膜蒸馏用抗污染PVDF膜的研究

发布时间：2018-08-07 18:00

【摘要】：膜蒸馏是用于分离水溶液的技术手段,在膜两侧水蒸汽压差的推动作用下,热侧膜表面产生的水蒸汽透过微孔膜到达冷侧并被冷凝收集,从而实现分离目的。膜蒸馏用膜研究的热点之一是提高膜的疏水性能以提高膜的抗无机污染能力。但是在膜蒸馏的实际应用过程中,多数被处理的料液不仅含有无机盐,而且含有有机物,在膜表面形成复合污染,因此提高膜的综合抗污染能力(抗无机污染和有机污染能力)是膜蒸馏膜研究的重要方向之一。本研究探索性地制备出了亲水-超疏水复合改性膜,以期获得优良的抗复合污染性能。首先,通过浸没沉淀法制备了聚偏氟乙烯(PVDF)平板膜。在铸膜液中二甲基甲酰胺(DMF)/N-甲基吡咯烷酮(NMP)为3:1的条件下,制备出了平均孔径为0.364μm、孔隙率为67.54%、接触角为112.94°的PVDF平板膜。其次,利用溶液相转移法对上述制备的PVDF平板膜进行了超疏水改性。当聚乙二醇(PG)的质量浓度为39%、PVDF的质量浓度为2%、涂覆液温度为50°C、蒸发时间为10s、凝固浴温度为60°C时,PVDF平板膜的接触角达到了154.8°。通过对改性后的PVDF超疏水膜进行直接接触式膜蒸馏实验发现,该膜具有优良的抗润湿性能和抗无机污染性能,并具有一定的抗有机污染性能。然后,在上述研究的基础上通过均相沉淀法对PVDF超疏水平板膜进行表面亲水化改性实验,优化出了PVDF亲水-超疏水膜的最佳改性条件,并对该复合膜的抗污染性能进行了研究。结果表明,改性液中纳米二氧化钛的质量浓度为43.6mg/L时被改性的膜具有最优性能;亲水-超疏水复合膜不仅具有优良的抗润湿性能和抗无机污染性能,而且其抗复合污染性能尤其是抗有机污染性能得到明显提升。本研究成果为进一步构建高性能膜蒸馏抗污染膜指出了一个可行的技术方向。
[Abstract]:Membrane distillation is a technical method for separating aqueous solution. Under the promotion of water vapor pressure difference on both sides of the membrane, the water vapor produced on the surface of the hot side membrane reaches the cold side through the microporous membrane and is condensed and collected to achieve the purpose of separation. One of the hotspots of membrane research for membrane distillation is to improve the hydrophobicity of membrane to improve its resistance to inorganic pollution. However, in the practical application of membrane distillation, most of the treated liquid materials not only contain inorganic salts, but also contain organic compounds, which form complex fouling on the membrane surface. Therefore, improving the comprehensive anti-fouling ability (inorganic pollution and organic pollution) is one of the important research directions of membrane distillation membrane. In this study, hydrophilic and superhydrophobic composite modified membranes were prepared in order to obtain excellent anti-pollution performance. Firstly, polyvinylidene fluoride (PVDF) flat membrane was prepared by immersion precipitation method. Under the condition that the dimethylformamide (DMF) / N-methylpyrrolidone (NMP) is 3:1, the PVDF flat membrane with average pore size of 0.364 渭 m, porosity of 67.54 and contact angle of 112.94 掳has been prepared. Secondly, superhydrophobic modification of the PVDF flat membrane was carried out by solution phase transfer method. When the mass concentration of polyethylene glycol (PG) is 39 and the mass concentration of polyethylene glycol (PG) is 2, the coating liquid temperature is 50 掳C, the evaporation time is 10 s, and the coagulation bath temperature is 60 掳C, the contact angle of the flat plate membrane reaches 154.8 掳. Through direct contact membrane distillation experiment of modified PVDF superhydrophobic membrane, it was found that the membrane had excellent anti-wetting performance and anti-inorganic pollution performance, and had certain anti-organic pollution performance. Then, on the basis of the above research, the surface hydrophilic modification of PVDF superhydrophobic plate membrane was carried out by homogeneous precipitation method, and the optimum modification conditions of PVDF hydrophilic-superhydrophobic membrane were optimized, and the antifouling performance of the composite membrane was studied. The results showed that the modified membrane had the best performance when the mass concentration of nano-TiO _ 2 in the modified solution was 43.6mg/L, and the hydrophilic-superhydrophobic composite membrane not only had excellent anti-wetting and anti-inorganic pollution properties, but also had the following advantages: 1. Moreover, the compound pollution resistance, especially the organic pollution resistance, was improved obviously. The results of this study point out a feasible technical direction for the further construction of high performance membrane distillation antifouling membrane.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.893

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