A proposal for bauxite quality control using the combined Rietveld - Le Bail - Internal Standard PXRD method - Part 2: Application to a gibbsitic bauxite from the Paragominas region, northern Brazil

In the bauxite industry - exploration, beneficiation and refining - two main chemical parameters are used for quality control: available alumina (AvAl2O3) and reactive silica (RxSiO2) content. Both are determined using a wet chemistry procedure that simulates the Bayer process at laboratory scale. For gibbsitic bauxites, the subject of this study, the available alumina is associated with the ore mineral gibbsite, and the reactive silica is associated with the deleterious mineral kaolinite. A significant innovation for this industry would be to characterize bauxite ores using mineralogical parameters, i.e., the wt% of gibbsite and wt% of kaolinite via Powder X-ray Diffraction Analysis (PXRD), which has been employed elsewhere but has been time-consuming and imprecise. A recent proposal for quantification of the main mineral components of bauxite ores for quality control in bauxite mining was developed by Paz et al. (2018) using the combined Rietveld - Le Bail - Internal Standard PXRD method. In this work, the method is tested using a Brazilian bauxite ore from the Paragominas region (Pará state, northern Brazil), and the results are evaluated against those from traditional wet chemistry (AvAl2O3 and RxSiO2). The study concluded that the PXRD method was able to produce results that were directly comparable with those from tradition chemical methods, and with the advantage of requiring only a single analytical instrument.