Dependence of Changes in Surface Charges on the Degree of Substitution of Mg by Al in Synthetic Smectites

Abstract

The dependence of the ζ-surface potential of synthetic aluminosilicates with a montmorillonite structure of systematically varying Na_2x(Al_{2(1 – x)},Mg_2x)Si₄O₁₀(OH)₂·nH₂O composition, where 0.1 ≤ x ≤ 0.9, on the chemical composition of the samples and the pH of the environment is studied. The influence of the degree of isomorphic substitution of magnesium atoms by aluminum on the nature of the change of the ζ‑potential is shown. An increase in the degree of isomorphic substitution and an increase in the pH of the medium is accompanied by an increase in the negative charge of the sample surface. The results obtained make it possible to select the optimal compositions of aluminosilicate sorbents for the extraction of differently charged ions from aqueous solutions with different pH values and for use as carriers of drugs.