Effects of Particle Size on the Attenuated Total Reflection Spectrum of Minerals

Udvardi, Beatrix and Kovács, István János and Fancsik, Tamás and Kónya, Péter and Bátori, Miklósné and Stercel, Ferenc and Falus, György and Szalai, Zoltán (2016) Effects of Particle Size on the Attenuated Total Reflection Spectrum of Minerals. APPLIED SPECTROSCOPY. ISSN 0003-7028 (In Press)

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This study focuses on particle size effect on monomineralic powders recorded using attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy. Six particle size fractions of quartz, feldspar, calcite, and dolomite were prepared (<2, 2–4, 4–8, 8–16, 16–32, and 32–63 mm). It is found that the width, intensity, and area of bands in the ATR FTIR spectra of minerals have explicit dependence on the particle size. As particle size increases, the intensity and area of IR bands usually decrease while the width of bands increases. The band positions usually shifted to higher wavenumbers with decreasing particle size. Infrared spectra of minerals are the most intensive in the particle size fraction of 2–4 mm. However, if the particle size is very small (<2 mm), due to the wavelength and penetration depth of the IR light, intensity decreases. Therefore, the quantity of very fine-grained minerals may be underestimated compared to the coarser phases. A nonlinear regression analysis of the data indicated that the average coefficients and indices of the power trend line equation imply a very simplistic relationship between median particle diameter and absorbance at a given wavenumber. It is concluded that when powder samples with substantially different particle size are compared, as in regression analysis for modal predictions using ATR FT-IR, it is also important to report the grain size distribution or surface area of samples. The band area of water (3000–3620 cm–1) is similar in each mineral fraction, except for the particles below 2 mm. It indicates that the finest particles could have disproportionately more water adsorbed on their larger surface area. Thus, these higher wavenumbers of the ATR FT-IR spectra may be more sensitive to this spectral interference if the number of particles below 2 mm is considerable. It is also concluded that at least a proportion of the moisture could be very adhesive to the particles due to the band shift towards lower wavenumbers in the IR range of 3000–3620 cm–1.

Item Type: Article
Subjects: Q Science / természettudomány > QC Physics / fizika > QC02 Optics / fénytan
Q Science / természettudomány > QD Chemistry / kémia > QD01 Analytical chemistry / analitikai kémia
Q Science / természettudomány > QD Chemistry / kémia > QD05 Crystallography / kristálytan
Q Science / természettudomány > QD Chemistry / kémia > QD06 Mineralogy / ásványtan
Depositing User: Dr. István János Kovács
Date Deposited: 04 Oct 2016 18:24
Last Modified: 04 Oct 2016 18:24

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