Water sorption coefficient

The soil-water sorption coefficient affects only the aqueous phase transport of pollutants this coefficient will decrease in relation to the temperature. In this way, the ability of the hot fluids to remove pollutants from the soil increases significantly. The effect of the temperature is specific to the soil type, water content, and type of pollutants. 

Different approaches were studied for obtaining both water sorption coefficient and water permeability coefficient. For that, some authors cut rectangular specimens of polymer films which are dried in vacuum oven at 50°C and their weight was measured until reaching no weight loss change. The films were immersed in a deionized water bath at 37°C. All specimens were weighed as a function of immersion time until the sorption process was complete. Then, the mass uptake at time t, and water solubility were calculated and thereafter water diffusivity, sorption and permeability coefficients. 

As has been shown in the previous section, for the considered elastoplastics the structure fractal dimension value i is equal to 2.0. In turn, this means that = 1.0 [27]. Now the water sorption coefficient for the considered nanocomposites can be calculated according to Equation 7.17. In Figure 7.19 the comparison of experimental Q and water sorption coefficient values calculated according to the proposed multifractal treatment for two series of PU/montmorillonite nanocomposites (PTMG/ MMT and PBAD/MMT) at experiment duration 1 and 5 days is assumed. As one can see, good correspondence of theory and experiment was obtained - the average discrepancy between and Q makes up about 20%, which is quite sufficient for preliminary estimations. 

Figure 7.19 The comparison of experimental Q and water sorption coefficient values calculated according to Equation 7.17 during 1 (1, 2) and 5 (3, 4) days for nanocomposites PTMG/MMT (1, 3) and PBAD/MMT (2, 4) [56]...

Hence, the results obtained in the present section suppose that the change in water sorption coefficient for PU/organoclay nanocomposites is actually connected with variation in the nonlinearity (meandering) coefficient at a change in the nanofiller contents. For the considered nanocomposites a special case is observed, when the fractal dimension of a chain part between its fixation points is equal to 1 and... 

Briggs also compared the RCF values to root water sorption coefficients obtained using macerated roots. The sorption coefficients were found to be similar to the RCF values for the hydrophobic compounds but continued to decline for the more polar compounds unlike the RCF values. Based on these results, Briggs et al. (1982) suggested that two components determine the total amount of chemical in the roots, the chemical associated with the water in the roots and the chemical associated with the lipophilic root solids, leading to the correlation (Briggs et al., 1982) ... 

Stem, wood, or wood component water sorption coefficients have been reported for... 

Instead of normalizing experimental wood water sorption coefficients to lignin, Trapp et al. (2001) reported two separate expressions for oak and willow that related wood water sorption coefficients (.Kwood) to log Kqw for 10 organic chemicals ranging in log Kovf from 1.48 to 6.20 ... 

Fig. 9. Parametric simulation using the MSD model of water flux vs feed concentration as a function of organic sorption coefficient, where for A,...

Swann R, Laskowski D, McCAll P, et al. 1983. A rapid method for the estimation of the environmental parameters octanol/water partition coefficient, soil sorption constant, water to air ratio, and water solubility. Residue Rev 85 18-28. 

Vapor pressure (VP), water solubility ( w), and soil sorption coefficients Koc) are key properties that govern volatilization of agrochemicals from soil. Volatile compounds such as 5 -ethyl dipropylthiocarbamate (EPTC) (VP 4.5 Pa,... 

Pure PHEMA gel is sufficiently physically cross-linked by entanglements that it swells in water without dissolving, even without covalent cross-links. Its water sorption kinetics are Fickian over a broad temperature range. As the temperature increases, the diffusion coefficient of the sorption process rises from a value of 3.2 X 10 8 cm2/s at 4°C to 5.6 x 10 7 cm2/s at 88°C according to an Arrhenius rate law with an activation energy of 6.1 kcal/mol. At 5°C, the sample becomes completely rubbery at 60% of the equilibrium solvent uptake (q = 1.67). This transition drops steadily as Tg is approached ( 90°C), so that at 88°C the sample becomes entirely rubbery with less than 30% of the equilibrium uptake (q = 1.51) (data cited here are from Ref. 138). 

The binding constants of a number of compounds were measured using dialysis, solubility and sorption techniques. The solubility technique was used for compounds which were not radiolabeled. All data was collected at pH = 8.3. The binding constants were then compared to the octanol/water partition coefficients for the compounds and the molar solubilities of the compounds. The data is presented in Table II. The Kow values were taken from the literature.18 22-2 The solubility values were determined in this research with the exception of DDT and Lindane, which were taken from the literature. A plot of log Kc vs. log Kow is presented in Figure 5. The slope of this line is 0.71, the intercept is 0.75 and the value of the correlation coefficient is 0.9258. The regression is highly significant... 

The data presented here indicates that the extent of binding for a particular compound is related to the octanol/water partition coefficient for that compound. This is very similar to the sorption of compounds from water to sediment. Compounds with log Kow values less than four (such as Lindane) will probably not be bound to an appreciable extent in the environment. Compounds with very high log Kow values (DDT and DEHP) may be bound to a significant extent. The extent of binding will depend on both the concentration of humic material and on the nature of the humic material. The humic materials used in this research showed dramatically different affinities for DDT. The reasons for this are poorly understood and deserve further study. 

Bucheli T, Gustafsson O (2000) Quantification of the soot-water distribution coefficient of PAHs provides mechanistic basis for enhanced sorption observations. Environ Sci Technol 34 5144-5151... 

KoC is an important parameter which describes the potential for movement or mobility of pesticides in soil, sediment and groundwater. Because of the structural complexity of these agrochemical molecules, the above simple relationship which considers only the chemical s hydrophobicity may fail for polar and ionic compounds. The effects of pH, soil properties, mineral surfaces and other factors influencing sorption become important. Other quantities, KD (sorption partition coefficient to the whole soil on a dry weight basis) and KqM (organic matter-water partition coefficient) are also commonly used to describe the extent of sorption. K0M is often estimated as 0.56 KoC, implying that organic matter is 56% carbon. 

There is a continuing effort to extend the long-established concept of quantitative-structure-activity-relationships (QSARs) to quantitative-structure-property relationships (QSPRs) to compute all relevant environmental physical-chemical properties (such as aqueous solubility, vapor pressure, octanol-water partition coefficient, Henry s law constant, bioconcentration factor (BCF), sorption coefficient and environmental reaction rate constants from molecular structure). 

Delle Site, A. (2001) Factors affecting sorption of organic compounds in natural sorbent/water systems and sorption coefficients for selected pollutants. A review. J. Phys. Chem. Ref. Data 30, 187-439. 

Sutton. C., Calder, J.A. (1975) Solubility of alkylbenzenes in distilled water and seawater at 25°C. J. Chem Eng. Data 20, 320-322. Swann, R.L., Laskowski, D.A., McCall, P.J., Vender Kuy, K., Dishburger, J.J. (1983) A rapid method for the estimation of the environmental parameters octanol/water partition coefficient, soil sorption constant, water to air ratio, and water solubility. Res. Rev. 85, 17-28. 

Once estrogens and progestagens have reached the waterways, a series of processes, such as, photolysis, biodegradation, and sorption to bed-sediments, can contribute to their elimination from the environmental water. Given the relatively low polarity of these compounds, with octanol-water partition coefficients mostly between 103 and 105, sorption to bed-sediments appears to be a likely process. Kd values calculated for estriol, norethindrone, and progesterone in a Spanish river (479,128, and 204, respectively) as the ratio between the sediment concentration (ng kg-1) and the water concentration (ng L 1) indicate that, in fact, these compounds exhibit a general tendency to accumulate in sediments. 

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