PVDF超疏水性膜制备及应用研究

发布时间：2018-07-26 13:39

【摘要】：温室气体CO_2成为全世界关注的热点,碳减排成为亟待解决的问题。膜吸收法脱除烟气中的CO_2具有运行费用低、避免环境二次污染的特点,但CO_2脱除效率受膜润湿行为的影响。超疏水性膜能够有效地减缓膜润湿行为,在膜吸收法碳捕集中有广阔的应用前景。传统的聚偏氟乙烯(PVDF)膜具有很好的疏水性,但却不能满足膜吸收法碳捕集的需要,因此,进一步提高PVDF膜的疏水性是其应用于碳捕集的关键。本文通过相转化法制备PVDF基膜,再经表面涂覆改性,增强了PVDF膜的疏水性,能够在膜吸收法碳捕集中稳定运行。首先,采用相转化法制备PVDF基膜,研究了凝固浴组成、致孔剂种类及添加量、PVDF固含量、铸膜液挤出速率对PVDF基膜疏水性、气通量、孔径及孔隙率的影响,确定了最佳基膜制备工艺,制备了气通量大、疏水性高的PVDF基膜。研究结果表明:以60wt.%的乙醇配制乙醇/乙酸乙烯酯为凝固浴,PVDF固含量为16wt.%,添加剂为5wt.%的PEG-400,铸膜液挤出速率为6mL·min-1时,制得基膜孔径小(0.975μm)且孔隙率大(75.12%),使得膜气通量也变大,达到276.09m3·m~(-2)·h~(-1),其中最为显著的变化是接触角增大到131.43°,具有较强的疏水性。其次,采用表面涂覆法对PVDF基膜进行超疏水改性,通过测试孔径、孔隙率、气通量及接触角,研究了分散剂、无机纳米粒子种类及添加量、胶黏剂聚二甲基硅氧烷(PDMS)添加量、硅烷偶联剂(KH-550)添加量对超疏水性PVDF膜性能的影响,优化涂覆工艺,制备了性能良好的PVDF超疏水性膜。研究结果表明:以异丙醇为分散剂,纳米CaCO3添加量为1wt.%,PDMS添加量为1.5wt.%,KH-550添加量为1wt.%,制得涂覆液,喷涂于PVDF基膜表面,接触角由131.43°提高到147.06°,疏水性显著提高,气通量为264.12m3·m~(-2)·h~(-1),膜孔径为0.959μm,孔隙率74.88%,气通量、孔径及孔隙率相较于未改性前均有所降低。最后,进行膜吸收法脱除模拟烟气中CO_2实验研究,考察了吸收液与膜的匹配性;研究了吸收液种类,浓度,烟气流量对CO_2脱除率的影响。结果表明:氨基乙酸钾(PG)吸收液与改性PVDF膜的匹配性最好;相同浓度PG和MEA吸收液的CO_2脱除率前者高于后者,吸收液浓度为2mol·L-1最宜,烟气流量增大CO_2脱除率降低。当PG吸收液浓度为2mol·L-1,烟气流量为0.06m3·h-1时,CO_2脱除率达81.43%。
[Abstract]:Greenhouse gas CO_2 has become a hot spot all over the world, and carbon emission reduction has become an urgent problem. The removal of CO_2 from flue gas by membrane absorption method has the characteristics of low operating cost and avoiding secondary environmental pollution, but the removal efficiency of CO_2 is affected by the membrane wetting behavior. Superhydrophobic membranes can effectively slow down the wetting behavior of membranes and have a broad application prospect in carbon capture by membrane absorption. The traditional polyvinylidene fluoride (PVDF) membrane has good hydrophobicity, but it can not meet the needs of carbon capture by membrane absorption method. Therefore, further improving the hydrophobicity of PVDF membrane is the key to its application in carbon capture. In this paper, PVDF substrate was prepared by phase inversion method, and then modified by surface coating. The hydrophobicity of PVDF film was enhanced, and the membrane could be concentrated and stable in carbon capture by membrane absorption method. Firstly, the phase inversion method was used to prepare PVDF substrate. The effects of coagulation bath composition, kinds of pore-forming agents and the amount of PVDF solid added, the extrusion rate of casting liquid on the hydrophobicity, gas flux, pore size and porosity of PVDF substrate were studied. The optimum preparation process was determined and the PVDF substrate with high gas flux and high hydrophobicity was prepared. The results showed that when ethanol / vinyl acetate was prepared with 60 wt.% ethanol as coagulation bath, the solid content of ethanol / vinyl acetate was 16wt.10, the additive was PEG-400 with 5wt.% additive, and the extrusion rate of casting solution was 6mL min-1, the pore size of the base membrane was 0.975 渭 m and the porosity was 75.12%, which resulted in the increase of membrane gas flux. When 276.09m3 m-2 h-1 is reached, the most significant change is the increase of contact angle to 131.43 掳, which has strong hydrophobicity. Secondly, the superhydrophobic modification of PVDF substrate was carried out by surface coating. By measuring pore size, porosity, gas flux and contact angle, the dispersant, the type and amount of inorganic nanoparticles and the amount of polydimethylsiloxane (PDMS) were studied. The effect of the amount of silane coupling agent (KH-550) on the properties of superhydrophobic PVDF films was investigated. The excellent PVDF superhydrophobic films were prepared by optimizing the coating process. The results showed that the coating solution was prepared by using isopropanol as dispersant, nano-scale CaCO3 was 1.5wt.and KH-550 was 1wt.5. the contact angle was increased from 131.43 掳to 147.06 掳, and the hydrophobicity was improved significantly. The gas flux is 264.12m3 m ~ (-2) h ~ (-1), the membrane pore size is 0.959 渭 m, the porosity is 74.88, and the air flux, pore size and porosity are lower than those before modification. Finally, the experimental study on the removal of CO_2 from simulated flue gas by membrane absorption method was carried out, and the matching between the absorbent and the membrane was investigated, and the effects of the type, concentration and flow rate of the absorbent on the removal rate of CO_2 were studied. The results showed that the potassium aminoacetate (PG) absorbent had the best match with the modified PVDF membrane, the CO_2 removal rate of the same concentration PG and MEA absorbent was higher than that of the latter, the optimum concentration of the absorbent was 2mol L-1, and the removal rate of CO_2 decreased with the increase of flue gas flow. When the concentration of PG absorbent is 2mol L-1 and the flue gas flow rate is 0.06m3 h-1, the removal rate of CO2 is 81.43.
【学位授予单位】：东北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ051.893

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