聚偏氟乙烯超滤膜的亲水改性研究

发布时间：2018-04-03 23:44

本文选题：聚乙烯醇　切入点：微孔膜　出处：《长春工业大学》2017年硕士论文

【摘要】：超滤膜广泛应用在食品、生物医药、废水处理以及超纯水的制备等领域。聚偏氟乙烯(PVDF)由于它具有高的机械强度,热稳定性,抗化学腐蚀力等优点,成为科学家们所关注的超滤膜材料。但是PVDF膜的本身的性质制约了它在水溶液系统的分离与纯化。主要问题就是PVDF具有低的表面能,PVDF本身疏水性很强,常常会导致膜纯水通量的降低。诸如含有蛋白质的料液通过膜材料的时候,蛋白质会容易在膜的表面以及膜孔上吸附,不利于膜的分离性能的提高,膜易受到污染,膜的使用寿命降低,运行的经济成本大大升高。因此科学家致力于对PVDF膜进行亲水改性,以制备高性能的膜,这一方法具有重大意义。本文从凝胶浴的组成以及铸膜液组成两方面入手对PVDF膜进行亲水改性,制备了亲水性的PVDF膜,并表征了膜的性能。结果如下:首先从改变凝胶浴方面使用PVA水溶液作为凝胶浴对PVDF膜进行亲水改性。使用不同用量的PVA水溶液作为凝胶浴,通过浸没沉淀相转化法制备了不同结构与性能的亲水微孔膜,即CPVA-PVDF-X膜(X为PVA在水中的质量分数)。运用电镜、TGA、ATR-FTI、机械强度、水接触角、超滤实验等表征膜的综合性能。实验证实,凝胶浴中PVA水溶液浓度越高,膜的断面指状孔所占面积越少,海绵状孔所占面积越多;膜的热稳定性提高;膜的机械性能增强;孔径分布变窄;PVDF膜纯水通量降低,BSA截留能力提升,膜的抗污染性能提高。随后,为了避免PVA在浸泡过程中溶解于水中,将上述制备的亲水微孔膜进行表面交联处理,制备了CCPVA-PVDF-X膜。并对交联后的膜进行扫面电镜观察、TGA、红外检测、机械强度、接触角(CA)和超滤实验表征。结果表面交联后的膜的机械强度、BSA截留率以及膜的抗污染性能与未交联的相比增强。最后从改变铸膜液的组成方面入手,利用PVA对SiO_2进行亲水改性后合成改性SiO_2,将不同质量分数的改性SiO_2与PVDF铸膜液混合,制备了PVA-SiO_2/PVDF膜。运用扫面电镜观察、红外测试、水接触角测试和超滤实验表征膜的综合性能。结果显示,改性SiO_2与普通SiO_2相比更亲水;随着铸膜液改性SiO_2浓度的增加,膜亲水性变强,而膜的通量先出现增长的趋势之后又减少。M5亲水性最强;纯水通量最高;膜抗污染性能最强。
[Abstract]:UF membrane is widely used in food, biomedicine, wastewater treatment and preparation of ultrapure water.Polyvinylidene fluoride PVDF (PVDF) has become the ultrafiltration membrane material for its high mechanical strength, thermal stability and chemical corrosion resistance.However, the properties of PVDF membrane restrict its separation and purification in aqueous solution system.The main problem is that PVDF has low surface energy and high hydrophobicity, which often leads to the decrease of pure water flux.For example, when the material containing protein passes through the membrane material, the protein will be easily adsorbed on the surface of the membrane and on the membrane pore, which is not conducive to the improvement of the separation performance of the membrane, the membrane is liable to be contaminated, and the service life of the membrane is reduced.The economic cost of operation is greatly increased.Therefore, it is of great significance to prepare high performance PVDF membranes by hydrophilic modification.In this paper, the hydrophilic modification of PVDF membrane was carried out from the composition of gel bath and the composition of casting membrane. The hydrophilic PVDF membrane was prepared, and the properties of the membrane were characterized.The results are as follows: firstly, the hydrophilic modification of PVDF membrane was carried out by using PVA aqueous solution as gel bath to change the gel bath.Hydrophilic microporous membranes with different structures and properties were prepared by immersion precipitation phase inversion method using different PVA aqueous solution as gel bath, that is, CPVA-PVDF-X membrane X was the mass fraction of PVA in water.The comprehensive properties of the membrane were characterized by electron microscope (TEM) TGAN ATR-FTI, mechanical strength, water contact angle and ultrafiltration test.The experimental results show that the higher the concentration of PVA aqueous solution in gel bath, the less the area of finger pore, the more the area of sponge pore, the better the thermal stability of membrane and the more mechanical property of membrane.The pore size distribution becomes narrower and the pure water flux of PVDF membrane decreases and the retention ability of BSA increases, and the fouling resistance of PVDF membrane is improved.Subsequently, in order to prevent PVA from dissolving in water during soaking, the hydrophilic microporous membrane was cross-linked and the CCPVA-PVDF-X membrane was prepared.The cross-linked films were characterized by scanning electron microscopy (SEM), IR, mechanical strength, contact angle (CAA) and ultrafiltration (UF).Results the mechanical strength and BSA rejection rate of the membranes after surface crosslinking were higher than those of the uncrosslinked membranes.Finally, by changing the composition of casting solution, the modified SiO-2 was synthesized by hydrophilic modification of SiO_2 by PVA. The PVA-SiO_2/PVDF membrane was prepared by mixing the modified SiO_2 with the cast solution of PVDF with different mass fraction.The comprehensive properties of the membrane were characterized by SEM, IR, water contact angle and ultrafiltration.The results showed that the modified SiO_2 was more hydrophilic than that of the ordinary SiO_2, and the hydrophilicity of the modified SiO_2 increased with the increase of the concentration of modified SiO_2 in the casting solution, while the flux of the membrane first increased and then decreased, the hydrophilicity of M5 was the strongest, and the pure water flux was the highest.The membrane has the strongest anti-fouling performance.
【学位授予单位】：长春工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ051.893

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