INFLUENCE OF SURFACTANT ADDITION ON THE STABILITY OF CONCENTRATED ALUMINA DISPERSIONS IN WATER

The goal of this study was to assess the effects of surfactant additio n on the stability and viscosity of concentrated alumina dispersions. The stabilizing effects of several candidate surfactants were investig ated for concentrated dispersions of two different pseudoboehmite alum inas at pH 4 and 7. The stabilities of concentrated alumina dispersion s treated by pH adjustment alone and by pH adjustment combined with su rfactant addition were compared to assess the degree to which the surf actant enhanced stability. The initial rate of mass removal from a sed imenting alumina dispersion was used as a measure of stability. The an ionic surfactants Surfine WNT-A and DOWFAX 3B2 were identified as effe ctive in enhancing the stability of concentrated alumina dispersions. The optimal doses of these surfactants for stabilizing 15% by weight V ERSAL(TM) 250 alumina dispersions at pH 4 were determined to be about 4.6 x 10(-5) mol g(-1) for both surfactants. On the basis of the initi al rate of mass removal, surfactant-stabilized 15 wt.% suspensions wer e found to be approximately 2.5 and 10.6 times more stable than simila r dispersions stabilized electrostatically by pH adjustment alone. The se more stable dispersions exhibited lower viscosities than observed f or the alumina dispersions not subjected to surfactant addition. The r esults indicate that the stability of concentrated alumina dispersions can be enhanced by anionic surfactant addition, and that such surfact ants may therefore help to control the rheology of concentrated disper sions of alumina in water.