陶瓷膜接枝改性及其在膜蒸馏过程中的应用

发布时间：2018-05-04 19:39

本文选题：膜蒸馏 + 疏水改性　；参考：《大连理工大学》2015年硕士论文

【摘要】：目前我国淡水资源短缺情况日益严重,而膜蒸馏由于具有操作简单、分离效率高等优点,以及操作温度较低,由此可利用太阳能和工业低温余热等廉价能源的优势,使其有望成为解决淡水资源紧缺问题的有效途径。膜蒸馏是一种新兴的膜分离技术,它是基于疏水多孔膜两侧的蒸汽压力梯度,在海水和苦咸水脱盐、水溶液中挥发性溶质脱除、废水处理等领域受到广泛关注。尽管膜蒸馏技术优点众多,但膜材料的性能限制了膜蒸馏过程的广泛应用。因此,制备高性能膜蒸馏用膜,使其能够长期稳定高效的运行且获得较大的渗透通量,是膜蒸馏技术工业化应用所急需解决的问题。在膜蒸馏采用的疏水微孔膜中,最常使用的为有机膜,主要有聚丙烯(PP)、聚四氟乙烯(PTFE)和聚偏氟乙烯(PVDF)。与有机膜材料相比,陶瓷膜具有更好的热稳定性和化学稳定性,但由于其不具备疏水性,所以不能直接用于膜蒸馏。本文在课题组前期工作的基础上,优选二甲基二氯硅烷对A1203管式陶瓷膜进行疏水改性,以此拓展疏水膜材料的来源。在此基础上,将改性后的陶瓷膜用于氯化钠水溶液的分离。研究发现,改性剂成功接枝聚合到陶瓷膜表面；改性陶瓷膜具有良好的疏水性能,且改性前后膜表面形貌和孔径没有明显变化；实验测得改性陶瓷膜的液体进入压力(LEP)为0.11MPa。改性后的陶瓷膜应用于NaCl溶液的气隙式膜蒸馏过程时,渗透通量随溶液温度和流量的增大时均增大、随溶液浓度的增大而减小；溶液温度是影响过程的主要因素；改性陶瓷膜对氯化钠的截留效果良好。研究结果证明,二甲基二氯硅烷改性的陶瓷膜可用于NaCl溶液的膜蒸馏过程。在气隙式膜蒸馏氯化钠水溶液常规实验的基础上,采取在膜管内加入湍流促进器、在液体中通入气体形成两相流的强化措施,探讨膜蒸馏过程的强化效果。结果表明,加入圆柱式湍流促进器、缠绕式湍流促进器和螺旋式湍流促进器均能提高渗透通量,强化效果强弱依次为螺旋式、缠绕式和圆柱式湍流促进器；通入两相流后,渗透通量增加了12-44%。
[Abstract]:At present, the shortage of fresh water resources in China is becoming more and more serious, while membrane distillation has the advantages of simple operation, high separation efficiency and low operating temperature, which can make use of the advantages of cheap energy such as solar energy and industrial low temperature waste heat. It is expected to be an effective way to solve the problem of shortage of fresh water resources. Membrane distillation is a new membrane separation technology. It is based on the steam pressure gradient on both sides of the hydrophobic porous membrane. It has attracted extensive attention in the fields of desalination of seawater and brackish water, removal of volatile solutes from aqueous solution and treatment of wastewater. Although membrane distillation technology has many advantages, the performance of membrane materials limits the wide application of membrane distillation process. Therefore, the preparation of high performance membrane for membrane distillation, so that it can run stably and efficiently for a long time and obtain large permeable flux, is an urgent problem to be solved in the industrial application of membrane distillation technology. Among the hydrophobic microporous membranes used in membrane distillation, organic membranes are mainly used, such as PP, PTFEand PVDF. Compared with organic membrane material, ceramic membrane has better thermal stability and chemical stability, but it can not be directly used in membrane distillation because it is not hydrophobic. Based on the previous work of our research group, dimethyldichlorosilane was selected to modify the A1203 tubular ceramic membrane by hydrophobic modification, so as to expand the source of hydrophobic membrane material. On this basis, the modified ceramic membrane was used for the separation of sodium chloride aqueous solution. It was found that the modified ceramic membrane had good hydrophobicity, and the surface morphology and pore size of the modified ceramic membrane had no obvious change. The liquid entry pressure of the modified ceramic membrane was 0.11 MPA. When the modified ceramic membrane is applied to the air gap membrane distillation process of NaCl solution, the permeation flux increases with the increase of solution temperature and flow rate, and decreases with the increase of solution concentration, and the solution temperature is the main factor affecting the process. The retention effect of the modified ceramic membrane on sodium chloride is good. The results show that the ceramic membrane modified by dimethyl dichlorosilane can be used in the membrane distillation process of NaCl solution. On the basis of conventional experiments of air gap membrane distillation of sodium chloride aqueous solution, the enhancement measures of adding turbulence promoter into membrane tube to form two-phase flow through gas in liquid were adopted to discuss the enhancement effect of membrane distillation process. The results show that the permeable flux can be increased by adding the cylindrical turbulence promoter, the twining turbulence promoter and the spiral turbulence promoter, and the enhancement effect is in turn helical, twining and cylindrical turbulence promoters. The osmotic flux increased by 12-44.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.893

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