Ionic liquids are known as organic salts having very low melting point ( <100 ℃). This unique organic liquid shows unusual properties such as negligible vapor pressure, high ionic conductivity, and high charge density. These ionic liquids have been coupled with polymer membrane to design functional membranes showing properties of ionic liquids. Similarly, polymerizable ionic liquids, containing vinyl group(s) on component ions, have been polymerized to get polyelectrolytes with very low glass transition temperature. Further these were cross–linked to prepare polymer gels keeping some properties of ionic liquids. Among many ionic liquids, there are some ionic liquids showing different hydrophobicity depending greatly on the temperature. Especially there are some salts showing lower critical solution temperature (LCST)–type phase change after mixing with water. Thermo–responsive polymer gels were prepared with these ionic liquids. A few applications of such functional ionic liquids have been mentioned from the viewpoint of the contact points with membrane science.
Reverse osmosis (RO) separation is an effective separation method. RO membranes have been developing as polymeric membranes. The main application of the polymeric RO membranes is seawater desalination. However, the polymeric RO membranes hardly applied to the tough conditions such as high temperature, organic solution and acid or base conditions. Inorganic related materials (zeolites, amorphous silica, clay, metal organic framework etc.) are stable under such tough conditions compared with polymers. These materials have been developing as RO membrane materials. The first inorganic RO membrane was LTA zeolite RO membrane that have been reported at 2000. In this review, the recent developments of inorganic related RO membranes were summarized. The RO performances of NaCl solution through the inorganic related membranes were discussed, and the development of the amorphous silica membranes prepared by using a counter diffusion CVD method were also summarized.
Two–dimensional nanosheet membranes have opened up a new avenue for fabricating size–selective molecular separation membranes, benefiting from their unique atomic thickness with micrometer lateral dimensions, high mechanical strength and chemical inertness. In this review, recent developments of nanoporous and stacked nanosheet membranes using such as graphene–based materials are summarized. Stacked niobate nanosheet membranes with a stable structure in water and good membrane performances are also introduced.
Water treatment technology using hollow fiber membrane has been developed rapidly since the 1980s due to the strengthening of water and wastewater quality standards and the limited treatment capability of traditional rapid sand filtration. The technology has been applied to a variety of fields, such as water purification, wastewater treatment and pretreatment of seawater desalination, now being widely recognized as an advanced water treatment process. The process has been further improved recently in terms of performance and efficiency, attracting increasing attention as a leading technology that can enable energy–saving operation. Kuraray has developed a new hollow fiber membrane module that can realize higher water permeability and higher turbidity water treatment. This module consists of high flux hydrophilic PVDF membrane and accordingly shows significantly higher pure water permeability ( >50 m3/hr/mod/100 kPa). Moreover, SS resistance has been improved by employing the one–end–free fiber structure and an air and water distributor located at the center of the module. Kuraray is proceeding with the study to achieve higher design flux and pump free operation with this innovative product.
Since the 1970 's, Asahi Kasei has been producing and selling ultrafiltration (UF) and microfiltration (MF) membrane modules manufactured with its proprietary technology. As a recent achievement, Asahi Kasei has coupled graft polymerization technology to its proprietary technology and successfully developed a protein adsorption membrane module for refining antibody pharmaceuticals. The membrane of the module has graft chains produced on its micropore surface and an anion-exchange group is fixed to the graft chains to induce protein adsorption, which offers a high capability to adsorb protein even at high permeate flux. Furthermore, the elaborately designed structure of the module enables high scalability. This technical report introduces the design concept and characteristic performance of this protein adsorption membrane module newly developed.
Japan Vilene Company has been developing nanofiber nonwoven fabrics by using electrospinning method. Electrospinning is a useful and effective method to produce nanofiber nonwoven fabrics with fiber diameter of 1 m or less. The nanofibers obtained by this method are homogeneous long fibers, and the nanofiber nonwoven fabrics have high porosity and sharp pore size distribution. In this report, we describe our development examples using nanofiber technique such as substrate for polymer electrolyte membrane, conductive porous sheet and inorganic fibrous nano powders.
Nanofibrous materials, which are some of the one–dimensional nanomaterials, have unique properties compared to their bulk solids (e.g., high specific surface area, high electrical conductivity, and good electrochemical activity). They are easy to form a 2–D or 3–D network structure. This network structure enables an efficient charge transport through the network backbone and an efficient chemical reaction at the surface. This reports describes thin–film applications of nanofiber networks in energy storage and optoelectronic devices.
Environmental problems such as global warming, pollution in our cities and the depletion of fossil fuel resources have conspired to make both the development of renewable energy and the shift to electrical transportation crucial. Proton exchange membrane fuel cells, which efficiently convert chemical energy into electrical energy via oxidation and reduction reactions, are receiving considerable attention as an alternative energy source because of their high energy efficiency and no emissions of pollutants. Electrical transportation applications require the storage of a large amount of energy on board vehicles so as to enable long cruising distances. Recently, we have prepared all solid polymer electrolyte membranes composed of ion conductive nanofibers and revealed that the composite membranes showed a higher ion conductivity (i.e. proton or lithium ions) than the membrane without nanofibers. In this paper, we reported the properties of novel all solid electrolyte membranes comprising an ion conductive nanofiber framework as fuel cells and lithium ion batteries.
Phagocytosis of phosphatidylserine (PS)–exposed erythrocytes by splenic macrophages determines the end of their 120–day lifespan. PS is usually maintained in the inner leaflet of plasma membranes by active transport from the outer leaflet via flippase (aminophospholipid translocase) using ATP. Since ATP is generated only through glycolysis in erythrocytes, the ATP content may reduce during storage because of decreased ATP production and consumption. Nevertheless, no obvious evidence exists for the correlation between intracellular ATP content and PS exposure, we therefore investigated this correlation in blood stored up to 120 days. PS–exposed erythrocytes increased by over 60- day storage while ATP content decreased to less than 0.2 mol/mL RBC, which corresponded to the michaelis constant (Km) for flippase. The adenine/inosine (A/I) treatment resulted in increased ATP content to normal level and significant decrease in PS–exposed cells. However, this treatment was not effective for PS exposure on erythrocytes stored over 75 days, despite the restoration of ATP content to ～ 0.5 mol/mL RBC, suggesting that flippase may be inactivated irreversibly in those cells. We suggest that ATP content less than 0.2 mol/mL RBC triggers PS exposure via inactivation of flippase and that A/I treatment enables to decrease PS–exposed erythrocytes stored for up to 60 days.
In conventional Membrane BioReactor (MBR) systems, aeration is needed not only to provide oxygen to activated sludge but also to prevent submerged membranes from fouling. It is essential to reduce the aeration rate in order to develop cost–effective MBR systems because blowers consume a lot of energy. In this study, we present a new cakeremoval strategy toward more cost-effective MBR systems. This strategy is based on the cake–removal by uplifting water flow, which is generated by mixers or pumps. We demonstrated that Trans Membrane Pressure (TMP) did not increase without aeration when the uplifting flow is >0.55 m/s in laboratory scale examinations. Pilot scale experiments where aeration rate was exactly equal to biological Actual Oxygen Required (AOR) were also conducted, TMP jumps have not been observed. To explore feasibility of full–scale plant, fluid dynamics simulations were conducted.