Biochar can facilitate sulfide to reduce organic contaminants, such as tetrachloroethylene (PCE). However, the biochar interface catalytic performance in complex water matrices is rarely investigated, and the combined roles of sulfide and hydrogeochemical component in the dechlorination of PCE remains unclear. This study explore the influence of environmental parameters on PCE dechlorination by a wood-based biochar (WW800). The enhanced reductive dechlorination by WW800 was a two-site heterogeneous catalytic process in two stages: (1) adsorption and (2) reduction. In the absence of ions, the removal of PCE included both stages. Ca2+ cation bridge was important in enhancing the reducibility of –COOH on WW800 bound sulfide. The co-existence ionic conditions of six redox zones were simulated, HCO3– inhibited the binding of sulfide to WW800, and SO42− inhibited both adsorption and reduction stages. These inhibitory effects were prior to the promotion of Ca2+. The combination of multiple ions with WW800 consumed the active groups (pyridine N, C=O and O-C=O), which limited the transformation of sulfides to strong nucleophilicity. Among the single influencing factors, Ca2+, HCO3–, initial concentration of PCE and temperature were positively correlated with the removal kinetics of PCE (P<0.05). The low concentration of Fe2+ and Mn2+ in the simulated zones did not significantly promote the removal of PCE. According to the kinetic changes of dechlorination reaction, the inhibition of PCE conversion by humic acid was due to the change of sulfide species caused by pH value change. The aquifer environment with low temperature (10–15 °C) and DO (0–6.6 mg/L) had little effect on PCE dechlorination. Our results show that the hydrochemical components in aquifer enhance PCE dechlorination by biochar with different influence mechanisms, which provides theoretical guidance for application of this method in the aquifer.

Tetrachloroethylene dechlorination from sulfide-containing aquifers by biochar depends on hydrogeochemical conditions in two aspects: Adsorption and catalysis