Effect of polyacrylic acid (PAA) adsorption on stability of mixed alumina‐silica oxide suspension

The influence of solution pH and polymer molecular weight on the stability of mixed alumina-silica oxide suspension in the absence and presence of polyacrylic acid (PAA) was studied. The composition of the adsorbent was: Al2O3 (96%) and SiO2 (3%). To obtain changes in the stability of the investigated systems as a function of time the turbidimetry method was applied. It was shown that the suspension without the polymer was characterized by the smallest stability at pH 9, whereas at pH 3 and 6 the systems are successively stable. PAA with the molecular weighs 2000 at pH 3 (large deterioration of system stability conditions) and PAA (all molecular weights) at pH 9 (considerable improvement of suspension stability) have a great effect on the alumina-silica stability. The specific conformation of PAA chains on the solid surface which depends on solution pH and polymer molecular weight is responsible for the stabilization–flocculation properties of polyacrylic acid in the colloidal suspension.