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 (PM) 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 PM 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. (C) 2012 Elsevier B.V. All rights reserved.