Abstract
Dissolution behavior of high-purity α-alumina particles was studied in acidic solutions (pH 2.6-5.5) and basic solutions (pH 7.2-9.3) containing Mg2+ ions at room temperature. The amount of dissolved α-alumina was dominated by the solubility limit of aluminium hydroxide formed on the surface of α-alumina. The α-alumina in an acidic suspension of 5 vol% solids dissolved to increase pH of the suspension and to produce a supersaturated solution of Al3+ ions in which nucleation and growth of aluminium hydroxide proceeded until the Al3+ concentration reached the solubility limit of aluminium hydroxide. Little adsorption of Mg2+ ions onto the positively charged alumina surface (<0.5μmol/m2) was examined in the acidic suspensions at pH 4.1-4.3. The amount of alumina dissolved in the basic suspensions was less than that in the acidic solutions. Weakly charged negative alumina surface of 1m2 in the basic suspension at pH 7.9 adsorbed Mg2+ ions of 1.9μmol.
