Aquifer flushing using a SDS/1-butanol based in-situ microemulsion: Performance and mechanism for the remediation of nitrobenzene contamination.

In-situ microemulsion flushing is an effective remediation technology for the removal of dense non-aqueous phase liquids (DNAPLs) from aquifers. Nitrobenzene (NB) is a typical DNAPL pollutant that is responsible for the serious contamination of many groundwater systems, while its removal using the flushing method has rarely been studied. In this study, bench scale, 1-D column and 2-D tank experiments were conducted to establish an efficient salt-free sodium dodecyl sulfate (SDS)/1-butanol based in-situ microemulsion flushing system for NB contaminated aquifers. Results showed that the NB/SDS/1-butanol/water microemulsion increased dissolved NB concentrations by more than 15-fold compared to the SDS-only solution. The formulation also presented good solubilization capacity at low temperature (5 ℃) and with clay media. NB was effectively removed from the aquifer by solubilization and mobilization via the formation of the microemulsion with the injected SDS/1-butanol solution. The flushing system also reduced the tailing phenomenon in later remediation stages, and exhibited weak reagent adsorption onto aquifer media. Furthermore, the vertical DNAPL migration to deeper aquifer was effectively controlled. Therefore, the constructed in-situ microemulsion flushing system is a highly efficient treatment method for NB contaminated aquifers, with this study providing valuable reference information on the optimal reagent parameters and the remediation mechanism.