Toray Industries, Inc. (headquarters: Chuo-ku, Tokyo; President: Akihiro Nikkaku; hereinafter referred to as “Toray”) today announced that it has succeeded in developing an ultralow pressure, highly durable reverse osmosis (RO) membrane1) with high water permeability and high durability by leveraging its proprietary microstructure control technology.
Toray polished the technology to form fine pores (which lets water molecule pass while blocking sodium ion, etc.) in the RO membrane and improved water permeability while maintaining its superior capability to remove ions and organic compounds. This enabled water treatment with lower pressure, resulting in energy saving of about 30%.
At the same time, the newly developed RO membrane is highly durable (the ability to sustain its performance to remove substances) against chemical cleaning, which is carried out during operation of water treatment plant to clean membranes when they become clogged with foreign substances in raw water. The membrane is expected to contribute to reduction of water treatment cost in applications such as brackish water desalination and wastewater treatment where chemical cleaning is required even more frequently because of the low quality of raw water.
Toray aims to commercially launch the new membrane in 2014 and will aggressively pursue sales expansion in the global market including Europe, North America, Latin America as well as in China and India among other Asian countries.
In recent years, RO membranes have gained popularity in water treatment plants around the world for addressing water problems (water shortage, water quality deterioration, etc.). There has been increasing requirement for improving removal properties to secure high quality water and enhancing water permeability to carry out the treatment with low energy. Demand for enhancement of durability of RO membranes against chemical cleaning and in long-term use has been especially strong to ensure consistent supply of high quality water from raw water with varying qualities, as the use of RO membranes expands significantly.
To meet the demands, Toray made efforts to stabilize pore structure against changing conditions by controlling the pore structure on a sub-nanometer scale2). As a result, in 2011 it succeeded in the development of a new RO membrane3) with drastically high durability.
Subsequently, Toray worked on combining the new technology of high water permeability with the highly durable RO membrane and succeeded in its development.
The technological highlights of the newly developed ultralow pressure, highly durable RO membrane are the two key points based on which microstructure control was performed.
1. Stabilization of fine pore structure through control of the primary structure
Functional layer of a reverse osmosis membrane is formed of a material of cross-linked polyamide4) with fine pore structure. Toray in the past has successfully developed membranes with high boron5) removal capability through control of pore size based on analytical study of the pore structure using positronium annihilation lifetime spectroscopy (PALS)6) and molecular dynamics simulation method7).
This time, it carried out in-depth analysis of the primary structure8) of cross-linked polyamide using nuclear magnetic resonance spectrometry9) and succeeded in establishment of the precise interfacial polymerization10) to stabilize the primary structure based on the information obtained in the analysis. This enabled the formulation of the functional polyamide layer whose fine pore structure is stable in changing environment and stronger against chemicals including acids, alkalis, and small amount of chlorine.
2. Increased number of fine pores by controlling intermolecular interactions
Toray achieved high water permeability of RO membrane which can be operated with low pressure by increasing the number of fine pores, as it expanded the minute spaces between polyamide molecules, through which usually water molecules do not permeate, by controlling interactions of cross-linked polyamide molecules.
Toray, by combining its four core technologies such as organic synthetic chemistry, polymer chemistry, biotechnology, and nanotechnology, so far has successfully developed RO membranes with high boron removal capability and low fouling membranes11) among high-functioning other RO membranes, and these products have won high acclaim around the world as Toray’s unique advanced materials.
The development of the ultralow pressure, highly durable RO membrane further diversifies the solutions it offers and is expected to contribute to solving the global water-related problems.
