Hydroxypropyl-β-Cyclodextrin Improves Removal of Polycyclic Aromatic Hydrocarbons by Fe3O4 Nanocomposites

The contamination of water bodies by polycyclic aromatic hydrocarbons (PAHs) poses a significant concern for the ecological systems, along with public health. Magnetic adsorption stands out as a green and practical solution for treating polluted water. To make the process more efficient and economical, it is important to create materials that not only absorb contaminants effectively but also allow for easy recovery and reuse. This study proposes a simple yet effective method for coating Fe3O4 nanoparticles with hydroxypropyl-β-cyclodextrin polymer (HP-β-CDCP). The physicochemical properties of the synthesized sorbent were characterized using a transmission electron microscope (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and Vibrating Sample Magnetometer (VSM) analysis. The adsorption performance of HP-β-CDCP/Fe3O4 nanoparticles was well-described by the pseudo-second-order kinetic model, thermodynamic analysis, and the Freundlich isotherm model, indicating multiple interaction mechanisms with PAHs, such as π–π interactions, hydrogen bonding, and van der Waals forces. Using HP-β-CDCP/Fe3O4 nanoparticles as the adsorbent, the purification rates for the fifteen representative PAHs were achieved within the range of 33.9–93.1%, compared to 15.3–64.8% of the unmodified Fe3O4 nanoparticles. The adsorption of all studied PAHs onto HP-β-CDCP/Fe3O4 nanocomposites was governed by pH, time, and temperature. Equilibrium in the uptake mechanism was obtained within 15 min, with the largest adsorption capacities for PAHs in competitive adsorption mode being 6.46–19.0 mg·g−1 at 20 °C, pH 7.0. This study points to the practical value of incorporating cyclodextrins into tailored polymer frameworks for improving the removal of PAHs from polluted water.