Preparation And Properties Of Functional CA Composite Nanofiber Membrane

As a novel technology to fabricate nanofibers, the electrospinning method attracts more attention and rapid development in recent years. Electrospinning nanofiber membrane shows great potential in the field of filtration and absorption for harmful substances due to its nano-sized diameter, high surface area and porosity.An eco-friendly materials, cellulose acetate as the main component, polyacrylonitrile as ingredients, CA/PAN composite nanofiber membranes were fabricated by electrospinning method. On the basis of this nanofiber, the functionalized CA/PAN composite membrane was obtained by modification through hydroxylamine hydrochloride. And hexavalent chromium ions adsorption behavior of resulted membrane was further investigated. To sum up, the main content of this thesis as follows:Firstly, the mixed solution properties of CA/PAN were discussed, and then the composite CA/PAN membrane was prepared by multiple nozzles electrospinning. SEM images showed that the spinnability of mixed solution was improved by PAN further blends in dimethyl sulfoxide solvent. The FT-IR results indicated that, the molecular interaction of CA and PAN existed in amorphous region in a certain degree.Secondly, the mechanical property and themal stability of composite membranes were also enhanced with the increasing of PAN content. And machenical strength of CA/PAN composite membrane reach maximum value, the breaking strength is294.6cN, and elongation at break is9.33%.But the mechanical strength was decreased with further increasing PAN content. Therefore, the optimal composite ratio of CA and PAN is7/3. On the basis, effects of spinning parameters on specific surface area and fiber diameter of composite membrane were further explored. And then the uniform diameter distribution of fibers with a size of200nm was optimized by orthogonal test. Finally, the amidoximated membrane was acquired by CA/PAN composite membrane modified with hydroxylamine hydrochloride solution. FT-IR analysis showed that, the amidoximated membrane was prepared successfully. To obtain the proper modified conditions, we have studied relationship between conversion rate of nitrile group and mechanical strength of conmposite membranes.The adsorption capacity for Cr (VI) shows that, adsorption performance of CA composite membrane was improved by modification significantly. The adsorption behavior of Cr (VI) can be well described by the Langmuir adsorption model, adsorption behavior is orientated process with a aturation value, the theoretical maximum adsorption at three temperature points each were74.29mg/g (30℃),77.10mg/g (40℃),79.24mg/g (50℃). The adsorption kinetics analysis indicates that adsorption process can be well consistent with pseudo-second-model. The adsorption thermodynamics found that, adsorption behavior for Cr (VI) is an endothermic and spontaneous process, and adsorption mechanism was including physical and chemical adsorption process. In the meanwhile, the ion exchange reaction was also carried out in combined process of membrane adsorption for Cr (VI).