Photocatalysis-self-Fenton system over edge covalently modified g-C3N4 with high mineralization of persistent organic pollutants

The Fenton process is a widely used to remedy organic wastewaters, but it has problems of adding H2O2, low utilization efficiency of H2O2 and low mineralization efficiency. Here, a new photocatalysis-self-Fenton process was exploited for the removal of persistent 4-chlorophenol (4-CP) pollutant through coupling the photocatalysis of 4-carboxyphenylboronic acid edge covalently modified g-C3N4 (CPBA-CN) with Fenton. In this process, H2O2 was in situ generated via photocatalysis over CPBA-CN, the photogenerated electrons assisted the accelerated regeneration of Fe2+ to improve the utilization efficiency of H2O2, and the photogenerated holes facilitated the enhancement of 4-CP mineralization. Under the conjugation of CPBA, the electronic structure of CN was opti-mized and the molecular dipole was enhanced, resulting in the deepening valence band position, accelerated electron-hole pair separation, and improved O2 adsorption-activation. Therefore, the incremental 4-CP degra-dation rate in the CPBA-CN photocatalysis-self-Fenton process was approaching 0.099 min-1, by a factor of 3.1 times compared with photocatalysis. The parallel mineralization efficiency increased to 74.6% that was 2.1 and 2.6 times than photocatalysis and Fenton, respectively. In addition, this system maintained an excellent stability in the recycle experiment and can be potentially applied in a wide range of pHs and under the coexistence of various ions. This study would provide new insights for improving Fenton process and promote further devel-opment of Fenton in organic wastewater purification.

Automated summary

A new photocatalysis-self-Fenton process was developed for the removal of persistent 4-chlorophenol pollutant. H2O2 was generated in situ via photocatalysis, and the photogenerated electrons and holes assisted in the regeneration of Fe2+ and mineralization of 4-CP, respectively. The CPBA-CN photocatalysis-self-Fenton process exhibited significantly higher degradation and mineralization efficiencies compared to traditional photocatalysis and Fenton. This study provides new insights for improving the Fenton process and further advancing wastewater purification.