Ultrafast Permeation of Organic Molecules Realized Using Porous Nanosheet
Permeation Rate of Water Increased by 1000 Times through Development of Nano Thin Film
2009.04.27
National Institute for Materials Science
Researchers in the Functional Thin Films Group of the Organic Nanomaterials Center at the National Institute for Materials Science, in joint research with the First-Principles Simulation Group 1 of the NIMS Computational Materials Science Center, developed an innovative separation membrane which is capable of ultrafast removal of organic molecules with a size on the order of 1.5nm dissolved water, and succeeded in clarifying the mechanism of permeation of water in the membrane.
Abstract
- Researchers in the Functional Thin Films Group of the Organic Nanomaterials Center (Managing Director: Izumi Ichinose) at the National Institute for Materials Science (NIMS; President: Teruo Kishi), in joint research with the First-Principles Simulation Group 1 of the NIMS Computational Materials Science Center (Managing Director: Takahisa Ohno), developed an innovative separation membrane which is capable of ultrafast removal of organic molecules with a size on the order of 1.5nm dissolved water, and succeeded in clarifying the mechanism of permeation of water in the membrane.
- In water treatment membranes, the treatment speed increases in inverse proportion to the thickness of the membrane. For this reason, the development of ultrathin membranes capable of removing dissolved ions and molecules has been a subject of active research in Japan and other countries in recent years. Membranes of this type contribute to solving water problems around the world by removing harmful substances such as agricultural chemicals, viruses, and the like from groundwater and rivers, and application to the field of medical treatment is also expected, for example, in artificial dialysis membranes. Water treatment membranes must withstand a large pressure difference on both sides of the membrane. Therefore, such membranes are generally manufactured using inorganic materials with high mechanical strength, such as aromatic polymides, ceramics, silicon, and the like. However, due to the difficulty of designing nanoscale flow paths in ultrathin water treatment membranes, it was not possible to realize high treatment speeds.
- In this research, the NIMS research team succeeded in forming an ultrathin protein-based (ferritin) freestanding membrane with a thickness of 30-100nm by using ultrafine inorganic fibers, and also increased the mechanical strength of the membrane by using a crosslinking agent called glutaraldehyde. Because a countless number of water flow paths with diameters of approximately 2nm are formed in the freestanding membrane, water can be passed through the membrane at an extremely high speed while blocking organic molecules. The team demonstrated that it is possible to concentrate an organic dye (protoporhyrin) at a rate of 6,000L/h・m2・bar using an ultrathin film with a thickness of 60nm. When compared with existing membranes having the same molecular-weight cutoff, this treatment rate is approximately 1000 times faster than that of ultrafiltration membranes (or nanofiltration membranes).
- A portion of these research results was obtained as part of the Research Project “Macroscopic Properties of Liquids in Interfacial Nanopores” (Research Representative: Izumi Ichinose) in the JST-CREST Research Area “Development of the Foundation for Nano-Interface Technology” (Research Supervisor: Dr. Seiji Shinkai). A report on this achievement was published in the April 26, 2009 online edition of Nature Nanotechnology. (X. Peng, J. Jin, Y. Nakamura, T. Ohno and I. Ichinose “Ultrafast permeation of water through protein-based membranes,” DOI number: 10.1038/NNANO.2009.90)
Figure (a) Concentration of a dye (protoporphyrin) using a protein-based (ferritin) membrane and (b) cross-sectional scanning electron microscope (SEM) image of the membrane.