Sorption of Organic Compounds from Aqueous Solutions

Sorption of Organic Compounds from Aqueous Solutions 

---

Sorption of Organic Compounds from Aqueous Solutions 413... 

For illustration, rubbery polymeric membranes, whose polymeric network is sufficiently elastic and mobile to allow comparatively large organic compounds to diffuse through it (Table 3.6-2), are in general used for the recovery of organic compounds from aqueous solutions. Because of its small size, the bulk solvent, water, unfortunately diffuses through the membrane even better. This is why in organo-philic pervaporation the selectivity is mainly achieved and determined by the ratio of the solubility coefficients (sorption selectivity. Table 3.6-2). Membrane selectivity, as defined in Eq. (7), is an intrinsic parameter and can differ from the overall process selectivity, as wiU be shown later. 

Figure 11.6 Sorption isotherms for two kinds of nonionic organic compounds from aqueous solutions to suspended kaolinite (a) slightly monopolar compound, pyrene, showing a linear isotherm up to its solubility (Backhus, 1990), and (b) monopolar compound, 1,3,5-trinitrobenzene, showing a hyperbolic isotherm (Had-erlein et al., 1996).

Figure 3.9 Sorption isotherms of parathion (squares) and lindane (circles) as single and binary solutes from water on Woodburn soil fom = 0.019) at 20°C. Open symbols are for single solute data and solid symbols for binary-solute data. [Reproduced from C. T. Chiou, T. D. Shoup, and P. E. Porter, Mechanistic roles of soil humus and minerals in the sorption of nonionic compounds from aqueous and organic solutions , Org. Geochem., 8, 9, Copyright 1985, with permission from Elsevier.]...

Chiou, C.T., Shoup, T.D., and Porter, P.E. Mechanistic roles of soil humus and minerals in the sorption of nonionic organic compounds from aqueous and organic solutions, Org. Geochem., 8(1) 9-14, 1985. 

Soil Organic Matter Organic compounds may exist in soil either in solution or the vapor phase and can be absorbed through the roots in either state, absorption from solution would be the most likely process. From the discussion of the sorption process in soil (see Sorption, Chapter 3) the concentration of the compound in aqueous solution, Caq, would be a function of the concentration in the soil (Csoii). and the soil distribution ratio, K, which in turn is dependent primarily on SOM content. One would predict that uptake would be inversely related to the level of SOM. Observations of the uptake of diel-drin by carrots raised in different soils provide an opportunity to evaluate this relation and demonstrate the dependence on the concentration of the compound in soil solution. If the uptake efficiency is defined by the ratio of the concentration of dieldrin in carrots to that in the soil it is clear that higher levels of soil organic matter reduce uptake by carrots (Table 5.6). The ATom for dieldrin is 6980 mL g from which values were calculated for dieldrin in each soil. Since = Cjoii/Caq the concentration of dieldrin in soil solution can be determined. If uptake is defined as Ccarrot/Caq consistent value... 

---