Extraction of Alumina from Nawan Kaolin by Acid Leaching

Abstract

This paper investigated the production of alumina from Nawan kaolin by acid leaching with sulfuric and hydrochloric acids. Kaolin was calcined at 850°C and was leached with 6 M acid at 90°C, 5M NaOH followed by HCl solutions were added to the leaching liquor, and the precipitated aluminum hydroxide was converted to alumina by calcination at 900°C. Materials were characterized by FTIR, XRD, and SEM techniques. The alumina extraction percent was determined at different leaching times (30-180 min) and solid/liquid ratios (0.05-0.15 g/ml). The purity of kaolin is about 95%. The percent of extraction of alumina rapidly increases with the solid/liquid ratio up to 0.1 g/ml then decreases thereafter. The percent of extraction of alumina is higher for HCl than H2SO4. The size of the chloride and sulfate ions is the key factor that controls the percent of extraction of alumina from calcined kaolin under the studied conditions.