REMOVAL OF ANTHRACENE CONTAMINATED SOIL USING MICRO- EMULSIFIED SOLVENT AND MIXED SURFACTANT

Micro-emulsified solvent (MES) prepared by adding soybean oil into anionic surfactant sodium dodecyl sulfate (SDS, NaC12H25SO4) was used in this study to investigate the removal of anthracene contaminated soil. The stability of emulsified surfactant was adjusted to prevent stratification between water layer and emulsified droplets (micelles) by changing the oil-to-surfactant ratio and the temperature. A previous study proved the use of a mixture of two surfactants to be more efficient than a single surfactant for desorption of the hydrophobic contaminants from soil. In this study, Triton X-100 and SDS were mixed at different ratios to study the increase of the removal efficiency (RE) of anthracene in soil. Extending the time and increasing the temperature of sonification decreased the size of the micelles. The optimal condition of making micro-emulsified surfactant was an oil-to-SDS ratio of 1.9 (v/v) at SDS 22.3 g L -1 under 75 °C, which allowed for the formation of micelles around 200 nm in size. The RE using MES was 3.5 folds higher than that of that using SDS (10 critical micelle concentration, CMC) only for anthracene contaminated soil at 500 ppm at a reaction time of 48 h. The RE of anthracene from soil of 100 ppm by mixed surfactant with the ratios of SDS (10 CMC) to Triton X-100 (10 CMC) at 3:7 and 7:3 were 53 and 78%, respectively. If only Triton X-100 was used, the RE was reduced to about 5%. In short, the MES and mixed surfactant can greatly increase the RE of hydrophobic contaminant in soils.