Colloids electrolyte effects

A. Doren and J. Goldfarb, Electrolyte effects on micellar solutions of nonionic detergents, J. Colloid Interface Sci. 32 (1970) 67-72. 

Chemical equilibrium in heterogeneous systems (from the thermodynamic standpoint) when capillary or electrical effects are of importance—Adsorption—Donnan s theory of membrane equilibria—Micelle theory of colloidal electrolytes... 

As shown in Table II, there was an increase in sorption with increasing ionic strength at pH 7.1, the opposite being obtained at pH 5. Such phenomena may be explained in terms of the types of sorbing species postulated earlier. It has been shown (20, 21, 22) that the nature of the sorption of radiocolloids from aqueous solutions differs from ionic sorption. For example, Schubert and Conn (23) found that the sorption of colloidal zirconium and niobium on a cation exchanger increased with increasing electrolyte concentration, while addition of electrolyte effectively competed with and reduced sorption of the ionic species. 

On the other hand we find complex flocculation or coacervation rather at relatively low electrolyte concentrations. They are the more pronounced the greater the charge density of the colloid. The effectiveness of the ions is in the main determined by their valency over which lyotropic influences are superposed. We sometimes find here that the sequence of the ions is just the opposite of that in the normal lyotropic series (for example of the monovalent anions, with the positive proteins, compare also p. 299, Fig. 22) and we have in this a clear indication of the complex character of the flocculation. 

The reversible reaction in gel formation plays an important role in colloid electrolyte-based lead-acid batteries. Like other chemical reactions, the temperature can have a strong effect on gel formation. The formation rate and stability of the gel are also dependent on pH, type of salts, quantity of silica dioxide, size of particles. 

The quantity and the size of Si02 have the most important effect on battery performance when a colloid electrolyte is used. The 3D structure of the electrode active layers will become stronger as the quantity of Si02 is increased. The size of colloid particles can affect the volume of the pores and the average pore size of the electrode active masses. Therefore, the volume of the pores and the average pore size will be smaller when the quantity of Si02 is increased. The effect of Si02 quantity on electrolyte structure is summarized in Table 5.9. 

Pelton RH. Electrolyte effects in the adsorption and desorption of a cationic polyacrylamide on cellulose fibers. J Colloid Interface Sci 1986 111 475-485. 

The solubility of the antitubercular drug, pyrazinamide, is directly proportional to the concentration of sodium p-aminosalicylate (sodium PAS) or sodium hydroxybenzoate in aqueous solution [305]. Thermal analysis has confirmed the complex formation between the drug and sodium PAS, but the authors [305] list the alternatives of complexation and normal increase in solubility in the presence of additive as the causes of solubilization. As the antituberculars are always used clinically in combination - sodium PAS is also an effective drug-this study may have some bearing on the efficacy of the combinations. It might be of interest for an investigation to be carried out on the solution properties of isoniazid, streptomycin, and sodium PAS mixtures, especially as streptomycin is thought to have some colloidal electrolyte properties of its own. 

Lecomte, S., Moreau, N.J., Manfait, M., Aubard, J. and Baron, M.H. (1995) Surface-enhanced Raman spectroscopy investigation of fluoroquinolone DNA/ DNA gyrase Mg interactions. 1. Adsorption of pefloxadn on colloidal silver-effect of drug concentration, electrolytes, and pH. Biospectroscopy, 1, 423-36. 

Stem layer adsorption was involved in the discussion of the effect of ions on f potentials (Section V-6), electrocapillary behavior (Section V-7), and electrode potentials (Section V-8) and enters into the effect of electrolytes on charged monolayers (Section XV-6). More speciflcally, this type of behavior occurs in the adsorption of electrolytes by ionic crystals. A large amount of wotk of this type has been done, partly because of the importance of such effects on the purity of precipitates of analytical interest and partly because of the role of such adsorption in coagulation and other colloid chemical processes. Early studies include those by Weiser [157], by Paneth, Hahn, and Fajans [158], and by Kolthoff and co-workers [159], A recent calorimetric study of proton adsorption by Lyklema and co-workers [160] supports a new thermodynamic analysis of double-layer formation. A recent example of this is found in a study... 

Surface active electrolytes produce charged micelles whose effective charge can be measured by electrophoretic mobility [117,156]. The net charge is lower than the degree of aggregation, however, since some of the counterions remain associated with the micelle, presumably as part of a Stem layer (see Section V-3) [157]. Combination of self-diffusion with electrophoretic mobility measurements indicates that a typical micelle of a univalent surfactant contains about 1(X) monomer units and carries a net charge of 50-70. Additional colloidal characterization techniques are applicable to micelles such as ultrafiltration [158]. 

Electroviscous effect occurs when a small addition of electrolyte a colloid produces a notable decrease in viscosity. Experiments with different salts have shown that the effective ion is opposite to that of the colloid particles and the influence is much greater with increasing oxidation state of the ion. That is, the decrease in viscosity is associated with decreased potential electrokinetic double layer. The small amoimt of added electrolyte can not appreciably affect on the solvation of the particles, and thus it is possible that one of the determinants of viscosity than the actual volume of the dispersed phase is the zeta potential. 

Among the various branches in colloid and interface science, polymer adsorption and its effect on the colloid stability is one of the most crucial problems. Polymer molecules are increasingly used as stabilizers in many industrial preparations, where stability is needed at a high dispersed phase volume fraction, at a high electrolyte concentration, as well as under extreme temperature and flow velocity conditions. 

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