Ishaq Ahmad, Ernst-Ulrich Hartge, Joachim Werther, Mohammad Younas


Bauxite is the major source of alumina. It is treated in the Bayer hydrometallurgical process to extract alumina. The impurities, especially silica in the form of kaolinite (clay), causes many problems in the Bayer’s process e.g. causitc soda losses and scaling on plant surfaces. The choice of digestion temperature depends upon the mineralogy of the ore. The bauxite is not directly send to the Bayer plant if the ratio of alumina to silica in the ore is less than 8 by weight.


Bauxite characterization involves the mineralogical and chemical analysis to observe the type and grade of ore and gangue minerals present; microscopic studies describe the morphology and the association of ore and gangue minerals in the ore. The sieve analysis is required to calculate the particle size distribution (PSD) of ore. It was observed that gibbsite is available as the only ore mineral and silica (clay) is the main gangue mineral present in the given bauxite which can be treated under low temperature digestion conditions in Bayer process. Moreover, on the basis of characterization studies it was also concluded that the given bauxite ore was unsuitable to send it directly as Bayer plant feed. Therefore, it was recommended that alumina to silica ratio should be increased before sending the ore as feed for Bayer process and washing is the most suitable beneficiation technique for the ore under study.


characterization, gibbsite, clay, washing, alumina to silica ratio

Full Text: 258_JPIChE 44 (1) 2016 23 - 28

Published by Pakistan Institute of Chemical Engineers (PIChE)

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