Fe₃O₄ nanoparticles were prepared by a co-precipitation method with the assistance of ultrasound irradiation, and then coated with silica generated by hydrolysis and condensation of tetraethoxysilane. The silica-coated Fe₃O₄ nanoparticles were further modified with 3-aminopropyltriethoxysilane, resulting in anchoring of primary amine groups on the surface of the particles. Horseradish peroxidase (HRP) was then immobilized on the magnetic core-shell particles by using glutaraldehyde as a crosslinking agent. Immobilization conditions were optimized to obtain the highest relative activity of the immobilized enzyme. It was found the durability of the immobilized enzyme to heating and pH variation were improved in comparison with free HRP. The apparent Michaelis constants of the immobilized HRP and free HRP with substrate were compared, showing that the enzyme activity of the immobilized HRP was close to that of free HRP. The HRP immobilized particles, as an enzyme catalyst, were used to activate H₂O₂ for degrading 2,4-dichlorophenol. The rapid degradation of 2,4-dichlorophenol indicated that the immobilized enzyme has potential applications for removing organic pollutants.

Graphene oxide/Fe₃O₄ (GO/Fe₃O₄) nanoparticles were synthesized by an ultrasonic-assisted reverse co-precipitation method, and then horseradish peroxidase (HRP) was covalently immobilized onto GO/Fe₃O₄ with 1-ethyl-3-(3-dimethyaminopropyl)carbodiimide (EDC) as a cross-linking agent. In order to enhance the phenol removal efficiency and prevent the inactivation of the enzyme, the polyethylene glycol with highly hydrophilicity was added in this reaction, because the adsorption capacity for the polymer by degradation was stronger than the HRP. The results showed that the immobilized enzyme removed over 95% of phenol from aqueous solution. The catalytic condition was extensively optimized among the range of pH, mass ratio of PEG/phenol as well as initial concentration of immobilized enzyme and H₂O₂. The HRP immobilized on GO/Fe₃O₄ composite could be easily separated under a magnetic field from the reaction solution and reused.

In recent years, environmental pollution has become more serious, especially the organic pollutants. Metal organic frameworks (MOFs) are promising materials used to degrade pollutants recently. Among them, Materials Institute Lavoisier frameworks (MILs) have been widely engaged due to their good stability and unique structural characteristics. This paper systematically analyses and summarizes the progress of MILs in degradation of organic pollutant by Fenton reaction in recent years. The MILs, especially four types of MILs, including MIL-100, MIL-101, MIL-88, and MIL-53, are first described and classified. Then, the common synthesis methods (hydrothermal synthesis, steam-assisted synthesis, and microwave-assisted synthesis) of MIL are summarized and compared. Modification and activation of MILs to obtain good degradation effect are also introduced and discussed. Finally, the applications of MILs in Fenton reaction are reviewed and their future development is prospected.