The ζ-potential for a concentrated colloidal dispersion: The colloidal primitive model vs. the cell model

The colloidal primitive model (CPM) for a concentrated colloidal dispersion is studied through the well established hypernetted chain/mean spherical approximation integral equations theory (HNC/MSA-CPM). For comparison the corresponding cell model (CM) theory and other simpler approaches are calculated. Important deviations of the CM results, are found: The HNC/MSA-CPM theory predicts a polarity inversion of ζ-potential for several conditions, always associated with charge reversal, whereas none of the other approaches predict such an inversion. We discuss the possible implications of our results in relation to electrophoretic mobility.