Acidity analysis of iron ore based on calibration-free laser-induced breakdown spectroscopy (CF-LIBS) combined with a binary search algorithm (BSA)

Abstract

Calibration-free laser-induced breakdown spectroscopy (CF-LIBS) combined with a binary search algorithm (BSA) is proposed to determine the acidity (CaO/SiO₂ mass ratios) of iron ore. It is based on the idea that different samples with a similar matrix ablated in the same conditions have the same plasma temperature. Ca I/Si I molar ratios are obtained by the intercepts on the Boltzmann plots drawn by using corrected spectral lines without self-absorption, and the number concentrations of primary ionization ions of the elements are evaluated by the Saha equation. Furthermore, one standard sample matrix-matched with unknown samples along with BSA is employed to obtain a more accurate plasma temperature. Noteworthily, BSA is a classical search method and utilized to search the optimal plasma temperature for the first time in CF-LIBS. The acidity of the iron ores can be calculated according to the obtained value of Ca/Si molar ratios. The calculated acidity of the unknown samples were close to the certified acidity based on the root mean square error (RMSE) and mean relative error (MRE) which were 0.0145 and 4.01%, respectively. The proposed CF-LIBS method can be used to determine the acidity of iron ores, and it provides a new method and technology for selection and quality control of iron ore.