UF membrane
Toray Industries, Inc. (Tokyo, Japan; www.toray.com) has developed a new polyvinylidene fluoride (PVDF) ultrafiltration (UF) membrane that has an “exceptional” virus removal rate, as well as a high water permeability, making it suitable for water purification. The company is accelerating application testing, with the aim to commercialize the technology.
Toray improved its PVDF UF-membrane technology to enhance pathogenic virus removal and water permeability without reducing safety or increasing costs.
In developing the improved PVDF UF-membrane, the challenge was to reduce pore diameters to remove viruses, without the resulting decrease in water permeability. Toray used phase-separation control technology to create a uniformly dense structure. By laminating layers that have homogeneous pore-size distribution, Toray created a uniform dense structure without coarse voids (exceeding 100 nm) through which viruses can pass. This uniform dense structure made it possible to create a thinner dense structure than conventional UF membrane, and showed 99.99% removal of the Essherichia coli phage MS2, which has a diameter of around 27 nm.
Because the dense structure increases resistance and impedes water flow, the company used a proprietary hollow-fiber membrane process technology to create a thin, uniformly dense structure. Excellent virus removal and water permeability was achieved by increasing the porosity in the bulk of the membrane, except for the uniform dense structure. This led to more water channels and boosted the overall membrane permeability.