Solubilization of Dodecane, Tetrachloroethylene, and 1,2-Dichlorobenzene in Micellar Solutions of Ethoxylated Nonionic Surfactants

Although surfactants have received considerable attention as a potential means for enhancing the recovery of organic compounds from the subsurface, only limited information is available regarding the micellar solubilization of common groundwater contaminants by nonionic surfactants. The purpose of this study was to examine the influence of surfactant properties and environmental fac tors on the solubility of dodecane, tetrachloroethylene (PCE), and 1,2-dichlorobenzene (DCB) in micellar solutions of Witconol 2722, Tergitol NP-15, and Witconol SN-120. A matrix of batch experiments was performed at 10 and 25 °C and in the presence of CaCl2 for surfactant concentrations ranging from 0.5 to 15% by weight. Although the hydrophile−lipophile balance (HLB) values of the surfactants are similar, Witconol 2722 solubilized approximately three times more organic than the other surfactants, which was attributed to the greater alkyl chain length and ethoxylation of Witconol 2722. Results of HLB scans, conducted using Tergitol NP surfactants, showed that solubilization capacity was related to the micelle core volume and that cloud point effects can reduce the aqueous solubility of PCE. These findings demonstrate the importance of considering the specific surfactant−organic interactions, cloud point tem perature, and macroemulsion formation when selecting nonionic surfactants for use in subsurface remediation ap plications.