REMOVAL OF IRON-BEARING MINERALS FROM GIBBSITIC BAUXITE BY DIRECT FROTH FLOTATION

Abstract

The refractory bauxite needs to present less than 2.5% of Fe2 O3 to be applied in the ceramics industry. The depletion of high Al2O3 grade deposits has stimulated the improvement of bauxite concentration methods in order to remove iron-bearing minerals. The objective of this study was to evaluate the influence of collector dosage, pH and milling time on the gibbsite flotation performance. Firstly, the sample mineralogical composition was determined by means of X-ray diffraction (XRD) and binocular loupe analysis. X-ray fluorescence (XRF) analysis was used to determine the sample chemical composition. Flotation was then accomplished by using hydroxamate as gibbsite collector, sodium silicate as silicate depressant and starch as iron-bearing minerals depressant. The bauxite Fe2 O3 content was reduced from 7.66% to 4.81-5.03%. In addition, the flotation performance decreased by diminishing the pH from 9.5 to 8.5 or increasing the pH to 10.5. The milling time influence on the flotation indicates that the presence of slime can significantly affect the gibbsite concentration.