance, mechanism insight and pathways

Abstract

The fast recombination of electron-hole pairs results in low photoactivity, limiting carbon nitride further application in wastewater purification. To address this issue, regulation of electron configuration via optimizing surface atom properties is a promising strategy for improving the separation of electron-hole pairs. Here, sea-urchin carbon nitride (SUCN-6) with C-v and O-s mediated electronic structures were facile prepared, endowing it with a decrease in transportation resistance of charge carriers and increased activation towards oxygen. Under visible light, the SUCN-6 showed a removal efficiency of ∼ 89% towards tetracycline (TC) in 20 min and no obvious decaying after five consecutive cycles. This TC photodegradation follows a first-order kinetic, and its kinetic constant reaches 0.0908 min−1, which is 2.35 folds higher than that of pristine carbon nitride. In addition, several crucial factors of practical wastewater purification (such as pH, TC concentration, water sources, inorganic salts, and organic matters) that might affect photoactivity were investigated. Moreover, the degradation pathways of TC and intermediates were detected by an HPLC-MS and electron spin resonance instrument, and a possible photodegradation mechanism over SUCN-6 was elucidated. This study offers new insights into the photocatalysis kinetics and photodegradation mechanism over carbon nitride for environmental remediation.