Surfactant recycling by solvent extraction in surfactant-aided remediation

As a part of the study on the surfactant-aided remediation of organic contaminants, solvent extraction was investigated to determine its efficiency for used surfactant recycling. The experiments used a glass column 70 cm height with an internal diameter of 3 cm. The convex orifice with four holes (4 mm outer diameter) was installed at the base of the column. Four percent aqueous surfactant solutions solubilizing toluene or 1,2,4-trichlorobenzene (TCB) as model contaminants were injected in the column. Acetone, hexane, and methylene chloride were used as the solvent, and the solvent was allowed to flow upward through the surfactant solution in the column and circulated by a pump. Toluene and 1,2,4-TCB were effectively removed from the aqueous solution of anionic surfactant diphenyl oxide disulfonate (DOSL, trade name Dowfax 8390) using hexane and methylene chloride as the solvent. The times required for 98% removal of the toluene and 1,2,4-TCB were 5 h with methylene chloride or hexane flow rates of 30 ml/min. This indicates that the present solvent extraction method may help recycle anionic surfactant solutions used for remediation of contaminated soil.