Preparation of Boehmite (AlOOH) powder from kaolin by acid leaching

Abstract

The Boehmite (AlOOH) powder was synthesised by the acid leaching of the kaolin. Here hydrochloric acid was used as a leaching agent. The kaolin was taken as a raw material and calcined at 750oC to form metakaolin. This metakaolin was leached with hydrochloric acid to get aluminium rich solution. During leaching process, the temperature was maintained at 90oC with continuous stirring and under reflux condition for 7 hours. The obtained leach solution was further treated with the slow addition of sodium hydroxide up to pH 8. The white precipitate was then collected and dried at 60oC for 24 hours and characterised by different techniques. The formation of boehmite phase was confirmed by x-ray powder diffraction study. The infrared analysis, particle size distribution and microstructural analysis were carried out to ascertain the bond type, distribution of powder particle and particle morphology. Further calcination of boehmite powder at higher temperatures shows the formation of various transition alumina phases.