Biosurfactant-enhanced removal of o,p-dichlorobenzene from contaminated soil

Surfactant-enhanced remediation is less applicable for the treatment of dichlorobenzene (DCB)-contaminated soil. In this study, water solubility enhancements of o-dichlorobenzene (o-DCB) and p-dichlorobenzene (p-DCB) by micellar solutions of biosurfactants (saponin, alkyl polyglycoside) and chemically synthetic surfactant (Tween 80) were measured and compared. Solubilities of o,p-DCB in water were greatly enhanced in a linear fashion by each of Tween 80, saponin, and alkyl polyglycoside. Solubility enhancement efficiencies of surfactants followed the order of Tween 80 > saponin > alkyl polyglycoside. However, the ex situ soil washing experiment demonstrated the opposite result. The removal efficiency of o,p-DCB by biosurfactant saponin and alkyl polyglycoside was higher than that of chemically synthetic surfactant Tween 80 in contaminated soil. This difference may be due to the different adsorption behaviors of the surfactants onto soil. In addition, elution kinetics for o,p-DCB were relatively fast, with apparent elution equilibrium reached within 360 min, and can be described by a pseudo first-order kinetic equation. The elution process of o,p-DCB in soil-aqueous systems obeyed four-parameter biphasic first-order kinetic model including rapid and slow phases. The results confirmed potential application of saponin and alkyl polyglycoside in elution solution for enhanced remediation of DCB-contaminated soil.