Degradation Of Methyl Orange Over Laccase Immobilized Of Fe₃O₄/SiO₂ Magnetic Support

Laccase is a green, nontoxic biological catalyst with strong oxidationproperties. Many non-biodegradable organic pollutants, such as phenolic compounds, aromatic amines, polynuclear polycyclic aromatic hydrocarbons and their derivatives, can be degraded effectively in the present of immobilized laccase and secondary pollution pollutants formed in the process could be suppressed greatly. However, immobilized laccase presents an incomparable obvious advantage over free laccase on thermal stability and operation stability. Many supports, like silica, activated carbon, polystyrene microspheres, chitosan and so on, have been successfully used to immobilizate laccase. In recent years, immobilizing laccase on nanostructured magnetic support with a core of Fe3O4 has received great attention due to its magnetically separable ability and better stability.As an inert material, SiO2 is an inert material, which can effectively protect Fe3O4 magnetic core by surface modification from acidic dissolution and further oxidation under high temperature. In the meantime, the abundant hydroxyl groups on SiO2 surface also benefits a further functionalization for laccase to immobilization. Therefore, a self-made Fe3O4 nanoparticles in the form of ferrofluid was used Fe3O4 as magnetic core in present thesis to perform the following study:(1) Coating directly the Fe3O4 nanoparticles in the form of ferrofluid with SiO2 was studied; (2) Coating SiO2 on Fe3O4 nanoparticles with different surface modification were employed to find out the effect of the surface modification of Fe3O4 nanoparticles on SiO2 coating, and characterization was carried out by using transmission electron microscopy (TEM), infrared spectroscopy (FTIR) and UV-visible absorption spectra (UV-Vis); (3) Immobilizing laccase on Fe3O4/SiO2 support with Cross-linking method and subsequently catalyzing the degradation of Methyl Orange were investigated.The result shows that magnetic Fe3O4/SiO2 nanoparticles can be prepared by directly coating SiO2 on the surface of Fe3O4 nanopartilces in the form of ferrofluid. in which the surface modification of Fe3O4 nanoparticles with the SiO2 dirtect synthesized magnetic Fe3O4/SiO2 nanoparticles. using chemical stably Fe3O4 nanoparticles as magnetic core, prepared without any stabilizer and or coupling agent, have a good performance on dispersion, size and magnetic separability was absent. The immobilized laccase on Fe3O4/SiO2 support this magnetic support was successfully obtained and showed a better magnetic separation under can be separated quickly using an external magnetic field. When used to degrade Methyl Orange solution, a high decoloriztion efficiency of 95.6% was achieved under ideal reaction conditions where the pH is three, the temperature is 20℃, the reaction time is 2h and the amount of ABTS is 750ml. Moreover, the immobilized laccase can still have a decoloriztion efficiency of 70% after for up to 10 consecutive operationscycles.