N e w s a n d V i e w s

Low-pressure reverse o s m o s i s m e m b r a n e Nitto Denko Corporation has developed an improved thin-film composite low pressure reverse osmosis membrane. Spiral wound modules containing the NTR-759 HR membrane have been tested in the production of ul t rapure water. Published results (Membrane, 16 (4), 1991, 223-232) indicate that the NTR-759 HR exhibits up to 99.5% NaCI rejection, 99.9% Na2SO4 rejection and 96% isopropanol rejection when tested at 1.5 MPa and 25°C on 1500 ppm solution. High permeate flux combined with good chloramine resistance were obtained at low operating pressures.

Kenichi Ikeda, Nitto Denko Corporation, 61-7, Aza-sasatani, Yamadera-cho, Kusatsu-city, Shiga 525, Japan.

Fabr ica t ion of charge- m o s a i c m e m b r a n e s Practical applications of charge-mosaic membranes are predicted soon by Japanese researchers (Membrane, 16 (4), 1991, 233-238). In these studies membranes were fabricated from pentablock copolymers of the BABCB type w polyflsopr ene-b-styrene-b-butadiene-b-(4-vlnylbenzyl) dimethylamine-b-isoprene) J by selectively introducing anion- and catlon-exchange groups into the micro-separated phases. The three layer lamellar s t ructure of the pentablock copolymer films was not disturbed by the modification.

Membranes showed negative osmosis for aqueous solutions of salts and highly selective transport for sodium chloride in mixed solutions of low molecular weight organic non-electrolytes and sodium chloride when the membranes were applied to a dialysis process. Selectivity was reported to be much higher than with conventional porous, reverse osmosis and dialysis membranes.

E x x o n buys s t a k e in Z e n o n Continuing its series of investments in companies developing membrane technology, Exxon Chemical Co

has acquired a 20% interest in Zenon Environmental Systems Inc, a Canadian company specializing in t reatment and recycling of industrial pollutants. Zenon Environmental Systems is a subsidiary of Zenon Environmental Inc of Burlington, Ontario.

Groundwater a r o m a t i c s r e m o v e d Crossflow filtration membranes are to be used to treat groundwater contaminated wlth polycyclic aromatic compounds, including naphthalene - - claimed by membrane producer X-Flow of Vriezenveen, NL, to be the first application of its kind. The X-Flow system is based on the use of PES, with the membranes mounted on stainless steel and with PVC housings. Filtration surfaces generally range from 0. I m 2 up to i0 m 2. The order, placed by ESD in Delfzfl, is for 500 m 2 of membrane area to treat 30 m3/hour of drinking water. The scheme should come on-line in March 1992.

Sof tware p r e d i c t s m o l e c u l e / sur face i n t e r a c t i o n s Researchers at the University of Pennsylvania have found that for the prediction of the interactions between newly-developed molecules and water as few as 90 water molecules will do what billions of molecules will do when they encounter an oily or a water-absorbing surface. They claim that a software program developed for a table top workstation can now remove the need for involved and expensive supercomputer analysis - - the work can be done in a few days by one person.

Joseph Hau tman and Michael Klein found that a cluster of 90 water molecules ~ l l form into a droplet when coming in contact with a neutral surface bu t will spread on a surface containing charges. Scientists could not assume that this was going to be the case because in a small group of molecules a larger proportion of necessity sit on the surface rather than in the interior. Molecules on surfaces have different properties to their inner counterparts: they can be more reactive because they have an exposed side, while interior molecules are completely surrounded by other molecules.

Speaking at the Fall meeting of the Materials Research Society, Professor Klein found it: "strange that nobody had done this before. Everything was

2 Membrane Technology