Organic Cosolvent Effects on Sorption Equilibrium of Hydrophobic Organic Chemicals by Organoclays

Abstract

Isotherms were measured for sorption of naphthalene and diuron by four organoclays in equilibrium with various mixtures of methanol and water. The organoclays were prepared from Wyoming montmorillonite by replacing the natural exchangeable cations of the clay by the quaternary ammonium ions TMA (tetramethylammonium), TMPA (trimethylphenylammonium), HDTMA (hexadecyltrimethylammonium), and BDTDA (benzyldimethyltetradecylammonium). TMPA-clay showed the greatest sorptive capacity for naphthalene, while BDTDA-clay was the most effective sorbent for diuron. The sorption mechanism for each sorbate−sorbent combination was related to the arrangement of the quaternary ammonium cations in the exchanged clay and the volume fraction of methanol in solution (f c). As expected from the solvophobic theory, the linear sorption coefficients decreased log-linearly with increasing f c in the binary solvent mixture, except for TMPA-clay at f c > 0.5. In addition to solute−solvent and solvent−sorbent interactions, an additional effect involving solute-organoclay interactions influenced the sorption of naphthalene and diuron by organoclays from aqueous and mixed solvents.

Sorption of 1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane (DDT) by clays and organoclays

“…Ex situ remediation may gradually be replaced by in situ remediation (Sui et al 2003). Among the many in situ remediation technologies, remediation of contaminated soils and groundwaters by organoclays has been a topic under development (Wang et al 1997;Pernyeszi et al 2006;Nzengung et al 1996;Ö zcan et al 2006;Zhou et al 2006;Oyanedel-Craver et al 2006;Hermosín et al 2006). Organoclays are synthesized by exchanging the naturally occurring inorganic cations with organic cations.…”

Biosorption and Transformation of Tetra-Chloroethylene and Trichloroethylene Using Mixed-Species Microbial Mats

“…Four sorption experiments were conducted using 14 C-labeled PCE and TCE from Sigma (Nzengung et al, 1996 and. Sorption batch experiments were set up using techniques similar to those previously described.…”

Engineering applications of organic surfactant modified bentonite in sorptive soil barriers.

“…As a result, the partitioning coefficient increases when the co-solvent fraction in the solution decreases. Increasing the co-solvent percentages in the solution will be accompanied by higher water solubility of organic components which results in lower affinity to the sorbents (Nzengung et al 1996). Rao et al (1990) concluded a similar result.…”

“…Previous studies indicated that the co-solvent may inhibit the sorption of organic sorbates onto organoclays (Nzengung et al 1997). The study of Nzengung et al (1996) Also, the effect of temperature on the sorption tendency of sorbents has been studied. Chiou et al (1979) indicated that the sorption of 1, 1, 1 -trichloroethane increases at higher temperature.…”

“…However, a small fraction of organoclays in GCL soil increases significantly the attenuation capability of non-polar organics, chlorinated organics, polycyclic hydrocarbons and pesticides from aqueous phase Jaynes and Boyd 1990;Jaynes and Boyd 1991;Larsen et al 1992;Montgomery et al 1991;Owabor et al 2010;Qu et al 2008;Smith et al 1990). Nzengung et al (1996)proposed that the organic contaminants can be absorbed by organically modified clays through the partitioning process, which mostly the partitioning coefficient of organoclays may be hundreds of thousands of times greater than those of natural soils.…”