Beneficiation of Bauxite by Acid Leaching

Abstract

Bauxite is the important ore for the production of Aluminum and also used for non-metallurgical purposes. Bauxite consists of hydrated aluminum oxide in the form of minerals like Gibbsite, Boehmite and Diaspore with impurities like Silika as Kaolinite & Quartz, Iron as Al-goethite & Hematite, Titania as Anatase & Rutile and other minor minerals. India having the limited reserve of naturally occurring high grade Bauxite except small deposits of Gujrat, and Maharashtra states. Bauxite deposits of Orissa are associated with the Eastern Ghats Super Group of rocks which form the East coast Bauxite deposits reserves about 2200 million tons. Despite the huge resources and good quality bauxite in the Eastern Ghats regions, but some industries located nearby are starving for suitable grade of Bauxite for their alumina production. This bauxite is mostly Gibbsitic in nature and quite suitable for production of metallurgical grade alumina. However, the average Fe2O3 content in Eastern Ghats bauxite is quite high (between 22 – 29%), which is mainly in the form of alumo-goethite and hematite which has to be removed by beneficiation processes and upgrade the quality of ore as per the requirement of the industries. The non-metallurgical grade of bauxite has to fulfill more rigid compositional requirement than that used for aluminium extraction. The average Fe2O3 content in Eastern Ghats Bauxite vary between 22-28% which is mainly in the form of alumo-goethite and hematite and have inverse relationship with the alumina value. Any technique which can reduce only iron content can make this bauxite suitable for non-metallurgical industries and also open up prospects of their export to aluminum industries. The present study has been taken up for reduction of iron of Eastern Ghats Bauxite by chemical dissolution of iron in Hydrochloric acid and experimental tests shows that this beneficiated Bauxite may be suitable for abrasive and refractory industries. It is found that by this processes the iron content can be reduced below three percent.