Mg-induced g-C3N4 synthesis of nitrogen-doped graphitic carbon for effective activation of peroxymonosulfate to degrade organic contaminants

The nitrogen-doped carbon derived from graphitic carbon nitride (g-C3N4) has been widely deployed in activating peroxymonosulfate (PMS) to remove organic pollutants. However, the instability of g-C3N4 at high temperature brings challenges to the preparation of materials. The nitrogen-doped graphitic carbon nanosheets (N-GC750) were synthesized by magnesium thermal denitrification. Magnesium undergoes the displacement reaction with small molecules produced by the pyrolysis of g-C3N4, thereby effectively fixing carbon on the in situ template of Mg3N2 and avoiding direct product volatilization. N-GC750 exhibited excellent performance during the PMS activation process and bisphenol A (BPA, 0.2 g/L) could be thoroughly removed in 30 min. A wide range of pH (3-11), temperature (10-40 degrees C) and common anions were employed in studying the impact on system. Additionally, N-GC750 showed satisfactory reusability in cycle tests and promising applicability in real water samples. Quenching experiments and electron paramagnetic resonance (EPR) measurements indicated that singlet oxygen was the main active species coupled with partial electron transfer in N-GC750/PMS system. Furtherly, the oxidation products were identified, and their ecotoxicity was evaluated. This work is expected to provide a reference for the feasibility of preparing g-C3N4 derived carbon materials and meaningful for PMS activation. (C) 2022 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.