Determination of the degree of structural heterogeneity of kaolinites by the decomposition of their IR spectra in the OH-stretching vibration region

A new approach to assessing the degree of defective structure of kaolinite minerals using their IR spectra in the region of stretching vibrations of OH groups is proposed. Three linear equations were obtained that relate the ratios of spectroscopic parameters to each other: A(v3)A(v3)+A(v2) = – 0.2177 FWHM(ν1)FWHM(ν4) + 1.247), FWHM(ν3)FWHM(ν2) = – 0.5804 FWHM(ν1)FWHM(ν4) + 2.8696), FWHM(ν3)FWHM(ν2) = 2.636 A(v3)A(v3)+A(v2), where: FWHM(νi) – full width at half maximum and A(νi) – integral intensity of Lorentz absorption bands at ν1 ~3697 cm–1, ν2 ~3670 cm–1, ν3 ~3652 cm–1 and ν4 ~3620 cm–1, respectively. These equations made it possible to establish criteria for decomposing IR spectra into individual bands, νi, and determining optimal values for the parameters FWHM(νi) and A(νi), with the help of which it is possible to calculate the contents of high ordered kaolinite, HOK, and low ordered kaolinite, LOK, phases in natural samples with an accuracy of ~5%.