X-ray Diffraction Microstructural Analysis of Swelling by Ethylene Glycol in Two Reference Clay Minerals

Abstract

Kaolinite and montmorillonite are two clay minerals with different structures: dioctahedral 1:1 without layer charge and dioctahedral 2:1 with low layer charge. X-ray-diffraction microstructural analysis of two fractions of two reference clays (with kaolinite or montmorillonite) from the Clay Minerals Society Source Clay Repository were performed by the Voigt function method to provide microstructural data not available in the baseline studies of this Repository. A rough agreement was found between crystallite sizes determined from X-ray diffraction patterns and from images by field-emission scanning electron microscopy. In addition, the influence of swelling by ethyleneglycol on crystallite size was studied by the mentioned method. Two factors were found to affect the crystallite size variation in ethylene-glycol-treated clay minerals: (i) the increase of the unit cell in [001] direction due to the interlayer absorption of ethylene glycol molecules in the case of swelling minerals and (ii) the physisorption at the surfaces of the crystallites. Both effects operate in the case of montmorillonite, whereas just the latter one is expected in kaolinite.

Applications of X-ray Powder Diffraction Microstructural Analysis in Applied Clay Mineralogy

“…Two fractions of two reference clays (kaolinite or montmorillonite from the Source Clay Repository) were studied using the Voigt function method [162]. A rough agreement was found between crystallite sizes determined from X-ray diffraction patterns and from images via field-emission scanning electron microscopy.…”

Investigations on the Interaction of EDTA with Calcium Silicate Hydrate and Its Impact on the U(VI) Sorption

“…The diffractograms (Figure 4a) do not indicate any significant changes of C-S-H after 30 days contact time with the studied EDTA solutions. However, the magnified diffractograms (Figure 4b) show that with increasing EDTA concentration in solution there is a gradual small shift of the peaks to higher 2θ values, which can be attributed to the incorporation of EDTA into the C-S-H phase [22,23]. In addition, FTIR spectra of C-S-H solid phases, which were separated after contact with aqueous solutions of varying EDTA concentrations have been obtained and are shown in Figure 5.…”