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.