Enhanced reductive degradation of tetrabromobisphenol A by biochar supported sulfidated nanoscale zero-valent iron: Selectivity and core reactivity

A core-shell structure of sulfidated nanoscale zero-valent iron deposited on biochar (S-nZVI/BC) was synthesized and the performance of S-nZVI/BC on tetrabromobisphenol A (TBBPA) degradation was investigated. Detailed characterizations indicated that controlling S content altered distribution of S species (i.e., S2-, S22-, and Sn2-) in shell and core and achieved higher hydrophobicity and lower electron-transfer resistance. S-nZVI/BC was highly reactive (∼4.3–11.3 times) and selective (∼78.9–152.6 times) over nZVI/BC for TBBPA degradation. Besides, BC improved reactivity and selectivity of S-nZVI by 0.17 and 1.35 times, respectively, deriving from increased electron-transfer, enhanced hydrophobicity, and more surface reduced S species. Thus, sulfidation and BC enhanced reactivity and selectivity of S-nZVI/BC by combining respective merits. Effects of initial TBBPA concentration, pH, and particles dosage on TBBPA degradation by S-nZVI/BC were also investigated. Remarkably, mechanism investigation revealed that core properties instead of shell dominated reactivity and TBBPA debromination mainly involved direct electron-transfer rather than atomic H.