Abstract
The thermal activation of Ngwo clay from southeastern Nigeria for optimal leaching of alumina was investigated. The clay assayed 24.63% Al2O3 and 52.15% SiO2, comprising mainly kaolinite mineral and free silica or quartz. The alumina locked up in the clay structure was rendered acid-soluble by thermal activation which transformed the clay from its crystalline nature to an amorphous, porous phase or metakaolinite. The clay samples were heated at calcination temperatures of 500°C, 600°C, 700°C, 800°C, and 900°C at holding times of 30, 60, and 90 minutes. Uncalcined clay samples and samples calcined at 1000°C (holding for 60 minutes) were used in the control experiments. After leaching the resulting clay calcines in 1 M hydrochloric acid solution at room temperature, it was observed that the clay calcines produced at 700°C (holding for 60 minutes) responded most to leaching. Samples calcined for 60 minutes also responded better than those held for 30 or 90 minutes. Based on activation energy studies, it was observed that calcines produced at 700°C (for 60 minutes) had both the highest leaching response (51.84% after 1 hour at leaching temperature of 100°C) and the lowest activation energy of 25.03 kJ/mol. It is concluded therefore that Ngwo kaolinite clay should be best calcined for alumina dissolution by heating up to 700°C and holding for 60 minutes at that temperature. The clay deposit has potential for use as alternative resource for alumina production in Nigeria where bauxite is scarce.
Highlights
IntroductionPrimary aluminium is produced by the electrolytic reduction of alumina (Al2O3)
About 90 percent of the world production of bauxite is used for making alumina, most of which is consumed in the manufacture of aluminium
The thermal treatment conditions required for transforming Ngwo clay to metakaolinite and subsequent leaching of alumina were investigated
Summary
Primary aluminium is produced by the electrolytic reduction of alumina (Al2O3). The alumina used is usually refined from bauxite, which has remained the most important ore for aluminium [5] [6]. About 90 percent of the world production of bauxite is used for making alumina, most of which is consumed in the manufacture of aluminium. West Africa holds the largest bauxite resources in the world [11] [12] [13]. The U.S Geological Survey put the world bauxite reserve at about 55 billion tonnes with West Africa having the highest share of
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
