Mechanisms of simultaneous removal of multiple chlorinated hydrocarbons in aquifers by in-situ microemulsion

The chlorinated hydrocarbons (CHs) are typically released to the aquifer as complex mixture, and the contaminant type takes the critical action on the in-situ microemulsion formation and solubilization behaviors. However, few interst has been paid to the solubilization behaviors of microemulsion for multiply CHs and the factors affecting selective solubilization. The current work investigated the effect of hydrogeochemical conditions on microemulsion competitive solubilization, and focused on the selective desorption and removal performance of in-situ microemulsion drenching under the various drenching situations. The results elucidated that the apparent solubility of CH was enhanced with adding inorganic salts and the decreasing temperature. In-situ microemulsion showed a preference for dissolving the more polar CHs (CF) in chlorinated hydrocarbon mixture. The selective solubilization was strengthened with increasing temperature, independent of alcohols and salts. The removal efficiency of microemulsion drenching for multiply CHs could achieve 96.0 %, improving with the tinier particle media and lower flow rates. Compared to other CHs, CF was more likely to be desorbed from aquifer medium in multicomponent systems. Furthermore, the selective desorption for multiply CHs was associated with flow rates, media size and residual saturation of contaminants. The inhibition for preferential desorption was more intense to the increase of injection velocity, media size and residual saturation. This insight of selective solubilization behavior can be used to advances the application of in-situ microemulsion drenching for site remediation of multiply CHs.