Kinetics and Mechanism of Adsorption of Anionic Dyes on Montmorillonite Modified with Sodium Metasilicate

The mechanism of adsorption of anionic dyes on montmorillonite modified with sodium metasilicate is investigated. The kinetics of dye adsorption is approximated by a pseudo-second order model, and the adsorption isotherm is analyzed on the basis of the Langmuir and Dubinin-Radushkevich models. The value of average free energy of adsorption E > 8 kJ/mol for all studied dyes, testifying to a surface chemical reaction between dye molecules and protonated silanol and aluminol groups on the surface of the edges of the aluminosilicate layers of the mineral. The adsorption of dyes is directly proportional to the increase in the temperature, mass, and charge of the organic anion and is inversely proportional to the increase in the ionic strength of the solution.