EFFECT OF ELECTROLYTE ON AGGREGATION OF HYDROPHOBIZED SILICA PARTICLES AND CHANGING
OF CONTACT ANGLE

Vilkova Natal'ya Georgievna, Doctor of chemical sciences, professor, sub-department of physics and chemistry, Penza State University of Architecture and Construction (28 G. Titova street, Penza, Russia), kpyotr10@pguas.ru
Nushtaeva Alla Vladimirovna, Candidate of chemical sciences, associate professor, sub-department of physics and chemistry, Penza State University of Architecture and Construction (28 G. Titova street, Penza, Russia), nushtaeva.alla@yandex.ru
Gorbunova Lidiya Sergeevna, Student, Penza State University (40 Krasnaya street, Penza, Russia), kpyotr10@pguas.ru

544.77

Materials and methods. Silica (Ludox and Aerosol) modified with cationic surfactant was used for stabilization of model foam and emulsion films. The contact angle q_W of aqueous phase flowing off was measured by the method of pressed drop at a glass plate, modified with silica suspension. The radius of aggregates of particles was determined by the method of sedimentation analysis. 
Results. Increase of hexylamine concentration in 2 % Ludox suspension with 0,01 mol/L NaCl leads to the growth of values of contact angles of water flow off by 5–10º. Increase of sodium chloride concentration by more than 0,4 mol/L in suspension with the same concentration of solid particles with hydrophobization degree ng = 0,5 mmol/g leads to the three times growth of the foam film thickness. At low degree of hydrophobization the contact angle value q_W increases up to 35–37º with adding of electrolyte (0,1 mol/L KCl). Increase of the electrolyte concentration leads to a 2,9 times decrease of the relative interfacial tension Δσ/σ.
Conclusions. Increase of the concentration of electrolyte in the aqueous phase resulted in the foam film thickness growth that indicated an increase in the radius of aggregates of the particles. The magnitude of the contact angle increased by addition of electrolyte only at low hydrophobization degree. Probably, the decrease of the relative interfacial tension reflects the influence of electrolyte on the interaction of aggregates of hydrophobized particles at the interface. 

 foams, emulsion, solid particles, interphase energy, contact angle.

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