Adsorption from water

In general, the extent of adsorption of plasticizers is inversely proportional to their solubility in water. The organic carbon-water partition coefficient, K., is a compoimd-specific term that allows the user to estimate the mobility of a plasticizer in saturated soil-water systems if the amount of organic carbon in the soil is known. A Kqc value is a measure of the affinity of a chemical to partition to organic matter which in turn will control the mobility of the solute in water. Organic carbon-water partition coefficients were compiled for the 23 plasticizers (Table 18.12). There is considerable range in the measured 

020 and 1,380 (5) Diisobutyl phthalate 1,386 (23) Di-n-butyl phthalate 1,360 Diallyl phthalate 5,100 Acetyl tributyl citrate s 

10 286.000 (21) Diisodecyl phthalate 482.000 (21) Di-(2-ethylhexyl) phthalate 300.000 Di-(2-ethylhexyl) azelate 560.000 Di-(2-ethylhexyl) sebacate 610.000 Di-n-octyl phthalate  

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Jaynes WF, Boyd SA (1991b). Hydrophobicity of siloxane surfaces in smectites as revealed by aromatic hydrocarbon adsorption from water. Clays Clay Miner 39 428-436... 

The role of nonaqueous solvents in adsorption processes can be exemplified by the adsorption of thiourea. A number of systematic studies ofTU adsorption on Hg electrodes fromprotic as well as aprotic solvents have been published. The results of TU adsorption from water, methanol,ethanol, ethylene glycol, acetone, and ni-... 

Surface water volatilization t/2 = 1.7 h from a model river 1-m deep flowing 1 m/s with a wind speed of 5 m/s and t,/2 = 14.9 d from a model pond with adsorption from water column (Howard 1997). 

Octanol is a partitioning medium just as water is a partitioning media. While there is nothing inherently special about octanol with respect to other organic liquids, the extent that an organic chemical partitions to octanol from water has become a standard for evaluating hydrophobicity (i.e., chemicals that partition more to octanol from water are more hydrophobic). Since HOPs that are more hydrophobic accumulate more in body tissues, partition more strongly to soils and sediments, and are typically more easily removed by adsorption from water, the extent that HOPs partition to octanol from water is a very important environmental indicator. 

In conclusion, we can assert that the pyrolysis and activation process applied for the manufacture of activated carbons from nutshells resulted in good quality adsorbents. We have demonstrated the influence of both processes on the speed of the benzene adsorption from water solutions. The hypothesis that the effective surface diffusion is the slowest step of the global process was used and the estimation of the effective diffusion coefficient resulted in values ranging between 2 and 6 X 10-10 m /s. 

For acetonitrUe/water systems it was found that acetonitrile forms thick adsorbed layer on the surface of hydrophobic bonded phase, while methanol adsorption from water formed a classical monomolecular adsorbed layer [166]. The thick adsorbed layer of acetonitrile provides a suitable media for the adsorption of liophilic ions on the stationary phase adding an electrostatic component to the retention mechanism, while monomolecular adsorption of methanol should not significantly affect adsorption of ions. 

For adsorption from water on hydrophobic surfaces, the hydrophobic parts in the molecule attach to the surface with the hydrophUlc part towards the solution. There is no reason for bllayer formation and hence (pseudo-)plateau values are lower than on hydrophilic surfaces. 

Fig.S. The influence of carboncontaining nanotubes nature (1-3 carbon nature, 4-6 organic nature) on the efficiency of the oilproducts adsorption from water surface...

The low ionic strength data also show that relatively small amounts of MAAc are necessary to cause great increases in y-globulin adsorption, e.g., an increase of almost fiftyfold between 0.02 and 1.5% MAAc. This finding confirms calculations which indicate that MAAc content in this range could reasonably explain the amount of y-globulin adsorption from water observed for hydrogels made with unpurified HEMA. 

Jada, A., Akbour, R.A., and Douch, J., Surface charge and adsorption from water onto quartz sand of humic acid, Chemosphere. 64, 1287, 2006. 

The approach described above has been applied to treat experimental data on adsorption of pyridine from the electrolyte solutions [61]. Using Eq. 28 made it possible to determine the slip length as a function of surface excesses of pyridine. In agreement with the theoretical prediction, it was found that bs grows with Ta. The values of bs did not exceed 0.3 nm and 1.2 nm for adsorption from butanol and water solutions, respectively. The dependence of slip length on surface excess was essentially linear (Eq. 30) for pyridine adsorption from butanol solution, but deviated from linearity for pyridine adsorption from water. The deviation was attributed to a reorientation of adsorbed pyridine molecules at the Au surface. 

We can write equilibrium constants for many types of chemical processes. Some of these equilibria are listed in Table 6.1. The equilibria may represent dissociation (acid/base, solubility), formation of products (complexes), reactions (redox), a distribution between two phases (water and nonaqueous solvent—solvent extraction adsorption from water onto a surface, as in chromatography, etc.). We will describe some of these equilibria below and in later chapters. 

Fig. 13.1 Relationship between adsorption from water and number of carbon atoms for various classes of compounds.

M. M. Ayad, A. A. El-Nasr, Anionic dye (acid green 25) adsorption from water by using polyaniline nanotubes salt/silica composite./Nanostruct Chem 2012, 3(1), 1-9. 

Ru atoms in the core, and therefore not oxidized, exert relatively little ligand effect on the surface Pt atoms with respect to OH adsorption from water activation, but may weaken the Pt-CO bond allowing hydrogen replacement at low potentials. 

At surfactant adsorption from air, the eqnilibrinm adsorption constant is described by Equation 8.C.45. And at snrfactant adsorption from water, the equilibrium adsorption constant is described by Eqnation 8.C.10. In these eqnations, the values of l/(D/5ft) and lylKTI2 mh are essentially different magnitndes. On the other hand, the values of vexp((wVo -2 )I2KT) and V exp((U - i)/KT) have the same or nearly the same magnitudes. These magnitudes reflect the energy-frequency parameters of the desorption stage of adsorbed molecules (i.e., molecules that come back to the water bulk from adsorption layer). Both these members can be depicted as X. Therefore,... 

It means that in the case when the equilibrium adsorption constant of SDS is equal to 1.1610" mol/dm (at adsorption of SDS from bulk water), the value of equilibrium adsorption constant of SDS at adsorption from air is 3.610 as smaller as at adsorption from water bulk, and it is equal to... 

FIG. 27 Plot of the initial rate of poly(ethylene oxide) adsorption from water onto silica versus the Reynolds number (1) for a polymer with molecular mass 246 x 10 and versus the molecular mass of poly(ethylene oxide) (2) when plotted according to Eq. (141). (From Ref. 70.)... 

IPS Adsorption from Water, Solutions of Salts and Saccharides ... 

H2O adsorption from water vapor has been extensively studied, first on powdered samples, more recently on single crystals. Most experiments on powders were carried out at high vapor pressures (> 1 torr). Experiments on single crystals are usually performed at low gas pressures (< 10 torr) because of the limitations of the modem surface science techniques. Powdered samples are highly defective and contain various crystalline orientations and stmctures. They are more representative of the behavior of passive films formed in aqueous solution. Studies on well-characterized surfeces of single crystals make it possible to investigate the role of surface defects and surface orientation on the mechanisms of chemisorption. 

Only adsorption by proton discharge in acid medium is eonsidered here [Eq. (4)] the expressions of the rates of adsorption from water are similar. The rates for the forward and reverse reaetions are... 

Benzophenone adsorption on samples was performed using two methods the solvent evaporation method for the case of ethanol [14], and, also, adsorption from water [15]. The former method consists in the addition of an ethanolic solution containing the probe to the previously dried powdered solid substrate, followed by solvent evaporation from the stirred slurry in a fume cupboard. In the case of water, the fibers were first swollen for at least two hours, and the addition of BZP was done by adding 500 micromoles of this probe dissolved in ethanol (saturated solution so that the added amount of ethanol was minimized). The water suspensions were kept under agitation for 24 hours and the modified cellulose (with the adsorbed BZP) was removed by filtration. From the initial 500 (xmole g of BZP, about 300 (xmole g remained into the powdered substrate (i.e., an increase in the retention capacity of the powdered substrate of about twelve times when... 

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