Adsorption of salicylic acid, 5-sulfosalicylic acid and Tiron at the alumina-water interface

The influences of three multivalent anionic electrolytes: salicylic acid, 5-sulfosalicylic acid and 1,2-dihydroxy-3,5-benzenedisulfonic acid disodium salt (Tiron) on the properties of alumina aqueous suspensions have been investigated in this paper. Zeta potential measurements show that the addition of Tiron results in a more dramatic increase in the absolute zeta potential in the alkaline region, as well as a shift of isoelectric point to the more acidic region than salicylic acid and 5-sulfosalicylic acid. Adsorption of a dispersant is promoted strongly by forming a complex between dispersant and Al atom. The adsorption ability is also related to molecular volume of the dispersant and its number of functional group which creates surface charge. The surface properties of alumina suspensions are examined by using FTIR analysis. The efficiency of the dispersant is characterized by observing the morphology of the sediments using scanning electron microscopy and measuring the sediment volume. The results show that Tiron is more effective than the other two dispersants. (C) 2002 Elsevier Science B.V. All rights reserved.