Catalytic performance and mechanism of biochars for dechlorination of tetrachloroethylene in sulfide aqueous solution

[Display omitted] •Biochar catalyzed the dechlorination of >99 % PCE in sulfide solution.•Catalytic effect remained stable under both neutral and alkaline pH conditions.•Both biochar and sulfide concentrations affected the dechlorination rate.•Carbon and oxygen adjacent to pyridine nitrogen on biochar were the active sites of biochar. Biochar (BC) has been investigated as a natural and economical activator to treat organic contamination. Compared with commercial carbon materials, BCs have a better prospect of large-scale application. For the first time, this study certified degradation of tetrachloroethene (PCE) in sulfide-containing aqueous solutions catalyzed by wormwood-based BCs pyrolyzed at 600 °C, 700 °C, and 800 °C (BC600, BC700, and BC800). Interestingly, BC800 could catalyze PCE dechlorination and form acetylene and chloride ion with over 99 % nontoxic transformation in neutral and alkaline pH conditions. Furthermore, materials surface properties, BC dosages and sulfide concentrations were considered as limiting factors for dechlorination, and the last one had the strongest influence. XPS analysis demonstrated that catalytic ability of BC was attributed to pyridine nitrogen (N6) on surface, because C and O adjacent to N6 strongly favor nucleophilic reactions. These results evaluated the applicability of degrading toxic chlorinated alkenes mediated by natural carbon materials in sulfide-containing environment.