Mechanism insights into Fe(III) reduction for enhanced aquatic contaminant degradation: The pivotal role of heterogeneous reductants

Abstract

The low cycle rate of Fe(III)/Fe(II), especially the reduction process of Fe(III), is one of the key factors limiting the contaminant degradation during the application of Fenton technology. Compared with the direct addition of homogeneous reductants, information on heterogeneous reductants on the process and mechanism of Fe(III) reduction remains scarce. In this study, the bacterial cellulose (BC) was selected as the substrate for gallic acid (GA) to prepare the heterogeneous reductant BC/GA composite to systematically investigate the atrazine (ATZ) degradation performance and mechanisms. The results showed that the apparent rate constant for BC/GA + Fe(III)/H2O2 system was 86 times and 9.8 times higher than those for Fe(III)/H2O2 and GA + Fe(III)/H2O2 systems, respectively, and almost 100 % of ATZ degradation was achieved within 20 min. The improved degradation rates were attributed to the enhanced generation of hydroxyl radicals. Furthermore, unlike the conventional homogeneous system, the heterogeneous GA was no longer directly involved in the Fe(III)/Fe(II) cycling process but mainly formed a complex with Fe(III) that reacted with H2O2. This study contributes to a better understanding of the enhanced Fe(III)/Fe(II) cycle process with the presence of heterogeneous reductant, thus providing new ideas on how to develop a more efficient heterogeneous reductant for contaminant degradation.