A New Alternative Desalination Membrane

Schematic of a coaxial electrospinning device. Credit: Elsevier

A new alternative seawater desalination membrane for producing drinking water.

According to the World Health Organization, about 785 million people worldwide lack clean drinking water sources. There is a huge amount of water on the earth, but most of it is seawater, and freshwater accounts for only about 2.5% of the total. One way to provide clean drinking water is to desalinate the seawater. Korea Civil Engineering and Construction Technology Research Institute (KICT) announced the development of an electrospinning nanofiber membrane with stable performance that converts seawater into drinking water by a membrane distillation process.

Membrane wetting is the most difficult problem in membrane distillation. If the membrane is wet during the membrane distillation operation, the membrane needs to be replaced. Progressive membrane wetting has been observed, especially with long-term manipulation. When the membrane is completely wet, the feed passes through the membrane and leads to poor quality permeate, leading to inefficient membrane distillation performance.

KICT’s research team, led by Dr. Yunchul Woo, has developed a coaxial electrospinning nanofiber membrane manufactured by an alternative nanotechnology called electrospinning. This new desalination technology shows that it may help solve the global desalination shortage. The developed technology can prevent the problem of wetting and improve the long-term stability of the membrane distillation process. The three-dimensional hierarchical structure should be formed by nanofibers in the membrane for higher surface roughness and therefore better hydrophobicity.

Coaxial electrospinning nanofiber membrane

Benefits of coaxial electrospinning nanofiber membranes. Credit: Elsevier

Coaxial electrospinning technology is one of the most advantageous and easy options for producing membranes with a three-dimensional hierarchical structure. Dr. Wu’s research team used poly (vinylidene fluoride-co-hexafluoropropylene) as the core and silica airgel mixed with a low-concentration polymer as the sheath to generate a coaxial composite film, which is superhydrophobic. Obtained the surface of the sex membrane. In fact, silica airgels have a much lower thermal conductivity compared to traditional polymers, and the reduced conduction heat loss increases the water vapor flux during the membrane distillation process.

Most studies using electrospinned nanofiber membranes for membrane distillation applications have shown high water vapor flux performance, but have worked in less than 50 hours. On the contrary, Dr. Wu’s research team applied a membrane distillation process using manufactured coaxial electrospinning nanofiber membranes for 30 days, or 1 month.

Coaxial electrospinning nanofiber membranes performed 99.99% salt removal for one month. Based on the results, the membrane worked well without wetting or fouling problems due to its low sliding angle and thermal conductivity. Temperature polarization is one of the major drawbacks of membrane distillation. Conductive heat loss can reduce water vapor flux performance during membrane distillation operations. Because this membrane has several important properties such as low sliding angle, low thermal conductivity, avoidance of temperature polarization, and reduction of wetting and fouling problems while maintaining supersaturated high water vapor flux performance. Suitable for long-term membrane distillation applications.

Dr. Wu’s research team pointed out that it is more important to have a stable process than high water vapor flux performance in a commercial membrane distillation process. “Coaxial electrospinning nanofiber membranes are likely to process sea aqueous solutions without suffering from wetting problems and may be suitable for pilot-scale and real-world membrane distillation applications,” said Dr. Wu. It states.

Reference: “Coaxial electrospinning superhydrophobic nanofiber membrane with 3D hierarchical surface for desalting by long-term membrane distillation” Yun Chul Woo, Minwei Yao, Wang-Geun Shim, Youngjin Kim, Leonard D. Tijing, Bumsuk Jung, Seung-Kim Hyun and Ho Kyung Sung, January 4, 2021 Membrane science journal..
DOI: 10.1016 / j.memsci.2020.119028

The Korea Civil Engineering and Building Technology Research Institute (KICT) is a government-sponsored organization established to contribute to the development of the Korean construction industry and the national economic growth by developing sources and practical technologies in the fields of construction and land management. It is a research institute.

This study was supported by an internal grant (20200543-001) from KICT in the Republic of Korea. The results of this project have been published in an international journal. Membrane science journal, April 2021, a well-known international journal in the field of polymer science (IF: 7.183 and rank # 3 in the JCR category).

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