Montmorillonite as a multifunctional adsorbent can simultaneously remove crystal violet, cetyltrimethylammonium, and 2-naphthol from water

The adsorptive behaviors of crystal violet (CV), cetyltrimethylammonium (CTMA), and 2-naphthol to montmorillonite (Mt) using a simultaneous-adsorption process were studied in this work. The adsorption results showed that under the experimental concentrations both CV and CTMA were almost completely removed by Mt. XRD and FTIR characterization results showed that the adsorbed CV and CTMA formed CTMA–CV aggregates within the interlayer spaces of Mt, and these aggregates served as accommodation spaces for the adsorption of 2-naphthol. The adsorption isotherms of 2-naphthol fitted linear equation well in the simultaneous-adsorption process, suggesting that partition should be the dominant mechanism for uptaking 2-naphthol. Combining the fact that CV alone formed aggregates showed nonlinear adsorption isotherms and much weaker adsorption capacity towards 2-naphtol than CTMA alone formed aggregates, one would expect that CTMA played a dominant role in the adsorption of 2-naphthol to CTMA–CV aggregates. In addition, the CTMA–CV aggregates have better adsorption capacity towards 2-naphthol than the combination of CTMA aggregates and CV aggregates do. FTIR results showed that CV could adjust the arrangement of CTMA in the CTMA–CV aggregates, which might be the reason for the enhanced adsorption capacity. Results of this work suggest that montmorillonite can be used as a low-cost and high-efficient adsorbent for the simultaneous removal of different types of organic contaminants from water.