Hydrophobic sorption

Southworth, G.R. and Keller, J.L. Hydrophobic sorption of polar organics by low organic carbon soils. Water, Air, Soil Pollut., 28(3-4) 239-248, 1986. 

Entropy-related adsorption, known as hydrophobic sorption, involves the partitioning of nonpolar organics from a polar aqueous phase onto hydrophobic surfaces, where they are retained by dispersion forces. The major feature of hydrophobic sorption is the weak interaction between the solute and the solvent. The entropy change is due largely to the destruction of the cavity occupied by the solute in the solvent and the destruction of the structured water shell surrounding the solvated organic. 

Entropy-related adsorption, denoted hydrophobic sorption (or solvophobic interaction) is the partitioning of nonpolar organics out of the polar aqueous phase onto hydrophobic surfaces. Fig. 5.6 shows a schematic model of forces that contribute to the sorption of hydrophobic organics, relevant to the subsurface environment. 

The effect of temperature on sorption equilibrium is a direct indication of the strength of the sorption process. The weaker the interaction between sorbent and sorbate, the less the effect of temperature (Hamaker and Thompson, 1972). While temperature can influence sorption, the strength and direction of the effect depends on the properties of the sorbent and sorbate and on the sorption mechanism. Adsorption processes are generally exothermic, so the higher the temperature, the less the adsorption (Hamaker and Thompson, 1972). Hydrophobic sorption, however, has been shown to be relatively independent of temperature (Chiou et al., 1979). 

Additional characteristics typically associated with hydrophobic sorption or partitioning include sorption isotherms that are linear over a relatively wide range of concentrations, sorption coefficients that are not strongly temperature dependent, and a lack of competition between sorbates (Chiou, 1989). 

Thus, while individual indices such as y or yv have been successful in modeling the sorption of non-polar hydrophobic compounds, they are not by themselves good indicators of any non-hydrophobic sorption component, since, for a given class of compounds, all MCIs show a general increase with molecular size. 

Hydrophobic sorption sorption process involving weak solute-solvent and sorbate-sorbent interactions. 

One striking result of this study was that dissolved total humic substances isolated from two sites in the mainstem (Ertel et al. 1986) exhibited A c values of +265 to +285%o (Hedges et al. 1986b). Although dissolved humic substances (isolated by hydrophobic sorption onto a resin column)... 

The Hydrophobic Effect Hydrophobic Sorption Hydrophobic ( water-hating ) compounds, for example, hydrocarbons and chlorinated hydrocarbons such as the polychlorinated biphenyls are soluble in many nonpolar solvents but not readily soluble in water. Because of the incompatibility of the hydro-phobic substance with water, these substances have a tendency to avoid contact with water and seek to associate with nonpolar environments such as the surface of a mineral or an organic particle (Tanford, 1980). The sorption of hydro-phobic substances to solid materials (particles, soils, sediments) that contain organic carbon may be compared with the partitioning of a solute between two solvents—water and the organic phase. 

Hyun, S. and Lee, L.S., Hydrophilic and hydrophobic sorption of organic acids by variable-charge soils. Effect of chemical acidity and acidic functional group. Environ. Sci. Technol., 38, 5413, 2004. 

Because many organic chemicals are nonionic and have low water solubilities, they will exist primarily in the sorbed state in soil- and sediment-water systems. The sorption of nonionic chemical occurs through hydrophobic sorption or partitioning to the organic matter associated with the soil or sediment (Karickhoff, 1980 Chiou et al., 1983). Furthermore, because desorption kinetics may be slow relative to hydrolysis kinetics, to accurately predict the fate of hydrolyzable chemicals in soil-and sediment-water systems an understanding of hydrolysis kinetics in the sorbed... 

Hydrophobic sorption of compounds with a long aliphatic chain on poly(4[5]-vinylimidazole) in binary mixtures of ethanol/water with water content higher than 30 vol. % has been revealed. 34 The polarity of the microenvironment of this polymer in these mixtures is lower than that of solvents used. 

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