Study On The Preparation Of PAN-Based Functional Nanofibers And Their Applications For Enzyme Immobilization

Nowadays,the electrospun nanofibers can be widely used in the field of mechanical electronics,biomedicine,environmental protection for their excellent properties such as high specific surface area and porosity,good fiber structure and modification.At first,the PAN-based blend nanofibers were generated by electrospinning in this project,subsequently,the nanofibers were modified to introduce a large number of hydroxyl groups,aldehydes,amino groups and other functional groups into the surface of the fiber,So that the blend nanofibers not only have the corresponding nanoscale effect,but also reflect strong functionality in the field of metal ion adsorption and biological enzyme immobilization.The PU/AOPAN/RC bend nanofiber membranes were prepared by electrospinning and chemical modification,and then the nanofibers were characterized by scanning electron microscopy and infrared spectroscopy.Research suggests that PU/AOPAN/RC blend nanofibers have the characteristics of small fiber diameter,large specific surface area and porosity.At the same time,the surface of nanofiber has successfully introduced many functional groups such as hydroxyl group and amidoxime group.After modification,the blend nanofibers membrane has good mechanical properties,and its hydrophilic performance has been greatly improved.In the study,the metal ions coordination properties of PU/AOPAN/RC nanofiber membranes were determined by plasma emission spectrometry.Results showed that the adsorption capacity of PU/AOPAN/RC nanofiber membranes to Fe(?),Cu(?)and Cd(?)ions were obviously higher than that of the conventional adsorbent materials at the optimum temperature and pH value.Meanwhile,there was a selective adsorption of metal ions on the blend nanofibers membrane,and the adsorption capacity of the three metal ions was Fe(?)>Cu(?)>Cd(?).Moreover,the nanofiber membrane also has excellent regeneration capacity.A variety of isothermal adsorption models were used to simulate the experimental data in the process of metal ion adsorption.It can be seen that the adsorption experiment data of Fe(?)and Cu(?)ions on the PU/AOPAN/RC nanofiber membrane are more suitable for simulating by the Freundlich isothermal model,and the Langmuir model has better fit to Cd(?)ion.In addition,the PU/AOPAN/RC nanofiber membrane was used as an ultrafiltration membrane to separate and purify the protein in the solution.And the experiment results indicated that compared with the PES commercial ultrafiltration membrane,the PU/AOPAN/RC nanofibers membrane on the basis of maintaining a high retention rate,the membrane flux has been greatly improved,and the nanofiber membrane can be reused many times.The Fe(?)-PU/AOPAN/RC blend nanofiber membrane was used as immobilized enzyme carrier,and the laccase was immobilized by coordination method;thereafter,the relative properties of laccase were determined.The scanning electron microscope and fluorescence microscope test of immobilized enzyme showed that the laccase could be uniformly and efficiently immobilized on the surface of Fe(III)-PU/AOPAN/RC blend nanofibers due to the formation of coordination bonds between metal ions and laccase proteins.Compared with free laccase,the nanofiber membrane immobilized laccase showed better resistance to the variations of temperature and pH value.The storage property of the immobilized laccase was not only obviousy improved,but also the laccase possessed excellent reusability.In addition,compared with other immobilized laccase supports,the electrospun PU/AOPAN/RC nanofiber membrane has excellent mechanical properties and regeneration capability on the basis of high enzyme fixation and retention activity.At the same time,the Km and Vmax value of the free and immobilized laccase were compared and analyzed.The results showed that a good affinity between the blend nanofibrous membrane carrier and laccaseThe AOPAN/MMT blend nanofibrous membranes were obtained by electrospinning and amidoxime modification.After modification with glutaraldehyde,the laccase was immobilized on the surface of nanofibers by physical adsorption and covalent approach.At the same time,the optimization of immobilization conditions and the relative properties of the immobilized laccase were also investigated in this thesis.Studies show that:When glutaraldehyde concentration of 5%,reaction time and enzyme immobilization time is 10 h and 12 h,respectively,the immobilized laccase had the best effect.Enzymatic kinetic analysis of free laccase and immobilized laccase showed that the immobilized laccase had a good affinity with the substrate.And immobilized laccase show a better stability for the change of temperature and pH value,it also had good storage stability and reusability.