Aplicação da espectroscopia de reflectância difusa na quantificação dos constituintes de bauxita e de minério de ferro.

This paper describes the application of diffuse reflectance spectroscopy in the development of a methodology for the identification and quantification of minerals in bauxite and iron ores. Selected samples containing a mineral variability were collected from the Iron Quadrangle (Minas Gerais) mines and from the region of Carajás (Pará). The different mineral concentrations were estimated from a combination of conventional methods such as chemical analysis, Mössbauer spectroscopy, Xray diffractions, magnetic susceptibility and optical microscopy. Diffuse reflectance spectra in the visible, near infrared and mid infrared regions were correlated to the mineralogical composition by chemometric algorithms. The mineralogical analysis showed satisfactory correlations, and on the average the statistical parameters were found to be close to R2 = 0.93 for bauxite and R2 = 0.87 for iron ores. Goethite [R2 = 0.96, average standard error of validation (RMSEC) = 3.6%] and hematite (R2 = 0.90, RMSEC = 7.3%) for iron ore. These results suggest that the diffuse reflectance spectroscopy is a fast and easy method for the simultaneous determination of various minerals present in bauxite and iron ores. [ABSTRACT FROM AUTHOR]