Studies on desilication of siliceous bauxite from Kashmir

Abstract

The paper outlines the methods used for high silica bauxites and records results of investigation on the removal of silica from the bauxite sample containing 55.35% Al2O3, 22.4% SiO2, 5.31% Fe2O3 and 2.9% TiO2, by calcination and leaching with caustic soda solution. The effect of calcination temperature, period of calcination and particle size of the sample were studied with respect to the subsequent desilication characteristics of the calcine. The dissolution characteristics of SiO2 and Al2O3 in the calcine were also studied with regard to alkali concentration, volume of leachant, temperature and period of leaching. It has been possible to remove over 89% SiO2 with a loss of 9.79% of Al2O3 from the sample crushed to-72 mesh B.S.S., calcined at 850°C for 4 hours, followed by leaching with 15% NaOH (W/V) solution at 95°C for one hour at Na2O/SiO2 ratio of 13. 4:1 and 3.33% solid in the leachant. The desilicated residue analysed 80.4% Al2O3, 4.45% SiO2, 8.56% Fe2O3 and 4.67% TiO2. (Mr. S.S. Bhoray, Senior Technical Assistant, Messrs V.S. Sampath and P.P. Bhatnagar, Scientists, National Metallurgical Laboratory, Jamshedpur)