Zeta potential hydrocarbons

Zeta-Potentials of Carbon Black Dispersions in Hydrocarbons with OLOA-1200 Dispersant (14-16)... 

Figure 7.7 Zeta potentials (calculated from electrophoretic mobility data) relating to particles of different ionogenic character plotted as a function of pH in acetate-veronal buffer at constant ionic strength of 0.05 mol dm 3, (a) Hydrocarbon oil droplets, (b) Sulphonated polystyrene latex particles, (c) Arabic acid (carboxylated polymer) adsorbed on to oil droplets, (d) Serum albumin adsorbed on to oil droplets...

Effect of the hydrocarbon chain length on the zeta potential of quartz in solutions of alkyl-ammonium... 

In case of using mixtures of two and more collectors, the selective hydrophobisation is accomplished simultaneously both due to chemisorption and physical adsorption. It is shown in [69] that the simultaneous use of fatty acids and hydrocarbon oils for calcium phosphate flotation from quartz different processes are observed. Fatty acid soaps form chemical compounds on the surface of the material floated, after which the hydrocarbon oil physically adsorbs. It has been experimentally established that hydrocarbon oil is transferred from quartz particles to the surface of floated phosphate. When using mixtures of anionics and nonionics, hydrophobisation of particle surfaces is also accomplished both due to the formation of chemical compounds and physical adsorption which is confirmed by measurements of the zeta-potential of the particles floated [70]. 

There is considerable evidence indicating that the zeta potential obtained from an elect rokinetic experiment is an adequate substitute for tj/o, particularly for dispersions in hydrocarbon media. Electrophoresis is therefore a useful technique for studying colloidal systems. 

Fundamental studies on such systems ate scarce, but some attention has been paid to dispersion in hydrocarbon solutions of surface-active agents for which the ionic concentrations are extremely small, e.g. 10 ° mol dm corresponding to I/k 10 psn. Since 1/k is large the capacity of the double layer is small and only a small surface charge density is necessary to obtain an appreciable surface potential Furthermore, the slow decay in potential from the surface means that the zeta potential, readily obtained from electrophoresis experiments, may be equated with considerable accuracy to the surface potential. 

The interaction of hydrocarbon and fluorocarbon surfactants on the surface of dispersed particles has been studied through a flocculation and redispersion process [65-67]. Dispersions of positively charged particles can be flocculated with an anionic surfactant. An excess of the anionic surfactant forms a bilayer on the particle surface and causes redispersion of the flocculated sol. This flocculation reversal was used to study the interaction between mixed surfactants on a solid surface. A dispersion of iron(ITI) oxide hydrate particles was flocculated with an anionic hydrocarbon or fluorocarbon surfactant at pH 3.5, where the sols had a positive zeta potential. Subsequently, a second fluorocarbon or hydrocarbon surfactant was added to the flocculated sol. The extent of redispersion depended on the interaction between the two surfactants on the solid particle surface. 

Figure 5.10 shows changes in zeta potential and turbidity of iron(III) oxide hydrate sols flocculated with NFIOO. The optimum flocculation concentration was about 3 X 10 mM NFIOO. The sols were redispersed by NF7 or NP7.5, a hydrocarbon-type nonionic surfactant (polyoxyethylene nonylphenyl ether with a polyoxyethylene chain of average 7.5 EO). The turbidity increased sharply. The zeta potential changed only a little, as expected for a nonionic surfactant. Sols flocculated by NFIOO were not redispersed by SDS. The inability of SDS, an anionic hydrocarbon surfactant, to redisperse the sols was attributed... 

Changes in zeta potential and turbidity of iron(III) oxide hydrate sols flocculated with lithium perfluorooctanesulfonate (LiFOS) are shown in Fig. 5.11. The nonionic surfactants NF7 and NP7.5 redispersed the sols. However, the anionic hydrocarbon surfactant LiDS (lithium dodecyl sulfate) had no significant effect. Accordingly, sols flocculated by LiDS were redispersed by a nonionic surfactant, NF7, but not by the anionic surfactant LiFOS (Fig. 5.12). 

Esumi et al [68] used dispersions of a-alumina as well to study the interaction between anionic fluorocarbon and hydrocarbon surfactants. The anionic fluorocarbon surfactants used were LiFOS and NFIOO, the anionic hydrocarbon surfactants were SDS and LiDS, and the nonionic surfactant was NP7.5. Like the flocculation behavior of iron hydroxide, a low concentration of an anionic surfactant precipitates alumina. A further addition of a surfactant, different from the first one, forms mixed bilayers and redisperses alumina. Measurements of zeta potentials, the size of adlayers, and the amounts of adsorbed surfactants indicated that mixed bilayers consisting of anionic hydrocarbon-nonionic hydrocarbon surfactants or anionic fluorocarbon-nonionic hydrocarbon surfactants are formed preferentially to hydrocarbon-fluorocarbon surfactant bilayers. 

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