Effect of Tiron adsorption on the colloidal stability of nano-sized alumina suspension

The colloidal stabilization of nano-sized alumina suspensions with 1,2-dihydroxy-3,5-benzenedisulfonic acid disodium salt (Tiron) at various pH is examined systematically to understand the primary mechanism of dispersion. Zeta potential measurements show that the addition of Tiron causes the isoelectric point from 8.2 to 4.5, as well as a dramatic increase in the absolute zeta potential. The adsorption studies indicate that adsorption saturation increases with the decrease in pH value. The surface properties of alumina suspensions are examined by using FT-IR analysis. In acidic medium, the electrostatic mechanism is found to be the primary mechanism governing dispersion. Under alkaline conditions, chemical interactions take place at the solid–water interface by forming an inner sphere complex between Al3+ ion and Tiron. The suspension stability is characterized by measuring the viscosity, sedimentation height and the effective diameter of particles. It is found that the optimum pH value is 8.5 and the optimal dosage of Tiron is 0.8 dmb% (dry mass base percent) of alumina.