PVDF超滤膜进行聚乙二醇甲基丙烯酸甲酯（PEGMA）紫外光照射接枝的膜面表征与抗污染分析

发布时间：2018-09-10 13:54

【摘要】：聚偏氟乙烯(PVDF)因突出的化学、机械和热稳定性等功能性而广泛用于膜材料制备，但由于其较低的表面能、强疏水性导致在膜分离过程中容易产生膜污染，限制了其进一步的发展应用。目前，工业中广泛采用对PVDF膜进行共混改性、化学改性、光接枝等改性，提高其亲水性和抗污染性。本文利用紫外光辐照将含有亲水性基团羰基和聚乙二醇的聚乙二醇甲基丙烯酸甲酯(PEGMA)接枝到疏水性的PVDF超滤膜表面，完成膜的亲水改性。同时还发现，通过加入交联剂N,N-亚甲基双丙烯酰胺(MBAA)可以减少接枝层的溶胀性。该方法采用紫外光辐照接枝，不会损坏膜材料的本体性能，，并且工艺简单、成本较低。本文主要研究不同改性条件下的膜改性效果，通过各种测试手段对该型膜进行表征，利用乳化油溶液和牛血清蛋白(BSA)溶液分离效率和抗污染性，还将改性膜用酸碱及次氯酸钠溶液进行接枝层的稳定性测试。实验通过紫外光辐照将PEGMA接枝到膜上，利用傅里叶红外光谱(FTIR)对产物进行检测，结果表明，PEGMA成功的接枝到膜表面；通过场发射扫描电镜(FESEM)的结果表明，接枝改性后膜的孔径缩小和孔隙率降低。在膜表面润湿性方面，研究结果表明经PEGMA接枝改性后膜的亲水性增强，随着接枝浓度和时间的延长，膜表面接触角不断下降，如原膜的接触角为77°左右，经80g/L的PEGMA接枝60min后接触角为58°左右。对于水通量，实验发现经PEGMA接枝后，随着接枝浓度和接枝时间的增加，膜纯水通量不断在下降，如原膜的纯水通量为184.9L/m2·h左右，经40g/L的PEGMA接枝60min后，纯水通量为162.2L/m2·h左右；加入MBAA后，膜的吸水率出现相反的趋势，接枝浓度和接枝时间的增加，膜的吸水率在不断的下降，且加入MBAA后比单纯PEGMA接枝接触角略微上升，纯水通量略微下降。在模拟污染实验中，在过滤BSA溶液时，原膜在起始过滤时截留率低于改性膜，而随过滤时间延长，原膜的截留率高于改性膜，而单纯PEGMA接枝后的截留率低于加入MBAA后接枝膜的截留率。以乳化油溶液和BSA溶液为过滤介质研究膜的抗污染性的过程中，结果表明，膜的抗污染能力的大小顺序为原膜PEGMA+MBAA的接枝膜PEGMA接枝膜。将膜浸泡于酸碱及次氯化钠溶液中，通过对比，发现改性膜在这三种溶液中的稳定性顺序为酸性环境强氧化性环境碱性环境。本项目研究成果不仅可以拓宽制备高性能超滤膜的技术思路，还可以为膜材料探寻、分离工艺设计、膜工艺的运行管理等相关的研究提供技术支持。
[Abstract]:Polyvinylidene fluoride (PVDF) (PVDF) is widely used in the preparation of membrane materials because of its outstanding chemical, mechanical and thermal properties. However, because of its low surface energy and strong hydrophobicity, it is easy to cause membrane fouling during membrane separation. It limits its further development and application. At present, the modification of PVDF membrane by blending, chemical modification and light grafting is widely used in industry to improve its hydrophilicity and pollution resistance. In this paper, (PEGMA) containing hydrophilic group carbonyl group and polyethylene glycol was grafted onto the surface of hydrophobic PVDF ultrafiltration membrane by UV irradiation, and the hydrophilic modification of the membrane was completed. It was also found that the swelling of the grafted layer could be reduced by adding the crosslinking agent N- N- methylene bisacrylamide (MBAA). This method can not damage the bulk properties of the film by UV irradiation, and the process is simple and the cost is low. In this paper, the effect of membrane modification under different modification conditions was studied. The membrane was characterized by various test methods, and the separation efficiency and antifouling property of the membrane were obtained by using emulsified oil solution and bovine serum protein (BSA) solution. The stability of the grafted layer was tested by acid-base and sodium hypochlorite solution. PEGMA was grafted onto the film by UV irradiation, and the product was detected by Fourier transform infrared spectroscopy (FTIR). The results showed that the grafted PEGMA was successfully grafted to the surface of the film, and the results of field emission scanning electron microscopy (FESEM) showed that, The pore size and porosity of the graft modified membranes were reduced. In terms of surface wettability, the results show that the hydrophilicity of the membrane modified by PEGMA is enhanced, and the contact angle of the membrane surface decreases with the prolongation of the grafting concentration and time, such as the contact angle of the original membrane is about 77 掳. The contact angle of 60min grafted with PEGMA of 80g/L is about 58 掳. For the water flux, it was found that the pure water flux of the membrane decreased with the increase of the grafting concentration and grafting time after grafting with PEGMA, such as the pure water flux of the original membrane was about 184.9L/m2 h, and the pure water flux of the original membrane was about 162.2L/m2 h after the grafting of 60min with PEGMA of 40g/L. With the addition of MBAA, the water absorption of the membrane showed a reverse trend. With the increase of grafting concentration and grafting time, the water absorption of the membrane decreased, and the contact angle of MBAA increased slightly compared with that of pure PEGMA, and the pure water flux decreased slightly. In the simulated pollution experiment, when the BSA solution was filtered, the rejection rate of the original membrane was lower than that of the modified membrane at the beginning of filtration, but with the increase of the filtration time, the rejection rate of the original membrane was higher than that of the modified membrane. However, the rejection rate of PEGMA grafted membranes was lower than that of MBAA grafted membranes. The antifouling ability of the membrane was studied by using emulsified oil solution and BSA solution as the filtration medium. The results showed that the order of the antifouling ability of the membrane was the PEGMA graft membrane of the original membrane PEGMA MBAA. The membrane was immersed in acid-base solution and sodium hypochloride solution. By comparison, it was found that the stability of the modified membrane in these three solutions was in the order of acidic environment, strong oxidizing environment and alkaline environment. The research results of this project can not only broaden the technical thinking of preparing high performance ultrafiltration membrane, but also provide technical support for the research of membrane material exploration, separation process design, membrane process operation management and so on.
【学位授予单位】：东华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.893;X505

【参考文献】