Adsorption of metal ions on stearic acid-nonadecane particles in aqueous solutions

The adsorption of metal ions at the stearic acid/electrolyte and nnonadecan e-stearic acid mixture/electrolyte interface was investigated by means of t he potentiometric titration, zeta potential and adsorption measurements. It was found that the studied colloidal suspensions exhibited an adsorption a ffinity towards multivalent metal ions. The adsorption of Ca2+, Cd2+ and Al ions caused a strong decrease of surface charge density and zeta potential values in this systems. The adsorption reactions occur by way of cation ex change with protons from two surface carboxyl groups. At high metal concent rations, in adsorption reactions there are involved also carboxyl groups fi -om the subsurface layer. On the basis of the adsorption data, the cation s urface complexation constants were calculated by Shindler's method.