Alumina recovery from kaolin with mineral impurities

Abstract

The alumina recovery from low grade kaolin (K-JS) treated through thermal and mechanical methods was investigated. High grade kaolin (K-SX) was used as comparison. The optimum calcination temperatures for K-JS and K-SX were both 600 °C, which resulted in 89.34wt% of alumina extraction from K-JS and 83.37wt% from K-SX. With the increase in calcination temperature, the chemical reactivity of calcined K-JS and K-SX to acid decreased. Mechanical treatment was much more effective in increasing the alumina extraction from activated kaolin. Around 99wt% of alumina was extracted from K-JS ground for 10 hours and 95wt% of alumina was extracted from K-SX ground for 20 hours. The IR results showed that the substitute of Al for Si occurred in calcined K-SX, however, the impurities in K-JS decreased this substitute. More alumina could be extracted from low grade kaolin than that from high grade kaolin under identical thermal or mechanical conditions.

Keywords

kaolin / alumina / calcination / milling / acid extraction

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