Voltammetric metal speciation in colloidal latex dispersions

Abstract

Two types of polystyrene latices, one with surface carboxylic groups and the other covered with a polymer shell containing carboxylic and sulphonic groups, were analyzed in terms of their metal ion binding properties. In-situ voltammetric experiments were carried out for zinc(II), cadmium(II) and lead(II) to characterize the thermodynamics and kinetics of their association with the surface groups in the latex particles. The kinetics were investigated experimentally through the time-scale dependencies, and set against theoretical predictions [De Jong, H. G. and Van Leeuwen, H. P., J. Electroanal. Chem., 1987, 234, 17; De Jong, H. G. and Van Leeuwen, H. P., J. Electroanal. Chem., 1987, 235, 1] on the basis of rigorous lability criteria and elementary complex formation rate constants. The core-shell latices appear to form relatively weak and labile complexes. In the case of highly charged latices, the metal/carboxylate surface complexes are stronger and lose lability at a high degree of dissociation.