EMULSION-MEDIATED TRANSPORT OF NONAQUEOUS-PHASE LIQUID IN POROUS-MEDIA - A REVIEW

A review of literature on the formation, characteristic properties, an d flow of emulsion in subsurface environment, and its potential impact on the transport of nonaqueous-phase liquids (NAPLs) is provided. Syn thesis of the literature indicates that emulsions can form during petr oleum recovery as a result of production of natural surfactants by soi l microorganisms, and the use of synthetic surfactants to clean up NAP L-contaminated soils and aquifers. The use of surfactants as a remedia tion technique to remove hazardous NAPLs from soil and groundwater has been explored in some detail. However, cost-effective and high-effici ency remediation approaches using surfactants have yet to be accomplis hed. This review suggests that the use of surfactants to remove NAPLs from soil may involve the formation and flow of emulsions in the subsu rface environment. The flow of emulsions may influence the transport o f hazardous NAPLs in the subsurface environment, depending on the type and stability of emulsion formed under specific conditions. In genera l, the flow of microemulsion enhances the transport of NAPLs through s ubsurface environments. Further investigation should focus on the form ation, stability, microbial degradation, and flow of emulsion in subsu rface environments when surfactants are used as a potential means for recovering NAPLs from soils and aquifers.