The Preparation Of Ion Exchange Membrane Based On Electrosp Inning

Among the numerous technologies for preparing non-woven nanofiber mats with nano-scale diameters, electrospinningprocesses significant advantages due to its simple, convenient and versatile preparing process andhas been fast becoming one of the best-developed nano-fiber preparing technology.The resulting porous nanofiber mats could be further modified by solvent vapor absorption and hot-press treatment, obtainingnovel membranes with a dense structure in a macroscopic scale but loose structure in a microscopic scale. Various ion exchange membranes with diversemorphology, pore structure, chemical composition and functional groupsbased on electrospinning have beenextensively reported. Compared with the conventional casting method, electrospinning not only offers the facility for controlling the internal microstructure and morphologyof ion exchange membrane, but also expands the membrane design programs. Furthermore, electrospinning provide the effective basis for explaining the ion transport phenomena through the membrane. Thus, the further exploration of electrospinning technique will attract continuouslyattentionand carry far-reachingsignificance for ion exchange membrane.In this context, we focused on developing a serials of novelion exchange membranes employingelectrospinning techno logy. Ion exchange membranes based on different polymeric materials and varied morphology were successfully fabricated and their potential in various separation process will be investigated in detail, the main contents are as follows:(1) Cation exchange membranes (CEMs) have been prepared from sulfonated poly (phenylene oxide)(SPPO) by electrospinning and hot-press treatment. Effect of various parameters, such as concentration, voltage and TCD (tip to collector distance) as well as the hot-press treatment conditions on properties of membrane has been fully investigated. When being applied in diffusion dialysis (DD) for alikali recovery from Na2WO4/NaOH solution, it exhibits higher hydroxide permeability (UOH,0.0097m/h) and selectivity (S,37.02) than that of direct casting SPPO (CSPPO) membrane, of which UOH is only0.0060m/h and S is21.66. Compared with previously reported DD membranes with UOH in the range of0.0014-0.0022m/h, Hot-pressed Electrospun SPPO (H-ESPPO) shows approx.4times higher in UOH. (2) The novel anion exchange membranes (AEMs) have been fabricated from quaternized poly (2,6-dimethyl-1,4-phenylene oxide)/Silicon dioxide hybrid material (QPPO-SiO2) by electrospinning and post-treatment (solvent fumigation and hot-press). While being used in a simulated iron polishing waste solution containinglmol/L HCl, and0.225mol/L FeCl2, the membrane exhibits both higher acid permeability (UH,0.053m/h) and selectivity (S,68.05) in comparison with the direct casting QPPO-SiO2hybrid membrane, of which possess relatively lower values of UH (0.041m/h) and S (49.45). Besides, compared with commercial DF-120membrane (UH=0.005-0.009m/h, and S=18.5-23.5), hot-pressed electrospun QPPO-SiO2membrane shows more than approx.7times higher UH and approx.3times higher S values.(3) For the first time here in we developed a new preparative pathway for bipolar membranes based on electrospinning and hot-press technique. The bipolar membranes are initially sandwiched and composed of sulfonated poly(phenylene oxide)(SPPO), polyethylene glycol (PEG) and Quaternized poly(phenylene oxide)(QPPO). Nanofibers mats were successfully fabricated by continuous electrospinning methodology and then through in turns solvent atmosphere treatment followed by hot-press technique to transform into transparent and dense bipolar membranes. The thickness of sublayer in bipolar membrane can be easily tuned by adjusting the electrospinning parameters. The compositions and structures of the membranes are proved and observed by scanning electron microscope (SEM). The dipolar performance is evaluated by current-voltage curves and production yield of acid and base. The experimental results proved that electrospinning combining with the post treatment process is an effective, simple, feasible and well controlled way to fabricate bipolar membranes. Furthermore, by using this method we can even easily change or add a new ion exchange membrane and interfacial layer materials according to their own requirements.(4) A series of novel electrospun proton selective membranes composed of SPPO and QPPO have been prepared based on electrospinning following by hot-press. The content of anionic charged polymer in PSMs can be effectively controlled by adjusting the ratio of electrospinning time. FTIR, SEM and TEM analysis have confirmed the existence and internal special structure of two components (SPPO and QPPO). The mosaic charged structure obtained cationic charged component (SPPO) and anionic charged component (QPPO), is endowed with much lower Zn2+leakage and excellent proton (H+) selectivity compared with commercial PSMs (CSO). The high-performance of as-prepared electrospun PSMs is ascribed to admixture of anionic charged group which is preferentially permeable to proton (H+) rather than multivalent (Zn2+) due to the difference of electrostatic repulsion between the cations and PSM modified with anionic component.