CAUSTIC INSOLUBLE ALUMINIUM CONTAINING NANOMINERALS IN BAUXITE FROM SOUTH WESTERN AUSTRALIA

Robert Gilkes, Saowanuch Tawornpruek, Nattaporn Prakongkep, Colin Scanlan, Wayne Tichbon, Alex Aboagye

Conventional and synchrotron XRD show that gibbsite, hercynite, corundum, poorly ordered aluminas, boehmite, goethite, hematite, maghemite, muscovite, kaolinite, anatase, quartz, and rutile are present in WA Darling Range bauxite. A signifi cant proportion of the Al in this bauxite is not dissolved by Bayer liquor. We have concentrated various aluminas, hercynite, iron oxides, kaolin and muscovite in the caustic insoluble residue and characterized these minerals using conventional and synchrotron X-ray diff raction and high resolution analytical electron microscopy (EDS, EELS, SAD, HRTEM).

Caustic soluble gibbsite [Al(OH)3] is the major aluminium mineral in these bauxites however the presence of caustic insoluble Al in nanometric corundum, hercynite, iron oxides, poorly ordered aluminas, and muscovite may substantially reduce aluminium extraction from some bauxite.