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Metal membrane for solar concentrator
News and Views
Composite membrane fabrication procedure 200 nm-diameter ores Sputter s thin (50 nm) layer of Au and attach a Cu lead wire
nopore support membrane
| Au layer
lead wire oxy Coat with 1 to 2 l~m thick Nation film
/ | Nation film
Anopore support
demonstrated using a simple cell divided by the composite, one half containing an electrolyte as a receiver solution and the other half containing the biomolecule to be released. The Nation film on the composite faces the solution containing the biomolecule, preventing the release of the large molecule into the receiver solution. Electro-release is initiated by passing a ~mall electric current through the gold film electrode which forms the central part of the composite. The current causes hydrogen to be evolved at the gold/ Nation interface, which in turn leads to rupturing of the Nation film layer. The solution containing the macromolecule is then able to flow through the membrane into the receiver solution. Thin films could be employed for in rive use, for easy release by a very small currents. Systems are envisaged consisting of multiple segments, addressable individually, so that release rates can be controlled by the number of segments activated. Implanted insulin delivery devices are foreseen as a potential use. The system and the experimental work are described in more detail in Journal of the Electrochemical Society, 1990, 137, p.2005.
Microencapsulation Encapsulation of drugs by conventional synthetic polymers involves the use of heat or organic solvents, which are often unsuitable for delicate naturally derived products such as proteins or liposomes. Equally natural polymers, such as alginate from seaweed extract, can be used but these may have biocompatibility problems. A new and novel synthetic polymer, which forms
Membrane Technology
a gel at room temperature, has been developed which is said to overcome these drawbacks to drug microencapsulation. Researchers at Massachusetts Institute of Technology and Pennsylvania State University have reported the development of a polyphosphazene, which gells in water by the addition of divalent cations {] Am Chem Soc, 1990, 112, 7832). The gel matrices can be used to encapsulate mammalian ceils, proteins and liposomes at room temperature without solvents. Poly[his(carhoxylatophenoxy)phosphazene], PCPP, is soluble in monovalent basic solutions such as sodium carbonate, but the addition of calcium ions results in rapid gelling, possibly by the formation of salt bridges between carboxylic groups of adjacent polymer chains, creating a crosslinked matrix.
O
0 ~C--OH Microspheres can be formed from the gel, which appears to have low toxicity, from experiments with cultured liver cells.
Nova sells geomembranes unit Nova Corp, Calgary, Alberta, Canada, has announced it has sold its geomembranes business, as part of a strategy to focus on resin production. The geomembranes operation was the company's only plastics processing activity, and the company will now concentrate on producing and selling resin. The business has been acquired by National Seal Co of Chicago for an undisclosed sum.
Metal membrane for solar concentrator Sandia National Laboratories and Dallas, Texas, based Solar Kinetics Inc have developed and tested a solar concentrator for electricity production based on a parabolic stretched metal membrane.
3
News and Views
Instead of the usual glass mirrors, the single facet dish is fabricated from a thin metal membrane in a hydraulic vacuum process and covered with a polymer film. The steel membrane made in this way is less expensive to fabricate to high tolerances than glass and weighs far less. In operation the 7m diameter dish tracks the sun, using computer assisted guidance, and reflects sunlight onto a receiver at the focal point of the dish. Concentration of light at the focal point is 5000 times greater than direct sunlight.
Grafted hollow fibre A research group at Kyushi University, Japan, has succeeded in grafting water soluble vinyl monomer to the surface of a tetrafluorethylene hollow fibre. The modified fibre obtained is capable fixing enzymes and also of efficiently concentrating/ separating metal ions, and retains activity for several thousand hours. The process, developed by a research group under Professor C Kajiyama, involves grafting under plasma discharge in a vacuum/inert gas. Under the action of the plasma, the fibre is brought into contact with acrylamide or acrylic acid, which polymerizes on the surface of the fibre at 25°C. Water soluble vinyl monomer is then chemically bound to the fibre, producing an insoluble graft polymer.
Pall sets up in UK In what has been said to be the company's first manufacturing investment in health care devices outside the USA, Pall has recently completed the construction of a new factory for membrane based health care products at St Columb, Cornwall, England. Pall Europe will manufacture state-of-the-art membrane products for diagnostics, blood filtration, breathing apparatus and other health care products at the site.
High purity nitrogen from UCIG Union Carbide Industrial Gases, USA, has introduced a range of modular, skid-mounted membrane units for production if nitrogen up to
4
99.9995% purity at rates from 8000 to 30,000 ft3/hr. Ultra-high purity nitrogen is required for inert atmospheres, purging and cooling, and for pressurized liquid transfer. To attain the ultra-high purity, nitrogen obtained by membrane separation of air is subjected to a further treatment step to remove remaining traces of oxygen. The gas is passed over a palladium catalyst and contacted with hydrogen, the resultant water vapour being subsequently condensed at dew points between -40°F and -80°F. UCIG say that the combined process is still much cheaper (the customary 20-50% is claimed) than conventional cryogenic air fractionation.
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High performance filter discs A new range of high performance filter discs based on polyamide membranes has been launched by Sartorius Filtration. The Sartolon 250 discs are some of the first products scheduled for manufacture at the company's recently completed new factory in Germany, and replace the Sartolon 200 series. The new range sells at the same price as the previous range but offers improved performance; maximum sterilisation temperature is increased from 127°C to 134°C. Also, greatly improved flow rates are claimed, on account of the more pronounced asymmetry, and the new membrane material is said to be tougher and more resilient. The product is more resistant to creasing. The company says the new introduction demonstrates its policy of offering more and better products for the same money.
Separation AIChE's 13th division The American Insitute of Chemical Engineers was set to ratify at its Chicago annual meeting, 5-30 November, the creation of Separation as its thirteenth specialities division. A division definition committee meeting is set for Orlando, and a formation committee meeting at Buffalo in June. Formation of a programme will begin at the institute's summer national meeting in August 1991. First formal divisional elections are scheduled for Autumn 1991. Separation has always been a core activity in chemical engineering, and is now a rapidly changing
Membrane Technology
Composite membrane fabrication procedure 200 nm-diameter ores Sputter s thin (50 nm) layer of Au and attach a Cu lead wire
nopore support membrane
| Au layer
lead wire oxy Coat with 1 to 2 l~m thick Nation film
/ | Nation film
Anopore support
demonstrated using a simple cell divided by the composite, one half containing an electrolyte as a receiver solution and the other half containing the biomolecule to be released. The Nation film on the composite faces the solution containing the biomolecule, preventing the release of the large molecule into the receiver solution. Electro-release is initiated by passing a ~mall electric current through the gold film electrode which forms the central part of the composite. The current causes hydrogen to be evolved at the gold/ Nation interface, which in turn leads to rupturing of the Nation film layer. The solution containing the macromolecule is then able to flow through the membrane into the receiver solution. Thin films could be employed for in rive use, for easy release by a very small currents. Systems are envisaged consisting of multiple segments, addressable individually, so that release rates can be controlled by the number of segments activated. Implanted insulin delivery devices are foreseen as a potential use. The system and the experimental work are described in more detail in Journal of the Electrochemical Society, 1990, 137, p.2005.
Microencapsulation Encapsulation of drugs by conventional synthetic polymers involves the use of heat or organic solvents, which are often unsuitable for delicate naturally derived products such as proteins or liposomes. Equally natural polymers, such as alginate from seaweed extract, can be used but these may have biocompatibility problems. A new and novel synthetic polymer, which forms
Membrane Technology
a gel at room temperature, has been developed which is said to overcome these drawbacks to drug microencapsulation. Researchers at Massachusetts Institute of Technology and Pennsylvania State University have reported the development of a polyphosphazene, which gells in water by the addition of divalent cations {] Am Chem Soc, 1990, 112, 7832). The gel matrices can be used to encapsulate mammalian ceils, proteins and liposomes at room temperature without solvents. Poly[his(carhoxylatophenoxy)phosphazene], PCPP, is soluble in monovalent basic solutions such as sodium carbonate, but the addition of calcium ions results in rapid gelling, possibly by the formation of salt bridges between carboxylic groups of adjacent polymer chains, creating a crosslinked matrix.
O
0 ~C--OH Microspheres can be formed from the gel, which appears to have low toxicity, from experiments with cultured liver cells.
Nova sells geomembranes unit Nova Corp, Calgary, Alberta, Canada, has announced it has sold its geomembranes business, as part of a strategy to focus on resin production. The geomembranes operation was the company's only plastics processing activity, and the company will now concentrate on producing and selling resin. The business has been acquired by National Seal Co of Chicago for an undisclosed sum.
Metal membrane for solar concentrator Sandia National Laboratories and Dallas, Texas, based Solar Kinetics Inc have developed and tested a solar concentrator for electricity production based on a parabolic stretched metal membrane.
3
News and Views
Instead of the usual glass mirrors, the single facet dish is fabricated from a thin metal membrane in a hydraulic vacuum process and covered with a polymer film. The steel membrane made in this way is less expensive to fabricate to high tolerances than glass and weighs far less. In operation the 7m diameter dish tracks the sun, using computer assisted guidance, and reflects sunlight onto a receiver at the focal point of the dish. Concentration of light at the focal point is 5000 times greater than direct sunlight.
Grafted hollow fibre A research group at Kyushi University, Japan, has succeeded in grafting water soluble vinyl monomer to the surface of a tetrafluorethylene hollow fibre. The modified fibre obtained is capable fixing enzymes and also of efficiently concentrating/ separating metal ions, and retains activity for several thousand hours. The process, developed by a research group under Professor C Kajiyama, involves grafting under plasma discharge in a vacuum/inert gas. Under the action of the plasma, the fibre is brought into contact with acrylamide or acrylic acid, which polymerizes on the surface of the fibre at 25°C. Water soluble vinyl monomer is then chemically bound to the fibre, producing an insoluble graft polymer.
Pall sets up in UK In what has been said to be the company's first manufacturing investment in health care devices outside the USA, Pall has recently completed the construction of a new factory for membrane based health care products at St Columb, Cornwall, England. Pall Europe will manufacture state-of-the-art membrane products for diagnostics, blood filtration, breathing apparatus and other health care products at the site.
High purity nitrogen from UCIG Union Carbide Industrial Gases, USA, has introduced a range of modular, skid-mounted membrane units for production if nitrogen up to
4
99.9995% purity at rates from 8000 to 30,000 ft3/hr. Ultra-high purity nitrogen is required for inert atmospheres, purging and cooling, and for pressurized liquid transfer. To attain the ultra-high purity, nitrogen obtained by membrane separation of air is subjected to a further treatment step to remove remaining traces of oxygen. The gas is passed over a palladium catalyst and contacted with hydrogen, the resultant water vapour being subsequently condensed at dew points between -40°F and -80°F. UCIG say that the combined process is still much cheaper (the customary 20-50% is claimed) than conventional cryogenic air fractionation.
I II
IIIllll
IIIIIIII
I
I
I
High performance filter discs A new range of high performance filter discs based on polyamide membranes has been launched by Sartorius Filtration. The Sartolon 250 discs are some of the first products scheduled for manufacture at the company's recently completed new factory in Germany, and replace the Sartolon 200 series. The new range sells at the same price as the previous range but offers improved performance; maximum sterilisation temperature is increased from 127°C to 134°C. Also, greatly improved flow rates are claimed, on account of the more pronounced asymmetry, and the new membrane material is said to be tougher and more resilient. The product is more resistant to creasing. The company says the new introduction demonstrates its policy of offering more and better products for the same money.
Separation AIChE's 13th division The American Insitute of Chemical Engineers was set to ratify at its Chicago annual meeting, 5-30 November, the creation of Separation as its thirteenth specialities division. A division definition committee meeting is set for Orlando, and a formation committee meeting at Buffalo in June. Formation of a programme will begin at the institute's summer national meeting in August 1991. First formal divisional elections are scheduled for Autumn 1991. Separation has always been a core activity in chemical engineering, and is now a rapidly changing
Membrane Technology