渗透蒸发膜亲水改性与水传递过程强化研究

发布时间：2018-03-15 23:29

  本文选题：渗透蒸发膜　切入点：丙酮脱水　出处：《天津大学》2015年博士论文　论文类型：学位论文

【摘要】：渗透蒸发因其具有低能耗、投资小、不受气液平衡限制等优点,在有机物脱水分离领域具有广阔的应用前景。本文以丙酮和水的渗透蒸发分离为研究对象,针对高分子膜的“trade-off”效应,通过增加水在膜中的溶解性和扩散性来解决“trade-off”效应。为了提高水在膜内的溶解性,本文通过掺杂亲水性无机颗粒或在高分子上接枝亲水性基团来提高膜的亲水性。同时为了提高水在膜中的扩散性,本文通过在膜中构建无机通道,为水的扩散提供高选择性的连续通道,强化水传递过程;或将水分子“活化”,即将大水分子簇变成小水分子簇,增加水分子的渗透性和扩散性,提高水通量。主要研究结果如下:首先,将亲水性钾型蒙脱土(K+MMT)掺杂到壳聚糖(CS)膜中,在膜中构建离子化水通道。利用K+MMT层间K+的水溶剂化效应,来提高膜对水的选择性,同时层状的K+MMT为水分子提供连续的传递通道并增大了聚合物链间距,强化水的传递。CS-K+MMT-10杂化膜在50oC、水含量为5wt.%时,渗透通量为1.56kg/m2h,分离因子为2200,比纯壳聚糖膜分离因子(249),提高了约8倍。其次,将疏水性多孔碳分子筛经过磺化接枝高亲水性磺酸根,然后将磺化碳分子筛(SCMS)掺入CS膜中,在膜中构建具有亲水位点的疏水通道。利用SCMS上磺酸根的亲水性提高水选择性,利用通道的疏水性降低水分子传递的能量壁垒,提高水通量。CS-SCMS-2杂化膜在50oC水含量为5wt.%时渗透通量为1.81kg/m2h,分离因子为832,与纯壳聚糖膜相比,通量和分离因子分别提高1.67倍和2倍。再次,利用强电解质在水中可完全电离,与弱电解质相比能和更多的水分子形成水合离子的性质,将CS中弱碱性的氨基改性成强碱性的胍基,合成壳聚糖胍(CG)。胍基通过诱导极化与更多的水分子形成水化层,提高水选择性;同时,利用胍基的“结构碎化”效应(“Structure breaking”effect),使大水分子簇变成小水分子簇,增强水分子的渗透性,强化水的传递。结果表明CG-50-pH2.5-1:2膜内胍基取代度为8.69%,在50oC、水含量为5wt.%时,其渗透通量可以达到1.9kg/m2h,分离因子为3300,比纯壳聚糖膜分别提高1.26倍和13倍。最后,选用氨基含量更高的聚乙烯胺(PVAm)为膜材料,采用类似的方法,将PVAm中的氨基改性成胍基,合成了聚乙烯胍(PVG)。随着胍基取代度的增加,膜的水接触角减小,亲水性增强。PVG-50-pH2-1:2膜内胍基取代度为18.41%,在50oC、水含量为5wt.%时,通量为2.32kg/m2h,分离因子为3781,性能高于壳聚糖胍膜。
[Abstract]:Because of its advantages of low energy consumption, low investment and no restriction of gas-liquid equilibrium, osmotic evaporation has a broad application prospect in the field of dehydration of organic compounds. In this paper, the separation of acetone and water by pervaporation is studied. In view of the "trade-off" effect of polymer membrane, the "trade-off" effect is solved by increasing the solubility and diffusibility of water in the membrane. In this paper, the hydrophilicity of the membrane was improved by doping hydrophilic inorganic particles or grafting hydrophilic groups on the polymer, and in order to improve the diffusion of water in the membrane, inorganic channels were constructed in this paper. Providing highly selective continuous channels for water diffusion to enhance the water transfer process, or "activating" water molecules, that is, changing large water molecules into small water molecules, thus increasing the permeability and diffusion of water molecules. The main results are as follows: firstly, the hydrophilic potassium montmorillonite (K MMT) was doped into the chitosan (CS) membrane, and an ionization water channel was constructed in the membrane. The water selectivity of the membrane was improved by using the water solvation effect of K between K MMT layers. At the same time, the layered K MMT provides a continuous transfer channel for water molecules and increases the polymer chain spacing. When the water transfer. CS-K MMT-10 hybrid film is 50oC, the water content is 5wt.%. The permeation flux was 1.56 kg 路m ~ (-2) h and the separation factor was 2200, which was about 8 times higher than that of pure chitosan membrane separation factor (249N). Secondly, the hydrophobic porous carbon molecular sieve was sulfonated onto high hydrophilic sulfonic acid radical, and then the sulfonated carbon molecular sieve (SCMS) was doped into CS membrane. Hydrophobic channels with hydrophilic sites were constructed in the membranes. The hydrophilicity of sulfonic acid on SCMS was used to improve the hydrophobicity, and the hydrophobicity of channels was used to reduce the energy barrier of water transfer. When the water flux. CS-SCMS-2 hybrid membrane was 50 鈩，

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