CALCIUM AS POTENTIAL DETERMINING ION IN AQUEOUS CALCITE SUSPENSIONS

Electrokinetic mobility was measured on calcite particles dispersed in aqueous solutions as a function of pH, ion concentration and type (Na+, Ca2+, CI-, S04 2-). Whatever the pH value, experimental results show a good correlation between electrokinetic potential and Ca2+ activity. Considering Ca2+ as a potential determining ion and using a simple complexation model at the surface, we show that the displacement of the isoelectric point can be attributed to the relative affinity of CO3 2- and Ca2+ for the surface.