| Magnetic polymer microsphere is a kind of microsphere with magnetism and special structure,which is composed of polymer and inorganic magnetic particles. Because it can be separated quickly and easily from mixtures by exterior magnctic field, also has the characteristics of polymer particles,which can be endowed with functional groups on its surface by copolymerization or surface modification, so they have been widely concerned. Magnetic polymer microsphere shows broad application prospects in the immobilization bacteria,immobilized enzyme,targeting drug, cell separation,and such. In this paper, in virtue of improved experimental methods on the of Chinese and foreign research results, we prepared Fe3O4/poly(styrene-divinylbenzene-methacrylic acid) [Fe3O4/poly(St-DVB-MAA)] magnetic composite polymer microsphere with good sphericity, narrow particle size distribution and strong magnetic responsivity.The properties of inorganic magnetic particles is mainly factors influence the nature of magnetic polymer microspheres magnetic responsiveness. The nanopartieles of Fe3O4 were prepared by a chemical precipitation method and modified by polyethylene glycol(PEG) and sodium dodecyl sulfate(SDS).The nanoparticles of Fe3O4 size is about 11.7 nm by transmission electron microscope(TEM) and X-ray diffraction(XRD). The nanopartieles of Fe3O4 encapsulated by PEG and SDS is carried out with Fourier transfer infrared (FT-IR).The specific saturation magnetization of nanopartieles of Fe3O4 reaches to 48.2emu/g at room temperature by a vibrating-sample magnetometer(VSM).Magnetic composite polymer microspheres were prepared through polymer encap -sulation of small Fe3O4 partieles,using dispersion polymerization of styrene in aqueous ethanol medium. Polyethylene glycol(PEG) and benzoyl peroxide(BPO) were utilized as stabilizer and initiator,respectively. The effect of monomer, magnetic fluid, dispersion medium, reaction temperature,dispersion medium,stabilizer, and initiator on the microsphere size and size distribution were investigated by optical microscope. The final magnetic microspheres were characterized by optical microscope, X-ray diffraction (XRD), Fourier transform infrared spectroscopy(FT-IR), thermogravimetric analysis(TGA), vibrating-sample magnetometer(VSM). Analysis of test results showed that the magnctic polyer microspheres with diameter of 350-450μm, as well spherieal, better monodisperse. The results indicated that the magnetic is heterogeneous structure with nanopartieles dispersed in magnetic mierosperes and shell with St-MAA, carboxyl functional groups and showed a trade surplus paramagnetic virtually no hysteresis. The magnetic composite polyer microsphere with the magnetic content was 17.07%.Monodisperse magnetic porous microspheres(MPMs) were prepared by dispersion polymerization in aqueous ethanol reaction media using polyethylene glycol(PEG) as a stabilizer and benzoyl peroxide(BPO) as an initiator and toluene and heptane as a porogen in suitable condition. The morphology analysis by optical microscope confirmed that the composite magnetic porous microsphere had a good sphericity with porous structure and a relatively uniform diameter of about 400μm. The MPM was characterized with monodisperse, low density(1180kg/m3), high specific surface area(11800m2/m3), large porous degree(67.6%), large porous volume(2.4mL/g) and narrow porous diameter distribution. The average porous diameter was within the range of bacteria diameter. According to the previous statement, it was known that MPM was good carriers for the immobilization of enzyme and microorganism. The saturation magnetization of the magnetic composite microspheres was found to be 3.75emu/g by a vibrating-sample magnetometer(VSM). So, MPM was also suitable as particles filled in magnetically stabilized fluidized bed (MSFB) for its strong magnetic responding capacity.With MPM as the carrier, Sulfate-reducing bacteria was immobilized by adsorption method, and applied in magnetic stabilized fluidized bed for desulphurization experiment. The biofilm formation process in the biodesulphrization system was studied during the start-up by scanning electromicroscope. Magnetic porous microspheres can immobilize a large number of desulfurization bacteria by calculating particle concentration, biofilm quantity with 109.80mg/g and biofilm concentration and maintain high concentration and dense biofilm during the operation. The sulfur production efficiency of the system can reach about 90% of the treated SO2 by magnetically stabilized fluidized bed (MSFB). |
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