Fe₃O₄ Nanoparticle/Hyper-Cross-Linked Polymer Composites for Dye Removal

A “dual-purpose reagent” strategy was developed for the facile synthesis of magnetic Fe 3 O 4 nanoparticle/hyper-cross-linked polymers (MHCPs). Ferric chloride serves both as a catalyst for the Friedel–Crafts reaction and as an iron source for the preparation of Fe 3 O 4 magnetic nanoparticles. This preparation method is advantageous in terms of simplicity, eco-friendliness, and cost-effectiveness. A variety of analytical techniques such as scanning electron microscopy, transmission electron microscopy, and Fourier transformed infrared spectra were employed to characterize the composites. The high density of aromatic and alkyl groups on hyper-cross-linked polymers (HCPs) enables them to exhibit a high affinity for dyes through hydrophobic and π–π interactions. The complexation of HCPs with magnetic nanoparticles makes the dye removal process simple, fast, and efficient. As a result, the MHCPs exhibited excellent adsorption performance for different azo dyes. The maximum adsorption capacity of Fe 3 O 4 /HCP TPB for crystal violet (CV) was up to 100.3 mg/g with an adsorption efficiency of 94.1%. The experimental data of CV adsorption on Fe 3 O 4 /HCP TPB were computed by different isotherm and kinetics models. The results showed that the experimental data were in close agreement with the Langmuir model and followed the pseudo-second-order kinetic model. In addition, even after 6 successive cycles of adsorption–desorption, acceptable removal efficiency was still retained. Based on these results, MHCPs are a promising adsorbent in the removal of dyes from the aqueous phase.