Effect of synthesis conditions on hydrothermal crystallization, textural characteristics and morphology of aluminum-magnesium montmorillonite

摘要

Studied was the effect of synthesis conditions on the process of hydrothermal crystallization, porosity and textural characteristics of aluminum-magnesium montmorillonite Na-2x(Al-2((1-x)),Mg-2x) Si4O10(OH)(2)center dot nH(2)O (0 < x < 1), with varying degrees of isomorphous substitution of magnesium for aluminum in the octahedral layers. Hydrothermal synthesis was carried out at temperatures from 200 to 350 degrees C, autogenous pressure from 20 to 70 MPa, and duration of synthesis from 5 to 288 h. Samples were examined by X-ray diffraction, scanning and transmission electron microscopy, and by low-temperature nitrogen adsorption. The crystallization of montmorillonite is affected to the greatest extent by the temperature and the duration of synthesis. Pressure has no effect within in the studied value range. The particle size of the samples in a plane perpendicular to axis c is 20 +/- 3 nm, and does not depend on the synthesis conditions and the chemical composition of the samples. Depending on the synthesis conditions, both delaminated samples in the form of nanolayers, in some cases, twisted into tubes, and package structure samples can be obtained. In addition, the specific surface area values may range from 80 to 680 m(2)/g. Thus, the samples with specified characteristics can be obtained by directed hydro thermal synthesis, which can enhance the potential uses of montmorillonite in areas (medicine, catalysis, nanocomposites) where there are special requirements to the physicochemical properties and morphology of the materials used. (C) 2016 Elsevier Inc. All rights reserved.