Separation and recovery of CO2 are one of the most important issues to prevent global warming problem. Several techniques have been developed, and RITE is now developing the molecule gate membrane, through which CO2 selectively permeates from CO2/H2 mixed gas, as a member of Molecular Gate Membrane module Technology Research Association (MGMTRA). The membrane performance depends on CO2 partial pressure, and for the feed of CO2/H2 of 40/60 vol/vol and total pressure of 2.4 MPa, CO2 permeance is 1 × 10–10 m3 (STP) m–2 s–1 Pa–1 and separation factor is 20 ～ 25 at CO2 partial pressure of 960 kPa, and 5 × 10–10 and 170 ～ 180 at 250 kPa. Long term durability is important for practical application, and the membrane showed stability for 600 h at 2.4 MPa operation. It is necessary to manufacture membrane with large membrane area and to produce membrane element, and MGMTRA has succeeded in manufacturing membrane with large membrane area by a continuous membrane–forming method. MGMTRA is now developing technology to produce membrane elements.

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In terms of greenhouse gas mitigation, an increase of natural gas demand has been expected. In most cases, natural gas from the well contains CO2 with up to a few tens %, and the CO2 should be removed to produce sales gas or liquified natural gas. JGC Corporation and NGK Insulators have established natural gas sweetening processes with a DDR type zeolite membrane. NGK has developed the DDR type zeolite membrane element with excellent CO2 selectivity and permeability over CH4 and succeeded in scaling up the membrane area to commercial size. With fabrications of the membrane module and the skid, JGC has investigated total CO2 capture processes using the membrane. Herein, features and current progress of the natural gas sweetening process by the DDR type zeolite membrane are reviewed.

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Stable, inexpensive and high–performance CO2 permeable membranes are of significant interest as materials for post–combustion CO2 capture. In this paper, we report that defect–free hydrogel membranes of thickness around 100 nm can be easily prepared by deposition of the hydrogel microparticles containing amines on the surface of porous support. The membranes showed CO2 selective permeability against N2.

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Carbon membranes are a type of inorganic membranes in which the active separation layer consists of carbon or carbides. Carbon membranes have excellent gas and vapor separation performances due to the molecular sieve effect. Carbon membranes can be applied to the separation of corrosive gases and organic solvents by taking advantage of the chemical resistance of carbon. This article summarizes our recent research and developments of carbon hollow fiber membranes in the field of chemical separation processes from a practical application perspective. The development of fabrication technique of carbon membrane modules is also discussed.

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Reverse osmosis (RO) membrane technology has been developed well since half century ago. Because of new threats like global warming and increasing clean water demand in developing countries for economic growth, new challenges on the conventional water supply systems, making it lower energy consumption for system operation and more robust membranes technology have been demanded. Nanocarbons such as carbon nanotubes have been a leading material of the emerging nanotechnology, and have contributed to environment and energy era. Nanocarbons are defined as carbon materials with innovative performances by controlling their structure in nanometer scale. We have been working to apply such advanced nanocarbons to form a thin composite as active layer for RO membranes and also intrinsic nanocarbon membranes by structure controlled diamond–like carbon (DLC) as an inorganic membrane. In the present review, CNT/PA nanocomposite membranes, nitrogen doped DLC membranes and graphene/graphene oxide composite membranes are demonstrated as new nanocarbon–based membranes with antifouling/chlorine resistant robust performances. Theoretical approaches based on computational chemistry have been done to explain these specific performances of nanocarbon membranes. We hope these new membranes and the related science can contribute to breakthrough for beyond the well–developed conventional membrane technology for the era of water and nanotechnology.

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Polysaccharides were considered as key foulants in membrane bioreactors (MBRs). In our recent studies, it was shown that polysaccharides causing membrane fouling in MBRs had the structures of lipopolysaccharides (LPSs), which are components of the cell wall of gram–negative bacteria. In the present study, membrane fouling caused by commercially available LPSs was investigated and was compared with that caused by other model polysaccharides used in previous studies. In a series of batch filtration tests using different microfiltration (MF) and ultrafiltration (UF) membranes, regardless of the membrane used, LPSs caused more severe membrane fouling than did alginate or dextran. The properties of LPSs were found to be considerably different from those of alginate and dextran. The results obtained in this study clearly showed the high fouling potential of LPSs.

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Reverse osmosis (RO) is one of the representative membrane separation technologies for separation of solute and solvent molecules such as desalination of seawater. Forward osmosis also attracts attention as a new separation method for energy saving and efficient concentration or desalination processes. The recent advance of molecular simulations for RO membranes in five years has been astonished. Also, the application of molecular simulation to study of FO membrane processes is in progress more and more. Molecular simulations under realistic experimental conditions can be implemented for RO membrane processes, and the reliability of simulation results is getting higher. For development of FO membranes, molecular simulations would be a useful tool for design of a novel water channel and characterization of its properties. The role of molecular simulations in development support of high performance separation membranes is expected to become expanded further in near future.

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MBR (Membrane Bio Reactor) was marketed in the 1990s. It was started to a small wastewater treatment plant at first. After then, MBR market spread to large–scale municipal wastewater treatment plant. For industrial wastewater treatment plant, many reclamation plants are operated. In the future, MBR targets various next generation technologies, for example effective utilization of the MBR’s activated sludge biomass.

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For large scale use of renewable energy, hydrogen society is necessary to overcome supply and demand mismatch in time and space. Polymer–electrolyte fuel cells (PEFCs) represent a superior system that exhibits high–efficiency, offering better power generation, meeting the desired levels of demand. However, in order to facilitate widespread use of fuel cells, cost and lifetime problems must be resolved. Solid alkaline fuel cells (SAFCs) are another system that holds the potential to achieve high–energy conversion efficiency without Pt catalysts. Although most of metal catalysts can be used under alkaline environment, development of durable electrolyte membranes in alkaline media is the key for this technology. We are systematically designing and developing new materials from the molecular level to the device level. In the fuel cell systems, different components such as membrane, catalysts, and catalyst layer share significant functions and work in a well–coordinated manner, and hence, the total cell system must be optimized for the best performance. The systematic design and developing approaches concerning membranes for PEFCs and SAFCs are proposing.

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Hydrogen stations, which are being developed for fuel cell vehicles, and examples of hydrogen use other than fuel cell vehicles, from the current state of hydrogen use in industrial fields are introduced. Use of hydrogen has been spreading from industrial use to energy applications including fuel cell vehicles. Commercial sales of fuel cell vehicles have started, and construction of a hydrogen refueling stations that supplies hydrogen to fuel cell vehicles is also proceeding. Efforts to manufacture and utilize hydrogen by using renewable energy have also begun. Region and demand will be expanded more than ever so it is required to construct a stable and efficient hydrogen supply system accordingly.

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Recent progress of metallic membranes, especially on those of palladium (Pd) alloys and vanadium (V) alloys is reviewed. On Pd alloy membranes, alloying effects of 5 and 6 group metals to suppress interdiffusion between Pd plate and Fe oxide particles are shown. Also, anomalous temperature dependence of hydrogen permeability in Pd–Ag alloy is shown, suggesting new possibilities of alloy design for Pd alloy membranes to be used in lower operating temperatures. On V alloys, recent topics obtained in JST–CREST project “Development of Innovative Hydrogen Production Technology from Energy Carriers Based on Vanadium Alloy Membranes” are introduced. It is highlighted that high hydrogen flow rate over 9 L/min. has been achieved using a quadruple–layered flat membrane device from a gas mixture of 3H2 ＋N2.

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Silica–based membranes for molecular separation, which includes both pure silica (SiO2) and organosilica, are reviewed. A new trend to fabricate silica–based membranes is summarized from the viewpoints of materials (ion–doping, organosilica, carbonized–template silica), structure control (interlayer–free, layered structure, hydrophobic intermediate layer), and fabrication processes (high–temperature firing, plasma–enhanced CVD, interfacial polymerization). Important applications to membrane reactors and the stability of organosilica membranes under hydrothermal conditions are introduced.

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Cellulose triacetate (CTA) has been used as a material for Reverse Osmosis (RO) membrane for many years, thanks to its superior chlorine resistance and high salt rejection. Recently, Forward Osmosis (FO) technology using osmotic phenomena between permselective membranes has drawn attention as a way of low energy desalination and water reclamation and reuse. Under these circumstances, CTA hollow fiber membrane for FO has been developed and its characteristics, performance and modules have been studied. Newly developed CTA hollow fiber membranes for FO can be applied to various FO operations. Therefore the design of hollow fiber membranes and modules needs to be optimized for each application including its pressure loss of feed solution and draw solution, and permeate flow rate.

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