Dual roles of biochar redox property in mediating 2,4-dichlorophenol degradation in the presence of Fe3+ and persulfate

Recent studies suggested that biochars could mediate the degradation of organic contaminants. The role of biochars in mediating organic contaminant degradation could be amplified in a Fenton-like reaction, and comparing biochars with varied properties may provide insightful information to understand the reaction mechanisms. In this study, biochar was applied in a Fenton-like reaction system with Fe3+ and persulfate (PS) to degrade 2,4-dichlorophenel (2,4-DCP). Biochars with different intensities of persistent free radicals (PFRs), oxygen-containing functional groups (OFGs), and redox properties were investigated regarding their roles in 2,4-DCP removal. Compared to biochar system, PS addition increased 2,4-DCP degradation and Fe3+ addition increased its sorption. The combination of PS and Fe3+ promoted 2,4-DCP degradation over 2 times higher. Various reactive oxygen species (ROS), including SO4 center dot-, HO center dot, and O-2(center dot-), were involved in 2,4-DCP degradation, contributing to around 50% of the overall 2,4-DCP degradation. The direct electron transfer between biochar particles and 2,4-DCP contributed to the rest of 2,4-DCP degradation. A significant positive correlation was observed between 2,4-DCP degradation and electron donating capacity (EDC) or Fe2+. We thus concluded that EDC-involved structures in biochars could either directly donate electron to 2,4-DCP, or reduce Fe3+ to Fe2+, which activated PS to generate ROS. This dual roles of biochar should be well considered in biochar application and production. This study provided a useful theoretical basis for manipulating biochar redox properties to enhance their application potential in pollution control. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Recent studies show that biochars play a crucial role in mediating the degradation of organic contaminants and can amplify the degradation in a Fenton-like reaction with Fe3+ and persulfate. Different properties of biochars have varying effects on the removal of 2,4-DCP, with the combination of persulfate and Fe3+ significantly promoting the degradation of the contaminant. The direct electron transfer between biochars and 2,4-DCP also contributes significantly to the degradation process.