Adsorption of methylene blue onto Al-pillared montmorillonite

Al-pillared montmorillonite (Al-MMT) was prepared with natural Na-type montmorillonite (Na-MMT) as raw material and aluminum polycation as a pillaring agent, which was evaluated as adsorbents for the removal of methylene blue (MB) from aqueous solutions. The materials were characterized by X-ray powder diffraction and N2 adsorption–desorption at low temperatures. The results showed that the aluminum polycation was intercalated into the layer of MMT to form a stable aluminum oxide pillar after calcination, which resulted in an increase of surface area and layers spacing of MMT. The adsorption capacity of Al-MMT for MB was higher than that of Na-MMT. Freundlich isotherm and pseudo-second-order kinetic models were more suitable to describe the adsorption process of MB on Al-MMT. The thermodynamic parameters indicated that the adsorption process was endothermic and spontaneous. The increasing solution pH could lead to an increase in the adsorption capacity of Al-MMT for MB.