Mixing effect of NaCl and surfactant on the remediation of TCB contaminated soil

Abstract

In order to evaluate the mixing effect of NaCl and surfactant on the remediation of TCB contaminated soil, column experiments were performed. Selected soils for this study were two Iowa field soils (Fruitfield, and Webster) and one Korea field soil (Pyeongtaek). We used four nontoxic, water-soluble anionic (DOSL, SLS) and nonionic surfactants (POE20, POE4). 1, 2, 4-trichlorobenzene (TCB) was chosen as the model contaminant. Selected electrolyte for this study was NaCl. The TCB contaminated soils were leached with surfactant solution of 4% (v/v) or 4% (w/v) with or without 5% (w/v) and 10% (w/v) NaCl. As controls, TCB contaminated soils were also leached with deionized water. For the nonionic surfactants (POE20, POE4), the mixing effect of NaCl on the solubilization of contaminant was insignificant. However, much greater mixing effectiveness was observed using anionic surfactant (SLS, single head structure) solutions containing electrolyte (NaCl) from two Iowa soils and one Korea soil. In contrast, another anionic surfactant (DOSL, double head structure) had little mixing effectiveness on the solubilization of TCB from three soils. However, the NaCl mixing effect of DOSL anionic surfactant was found after leaching of 2500 ml solution with Pyeongtaek soil. The effect of NaCl in changing effectiveness was due to Na+ (counterion) effects. The maximum recovery of added TCB in column tests was 97% for 4% (w/v) aqueous SLS anionic surfactant + 10% (w/v) NaCl. A little effectiveness of 4% (v/v) DOSL (anionic surfactant) with electrolytes may be due to small adsorption of the double-head sulfate polar heads onto soil particles. Therefore, these results showed that the key factor in the variation of TCB removal effect due to surfactant + NaCl leaching was not surfactant types but surfactant structure. Also, results of this study suggest that the anionic surfactant (SLS) solutions containing electrolyte (NaCl) is a good candidate for surfactant-assisted remediation of TCB contaminated soil.