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Andean geology

On-line version ISSN 0718-7106

Abstract

QUERO-JIMENEZ, Pedro C. et al. Local Cuban bentonite clay: composition, structure and textural characterization. AndGeo [online]. 2021, vol.48, n.3, pp.546-556. ISSN 0718-7106.  http://dx.doi.org/10.5027/andgeov48n3-3362.

The physic and chemical characterization of the bentonite clay from the Chiqui Gómez deposit, central Cuba, (Cuban bentonite clay) shows that it is mainly constituted by sodium montmorillonite (>90%), with a structural formula for one-layer unit determined as (Na3.99Al0.01)(Al1.11Fe3+0.49Mg0.18Ti0.07)(Ca0.24Na0.15K0.01)O10(OH)2. The Cuban bentonite clay has a specific surface area of 80 m2g-1, a pore volume of about 0.0776 cm3g-1, 61% porosity and both N2 adsorption-desorption isotherms exhibit a hysteresis loop of IV type. The thermogravimetric analysis (TGA) of the studied mineral presents the first endothermic peak, characteristic of montmorillonite, in 48.1 °C and others less accentuated (80.8, 94.0, 119.8 °C) characteristic of sodium montmorillonite, that corresponds to the loss of water, and can be extended up to 250 °C. The FT-IR spectra show the existence of Si-OH, Al-Al-OH, Al-Fe-OH, Al-Mg-OH and Si-O-Si functional groups in all clay samples, bands between 1,120 and 461 cm-1 correspond to phyllosilicate structures and OH stretching vibrations were observed. pH at the point of zero charge (pHPZC) obtained has a value of 8.1, which allows montmorillonite to be classified as basic.

Keywords : Cuban bentonite clays; Montmorillonite; Characterization.

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