A Novel Superadsorbent β-cyclodextrin Crosslinked Coffee Grounds Biopolymer To Remove Organic Molecules From Water Matrices

Herein, a new superadsorbent was synthesized via a crosslinking reaction using β-cyclodextrin and coffee grounds and employed to remove two organic cationic molecules, methylene blue and crystal violet. The interactions between adsorbent-adsorbate in aqueous media were also investigated. The material was characterized by FTIR, XRD, SEM, EDX, and DSC techniques, and adsorption was investigated through the kinetic, isotherms, and thermodynamic parameters. Sips isotherm was the more suitable model for fitting the adsorption equilibrium, while the pseudo-first-order model for both dyes described the kinetic data well. The new adsorbent presented impressive adsorption capacity values, higher than 1500 mg g−1. This high adsorption capacity results from three main mechanisms: electrostatic attraction, hydrogen bonds, and hydrophobic interactions between the hydrophobic parts of dyes and the inner hydrophobic cavity of cyclodextrin. Thermodynamic parameters revealed an endothermic and spontaneous process with increased randomness in the liquid-solid interface. Overall, the adsorbent exhibited an excellent performance for dye removal and potential use in wastewater treatment plants.