Hydrothermally treated vermiculites: Ability to support products for CO2 adsorption and geological implications

Abstract

The proposal of this research was to obtain products with higher porosity and specific surface area than the raw vermiculite for its possible application as a support material for CO2 adsorption. In addition, it was proposed to analyze the possible geological implications of the products resulting from the hydrothermal treatment of vermiculites in relation to their genesis. Hydrothermal treatment in the presence of CO2, at low temperature and pressure conditions, was carried out in two vermiculites from Uganda and China, with different behavior to thermal exfoliation and microwave irradiation. The untreated and treated samples were characterized by several techniques: X-ray diffraction (XRD) for obtaining the mineral composition; thermogravimetry (TG - DTG) for analyzing the thermal behavior; and BET isotherms for obtaining textural parameters. In addition, the hydrothermal solutions were characterized by the pH and the measuring of the lixiviated elements with inductively coupled plasma mass spectrometry (ICP-MS). Vermiculite can be a suitable support for CO2 adsorbents, based on the SBET and Qm values, and it is susceptible to carbonation. The hydrothermal treatment produced water loss in the expanded vermiculites by CO2 replacement; as consequence, amorphization occurred in the purer Ugandan sample, and vermiculitization occurred in the less pure sample from China.The vermiculitization process indicates that the geological origin of vermiculite may be hydrothermal from phlogopite.