The Sorption of Polymers

Humus in Soils. Humus in solid form (colloids, or coatings on mineral surfaces) can immobilize many pollutants. 

1) Non-ionic organic molecules such as organo phosphates, chlorinated hydrocarbons (e.g., polychlorinated biphenyls PCB) are absorbed according to Eq. (4.42). 

3) Metal ions can bind to the functional groups of humus by surface complex formation, e.g., 

On the other hand, one needs to be aware that soluble humic and fulvic acids can form complexes with organic compounds and render these substances more mobile (cf. Davis, 1984). 

Polyvinyl alcohol Polystyrene sulfonate Polyvinyl pyridinium 

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Figure 7 Effect of added salt on the sorption of Polymer JR 125 by bleached hair 0.1% polymer solutions. (From Ref. 7.)... 

Experiments with bleached hair (7), in which the effect of ionic surfactants on deposition of the polycation was studied in more detail, yielded results that, in general, paralleled those obtained for virgin hair. One finding of obvious potential importance was that the sorption of polymer decreased approximately in proportion to the amount of anionic surfactant (SDS) present, presumably owing to progressive tie-up of the polycation in negatively charged complexes. 

Figure 7 Effeet of salts and surfaetants on the sorption of Polymer IR-125 by eotton 0.1% polymer solution.

Polymer-Fluid Equilibria and the Glass Transition Most polymer systems fall in the Class HI or Class V phase diagrams, and the same system can often change from one class into the other as the polymer s molecular weight changes. Most polymers are insoluble in CO9 below 100°C, yet CO9 can be quite sohible in the polymer. For example, the sorption of CO9 into silicone rubber is highly dependent upon temperature and pressure, since these properties have a large influence on the density and activity of CO9. 

Smith, S.E. 1947. The sorption of water by high polymers. J. Amer. Chem. Soc. 69, 646-651. Sobolev, A.P., Segre, A., and Lamanna, R. 2003. Proton high-held NMR study of tomato juice. Magn. Reson. Chem. 41, 237-245. 

Chin, Y.-P. and Weber, W.J., Jr. Estimating the effects of dispersed organic polymers on the sorption of contaminants by natural solids. 1. A predictive thermodynamic humic substance-organic solute interaction model, Environ. Sci Technol., 23(8) 978-984, 1989. 

Acetylation may be controlling the moisture sensitivity due to the lignin and hemlcellulose polymers in the cell wall but not reducing the sorption of moisture in the cellulose polymer because... 

EXTRACT and O-METHYLATED EXTRACT. The sorption of benzene by the extract and the O-methylated extract is characterized by a rapid, initial uptake followed by a very slow approach to equilibrium. Such sorption behavior is very similar to that of glassy polymers. Thus we have chosen to interpret the sorption curves shown in Figures 2 and 3 in terms of the Berens-Hopfenberg model developed for the sorption of organic vapors into glassy polymers.(lS) By doing so, we attempt to correct the total sorption values for surface adsorption in order to calculate x parameters. 

Certain SEC applications solicit specific experimental conditions. The most common reason is the limited sample solubility. In this case, special solvents or increased temperature are inavoid-able. A possibility to improve sample solubility and quality of eluent offer multicomponent solvents (Sections 16.2.2 and 16.8.2). The selectivity of polymer separation by SEC drops with the deteriorating eluent quality due to decreasing differences in the hydrodynamic volume of macromolecules with different molar masses. The system peaks appear on the chromatograms obtained with mixed eluents due to preferential solvation of sample molecules (Sections 16.3.2 and 16.3.3). The multicomponent eluents may create system peaks also as a result of the (preferential) sorption of their components within column packing [144,145]. The extent of preferential sorption is often sensitive toward pressure variations [69,70,146-149]. Even if the specific detectors are used, which do not see the eluent composition changes, it is necessary to discriminate the bulk sample solvent from the SEC separated macromolecules otherwise the determined molecular characteristics can be affected. This is especially important if the analyzed polymer contains a tail of fractions possessing lower molar masses (Sections 16.4.4 and 16.4.5). 

The sorption of a penetrant by a class (a) membrane can be treated most simply, if the processes of sorption in the polymer matrix and into each kind of specific sorption site within it can be treated as mutually independent and hence additive. Under these conditions, each sorbed species may similarly be expected to contribute additively to the total diffusion flux. Hence, if there are N — 1 kinds of specific sorption sites, the overall sorption and permeability or diffusion coefficients can be written as... 

The sorption of a weak electrolyte by a charged polymer membrane is another case where Nernst + Langmuir-like dual mode sorption, involving the undissociated and dissociated species respectively, may be expected. The concentration of each species in solution follows, of course, from the dissociation constant of the electrolyte. The sorption isotherms of acetic acid and its fluoroderivatives have been analysed in this manner, and the concentration dependence of the diffusion coefficient of acetic acid interpreted resonably successfully, using Nylon 6 as the polymer substrate 87). In this case the major contribution to the overall diffusion coefficient is that of the Nernst species consequently DT2 could not be determined with any precision. By contrast, in the case of HC1, which was also investigated 87 no Nernst sorption or diffusion component could be discerned down to pH = 2 and the overall diffusion coefficient obeyed the relation D = DT2/( 1 — >1D), which is the limiting form of Eq. (25) when p — 00. 

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