Study of the physicochemical characteristics of dispersions of n -alkanes C 23 H 48 and C 28 H 58 in water: zeta potenti
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Russian Chemical Bulletin, International Edition, Vol. 69, No. 7, pp. 1306—1310, July, 2020
Study of the physicochemical characteristics of dispersions of n-alkanes C23H48 and C28H58 in water: zeta potential and temperatures of phase transitions* V. N. Kuryakov,a D. D. Ivanova,b and K. I. Kienskayab aOil
and Gas Research Institute of the Russian Academy of Sciences (OGRI RAS), 3 ul. Gubkina, 119333 Moscow, Russian Federation. Fax: +7 (499) 135 7311. E-mail: [email protected] bD. Mendeleev University of Chemical Technology of Russia, 9 Miusskaya pl., 125047 Moscow, Russian Federation. Fax: +7 (499) 978 8660
The effect of pH on the zeta potential of dispersions of individual n-alkanes C23H48 and C28H58 with particle sizes of the order of 100 nm, which were prepared by ultrasonic dispersion without the addition of surfactants, was studied. It is shown that at pH ranged from 4 to 12, the investigated n-alkanes form stable dispersions in water. They are characterized by a high zeta potential varying from –30 to –50 mV. The phase transition temperatures (melting point, crystallization temperature, formation of rotator phases) were determined for the dispersions using an optical method. Key words: dispersion, emulsion, zeta potential, phase transitions, rotator phases, n-alkanes
Paraffin emulsions and dispersions are widely used in various industries, such as the production of paper, particle boards, and wood-composite materials with increased water resistance. They are used as water repellent additives in the production of laminated panels and concrete structures. Stable submicron emulsions are in demand in pharmaceuticals and cosmetology.1,2 One of the promising applications of paraffin emulsions and dispersions is their use as heat-transfer agents of increased efficiency, which are called phase change materials (PCM).3—6 The stability of emulsions and dispersions is of paramount importance for their practical application. It should be noted that a substantial part of studies of paraffin emulsions is devoted to ternary systems including n-alkane, water, and a surfactant. This is due to the fact that a component stabilizing the system is required to obtain a stable emulsion of the oil-in-water type. Most often a surfactant or a mixture of surfactants is used for this purpose. At the same time, the concentration and type (cationic or anionic) of a surfactant strongly affect the physicochemical characteristics of such a system. Surfactant stabilized emulsions with droplet sizes not exceeding 100 nm are commonly referred to as microemulsions, while those with drops greater than 100 nm are called * Based on the materials of the XXI Mendeleev Congress on General and Applied Chemistry (September 9—13, 2019, St. Petersburg, Russia).
macroemulsions.2 Microemulsions are formed spontaneously. In addition, they are thermodynamically stable in contrast to macroemulsions. Stable emulsions with droplet sizes 12), it substantially decreases to almost zero value. The zeta potential values close to zero that were observed Ze
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