Extraction of Aluminum Oxide from Local Kaolin Clay Deposits in Ethiopia

Abstract

The need for aluminum is growing worldwide, which has sparked interest in finding alternate ways to make alumina from materials other than bauxite, particularly clays. This article examines the use of sodium carbonate as a leaching agent in the lime sintering process to recover alumina from kaolin. Excavated from Tarmaber, Ethiopia, kaolin clay contains a content of 32.88%, which has a relatively good composition. Collecting and grounding raw kaolin to micrometer-level particle size is the first task. The recovery of kaolin alumina was studied at sintering temperatures of (T<sub>1</sub>=800°C, T<sub>2</sub>= 900°C & T<sub>3</sub>=1000°C) at different sintering times of (t<sub>1</sub>=1 hr, t<sub>2</sub>=2 hrs & t<sub>3</sub>=3 hrs). After the raw material was burned at the given temperatures and times, it was cooled for the night in the furnace and leached with different concentrations of sodium carbonate (M<sub>1</sub>=50 g/l, M<sub>2</sub>=60 g/l & M<sub>3</sub>=70 g/l). The response surface methodology (RSM) in combination with the central composite design was used to optimize the operating parameters. The optimization result shows that the optimal conditions were a calcination temperature of 953.84°C, a sintering time of 2.99 h, and a leaching agent concentration of 70 g/l. At this optimal condition, the yield of Alumina was 1.05 g of 20 g of Kaolin clay. The resulting Alumina was crystalline in structure (from XRD analysis), contains 89.05% Al<sub>2</sub>O<sub>3</sub> (from silicate analysis) and a large broad band between 400-1000 cm<sup>-1</sup> is attributed to Al-O-Al stretching of Alumina (from FT-IR analysis). So, it is possible to conclude that alumina production from no bauxite ores is possible.