Adsorption of sulfamethoxazole and tetracycline on montmorillonite in single and binary systems

The contaminantsin environment generally do not exist alone and possess different physical and chemical properties, their environmental behavior and mechanism of action in environment are more complicated. Montmorillonite was employed as adsorbent to remove tetracycline (TC) and sulfamethoxazole (SMZ) respectively and simultaneously under batch kinetic and different solution conditions. As the contaminant present singly, it only had a good effect to TC removal. The experimental data were well fitted to pseudo-second-order kinetic model, and the adsorption behavior followed the Langmuir isotherm indicated that TC adsorption was a monolayer coverage and charge-limited adsorption process. In addition, the TC molecular arrangement in the interlayer were analyzed experimentally and through simulation. While the contaminants co-exist, not only TC but also SMZ was removed effectively. SMZ adsorption mechanism were investigated through adsorption equilibrium experiment, characterization and molecular dynamics simulation. Experiment data showed that the best agreement was obtained with the Freundlich model and the adsorption mechanism was proved that SMZ was trapped by hydrophobic interaction.