The quantitative analysis of boehmite in bauxite is of fundamental importance to determine the digestion conditions in the Bayer process. However, no method is reported in literature to perform this analysis. Hence, X-ray diffraction was used in this work to quantify boehmita, gibbsite, hematite and goethite in bauxite. A sample from Ghana containing 45% of gibbsite and 43% of boehmite was subjected to a caustic leaching at 160oC for the removal of gibbsite. The residue, virtually exempt of gibbsite, was treated with the dithionite-citrate-bicarbonate system for the removal of the iron oxy-hydroxides. The final product contained about 85%-89% of boehmite and 9% of TiO2. Calibration curves correlating the intensities of the X-ray diffraction peaks with the amounts of the mineralogical phases were obtained after mixing known quantities of gibbsite, hematite and goethite to the purified bauxite sample. Highly significant correlations were obtained for the crystallographic planes (020), (051), (002) and (251) of boehmita; (110), (200), (11-2) and (024) of gibbsite; (012), (024) and (110) of hematite; e (110) and (021) of goethite. These correlations can be used to quantify the amounts of the above mentioned phases in a unknown bauxite sample.
X-ray diffraction; boehmite; gibbsite; quantification
