To fully utilize the sorption traits of organobentonites to control volatile organic compounds (VOCs) pollution, the sorption mechanisms of VOCs with organobentonites need to be understood adequately. The sorption of VOCs as vapors to a typical organobentonite, modified with cetyltrimethylammonium bromide (CTMAB-bentonite), was characterized using a linear solvation energy relationship (LSER) of the type log Kc=c+rR2+sπ2H+aΣR2H+bΣβ2H+llog L16. The fitted LSER equation, log Kc=0.434+0.968R2-0.0886π2 H+2.170ΣαR2H+1.611Σα2H+0.417log L16, was obtained by a multiple regression of the partition coefficients of 22 probe solutes against the solvation parameters of the solutes. The coefficients of the LSER equation show that CTMAB-bentonite is a sorbent with nonsignificant ipolarity/polarizability, interacts with solutes partly throughð-/n-electron pairs, behaves both as ydrogenbond donor and hydrogen-bond acceptor, and can interact with solutes by cavity/dispersion interactions. The related terms in LSER suggest that the potential factors governing the sorption of VOCs onto CTMAB-bentonite are dispersion interactions, hydrogen-bond acidity interactions, hydrogen-bond basicity interactions, and ð-/n-electron interactions. The dispersion interaction is recognized o be the predominant parameter for most solutes, whereas the contributions of the other parameters depend on specific solutes. The derived LSER equation successfully predicted the VOC partition coefficients and the selectivity of CTMABbentonite for the VOCs. The relationship between LSER and adsorption/partition model was compared. The classification of sorption mechanisms by LSER goes on the molecular interaction types between sorbate and sorbent, and classification by adsorption/partition model goes on the property difference among various components of sorbent. The LSER approach coupled with inverse gas chromatography (IGC) is a comparatively simple and reliable tool to rapidly haracterize the sorption mechanism of VOCs with solid sorbents such as CTMAB-bentonite, and may potentially be applied to the design of an organoclay sorbent for control of VOCs.

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.

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.

A series of dual-cation organobentonites are synthesized by replacing the metal ions in bentonite with both long-chain alkyl quaternary ammonium cations, such as dodecyltrimethylammonium (DTMA), benzyldimethyltetradecylammonium (BDTDA), cetyltrimethylammonium (CTMA), octodecyltrimethylammonium (OTMA), and short-chain alkyl quaternary ammonium cations, such as tetramethylammonium (TMA). The influential factors, mechanisms and characteristics of polar and ionizable organic contaminants, such as p-nitrophenol, phenol, and aniline, and sorption to dualcation organobentonites from water are investigated systematically and described quantitatively. The sorption properties are affected by treatment conditions, such as pH, amount of organobentonite, and shaking time; structure of organobentonites, such as interlayer spacings and organic carbon contents; and the properties of organic compounds, such as solubility and octanol-water coefficient partition. Sorption isotherms of p-nitrophenol, phenol, and aniline are typically nonlinear. Both adsorption and partition contribute to the sorption of organic compounds to dual-cation organobentonites. The separate contributions of adsorption and partition to the total sorption of organic compounds to dual-cation organobentonites are analyzed mathematically, e.g., QA) a ln Ce+b-Koc

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.