Studies On Synthesis Of Magnetic Crosslinked Chitosan Microspheres And Its Properties Of Adsorbing For U(vi)

In recent years, the development of polymer materials trends to be high- performance ,multi-function.Specialpropertiesofpolymercompositemicro-sphereshaveattractedmoreand more people to research it. The high polymer compound materials, particularlymagnetic high polymer materials, have attracted more attention in nanometer magneticmaterials domains. This paper systematically studied the influence of preparationprocessing parameters and surfactant on stability of water-based magnetic particles, andstudied the preparation of magnetic chitosan microsphere crosslinked by differentcrosslinkingagent usinguniform designmethod..Finallyweinspectedadsorptioneffect ofmagneticmicrospheres touranium,andthestructureandmorphologyof magneticchitosanmicrosphere were detected by scanning electron microscope (SEM), X-ray diffraction(XRD)andinfraredspectra(IR),theresultsareasfollowing:In water-based magnetic fluid preparation process, reaction temperature, pH, stirringspeed, ultrasonic dispersing time, reaction time, NFe2+ /NFe3+and different surfactants havetremendous influence on the properties of magnetic fluid. The order of factors influencingon the properties of magnetic fluid are heating temperature > NFe2+/ NFe3+ > reaction time>pH > stirring speed > ultrasonic dispersing time according to the orthogonal experiment.And the optimum conditions are: temperature 45℃, pH 9, NFe2+/ NFe3+ 1:2, the reactiontime 30min, ultrasonic dispersing time 30min, stirring speed 2000rpm. The resultsmeasured by X-raydiffractometer demonstrate that Fe3O4 is the main part of the magneticfluid.The Fe3O4 crystalline forms of magnetic fluid don't change, which are modified bydifferent surfactant. According to the Scherrer equation, the average diameter of Fe3O4is28nm.The preparation of magnetic microspheres was designed by uniform design method,andtheoptimumlevel offactorsineachgroupwasobtainedbythespecial dataprocessingsoftware.The results of modified magnetic microspheres adsorption to uranium indicated thatthis process had the advantage of fast adsorption and high removal efficiency. For 10mg/Luranium solution, the removal rate is 99% after 2 minutes. The removal efficiency of50mg/L uranium solution can be up to 98% 8 minutes later, and the rate of 100mg/Luranium solution achieved more than 98% after 10 minutes. The sequence of factors influencingonadsorptionis:Uraniuminitialdensity>pH>biosorbentdose>temperature.And the optimum conditions are: pH 4, Uranium initial density 200mg/l, biosorbent dose0.7g,temperature40℃.The modified magnetic microspheres can be eluted with 0.1mol/L NaOH, 0.5mol/LNaOH, 0.1mol/L EDTA. After desorption 4 times, the removal efficiency can still reachemore than 90%, which can explained the modified magnetic microspheres have goodavailability of reusing and provided the possibility for practical application. The particalsize of modified magnetic microspheres measured by SEM belonged to micrometer level.Its surface was porous and presents many small holes. IR-spectrum of modified magneticmicrospheres existedtheC=Ncharacteristicabsorptionpeakat 1649cm-1,whichindicatedthat crosslinking agent D reacted with chitosan.Bythe phase analysis in the XRD patternswe could see that the Fe3O4 diffraction peak appeared at 30.0℃, 35.5℃and 62.5℃, Itproved that the spinel structure of Fe3O4, existed in modified magnetic microspheres, didnot change. The result also indicated that the modified magnetic microspheres hadwrappedFe3O4successfully.