Synthesis and Characterization of Halloysite–Cyclodextrin Nanosponges for Enhanced Dyes Adsorption

Inorganic−organic nanosponge hybrids based on halloysite clay and organic cyclodextrin derivatives (HNT-CDs) were developed by means of microwave irradiations in solvent-free conditions. The HNT-CDs nanomaterials characterized by FT-IR, TGA, BET, TEM, SEM, DLS, and ζ-potential have showed a hyper-reticulated network which possesses both HNT and cyclodextrin peculiarities. The new HNT-CDs nanosponge hybrids were employed as nanoadsorbents,first choosing Rhodamine B as the dye model, and furthermore for the removal of some cationic and anionic dyes, under different pH values (1.0, 4.54, and 7.4). The collected results showed that the pH solution as well as the electrostatic interactions affect the adsorption process. Factors controlling the adsorption process were discussed. The experimental adsorption equilibrium and kinetic data were best described by the Freundlich isotherm model. Excellent adsorption efficiency for cationic dyes were observed with respect to anionic ones. The results suggest that HNT-CDs nanosponge hybrids are a good nanoadsorbent for selective adsorption of cationic dyes with respect to the anionic ones from aqueous solutions.