The photocatalytic mineralization of phenolic wastewater via self-generation and -activation of H2O2 technology

Abstract

Achieving efficient photocatalytic degradation and mineralization of phenolic pollutants under mild conditions is the key to solving the environmental crisis. Herein, a novel self-generation and -activation of H2O2 technology is achieved on graphitic carbon nitride (GCN)/anthraquinone-based covalent organic frameworks (TD-COF) heterojunction photocatalysts (CNTD-X). Some of the photogenerated electrons (e-) that migrate directionally to the surface of TD-COF could generate H2O2via oxygen reduction reaction (ORR) route, while the e- gathered around anthraquinone can reduce it to stable semi-quinone radicals, which can further release hydroxyl radical (·OH) through electron transfer with H2O2. The photogenerated holes (h+) gathered on the surface of GCN would provide important raw materials for ORR reaction through oxidation of water, and participate in the mineralization process of pollutants. With the ring opening of·OH and the oxidation of h+, this heterojunction system can achieve efficient phenolic pollutants removal. The optimal sample of CNTD-0.02 possesses an incredible phenol removal (99.4%) within 12 min under visible light irradiation (λ > 420 nm), and total organic carbon (TOC) analysis shows 81% phenol is converted into CO2 and H2O. The photo-degradation rate of CNTD-0.02 is about 204.2 and 26.8 times that of GCN and TD-COF, respectively. This novel photocatalytic strategy over CNTD-X could also be applied in other phenolic pollutants removal, and our work paves a new way for environmental remediation in clean and efficient technology.