Impact of anionic and cationic polyacrylamide on the stability of aqueous alumina suspension—comparison of adsorption mechanism

In the present study, particular emphasis was put on the effects of the type of functional groups of anionic and cationic polyacrylamide (PAM) and solution pH on the mechanism of polymer adsorption on the surface of dispersed alumina. The polymer-adsorbed amount, surface charge density and zeta potential of solid particles without and with PAM, as well as the stability of Al 2 O 3 suspension containing the polymer, were determined. For this purpose, the spectrophotometry, potentiometric titration, microelectrophoresis and turbidimetry were applied. It was shown that adsorption of anionic PAM decreases with the pH rise, whereas in the case of cationic PAM, it increases. High adsorption level is a result of more coiled structure of adsorbed macromolecules. The anionic PAM has greater impact on the suspension stability deterioration in comparison to the cationic polymer in the whole range of studied pH values. The more pronounced effect of alumina suspension destabilization in the anionic PAM presence was obtained at pH 6, at which solid surface charge neutralization occurs.