NONIONIC SURFACTANT-ENHANCED SOLUBILIZATION AND RECOVERY OF ORGANIC CONTAMINANTS FROM WITHIN CATIONIC SURFACTANT-ENHANCED SORBENT ZONES .1.EXPERIMENTS

Recent studies have shown that cationic surfactants can be used to inc rease the organic carbon content of aquifer materials, creating enhanc ed sorbent zones for hydrophobic organic contaminants (HOCs) migrating in groundwater. The coupling of nonionic surfactant-enhanced solubili zation of HOCs to the cationic surfactant-enhanced sorption zone conce pt is examined as a possible groundwater remediation scheme. The parti tioning behavior of 1,2,4-trichlorobenzene (TCB) and lgepal CO 730 (CO 730, a nonionic surfactant), both singly and jointly, were determined in batch hexadecyltrimethylammonium (HDTMA, a cationic surfactant) ch loride-modified aquifer material/water systems. The apparent CO 730 cr itical micelle concentration (cmc) was found to decrease by a factor o f 17 due to nonideal mixed micelle formation in the presence of low aq ueous phase HDTMA concentrations that resulted from exposure to HDTMA- modified aquifer material. A greater portion of CO 730 will be present in the micellar psuedophase (the HOC solubilizing phase) as a result of the lowered cmc. The TCB partitioning behavior in the HDTMA-modifie d aquifer material/water systems was found to be dependent upon the aq uifer material organic carbon content, the apparent CO 730 cmc, and th e partitioning of TCB between the micellar pseudophase and the bulk aq ueous phase containing surfactant monomers. The batch experiments indi cate that the micellar pseudophase would be a more favorable partition ing medium for TCB relative to the solid phase organic carbon within a n enhanced sorbent zone. One-dimensional column experiments were perfo rmed using HDTMA-treated and untreated aquifer materials to determine the transport behavior of CO 730 and to assess the feasibility of usin g CO 730 to solubilize and recover TCB bound within a cationic surfact ant-enhanced sorbent zone. Complete removal (> 99%) of the bound TCB w as achieved using a 12-column pore volume Rush of 50 g/L CO 730. The c olumn experiments demonstrated that a nonionic surfactant can effectiv ely remove an HOC from a cationic surfactant-enhanced sorbent zone.