Enhancement of organic contaminants degradation at low dosages of Fe(III) and H2O2 in g-C3N4 promoted Fe(III)/H2O2 system under visible light irradiation

Abstract

Developing a low-cost and environmental friendly way to promote the Fe(III)/Fe(II) cycling is crucial to enhance the efficiency of Fenton reaction. In this study, g-C3N4 was introduced into the Fe(III)/H2O2 system as electron donor to accelerate Fe(III)/Fe(II) cycling and improve the degradation of organic pollutants under visible light. The g-C3N4/Fe(III)/H2O2/light system can achieve excellent degradation of different kinds of organic pollutants under low Fe(III) and H2O2 dosages. The central composite design (CCD) and response surface methodology (RSM) were applied to evaluate the effects of g-C3N4 dosage, Fe(III) dosage, H2O2 dosage and light intensity on the DMP degradation efficiency. The mechanisms were investigated by quenching experiments and electron spin resonance (EPR) analyses that the photo-generated electrons and O2– were responsible to the Fe(III) reduction through interfacial and aqueous pathways, respectively. OH was the dominant reactive radical in the DMP degradation. Moreover, DMP degradation routes were proposed including the elimination of specific groups, the hydroxylation process and the ring-opening reactions. This study demonstrates an economical and green approach which provides a promising direction for the practical application of g-C3N4 based photocatalysis by integrating it with the Fe(III)/H2O2 Fenton process.