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

Abstract

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 µm). It is found that the width, intensity, and area of bands in the ATR FT-IR 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 µm. However, if the particle size is very small (<2 µm), 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) is similar in each mineral fraction, except for the particles below 2 µm. 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 µm 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.

Preparation of pH Responsive Polystyrene and Polyvinyl Pyridine Nanospheres Stabilized by Mickering Microgel Emulsions

“…The appearance of new strong band at 3462 cm −1 , NH stretching, elucidates the incorporation of MBA with PAAm, PAMPS, and PAMPS-Na. The shift of wavenumber values of the strong intense CONH at band 1666 cm −1 (Figure 1a), 1697 cm −1 for PAMPS and PAMPS-Na observed (Figure 1b,c), or the S=O asymmetric stretching and symmetric S=O stretching at 1400 and 1043 cm −1 (Figure 1b,c) compared to their reported values in the literature [35] elucidate the decreasing of PAAm, PAMPS, and PAMPS-Na sizes [36]. These shifts refer to the decrease in the wavelength and penetration depth of the IR light intensity [37].…”

An Exploratory Study on the Effect of Petroleum Hydrocarbon on Soils Using Hyperspectral Longwave Infrared Imagery

“…This might be the attribute to the grain size as Hamra has a coarser grain size than Evrona and Kokhav. A soil with a coarser grain size (Hamra) absorbs more light (a good absorber) than soil with fine particles (Kokhav) [28][29][30], which might result in a more intense radiance emission (a good emitter) of the soil with a coarser grain size (Hamra) and thus a stronger signal. Another factor that should be taken into consideration is that the crude oil has a more specific surface area in finer particles and thus spreads over a larger area, which might cause the crude oil effect to be less dominant in the emitted radiance.…”

Application of infrared spectroscopy for the prediction of nutritional content and quality assessment of faba bean (Vicia faba L.)

“…As the signal amplitude depends to a large degree on the pressure applied, it can be quite difficult to obtain quantitative results from ATR–FTIR. The particle/grain size can have an impact on the spectra obtained, particularly for ATR–FTIR spectroscopy (Lee, Liong, & Jemain, 2017; Udvardi et al, 2017). However, grain size also impacts upon the spectra obtained from NIRS (Rinnan, Berg, & Engelsen, 2009; Wiley, Tanner, Chandler, & Anderssen, 2009).…”