Integrated investigations of the electrosurface properties of nonaqueous disperse and capillary systems

Abstract

Survey of the experimental results obtained in the Department of Colloid Chemistry of St. Petersburg State University on the integrated investigations of the electrosurface properties of various nonaqueous disperse and capillary systems covering a wide range of electrolyte solutions in various organic solvents: amphoteric ethanol and 1-butanol; dipolar aprotic dimethylsulfoxide, dimethylformamide, acetone and nitromethane; nonpolar n-heptane in contact with SiO 2, TiO 2, Al 2O 3 and glass. Electrokinetic potential ζ and charge σ ζ , adsorption of ions Γ, surface conductivity K s of powdery silica, titania and alumina were determined depending on the concentration 10 − 5 –10 − 2 M of LiBr, KBr, NaBr, CsBr, HBr, NaCl, NaOH, HCl, various tetraalkylammonium bromides and ionic surfactants in the above cited solvents. Special attention was paid to the consistency of the results of ζ-potential evaluation obtained from the streaming potential and electrophoretic mobility data using the most commonly known theoretical expressions. It was shown that the surface conductivity must be taken into account in all cases for the evaluation of correct ζ-potential values. The surface conductivity and ζ-potential for the porous quartz plugs and glass membranes were determined as the functions of concentration of the anionic surfactants in n-heptane containing controlled traces of water. It was also shown that in the cases of the less polar solvents and more polar solids the enormous values of surface conductivity are due to the adsorption of the traces of water and in the cases of more hydrophylic liquids due to the overall adsorption of all ionic components from the solutions.