Expansibility of vermiculite (Santa Luzia, Brazil) irradiated with microwave

Abstract

The effect of microwave heating on the expansion of vermiculite was studied at a level of 700 W for 4 min exposure time and compared with raw vermiculite. In this study, the characterization of vermiculite from a mine in the northeast region of Brazil was performed using thermogravimetry, N 2 -adsorption, cation exchange capacity, X-ray powder diffraction (XRD), infrared (IR) spectroscopy, X-ray fluorescence spectroscopy (XRF), and scanning electron microscopy (SEM). Following the microwave heating, the vermiculite was characterized using XRD, IR spectroscopy, and SEM. Microwave irradiation of the vermiculite sample caused structural changes such as loss of crystallinity and disorder, as revealed by the XRD patterns, but did not cause expansion. Results from SEM and IR spectroscopy showed that the microwave heating did not cause profound alterations to the morphology, clay structure, and chemical composition of the vermiculite.

Renewable and Selective Vermiculite Fixed Bed for the Rare-Earth Dysprosium Recovery

“…Figure 5 presents the FTIR spectra of the spent material that shows peaks referring to interlamellar water, 3400 and 1630 cm −1 , OH stretching and bending vibrations, respectively, and bands located in the 1300−500 cm −1 range that reveal structural characteristics of clay minerals. 31,32 The silicate characteristic bands are found at 999.5 cm −1 , representing Si− O's stretching vibrations, at 745 cm −1 , indicating the Si−O−Si (Al) stretching, and at lower frequencies 522 and 459 cm −1 , meaning Si−O bending. 33 At 675 cm −1 , the characteristic stretching vibration of the interlayer metal bond (M−O) 34 indicates that magnesium, the exchangeable cation of this expanded vermiculite, 24 replaced dysprosium in the interlayer spaces maintaining the original vibrational characteristic of the M−O bonds.…”