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Silk protein reveals controlled release capability
News and Views The range includes: fiat m e m b r a n e discs, blotting sheets a n d prefilters for laboratory analysis requiring cellulosic, PTFE a n d microflbre glass media, as well as sterile m e m b r a n e s for microbiological analyses. Further Informatlon from: Helapet Lid, 1 London Road, B e r k h a m s t e d , Hefts HP4 2BU, UK. Tel: 0442 8771 79. Fax: 0442 876744.
Silk protein reveals c o n t r o l l e d release capability Fibroin m e m b r a n e s can be used to control drug delivery by m a n i p u l a t i n g pH levels, investigators at the J a p a n e s e National Institute of Materials a n d Chemical Research have found. Fibroin is an insoluble protein which is the main constituent of raw silk fibres. At pH 4.5, the electrical charge on the surface of the m e m b r a n e will alternate between positive and negative which can be u s e d to change the permeability of drugs. Most of the amino acids in fibroin are mechanically strong, hydrophobic, a n d a certain percentage of them are positively or negatively charged. The researchers found that at pH levels u n d e r 4.5, the m e m b r a n e tends to carry a positive charge which will attract negatively charged sodium phenolsulfonate to e n h a n c e the permeability of the fungicide. On the other hand, a n o t h e r fungicide, benzyltrimethyl a m m o n i u m , becomes more permeable when the m e m b r a n e is placed in media of more t h a n pH 4.5. One possible application is pH-driven automatic delivery control of fungicides where the chemicals are discharged only w h e n the acidity of waste water increases or decreases. Another possibility is drug delivery s y s t e m s for anti-cancer agents in which the m e m b r a n e discharges the d r u g only in c a n c e r o u s tissues of a specific pH level. Further information from: National Institute of Materials and Chemical Research 1-I. Hlgashl, Tsukuba City, Ibarakl Prefecture 305, Japan. Tel: +81 298 54 4443. Fax: +81 298 54 4422.(c)
NAMS m e e t i n g to be held in Oregon The Seventh Annual Meeting of the North American Membrane Society (NAMS) will be held in Portland, Oregon. USA, from 2 1 - 2 4 May 1995. The planned sessions will cover topics ranging from molecular a n d system modelling to novel m e m b r a n e materials m a n d from R&D funding sources to system economics~hybrids~scale-ups.
M e m b r a n e T e c h n o l o g y No. 5 3
There will be sessions focused on separations problems a n d m e m b r a n e - b a s e d solutions in the refining a n d chemical process industries. A key aspect of the meeting will be a strong e m p h a s i s on poster presentations a n d the one-on-one interaction that is typically catalyzed b y those gatherings. Dr Doug Lloyd, the President of NAMS, will chair the poster sessions, along with recognized experts in each selected technical area. Several w o r k s h o p s will be offered during two days prior to the start of the m a i n meeting. Further Informatlon from: B e n d Research Inc, 64550 Research Road, Bend, OR 97701-8599, USA. Tel: +1 503 382 5879. Fax: +1 503 382 2713.
Recovering y t t r i u m from w a s t e w a t e r by ESPLIM A s u m m a r y of the work carried out b y researchers in China on a laboratory and on-the-spot test of yttrium recovery from wastewater b y a n electrostatic p s e u d o liquid m e m b r a n e (ESPLIM) is presented in the Journal of Membrane Sctence (93, pp 137-147). The ESPLIM process is a c o n t i n u o u s separation process in which extraction a n d stripping take place simultaneously inside a single extraction vessel. In the mixing sections of the vessel a n ac electric field is applied to achieve p h a s e dispersion for both extraction a n d stripping. In the settling sections of the vessel, the organic a n d a q u e o u s p h a s e s are separated by gravity. The ESPLIM process is similar to liquid m e m b r a n e s , but it avoids the p r o c e d u r e s of emulsification a n d demulsification which are indispensable for emulsion liquid m e m b r a n e s (ELM), a n d so the process is simplified. The leakage a n d 'swelling' rates c a n be controlled to be m u c h lower t h a n those of ELM, which implies a high extraction efficiency and high concentration capability of solute by this process. The u s u a l way for recovering Y(M) from the effluent generated in rare earth (RE) extraction processes is by oxolate precipitation. This process, however, u s e s a large a m o u n t of reagents a n d recovery is only a r o u n d 90%. A multicell pilot device was m a n u f a c t u r e d in the laboratory. The system studied was the effluent from a solvent extraction process of the Jiangxl Rare Earth Company. It contained 1.0 g / L REs [-94% Y(III) a n d 5% La(III)], as well as calcium a n d a m m o n i u m chloride. The extractant was 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (P507}. The effects of the applied field, extractant concentration, feed concentration, pH a n d flow rate on Y(M) extraction were studied for optimizing the process. An economic evaluation was also carried out.
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Silk protein reveals c o n t r o l l e d release capability Fibroin m e m b r a n e s can be used to control drug delivery by m a n i p u l a t i n g pH levels, investigators at the J a p a n e s e National Institute of Materials a n d Chemical Research have found. Fibroin is an insoluble protein which is the main constituent of raw silk fibres. At pH 4.5, the electrical charge on the surface of the m e m b r a n e will alternate between positive and negative which can be u s e d to change the permeability of drugs. Most of the amino acids in fibroin are mechanically strong, hydrophobic, a n d a certain percentage of them are positively or negatively charged. The researchers found that at pH levels u n d e r 4.5, the m e m b r a n e tends to carry a positive charge which will attract negatively charged sodium phenolsulfonate to e n h a n c e the permeability of the fungicide. On the other hand, a n o t h e r fungicide, benzyltrimethyl a m m o n i u m , becomes more permeable when the m e m b r a n e is placed in media of more t h a n pH 4.5. One possible application is pH-driven automatic delivery control of fungicides where the chemicals are discharged only w h e n the acidity of waste water increases or decreases. Another possibility is drug delivery s y s t e m s for anti-cancer agents in which the m e m b r a n e discharges the d r u g only in c a n c e r o u s tissues of a specific pH level. Further information from: National Institute of Materials and Chemical Research 1-I. Hlgashl, Tsukuba City, Ibarakl Prefecture 305, Japan. Tel: +81 298 54 4443. Fax: +81 298 54 4422.(c)
NAMS m e e t i n g to be held in Oregon The Seventh Annual Meeting of the North American Membrane Society (NAMS) will be held in Portland, Oregon. USA, from 2 1 - 2 4 May 1995. The planned sessions will cover topics ranging from molecular a n d system modelling to novel m e m b r a n e materials m a n d from R&D funding sources to system economics~hybrids~scale-ups.
M e m b r a n e T e c h n o l o g y No. 5 3
There will be sessions focused on separations problems a n d m e m b r a n e - b a s e d solutions in the refining a n d chemical process industries. A key aspect of the meeting will be a strong e m p h a s i s on poster presentations a n d the one-on-one interaction that is typically catalyzed b y those gatherings. Dr Doug Lloyd, the President of NAMS, will chair the poster sessions, along with recognized experts in each selected technical area. Several w o r k s h o p s will be offered during two days prior to the start of the m a i n meeting. Further Informatlon from: B e n d Research Inc, 64550 Research Road, Bend, OR 97701-8599, USA. Tel: +1 503 382 5879. Fax: +1 503 382 2713.
Recovering y t t r i u m from w a s t e w a t e r by ESPLIM A s u m m a r y of the work carried out b y researchers in China on a laboratory and on-the-spot test of yttrium recovery from wastewater b y a n electrostatic p s e u d o liquid m e m b r a n e (ESPLIM) is presented in the Journal of Membrane Sctence (93, pp 137-147). The ESPLIM process is a c o n t i n u o u s separation process in which extraction a n d stripping take place simultaneously inside a single extraction vessel. In the mixing sections of the vessel a n ac electric field is applied to achieve p h a s e dispersion for both extraction a n d stripping. In the settling sections of the vessel, the organic a n d a q u e o u s p h a s e s are separated by gravity. The ESPLIM process is similar to liquid m e m b r a n e s , but it avoids the p r o c e d u r e s of emulsification a n d demulsification which are indispensable for emulsion liquid m e m b r a n e s (ELM), a n d so the process is simplified. The leakage a n d 'swelling' rates c a n be controlled to be m u c h lower t h a n those of ELM, which implies a high extraction efficiency and high concentration capability of solute by this process. The u s u a l way for recovering Y(M) from the effluent generated in rare earth (RE) extraction processes is by oxolate precipitation. This process, however, u s e s a large a m o u n t of reagents a n d recovery is only a r o u n d 90%. A multicell pilot device was m a n u f a c t u r e d in the laboratory. The system studied was the effluent from a solvent extraction process of the Jiangxl Rare Earth Company. It contained 1.0 g / L REs [-94% Y(III) a n d 5% La(III)], as well as calcium a n d a m m o n i u m chloride. The extractant was 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (P507}. The effects of the applied field, extractant concentration, feed concentration, pH a n d flow rate on Y(M) extraction were studied for optimizing the process. An economic evaluation was also carried out.
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