Sorption of Perchloroethylene by Surfactant-Modified Zeolite as Controlled by Surfactant Loading

Abstract

The sorption of nonpolar hydrophobic organic compounds by soil organic matter has long been attributed to a partitioning mechanism, with the sorption coefficient proportional to the fractional organic carbon content of the soil. However, deviations from this linear proportionality have been observed and reported in the literature by many authors. In our study a natural zeolite was modified with a cationic surfactant to achieve different fractional organic carbon contents and different surfactant molecule configurations on the surface. The sorption of perchloroethylene (PCE) by the surfactant-modified zeolite (SMZ) was found to be dependent on the bound surfactant molecule configuration as well as on the fractional organic carbon content. Below monolayer coverage by the surfactant, the PCE sorption coefficient on SMZ was proportional to the fractional organic carbon content. Above monolayer coverage, increasing fractional organic carbon content resulted in minimal further increase in the PCE sorption coefficient. The change in PCE sorption behavior was attributed to the structural differences between sorbed surfactant monolayers and bilayers. The surfactant surface configuration has a significant impact on the effective volume and density of the bound organic phase that is responsible for partitioning nonpolar organic compounds. The ratio of the organic carbon-based distribution coefficient (K oc) for the monolayer versus that for the bilayer systems was 1.7, similar to the estimated bilayer to monolayer hydrocarbon density of 1.3. Our results reinforce the notion that the structure of natural organic matter as well as its quantity controls the sorption of nonpolar organics to soils and sediments.

Sorption of methyl-parathion and carbaryl by an organo-bentonite

“…This observation has been attributed to differences in structure between sorbed and dissolved surfactant aggregates. Li and Bowman (1998) demonstrated that the perchloroethylene distribution coefficient on surfactant-modified zeolite is a function of CTMAB loading and resultant organic phase density. Perchloroethylene is most efficiently sorbed by surfactant-modified zeolite when the surfactant is present at or below full monolayer coverage.…”

“…The distribution coefficients (K ss ) for sorbed surfactants were highest at low surfactant loadings, decreasing sharply as loading levels increased. Li and Bowman (1998) found that the sorption of perchloroethylene by a surfactant-modified zeolite was dependent on the configuration of the bound surfactant molecules, as well as on the fractional organic carbon content. Likewise, Sun and Jaffe (1996) found that the partitioning of phenanthrene into an adsorbed dianionic surfactant phase is generally 5-7 times more effective than into the same surfactant in water.…”

Antibacterial Activity of Cetyltrimethylammonium Bromide Modified Silver-Bentonite

“…This can be understood by the mechanism of surfactant attachment on clay framework. It is well-known for a long time that surfactant modified clay or organoclay has the ability to adsorb and retain anionic compound [27][28][29]. Due to the molecular structure of cationic surfactant like CTAB that consists of two essential parts: (1) head positive group of quaternary ammonium and (2) hydrophobic tail of hydrocarbon chain (C16) and the capability of this surfactant to form micelles in the solution, the attachment of cationic surfactant on clay creates organic rich layer on the clay surfaces [16].…”

Peer Reviewed: In-Situ Treatment of Chromium-Contaminated Groundwater

“…This barrier is actually a cross between chemical and biological methods, because the compost acts as a carbon source for microbial populations, which are active in the reduction of the chromium. Naturally occurring zeolite coated with cationic surfactants has also been investigated as an adsorbant for chromium in permeable reactive barriers (18).…”