Acid matrix production from treated natural vermiculite-hydrobiotite

Abstract

Given the potential of acid-activated clays in adsorptive and catalytic processes, several studies focusing on acid matrices have grown over the years, making it possible to study vermiculite, a mineral composed of a type 2:1 unit cell with tetrahedral and octahedral sheets. Therefore, this work aimed to study vermiculite treated with acids for the production of matrices. In this work, the treatment of natural vermiculite-hydrobiotite, with nitric acid in concentrations of 0.25, 0.50, 0.75, and 1 mol.L-1, followed by the dealumination process with sulfuric acid 25% v/v, aiming the production of acid matrices for applications as support for biocatalysts, chemical adsorbents, among others. The produced materials were characterized using different techniques, including X-ray fluorescence spectroscopy, X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and isotherm adsorption using the BET method. The results showed that after acid leaching the vermiculite showed a high SiO2content, high Brønsted and Lewis surface acidity, good adsorption/desorption performance, and significant growth of the specific surface area, qualifying the vermiculite as a promising material for future applications in catalytic and biocatalytic processes. The acid concentration had a considerable influence on the compositional and textural modification of vermiculite-hydrobiotite.