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Researcher team of Jiang Heqing, Qingdao Institute of Energy Research, Chinese Academy of Sciences has made new progress in the research of high-performance nanocomposite membranes
2020-01-06 Source: Polymer Technology

Reverse osmosis technology based on polyamide membrane is one of the effective ways to achieve seawater desalination. Introducing nanomaterials such as zeolite molecular sieves, mesoporous silica, and carbon nanotubes into polyamide membranes can improve the water flux of composite membranes. Due to the poor interface compatibility between common nanomaterials and polymer matrices, the separation selectivity of composite membranes will be significantly reduced while increasing the water flux. In response to this problem, a team of researchers from the Jiangheqing Institute of Qingdao Energy Research Institute of the Chinese Academy of Sciences recently used amine-functionalized mesoporous polymer spheres as a filler material. Nanocomposite membrane with high water flux and high salt rejection.

First, the group synthesized mesoporous polymer beads (NMPS) using a soft template method. Its size is 66 5 nm. It has good monodispersity, rich amine functional groups, and large mesoporous pore size. 5.6 nm. These characteristics laid the foundation for the dispersion of NMPS in polymer films and the improvement of composite film properties.

Figure 1. Schematic diagram of high-performance nanocomposite membrane design

Figure 2.Characterization of mesoporous polymer beads; (a, b) TEM image, (c) NMPS sol photo, (d) NMPS size distribution diagram, (d) N2 adsorption and desorption isotherm and pore size distribution diagram

The team further prepared mesoporous polymer sphere (NMPS) -doped polyamide nanocomposite films by interfacial polymerization, and adjusted the interfacial microstructure between the NMPS doped amount and the polyamide matrix. -2 h -1 ,比纯聚酰胺膜提高了62%,同时其截留率达98.7%,与聚酰胺膜持平。 At a test pressure of 16 bar, the separation performance of the nanocomposite membrane for NaCl solution was investigated. The results showed that the optimal composite membrane water flux was 55 L m -2 h -1 , which was 62% higher than that of pure polyamide membrane. The rejection rate is 98.7%, which is the same as the polyamide film. By taking advantage of the rich mesoporous structure of NMPS and the advantages of amine functional groups, the "trade-off" effect between flux and rejection in the composite membrane was effectively overcome, and the goal of simultaneously improving both was achieved.

Figure 3. Nanocomposite membrane separation performance diagram

In addition, the team also explored the separation mechanism of nanocomposite membranes. The separation performance of nanocomposite membranes mainly depends on the interaction between the continuous phase of the polymer and the nanomaterial. A certain amount of NMPS can be uniformly dispersed in the polyamide matrix and has good interfacial compatibility with the polymer. The introduction of mesoporous channels in the composite membrane while ensuring the integrity of the separation layer can therefore increase the water flux at the same time. And rejection rate; when a large amount of NMPS is incorporated into the film, the nanomaterials first form larger aggregates, so their dispersion in the polymer matrix is limited, and at the same time, some uncontrollable defects will be introduced, causing the rejection rate to decrease , Film performance is attenuated. This research work provides a new idea for the design and development of high-performance nanocomposite films.

Figure 4. Exploration of the separation mechanism of nanocomposite membranes

Related results were published in the Journal of Membrane Science (J. Membr. Sci., DOI: 10.1016 / j.memsci. 2019.117783). The first author of the paper is Song Xiangju , PhD student of Qingdao Institute of Bioenergy and Process, Chinese Academy of Sciences, and the corresponding authors are Researcher Jiang Heqing and Researcher Wang Guanghui .

Paper link: http://doi.org/10.1016/j.memsci.2019.117783

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