Fast removal of trichloroethene from groundwater using surfactant amended bone char and green rusts mixture: Mechanism of surface interface interaction

Abstract

Green rust and bone char (GR-BC) mixture is reported as an effective reducing reagent for chlorinated ethenes dehalogenation. However, surfactant amendment might be required before the injection of GR-BC into the contaminated sites, which could enable better distribution of the reagent and even better dehalogenation performance. In this study, different surfactants were screened and optimal mixing methods were developed. The result shows that the pre-mixing of BC and anionic surfactants would enhance TCE dehalogenation, and faster dehalogenation was observed at higher BC and surfactant concentrations. 20 μM of TCE was eliminated in 2 h (kobs = 4.08 h−1) in the pre-mixture of 1 g/L BC and 0.16% anionic surfactants with 30 mM [Fe (II)] GR addition. The major dehalogenation products were non-chlorinated C2 (acetylene and ethane) and possible C3 ~ C6 compounds while chlorinated product was not detected. Ionic and nonionic surfactants would generally inhibit the TCE dehalogenation whatever mixing method was used. This result suggests that pre-mixing of BC and selected anionic surfactants would benefit interactions among BC, GR and TCE, which could significantly enhance the TCE dehalogenation. Furthermore, this pre-mixing approach might provide a way to formulate suitable suspensions to facilitate the reagents injection and distribution in contaminated groundwater.