PVDF静电纺丝纳米纤维疏水膜的制备及其膜蒸馏特性研究

发布时间：2018-04-25 21:46

本文选题：PVDF + 静电纺丝　；参考：《南昌大学》2015年硕士论文

【摘要】：针对当前膜蒸馏用膜通量低、疏水性差等限制膜蒸馏技术规模化应用的突出问题,基于静电纺丝技术原理,开展新型聚偏氟乙烯(PVDF)静电纺丝纳米纤维疏水膜制备研究。考察了不同纺丝液体系对膜形貌结构与性能的影响,优化了静电纺丝过程中的工艺参数;并以制备的PVDF纳米纤维疏水膜为膜蒸馏用膜,进行了直接接触式膜蒸馏实验研究。主要研究成果如下:(1)考察了混合溶剂(DMF/丙酮)对纺丝液表面张力、粘度、电导率及疏水膜性能的影响。实验结果表明,随着混合溶剂中丙酮含量的增加,纺丝液的表面张力、粘度及电导率呈下降趋势,纳米纤维间珠粒数量显著减少;纤维直径及膜厚度均有所增大;当混合溶剂中二甲基甲酰胺与丙酮比例为9:1时,纳米纤维膜的孔隙率为83%,膜接触角可达142.8°,表现出较好的疏水性。(2)在二甲基甲酰胺与丙酮混合比例为9:1的条件下,进行了高分子聚合物含量对纺丝液基本性质与膜形貌结构及分离性能的影响研究。研究结果表明,提高纺丝液中PVDF含量,会降低纺丝液的表面张力与电导率,减少纳米纤维间珠粒数量,而纤维的直径增大;直接接触式膜蒸馏脱盐应用实验表明,PVDF质量分数为12wt%条件下制备的疏水膜,其通量可达62.38 kg/m2·h,产水电导率为8μS/cm,盐截留率达到99.99%以上。(3)考察了静电纺丝工艺参数对PVDF纳米纤维疏水膜结构形貌及分离性能的影响。当电压低于12 kV时,由于电场力不足,最终会产生较大斑块,进一步影响膜通量;随着电压升高,纤维排布呈逐渐致密趋势,但对膜的疏水性影响轻微;纺丝液流速的增加会使纤维直径增大,纳米纤维膜变厚;接受距离对膜的形貌影响较小,但接受距离的增大会导致纤维排列较为疏松;提高静电纺丝接受器-转鼓的转速,会导致膜通量降低,实验范围内最优的转速为10 r/min。在连续稳定运行150小时膜蒸馏试验后,通量下降了30%,但产水电导率为15μs/cm以下;连续三次膜蒸馏浓缩试验,膜在清洗后,初始通量恢复率较高,分别达到了98%和96%。
[Abstract]:In view of the outstanding problems such as low membrane flux and poor hydrophobicity in membrane distillation at present, based on the principle of electrostatic spinning technology, the preparation of novel hydrophobic membrane of PVDF nanofibers was studied. The effects of different spinning liquid systems on the morphology, structure and properties of the membranes were investigated, and the process parameters during electrostatic spinning were optimized, and the direct contact membrane distillation experiments were carried out using the hydrophobic membranes of PVDF nanofibers as membrane distillation membranes. The main results are as follows: (1) the effects of the mixed solvent (DMF / acetone) on the surface tension, viscosity, conductivity and hydrophobic properties of the spinning solution were investigated. The results showed that with the increase of acetone content in the mixed solvent, the surface tension, viscosity and conductivity of the spinning solution decreased, the number of beads between nanofibers decreased significantly, and the fiber diameter and film thickness increased. When the ratio of dimethylformamide to acetone in mixed solvent is 9:1, the porosity of nanofiber membrane is 83 and the contact angle of the membrane is 142.8 掳, which shows good hydrophobicity at 9:1 when the mixture ratio of dimethylformamide and acetone is 9:1. The effects of polymer content on the basic properties, morphology and separation properties of the spinning solution were studied. The results show that increasing the content of PVDF in spinning solution can reduce the surface tension and conductivity of spinning solution, reduce the number of beads between nanofibers, and increase the diameter of fibers. The direct contact membrane distillation desalination experiment showed that the hydrophobic membrane was prepared under the condition of PVDF mass fraction of 12 wt%. The effects of electrospinning parameters on the morphology and separation properties of PVDF nanofibers hydrophobic membrane were investigated. The flux was 62.38 kg/m2 / h, the water conductivity was 8 渭 S / cm, and the salt rejection was 99.99%. When the voltage is lower than 12 kV, due to the lack of electric field force, large plaque will be produced, which will further affect the membrane flux, with the increase of voltage, the fiber arrangement becomes more dense, but has a slight effect on the hydrophobicity of the membrane. The increase of spinning liquid velocity will increase the diameter of the fiber and the thickness of the film. The acceptance distance will have little effect on the morphology of the film, but the increase of the acceptance distance will lead to the loose arrangement of fibers, and increase the rotational speed of the electrostatic spinning receptor-drum. The optimal rotational speed in the experimental range is 10 r / min. After 150 hours of continuous operation, the flux decreased by 30%, but the conductivity of water production was less than 15 渭 s/cm, and the recovery rate of initial flux reached 98% and 96% respectively after cleaning.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.893

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