Quantitative elemental analysis of high silica bauxite using calibration-free laser-induced breakdown spectroscopy.

Abstract

Bauxite is a primary ore of aluminum. Precise information about bauxite mineralogical composition is challenging and crucial for efficient aluminum extraction and for the determination of its appropriateness for different industrial applications. For the qualitative and quantitative analysis of bauxite ore, we performed laser-induced breakdown spectroscopy (LIBS) in conjunction with x-ray diffraction (XRD), x-ray fluorescence spectroscopy (XRF), scanning electron microscopy coupled with energy dispersive x-ray spectroscopy (SEM-EDS), and Fourier transform infrared spectroscopy (FTIR). Analysis of the acquired optical emission spectrum revealed the presence of Si, Al, Fe, K, Ti, Ca, Mg, Na, Cr, and Sr. The plasma temperature and electron number density values estimated using Boltzmann plot and Stark-broadening line profile methods were 5600K and 7.65×1017 cm-3, respectively. In the present study we show that a calibration-free LIBS method presents a powerful solution, enabling quantitative analysis of multi-element bauxite ore better than traditional analytical techniques. The bauxite quantification obtained using CF-LIBS under the assumption of local thermodynamic equilibrium and optically thin plasma was Si=47.31%, Al=31.90%, Fe=16.54%, K=2.45%, Ti=1.64%, and Ca=0.16%, and its comparison with the outcome from XRD, XRF, SEM-EDS, and FTIR not only assisted but potentially enhanced the mineralogical composition understanding of bauxite ore in the present study.