Magnetic β-Cyclodextrin/UiO-66 Hybrid Composites as High-Performance Adsorbents for Organic Dye Removal

Dye wastewater poses a significant environmental threat, making the development of efficient and reusable adsorbents essential. In this study, we prepared a magnetic UiO-66 composite modified by β-CD (UiO-66@β-CD@Fe3O4) and evaluated the adsorption properties of this material on crystal violet and Congo red in aqueous solutions. β-CD was added to improve the host–guest interaction with dyes, and the Fe3O4 core made magnetic separation simple. Kinetic analysis supports the pseudo-second-order model, indicating that chemisorption is the main factor controlling the adsorption rate. Based on the Langmuir isotherm, the data suggest that adsorption occurs as a monolayer on a homogeneous surface. Maximum adsorption capacities were 542.75 mg/g for Congo red and 377.25 mg/g for crystal violet. Calculated thermodynamic values reflected an endothermic and energetically favorable adsorption mechanism. Additionally, the magnetic properties of UiO-66@β-CD@Fe3O4 enabled easy separation by using an external magnet. Strong adsorption performance was maintained by the material even after several adsorption–desorption cycles, indicating its reusability. UiO-66@β-CD@Fe3O4 exhibits promising performance in addressing dye-contaminated wastewater, confirming its application potential.