Comparison of the Poly(vinyl alcohol) Adsorption Behaviour on the Mixed Oxides with Different Surface Structure
The adsorption and electrokinetic properties, as well as the stability of the mixed oxide suspensions in the absence and presence of poly(vinyl alcohol) – PVA were studied. Two alumina-silica-titania (AST) oxides were used: AST50
(TiO2 : 50 %, SiO2 : 28 %, Al2O3 : 22 %) and AST71 (TiO2 : 71 %, SiO2 : 8 %, Al2O3 : 21 %). All measurements were carried out in the pH range 3 – 9 as a function of the polymer molecular weight (72 000 and 100 000 Da) and degree of PVA hydrolysis (86 % and 98 %). The obtained results indicated that the PVA adsorption strongly depends on the solution pH – for AST50 it decreases and for AST71 increases with the pH rise. This is caused by various PVA chains conformation on the solid surfaces with different structures. The adsorption of poly(vinyl alcohol) influences on the stability of the mixed oxides suspension. The greatest effects were observed in the presence of PVA 100 000 at pH 3 for AST50 suspension and at pH 9 for AST71 system. In these cases, polymer addition leads to significant improvement of stability conditions of examined systems.
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