Hybridization of magnetic MOF composites with 3D terminal carboxyl hyperbranched polymers for dye wastewater treatment

To enhance the physical and chemical properties and stability of magnetic MOFs, and to improve their adsorption and reuse performance, an innovative modification strategy involving hybridization with three-dimensional (3D) terminal carboxyl hyperbranched polymers was employed. A novel polymer composite material, Fe₃O₄@MOF/HBPC, was synthesized and its morphological characteristics were analyzed. The adsorption properties of Fe₃O₄@MOF/HBPC were tested by removing Malachite Green (MG) from aqueous solutions. Various influencing factors, including dosage, pH, and temperature, as well as adsorption kinetics, isotherms, and thermodynamics were investigated. The results showed that the stretching vibration peaks of Fe₃O₄@MOF/HBPC appeared at 1708 cm⁻¹, 1408 cm⁻¹, 1278 cm⁻¹, 1112 cm⁻¹, and 543 cm⁻¹, corresponding to the CO, –COO⁻, O–H, C–O, and Fe–O bands, respectively. Fe₃O₄@MOF/HBPC exhibited a negative charge and a spherical structure. The composite material contained the elements O, C, Fe, and N, and the assembly process had a minimal impact on the crystal structure. For MG removal, the optimal reaction conditions were a dosage of 20 mg and pH 6. The adsorption process followed a pseudo-first-order kinetic model and a Langmuir isotherm model, and it was found to be endothermic and spontaneous, involving both physical and chemical adsorption. Regarding recycling and reuse, Fe₃O₄@MOF/HBPC demonstrated a recycling efficiency of over 90.8%, with a removing efficiency of MG of above 87.5% after three cycles, indicating excellent stability and reusability.