BOEHMITE REVERSION: PREDICTIVE TEST AND CRITICAL PARAMETERS FOR BAUXITES FROM DIFFERENT GEOGRAPHICAL ORIGINS
Authier-Martin, M., Girard, R., Risto, G., and Verville, D.
Under low temperature Bayer conditions, boehmite present in bauxite is not dissolved and may promote the precipitation of dissolved alumina as re-precipitated boehmite on natural boehmite seed. This paper will describe a laboratory test developed to characterize and classify bauxites in their respective propensity to promote boehmite reversion. Using such analytical tools as differential scanning calorimetry and transmission electron microscopy, we can quantitatively measure the alumina losses linked with boehmite reversion and infer which boehmite characteristics are most prone to promote this reaction. Results obtained for bauxites of widely different origins will be presented and we will show, with a few selected examples, how these laboratory results relate to actual plant data. The test limitations will also be discussed.