Electrophoretic mobility of colloidal alkane particles in electrolyte solutions

Abstract

The electrophoretic mobility of intrinsically uncharged docosane particles has been measured in aqueous HCl, KCl, CaCl₂ and AlCl₃ electrolyte solutions over the concentration range 10^–5–0.1 mol dm^–3. The measured mobilities are large and vary with both electrolyte type and concentration. Interpretation of the mobilities using the standard electrokinetic theory of O'Brien and White (J. Chem. Soc., Faraday Trans. 2, 1978, 74, 1607) indicates that the magnitude of the effective electrokinetic surface charge, σ, increases with electrolyte concentration for the KCl, CaCl₂ and AlCl₃ electrolytes. The effective electrokinetic surface charge is negative in HCl, KCl and CaCl₂ solutions while in AlCl₃, σ turns from negative to positive. The ζ potential shows a maximum absolute value in both KCl (negative) and AlCl₃ solutions (positive).