Size Classification vs. Mineral Distribution and Its Implication in Optimum Utilization of Khondalite-Hosted Bauxite Ore
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ORIGINAL ARTICLE
Size Classification vs. Mineral Distribution and Its Implication in Optimum Utilization of Khondalite-Hosted Bauxite Ore from Eastern India Sudakshina Sahoo1 • Patitapaban Mishra1 • Purna Chandra Mishra2 Somnath Khaoash1 • Birendra Kumar Mohapatra1
•
Received: 27 August 2019 / Accepted: 30 May 2020 Ó The Indian Institute of Metals - IIM 2020
Abstract Three typical litho-types such as ‘saprolite,’ ‘bauxite’ and ‘laterite/lateritic ore’ from different levels of khondalite-hosted bauxite profile of Baphlimali plateau, Rayagada district, Odisha, Eastern India, have been studied. Mineralogical variations between different size fractions are interpreted for their optimum utilization. Mineralogy of individual bulk and its respective classified fractions are established from their XRD, DTA and TGA patterns. The saprolite, present in the lower most level of the profile, is rich in aluminum silicate (kaolinite), does not find use in alumina refinery and is usually considered as waste. However, if it is size-classified, the - 2.0 ? 0.50 mm fraction, measuring over 21% by volume of the bulk, is found to contain substantial amount of gibbsite that can be separated and utilized for alumina recovery. The bauxite, present at the intermediate level of the profile, is rich in aluminum hydroxide (gibbsite). However, sometimes it contains hematite as major impurities (Fe * 10%). Though such ore is of metallurgical grade, around 26 vol% of the ore can be used for refractory purpose by simple separation of \ 0.15 mm fraction. The ‘laterite,’ present in the upper most level of the profile, constitutes a mixture of gibbsite, kaolinite, hematite/goethite. Though its Fe-content is within permissible limit, the reactive silica contributed by kaolinite inhibits its use in alumina refinery. However, separation of - 2.0 ? 0.25 mm size fraction from the bulk, amounting to 42% by volume, reduces kaolinite content appreciably. The study thus demonstrates & Patitapaban Mishra [email protected] 1
Department of Geology, Ravenshaw University, Cuttack, Odisha 753003, India
2
Directorate of Geology, Bhubaneswar, Odisha, India
that by simple size classification, different litho-types from a bauxite profile can be optimally utilized. Keywords Bauxite Saprolite Laterite Size classification Khondalite Group of rocks
1 Introduction Bauxite is the principal ore of aluminum which is one of the most important non-ferrous metals used in the modern industry and also an essential ore for refractory and chemical industries. The bauxite is processed into alumina (Al2O3) through a wet chemical, caustic soda leaching method, known as Bayer’s process and then to aluminum metal via an electrolytic method, the Hall–Heroult process. Around 80% of Indian bauxite resources are of metallurgical grade, while the refractory and chemical grades account for only about 3% [1]. East Coast bauxite is one of the potential deposits in Eastern India. As our resource is finite and non-replenishable, it is necessary to recover every ounce of bauxiti
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