β-Cyclodextrin functionalized SBA-15 via amide linkage as a super adsorbent for rapid removal of methyl blue

To remove the bulky aqueous organic dye e.g. methyl blue (MB) from water, ordered mesoporous silica SBA-15 has been functionalized with β-cyclodextrin (β-CD) via amide linkage. The surface physical and chemical properties of the surface of the resulted β-CD-functionalized adsorbents (abbrev. SBA15-A-CD) were characterized systematically. The results indicate that the channels of SBA-15 were uniformly modified with amine groups and were further β-CD-terminated via amide linkages, without ruining its ordered mesoporous structure. The effects of contact time, pH, ionic strength, temperature and salt on the adsorption performance were explored. SBA15-A-CD showed maximum adsorption capacity for MB up to 1791 mg·g^-1 combined with excellent recyclability. Besides, the adsorption behavior of MB onto SBA15-A-CD has been investigated by DFT calculation and two-dimensional NMR. Specifically, the enhanced adsorption capacity for MB stems from the tailored host-guest interaction between β-CD cavity and aromatic moiety of MB in combination with the electrostatic attraction between amine groups and sulfonated group of MB. These findings offer good opportunities for improving the ability of mesoporous silica in adsorption of bulky anion dyes in wastewater.