Preparation Of Fe₃O₄ Magnetic Composite Microspheres And Their Application In Protein Separation And Photocatalysis

With the rapid development of nano-technology,many new nano-materials with special structure have been developed,and widely applied in biomedical,chemical industry and other fie lds.However,it is difficult to separate nano-materials in the practical application and production process,which limits their applications in adsorption separation,catalysis,etc.Magnetic nanomaterials can solve the problem of difficult recovery of nanomaterials.Fe3O4-based magnetic composite spheres have been applied in many areas,including magnetic separation,catalysis,biomedical,bio-medicine and so on.Because of their unique superamagnetic,biocompatibility,excellent catalyt ic and adorption proterties.In this thesis,Fe3O4-based magnetic composite microspheres were synthesized with Fe3O4 microspheres as magnetic core.We have focus on the study of preparation,structure,morphology,magnetic properties,adsorption properties and catalyt ic properties of the Fe3O4-based magnetic composite microspheres.Small particle size Fe3O4 microspheres were prepared by pyrolys is at high temperature.The effects of temperature and time on the preparation of Fe3O4 microspheres were studied.Fina lly,12 nm Fe3O4 microspheres were obtained.O n the basis of this,Fe3O4/Si O2 microspheres were prepared by reverse microemuls ion method.The hydroxyl groups on the surface were aminated by APTES.The surface with N H2 was activated by glutaraldehyde,so C HO were on surface of microspheres.The aldehyde and protein can form amide bonds,thus protein A were immobilized on the surface of microspheres.By changing the reaction time,temperature and other factors,The adsorption capacity of the nanoparticles was approximately up to 203 mg/g of protein A could be uniformly immobilized onto the modified Fe3O4/Si O2 magnetic microspheres.Because of the specific adsorption between protein A and monoclonal antibody,the prepared functional microspheres were used to separate the antibody,and the separation efficiency was 95.4%.The magnetic mesoporous Fe3O4/Si O2/m Si O2 microspheres were synthesized.First,Fe3O4 microspheres were prepared through solvothermal method.Then a dense layer of Si O2 was coated on the surface of Fe3O4 microspheres.The surfactant CTAB were used as template,a layer of mesoporous Si O2 was coated on the surface of Fe3O4/Si O2 microspheres,Fe3O4/Si O2 /m Si O2 microspheres were obtained with sanwhich-like structure.The effects of p H,temperature and time on the adsorption properties of magnetic Fe3O4/Si O2 /m Si O2 microspheres on BSA were systematically studied.The results show that that the maximum adsorption capacity of Fe3O4/Si O2/m Si O 2 microspheres is at the isoelectric point of BSA.Feandlich adsorption isotherm and Langmuir adsorption isotherm model were used to analyze the adsorption data of Fe3O4/Si O2 /m Si O2 microspheres on BSA.The results show that Langmuir isotherm model provided a better fit with the adsorption of BSA on Fe3O4/Si O2 /m Si O2 microspheres mesoporous microspheres,and the theoretical maximum adsorption capacities at 20?,30? and40? are 253,289 and 300mg/g,respectively.The aqueous Fe3O4 microspheres were synthesized as magnetic cores and Fe3O4/agarose microspheres were prepared by reverse entrapment method.There were characterized by optical microscopy.The hydroxyl groups on the surface of agarose were modified with epichlorohydrin,and activated by glutaraldehyde.Protein A was immobilized o n the surface of magnetic agarose.Antibody was purified because of the specific adsorption between protein A and antibody Ig G.The specificity of functional microspheres was analyzed by gel electrophoresis and high performance liquid chromatography(HPLC).The non-specific adsorption of Fe3O4/agarose microspheres was small.Magnetic Fe3O4/Si O2-Bi2 Mo O6 composite microspheres were synthesized.SEM and TEM showed that Fe3O4/Si O2 microspheres were immobilized on the surface of Bi2 Mo O6.The as-prepared Fe3O4/Si O2-Bi2 Mo O6 composite microspheres exhibited superparamagnetism and good magnetic response.The Rh B dye was used as the environmental pollutant.The photocatalyt ic activity of Fe3O4/Si O2-Bi2 Mo O6 composite microspheres for degradation of Rh B under visible light irradiation was analyzed.The pseudo-first-order model was employed to fit the photocatalyt ic data,and all the plots of ln(C0/C)versus irradiation time(t)are nearly linear,indicating good linear dependence relations.The Fe3O4/Si O2-Bi2 Mo O6 composite microspheres could be easily separated by applying an external magnetic field after photocatalyt ic experiments.The composite microspheres also displayed excellent stability after reusing several times.The photocatalytic mechanism of Fe3O4/Si O2-Bi2 Mo O6 composite microspheres was analyzed by the capture experiment.The results showed that the main active species for the degradation of Rh B were O2.-and.O H,and a hypothetical mechanis m of the Fe3O4/Si O2-Bi2 Mo O6 compostie microspheres is proposed.