Mineralogical and thermal characteristics of low-grade Jinlong bauxite sourced from Guangxi Province, China

Abstract

Characteristic samples from the No. 1 ore body of the Jinlong bauxite deposit in Guangxi Province, China, were assessed to determine their chemical composition using whole-rock geochemical analysis, their mineral components using X-ray diffraction, their thermal characteristics via differential thermal analysis, thermogravimetry and differential thermogravimetry, and their dissemination characteristics by scanning electron microscopy/energy-dispersive spectrometry. The results show that the average Al2O3 content in the Jinlong bauxite deposit is 41 % and that the Al2O3/SiO2 ratio is approximately 2.17, and thus, the ore may be defined as low-grade bauxite. The main minerals found in the ore were diaspore (20.3–43 %), gibbsite, clays and hematite. In differential thermal analysis results, the bauxite samples exhibit two distinct endothermic peaks, with the dehydration of gibbsite occurring in the 200–260 °C range and the dehydration of diaspore occurring in the 524–550 °C range. Thermogravimetry and differential thermogravimetry indicate four decomposition stages: evaporation of adsorbed water (50–160 °C), gibbsite decomposition (190–280 °C), goethite decomposition (190–280 °C) and diaspore dehydroxylation (460–580 °C). The diaspore belongs to the orthorhombic dipyramidal class and exists primarily in three dissemination forms—euhedral and subhedral grain, bean and oolitic shaped, and aphanitic and microcrystalline aggregates, and is always accompanied by kaolinite and pyrophyllite.