Cyclodextrin/silica hybrid adsorbent for removal of methylene blue in aqueous media

Abstract

Functionalization of a silica surface using cyclodextrin was performed using citric acid as a bonding agent. The material obtained was characterized using spectroscopic, X-ray, and thermogravimetric analyses. The effectiveness of the product for removal of dyes from aqueous media was evaluated using methylene blue as a model molecule, for which the best adsorption was achieved at pH values higher than 3.5. The correlation coefficients obtained using the Langmuir isotherm enabled elucidation of the adsorption mechanism. The maximum capacity of the nano-adsorbent for adsorption of the dye was 212 mg g−1. Thermodynamic tests performed at 25, 35, and 45 °C showed that the mechanism was spontaneous and temperature-dependent, with adsorption following the pseudo-second order kinetic model and being fastest during the early stages, with equilibrium achieved after around 3 h. The results showed that hybrid materials based on cyclodextrin can be used for removal of dyes from aqueous media, and could therefore substitute other more expensive adsorbents. Advantages of these new materials include ease of preparation, relatively low cost, and good adsorption properties.