A novel surface-active monomer decorating a self-floating adsorbent with high pH adaptability for anionic dyes: π-π stacking

Abstract

It remains a challenge to remove anionic dyes under alkaline conditions. In this study, we studied the pH independent adsorption of anionic dyes on a surface-active cationic monomer, benzyl(methacryloyloxyethyl)dimethylammonium chloride (BMDAC), which was used to decorate a self-floating adsorbent, BDSA. To compare the pH adaptability, a traditional cationic monomer, methacrylatoethyl trimethyl ammonium chloride (MTAC), which is similar to BMDAC in terms of its structure but does not contain aromatic groups, was used instead of BMDAC to prepare another adsorbent, MDSA. Through comparison of characterization and adsorption experiments, we found that BDSA could maintain a high dye-removal efficiency under different pH conditions. The AG25 removal rate was above 90% in the pH range of 2–10. In addition, BDSA showed outstanding recovery and reutilization performance; its adsorption capacity remained above 80% after five cycles of use. The π-π stacking between the benzyl group in BDSA and the aromatic ring in the dye molecule was found to enhance the adsorption interaction, which was confirmed by theoretical calculations. With its excellent adsorption capacity for anionic dyes, high pH adaptability, easy separation ability and good reusability, BDSA is an ideal candidate for dye wastewater treatment.