Features of the Hydrothermal Synthesis of Montmorillonite in an Acidic Medium

Abstract

The process of the hydrothermal crystallization of montmorillonite Na_2x(Al_2(1 – x),Mg_2x)-Si₄O₁₀(OH)₂ · nH₂O (0 < x ≤ 1) is studied in a weakly acidic medium with pH 4–4.5 at 220°С using HF as a mineralizer. The results of the study showed that montmorillonite samples in the acidic medium can be obtained both with the use of the HF mineralizer and without it. Under any conditions of carrying out the synthesis, there is an insignificant amount of corundum in the final product. It is established that a weakly acidic medium favors the formation of a dioctahedral structure of smectites with insignificant isomorphic substitutions (0.5 ≤ x ≤ 1). At a higher aluminum content, the acidic medium does not contribute to the formation of two-dimensional silicon-oxygen layers.