膜蒸馏用膜的制备、改性及分离性能研究
发布时间：2018-07-18 07:27
【摘要】：膜蒸馏(membrane distillation,MD)就是把膜应用到蒸馏装置中,利用膜两侧的温度差所引起的传递组分的蒸汽压力差为传质驱动力以达到物质分离的目的。膜蒸馏装置根据应用不同可以分为直接接触膜蒸馏、真空膜蒸馏、气扫式膜蒸馏、气隙式膜蒸馏等,在本文中主要研究的是直接接触膜蒸馏用PVDF平板膜的制备、改性及分离性能。在PVDF平板膜制备过程中,分别考察了凝胶浴温度、停留时间及添加剂用量对所制备膜结构和性能的影响。通过正交实验可以得出如下结果:三个因素对PVDF平板膜结构和性能的影响顺序为添加剂用量停留时间凝胶浴温度。在该实验条件下,制备PVDF平板膜的最佳方案为:添加剂用量为3%(W/W),停留时间(5s),凝胶浴温度为(50℃)。本文使用了两种不同的方法(即共混改性和表面改性)进行改性实验:a、以共混改性制备PVDF平板膜的过程中,本论文设置了两组对比:Si O2与Ti O2,Al2O3与Ti O2分别共混;甘油/Ti O2,PMMA/Ti O2分别共混改性。在共混改性实验中通过控制混合添加剂的比例去考察所制的膜的性能,结果表明甘油/Ti O2共混后制得的膜效果较好,并且最佳用量为Ti O23%(W/W)、甘油0.4g。b、在表面改性的过程中,考察了PEG-600的用量、温度、硬脂酸丙酮溶液的浓度、纳米Ti O2粉末颗粒的加入量、在硬脂酸丙酮溶液中的浸泡时间等因素对所制得的PVDF平板膜结构和性能的影响。结果表明在该实验条件下的最佳改性方案为:在硬脂酸丙酮溶液中浸泡时间为3h,硬脂酸丙酮溶液的浓度为0.05mol/L,PEG-600的加入量为6ml,纳米颗粒Ti O2粉末的加入添加量为0.2g,温度为50℃。最后通过超滤杯、扫描电镜(SEM)、傅里叶红外光谱分析仪(FTIR)、接触角测量仪等仪器对制备的改性PVDF膜进行分析测试,得到如下结论:改性后的PVDF平板膜通量高于改性前,截留率比改性前也要高,并且改性后膜表面呈现的是微米结构,此结构是导致疏水的原因,从而说明改性是可行的。最后把改性后的膜应用到直接接触膜蒸馏装置中,研究料液温度、料液浓度和料液流速等因素对蒸馏过程的影响。通过实验得到膜蒸馏运行中最优的实验条件如下:料液温度为50℃左右最为适宜;考虑到浓差极化对膜污染的影响,选取料液浓度为15g/L;而料液流速对膜蒸馏通量的影响比较显著,因此实验选取5L/h作为实验的一个最优选择。同时在较优的实验条件(料液温度50℃、料液浓度15g/L和料液流速5L/h)下对所制得的膜应用脱盐实验去分析性能,冷却水侧冷却水的电导率值基本没有变化,表面改性后PVDF平板膜的脱盐率可以达到90%左右。
[Abstract]:Membrane distillation (membrane distillation MD) is the application of membrane to the distillation unit. The steam pressure difference caused by the temperature difference between the two sides of the membrane is used as the driving force for mass transfer to achieve the purpose of material separation. The membrane distillation unit can be divided into direct contact membrane distillation, vacuum membrane distillation, air-sweep membrane distillation, air gap membrane distillation, etc. In this paper, the preparation of PVDF flat membrane for direct contact membrane distillation is studied. Modification and separation properties. The effects of gel bath temperature, residence time and the amount of additives on the structure and properties of PVDF flat membrane were investigated. The results are as follows: the order of influence of three factors on the structure and properties of PVDF flat membrane is the residence time gel bath temperature. Under the experimental conditions, the best method for preparing PVDF flat membrane is as follows: the dosage of additive is 3% (W / W), the residence time (5 s), and the gel bath temperature (50 鈩，
本文编号：2131186
[Abstract]:Membrane distillation (membrane distillation MD) is the application of membrane to the distillation unit. The steam pressure difference caused by the temperature difference between the two sides of the membrane is used as the driving force for mass transfer to achieve the purpose of material separation. The membrane distillation unit can be divided into direct contact membrane distillation, vacuum membrane distillation, air-sweep membrane distillation, air gap membrane distillation, etc. In this paper, the preparation of PVDF flat membrane for direct contact membrane distillation is studied. Modification and separation properties. The effects of gel bath temperature, residence time and the amount of additives on the structure and properties of PVDF flat membrane were investigated. The results are as follows: the order of influence of three factors on the structure and properties of PVDF flat membrane is the residence time gel bath temperature. Under the experimental conditions, the best method for preparing PVDF flat membrane is as follows: the dosage of additive is 3% (W / W), the residence time (5 s), and the gel bath temperature (50 鈩，
本文编号：2131186
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