New insights into the role of biochar and Cu-biochar in enhanced degradation of sulfonamides by ferrate: Involvements of electron transfer and hydroxyl radical oxidation pathways

In this study, orange peel and tea waste were successfully prepared into orange peel biochar (OBC) and tea waste biochar (TBC). OBC, TBC, and conventional corn straw biochar (CBC) were employed to facilitate the oxidative degradation of sulfamethoxazole (SMX) with ferrate (Fe(VI)) under neutral conditions (pH 7.0). The degradation of SMX was enhanced with the increase of the preparation temperature (400–600 °C) of OBC and TBC. The pyridine N on OBC and TBC dominated the enhancing degradation of SMX by Fe(VI) through an electron transfer pathway. OBC prepared at 600 °C (OBC600) was further modified by different Cu loading amounts. The degradation efficiency of SMX by Cu-loading/OBC600 was more significant than that by OBC600. H₂O₂ generated from the decay and oxidation of Fe(VI) was consumed by generated Cu(I) in Cu-loading/OBC600 followed by the generation of hydroxyl radical (•OH). This study established a novel strategy utilizing biochar while advancing mechanistic understanding of Fe(VI) activation processes, which was an environmentally friendly drinking water pre-treatment involving Fe(VI) and biochar and modified biochar.