Utilization of kalapsha kaolin to prepare high purity alumina

Abstract

KALABSHA kaolin was calcined at 700°C then treated with hydrochloric acid to produce aluminum chloride hexahydrate. The hexahydrate was obtained in crystalline form through injection of hydrogen chloride gas in saturated solution and purified on several steps to obtain alumina of high purity. Acid leaching conditions, namely, acid to kaolin stoichiometric ratio(S), reaction time (t) and reaction temperature (T) were optimized using surface response methodology. A maximum alumina recovery of 83.2% was predicted on using 1.4 stoichiometric acid to solid ratio, a reaction temperature of 104°C and a reaction time of 3 hours. This result was then assessed experimentally. The hexahydrate crystals obtained were subsequently purified in a three stage process to increase their purity to 99.961%. Calcination of these crystals for 4 hours at 1100°C produced highly crystalline alumina with purity 99.9%.