In Ukrainian

Abstract

The purpose of this research article is to study the influence of additives of cationic surfactant - benzethonium chloride and the pH of the initial solutions from which suspensions were prepared on the electro-surface properties of titanium dioxide of rutile modification in its aqueous suspensions as well as to detect changes in the ratio between positively charged and negatively charged surface hydroxyl groups due to adsorption of surfactant molecules. In this study, we used powdered rutile-form titanium dioxide (average particle diameter 0.23 µm and specific surface area 14.6 m 2 /g), the surface of which was modified with inorganic oxides (Al 2 O 3 , 4 %, and SiO 2 , 2 %) and graft hydrocarbon chains in order to impart required optical properties and regulate of hydrophobic–hydrophilic balance. Benzethonium chloride is an industrial surfactant that is widely used to regulate the colloidal and chemical properties of many disperse systems. According to the results of the research, it has been found that additives of benzethonium chloride to aqueous suspensions of titanium dioxide have a significant effect upon its electro-surface properties. By using the 2-pK model of a double electric layer and a multistage model of surfactant adsorption on a solid surface, it has been found that the adsorption of benzethonium chloride molecules results in a decrease in the number of surface neutral hydroxyl groups and in the redistribution of superficial positive and negatively charged hydroxyl groups. The character of the redistribution of these groups depends on the pH of the aqueous solutions on the basis of which the suspensions of titanium dioxide were prepared. By evaluating the effect of adsorption of benzethonium molecules on the electro-surface properties of titanium dioxide in its aqueous suspensions, three sites of their dependence on the pH of the initial solutions can be distinguished: the first in the range from pH ≈ 2 to pH ≈ 5, the second in the range from pH ≈ 5 to pH ≈ 9 and the third in the range from pH ≈ 9 to pH ≈ 12. The dependence analysis of the adsorption of benzethonium chloride molecules on the pH of the initial solutions shows that adsorption increases slightly in the first section, does not show any significant fluctuations in the second one, and increases significantly in the third one due to an increase in the pH of the output solutions. The adsorption quantities of benzethonium chloride on titanium dioxide which have been theoretically predicted according to the proposed model, are in good agreement with the experimental results. An increase in the concentration of benzethonium chloride in suspensions involves the displacement of the isoelectric point of the investigated suspensions of titanium dioxide into the alkaline region. The obtained results are in good agreement with the experimental results of the study of the dependence of the zeta potential of titanium dioxide suspensions on the concentration of benzethonium chloride. The found dependencies allow to purposefully regulate properties of aqueous suspensions of titanium dioxide for production of necessary technological compositions.