Adsorption of anion and cation dyes onto pillared montmorillonite

Al 2 O 3 - and Al(Ce) 2 O 3 -pillared montmorillonite materials were synthesized using the intercalation of large-sized polyhydroxocomplexes of aluminum and aluminum/cerium in order to obtain adsorbents for removing the water-soluble anionic (acid red, AR) and cationic (methylene blue, MB) dyes. It was shown that the adsorption of dyes heavily depended upon the pH of the medium reaching a maximal adsorption capacity for AR at low pH and for MB at high pH. The distinction between the adsorption efficiencies for dyes observed in the materials with a different pillar structure was interpreted in the light of both the charge states (the ζ-potential) of tactoids in suspensions and texture properties of adsorbents investigated by small-angle X-ray diffraction and porosimetry. We used the classic models to describe adsorption: the kinetic pseudo-first-order and pseudo-second-order models and the equilibrium Langmuir and Freundlich equations.