VOLTAMMETRIC METAL SPECIATION IN COLLOIDAL LATEX DISPERSIONS

Two types of polystyrene latices, one with surface carboxylic groups a nd the other covered with a polymer shell containing carboxylic and su lphonic groups, were analyzed in terms of their metal ion binding prop erties. In-situ voltammetric experiments were carried out for zinc(II) , cadmium(II) and lead(II) to characterize the thermodynamics and kine tics of their association with the surface groups in the latex particl es. The kinetics were investigated experimentally through the time-sca le dependencies, and set against theoretical predictions [De Jong, H. G. and Van Leeuwen, H. P., J. Electroanal. Chem., 1987, 234, 17; De Jo ng, H. G. and Van Leeuwen, H. P., J. Electroanal. Chem., 1987, 235, 1] on the basis of rigorous lability criteria and elementary complex for mation rate constants. The core-shell latices appear to form relativel y weak and labile complexes. In the case of highly charged latices, th e metal/carboxylate surface complexes are stronger and lose lability a t a high degree of dissociation. (C) 1998 Elsevier Science Ltd. All ri ghts reserved.