Effect on 2,2′-bipyridine adsorption of poly(vinyl alcohol) adsorbed on Na+-kaolinite

The adsorption (pH 6) of 2,2′-bipyridine (BP) on Na+-kaolinite and on samples of the same clay containing 4.35 and 7.45 mg/g, respectively, of previously adsorbed poly(vinyl alcohol) (PVA) was studied. Specific adsorption of BP decreases with increasing clay particle size in the suspension as a result of particle association. Aqueous suspensions with a 1-4% concentration of kaolinite exhibit flocculation in the absence or presence of PVA, forming clusters of 43-64 units of single clay particles. The PVA adsorbed on the surface of sodium kaolinite particles causes partial dispersion of the kaolinite in the aqueous suspension; however, 7.45 mg/g of PVA adsorption or even lower (4.35 mg/g) is not able to fully impede the association of kaolinite particles.