DETERMINATION OF THE EFFECTS OF A BIPOLAR POLYPYRIDYLOSMIUM(II) COMPLEX ON THE STABILITY OF MONTMORILLONITE COLLOIDS

Adsorption of a large cationic complex on the surface of a montmorillo nite colloid results in flocculation of the colloid. This destabilizat ion of the colloid does not occur when the cationic complex has been m odified to contain a side-chain terminating in an anionic group (i.e., the complex is bipolar). The influence of such a bipolar complex on t he particle sizes in montmorillonite colloids was examined using a pol ypyridylosmium(II) complex. Laser Doppler velocimetry was employed to determine the particle-size distributions in montmorillonite colloids containing various concentrations of the osmium complex and 1.00 g L-1 of clay. At loadings below the cation-exchange capacity of the clay, the particle-size distribution was independent of the total concentrat ion of the bipolar osmium(II) complex. Under these conditions, at leas t 98% of the complex was adsorbed on the clay. (C) 1998 Academic Press