Study On Construction And Filtration Performance Of Polypropylene / Polyacrylonitrile - Carbon Nanotube Gradient Structure Fiber Composite Membrane

With a large specific surface area, small pore size, high porosity and good permeability, electrospun nanofiber membrane has been more and more widely used in the field of filtration. Although electrospun membranes have high filtration efficiency, the large filtration resistances of them are very high. Moreover, mechanical properties of them are also poor. To solve this problem, this paper put forwords a method to assemble the oxidized carbon nanotubes (OCNTs) with large specific surface area and high adsorption properties onto the surface of electrospinning polyacrylonitrile (PAN) nano fiber membrane, which were supported by a layer of polypropylene (PP) nonwoven, in order to build a multilevel micro/nano gradient structure of PP/PAN-CNTs fiber composite membrane. The fiber composite membranes as prepared were with both high water flux and a high rejection rate on indigo dye. The main research contents of this paper include the following aspects:(1) This paper has explored the influence factors for surface topography structure and hydrophilic of PP/PAN-CNTs composite membrane with different preparation methods, focusing on exploring electrostatic spraying method. The characterization of surface topography, surface element content distribution, specific surface area and pore size distribution of the PP/PAN-CNTs composite membranes by electrostatic spraying method with different additive amount of CNTs were demonstrated clearly. The results showed that when the time of electrostatic spraying CNTs was 0.5h, the specific surface area of the composite membrane increased 62.1% and the average pore size decreased 1.32% comparing with pure PP/PAN fiber membrane. And when spraying time was 1h, the specific surface area of the composite film increased 1.78 times and the average pore size reduced 3.28% comparing with pure PP/PAN fiber membrane. When the spraying time is 2h, the surface area of composite membrane increased 2.63 times and the average pore size reduced 3.98%.(2) The filtration performance for indigo dyes and filtration mechanism of PP/PAN-CNTs composite membrane prepared by electrostatic spraying method were charactered and analyzed. Compared with pure PP/PAN fiber membrane, the hydrophilic properties of fiber composite membranes assembled with CNTs prepared by electrostatic spraying have greatly improved and the retention rate for indigo dyes of PP/PAN-CNTs composite membrane has been significantly improved. Besides, the mechanical properties of them are improved to some extent. Experimental results showed that when the time of electrostatic spray CNTs was 1 h, the retention rate for indigo dye of the composite film was 98.73% and the water flux was 3891.85 L/m2 h. Compared with pure PP/PAN fiber membrane, its rejection rate increased 3.11 times, while the water flux only reduced 17.30%.