A series of anion-cation organobentonite are prepared by incorporating both cationic surfactant bromide dodecyltrimethylammonium (DTMAB) and anionic surfactant sodium dodecyl sulfate (SDS) to bentonite. The results indicate that the organic carbon contents of the organobentonites are proportional to the amounts of anionic and cationic surfactants in bentonite. The amount of organic pollutant removed from water depends greatly on the amount of SDS and DTMAB in the bentonite. Partition and adsorption contributions to the sorption amount of p-nitrophenol on organobentonites are described quantitatively. The mixed surfactants on anion-cation organobentonites excellently created partition mediums for organic pollutants in water. The removal rate of organic pollutants from water is improved by synergistic solubilization in both anionic and cationic surfactant moieties of the organobentonites. The effect of synergistic solubilization results mainly from partition at higher concentrations or adsorption at lower concentrations.

Cetyltrimethylammonium bromide (CTMAB)-bentonite was produced by the exchange of tyltrimethylammonium (CTMA) cations for inorganic ions on the internal and external surfaces of bentonite. CTMAB-bentonite was used to remove organic contaminants of varying polar character from water. The properties and mechanisms for CTMABbentonite to sorb benzene, toluene, ethylbenzene, nitrobenzene, aniline, phenol, and p-nitrophenol in water were investigated in some detail. Benzene, toluene, and ethylbenzene orption to CTMAB-bentonite was characterized by linear isotherms, indicating solute partition between water and the organic phase composed of the large alkyl functional groups of the CTMA cations. Phenol and p-nitrophenol sorption to CTMAB-bentonite was caused primarily by adsorption with relatively strong solute uptake. Their isotherms were nonlinear. Nitrobenzene and aniline sorption to CTMAB-bentonite was weak, and the isotherms were approximately linear. Their sorption was caused by both partition and solute uptake. The sorption data were also evaluated in terms of the octanol-water partition coefficients of the organic compounds.

Sorption of organic contaminants (phenol, p-nitrophenol, and naphthalene) to natural solids (soils and bentonite) with and without myristylpyridinium bromide (MPB) cationic surfactant was studied to provide novel insight to interactions of contaminants with the mineral-adsorbed surfactant. Contaminant sorption coefficients with mineral-adsorbed surfactants, Kss, show a strong dependence on surfactant loading in the solid. At low surfactant levels, the Kss values increased with increasing sorbed surfactant mass, reached a maximum, and then decreased with increasing surfactant loading. The Kss values for contaminants were always higher than respective partition coefficients with surfactant micelles (Kmc) and natural organic matter (Koc). At examined MPB concentrations in water the three organic contaminants showed little solubility enhancement by MPB. At low sorbed-surfactant levels, the resulting mineraladsorbed surfactant via the cation-exchange process appears to form a thin organic film, which effectively "adsorbs" the contaminants, resulting in very highKss values. At high surfactant levels, the sorbed surfactant on minerals appears to form a bulklike medium that behaves essentially as a partition phase (rather than an adsorptive surface), with the resulting Kss being significantly decreased and less dependent on the MPB loading. The results provide a reference to the use of surfactants for remediation of contaminated soils/sediments or groundwater in engineered surfactant-enhanced washing.

Uptake, accumulation and translocation of phenanthrene and pyrene by 12 plant species grown in various treated soils were comparatively investigated. Plant uptake and accumulation of phenanthrene and pyrene were correlated with their soil concentrations and plant compositions. Root or shoot accumulation of phenanthrene and pyrene in contaminated soils was elevated with the increase of their soil concentrations. Significantly positive correlations were shown between root concentrations or root concentration factors (RCFs) of phenanthrene and pyrene and root lipid contents. The RCFs of phenanthrene and pyrene for plants grown in contaminated soils with initial phenanthrene oncentration of 133 mgkg 1 and pyrene of 172 mgkg 1 were 0.05-0.67 and 0.23-4.44, whereas the shoot concentration factors of these compounds were 0.006-0.12 and 0.004-0.12, respectively. For the same soil-plant treatment, shoot concentrations and concentration factors of phenanthrene and pyrene were generally much lower than root. Translocations of phenanthrene and pyrene from shoots to roots were undetectable. However, transport of these compounds from roots to shoots usually was the major pathway of shoot accumulation. Plant off-take of phenanthrene and pyrene only accounted for less than 0.01% of dissipation enhancement for phenanthrene and 0.24% for pyrene in planted versus unplanted control soils, whereas plant-promoted biodegradation was the predominant contribution of remediation enhancement of soil phenanthrene and pyrene in the presence of vegetation.

enhanced in a linear fashion by each of Triton X-100 (TX100), Triton X-305 (TX305), Brij 35, and sodium dodecyl sulfate (SDS). Solubility enhancement efficiencies of surfactants above the critical micelle concentration (CMC) follow the order of TX100> Brij 35>TX305>SDS. PAHs are solubilized synergistically in mixed anionic-nonionic surfactant solutions, especially at low surfactant concentrations. The synergistic pwer of the mixed surfactants is SDS-TX305>SDS-Brij35>SDS-TX100. Synergistic effect of a given mixed-surfactant solution on different PAHs also appears to be linearly related to the solute logKow. The noted synergism for the mixed surfactants is attributed to the formation of mixed micelles, the lower CMC of the mixedsurfactant solutions, and the increase of the solute s molar solubilization ratio or micellar partition coefficients ðKmcÞ because of the lower polarity of the mixed micelles. Suitable quantity of inorganic cations can enhance the solubilization capacities of anionic–nonionic mixed urfactants, the effect being Mg2+>NH+4>Na+. The water solubility of pyrene was slightly increased by anthracene and significantly increased by 1,2,3-TCB in the presence of SDS-Brij 35. Mixed surfactants may mprove the performance of surfactant-enhanced remediation of soils and sediments by decreasing the applied surfactant level and thus the remediation cost.