THE INFLUENCE OF SURFACTANTS AND PH OF ENVIRONMENT ON THE ELECTRO-SURFACE PROPERTIES OF AQUEOUS SUSPENSION OF TITANIUM DIOXIDE
Journal Title: Праці Наукового товариства ім. Шевченка - Year 2018, Vol 53, Issue
Abstract
To regulate the electro-surface properties of aqueous suspensions of amphoteric oxides and their aggregative stability, changes in the pH of the medium and the addition of surfactants are often used. In this work, the effect of two surfactants: anionic – sodium dodecylbenzene sulfonate and cationic – benzethonium chloride on the electrical properties of aqueous suspensions of titanium dioxide of rutile modification in a wide range of pH solutions has been studied. The investigated titanium dioxide powder with an average particle diameter of 0.23 ± 0.03 μm was modified with inorganic oxides (4% Al2O3 and 2% SiO2) and grafted organic groups to provide the necessary properties and adjust the hydrophilic-lipophilic balance. Solutions of surfactants and suspensions were prepared in bidistilled water with a specific electrical conductivity of no more than 0.27 mS/m. The acid-base balance was varied by adding corresponding volumes of HCl or KOH solutions. It is shown that the electro-surface properties of titanium dioxide suspensions depend on both the pH of the medium and the adsorption of surfactants, which in turn depends on the pH of the medium. The cumulative effect of the physico-chemical processes occurring in suspensions of titanium dioxide was estimated by the difference in pH of suspensions made on the basis of aqueous solutions, and the pH of the suspensions made from solutions of surfactants, ΔрН. Such changes in the pH of suspensions in the presents of surfactants in comparison with the pH of suspensions without surfactants can be caused by a series of interconnected physico-chemical processes that can take place both in suspension volume and on solid surfaces of titanium dioxide, namely: a) ionization of water molecules; b) hydrolysis of a salt of weak acid and a strong base – sodium dodecylbenzenesulfonate; c) hydrolysis of a strong acid salt and a weak base – benzethonium chloride; d) supramolecular formations in solutions of surfactants (micelles); e) adsorption of surface-active substances and their micelles on a solid surface; f) adsorption / desorption of hydrogen ions on a solid surface. The obtained results are in good agreement with modern ideas about the adsorption of ionic surfactants on charged surfaces and show that the adsorption of molecules of surfactants on an identically charged surface is negligible. The value of ΔрН is almost independent of their concentration for benzethonium chloride in the acidic region and sodium dodecylbenzenesulfonate in the alkaline region, and vice versa – the adsorption of surfactant molecules on the opposite charged surface is significant and the value of ΔрН essentially depends on their concentration for benzethonium chloride in the alkaline region and sodium dodecylbenzenesulfonate in the acidic region, respectively.
Authors and Affiliations
Roman Petryshyn, Zinovy Yaremko
Keywords
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