LOW-TEMPERATURE MICROEMULSIONS FOR THE IN-SITU EXTRACTION OF CONTAMINANTS FROM SOIL

A complex microemulsion system using rape oil-methyl ester as the oil component, anionic and non-ionic surfactants and brine was developed f or the in situ extraction of hydrophobic contaminants at temperatures of about 10 degrees C. The phase behaviour at different compositions o f quaternary, quinary and hexanary systems was studied. The behaviour was governed by the anionic surfactant. The concentration of brine str ongly influences the phase behaviour. In addition, increasing the salt concentration leads to the suppression of liquid crystals. The additi on of a third, very bulky surfactant further suppresses the formation of liquid crystals for equal mass fractions of oil and brine. Equal am ounts of oil and water are necessary to avoid the formation of liquid crystals. A system with low surfactant concentration was chosen to det ermine the viscosity and surface tension. First column experiments wer e performed in order to determine the flow behaviour and the amounts o f microemulsion components adsorbed onto soil. In a batch experiment, the extraction efficiency of the microemulsion system was investigated at 10 degrees C for polychlorinated biphenyls from a doped soil. It w as better than the efficiency of the toluene extraction. Microemulsion systems seem to be excellent media for the in situ remediation of hyd rophobic contaminants from soil. (C) 1998 Elsevier Science B.V. All ri ghts reserved.