Adsorption of cationic and anionic dyes on montmorillonite in single and mixed wastewater

Montmorillonite was employed as adsorbent to remove cationic and anionic dyes respectively and simultaneously. When the dye present singly, it only had a good effect to cationic dye removal. The experimental data well fitted to pseudo-second-order kinetic model, and the adsorption behavior followed the Langmuir model revealed that cationic dye adsorption was a monolayer coverage and charge-limited adsorption process. Molecular arrangement of the contaminants in the interlayer were analyzed by molecular simulation. As the cationic and anionic dyes co-exist, both cationic and anionic dyes could be removed. The adsorption mechanism of anionic dyes, under the circumstances, were investigated through equilibrium experiment, XRD and molecular dynamics simulation. The experimental data showed that anionic dyes in mixed wastewater were fitted Freundlich model well and the mechanism of anionic dyes removal was trapped by hydrophobic interaction on account of organic phase formed by cationic dyes in the interlayer.