The Preparation And Gas Seperation Properties Of MOFs/PDMS Mixed Matrix Membranes

Compared with other traditional separation methods, membrane separation technology has the advantages of high efficiency, energy and space saving. However, the current commercialized separating membrane materials mainly stand for polymer materials, which usually can not afford high selectivity and permeability at the same time. That is to say, they are of negative correlation. In order to overcome the limitation of polymer materials, adding functional particles during the membrane separation process becomes common. Because of the unique skeleton-type structure, large specific surface and organic-inorganic characters of Metal Organic Frameworks (MOFs), in this paper, that MOFs/polymer were mixed to form mixed matrix membrane (MMMs) and that MMMs were used for the separation of CO2/N2and nanofiltration of organic solvent were primarily studied.For the easiness of resources and synthesis, as well as the good thermal stability and chemical stability of HKUST-1and MIL-52, in this paper, these two MOFs were added into PDMS to form Mixed matrix membrane (MMMs). Besides, in consideration of the large amount of chromium ion in the electroplating waste water, and from the perspective of rational utilization of resources, this article coarsely researched the separation of wastewater simulated liquid and the forming process of MIL-53. As the result, the crystal structure and size distribution of MIL-53particles which was synthesized in the hydrothermal condition of220℃and36h were both good, which satisfied the requirement of the following study.At room temperature, these two kinds of MOFs were added into silicone rubber (PDMS), with polyether imide (PEI) or polypropylene (PP) ultrafiltration membrane as the base film to form the MMMs. The result of testing the influence of different activation condition, content and layer numbers showed that when adding HKUST-1and MIL-53after activation in the propotion of20wt.%and10wt.%separately, and coating2-3times, the MMMs formed had the best performance. Because of the increase of gas molecules hold degree of MOFs skeleton structure, the CO2/N2and O2/N2selectivity of MMMs with HKUST-1reached separately1.3and1.4times as the MMMs without modified particles. Meanwhile, the O2flux increased to123%, and CO2flux increased to130%; As to the MMMs with MIL-53, the CO2/N2selectivity achieved1.56times as well. At last, the solvent resistant nanofiltration separation performance of MMMs was studied in this experiment. Choosing rhodamine B/isopropanol as the separation system, for the MMMs with10wt.%MIL-53, the rejection rate of rhodamine B rose from86.5%to94.5%. Also, the MMMs ran well in the8hours-long test in solvent condition, which proved the stable performance and strong solvent resistant ability.