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Electrochemical cell membrane
Patents very p u r e s o l u t i o n of s o d i u m chloride, or p o t a s s i u m chloride or s u l p h a t e , so t h a t m u l t i v a l e n t ions do not d a m a g e the p e r m e a b l e m e m b r a n e . This i n v e n t i o n is d e s i g n e d to u s e a n i m p u r e solution, with c o n s e q u e n t cost savings. The invention c o n s i s t s of a n e l e c t r o c h e m i c a l u n i t cell with four c h a n n e l s , several cells forming a bipolar membrane stack. Each u n i t cell is f o r m e d from a cation-selective m e m b r a n e , a bipolar membrane, an anion-selective m e m b r a n e and a cation-selective m e m b r a n e which selectively p a s s e s m o n o v a l e n t cations. Brine is fed as s h o w n in t h e figure, a n d d i r e c t c u r r e n t is applied. B a s e a n d a c i d are g e n e r a t e d a n d flow t h r o u g h two of the c h a n n e l s . The f o u r t h c h a n n e l is initially c h a r g e d with a purified salt solution. In the remaining channel, the impure feed brine b e c o m e s d e p l e t e d of m o n o v a l e n t cations.
Patent number: US 5 2 5 0 1 5 9 Date: 5 October 1993 Inventor: D.J. B u t t e r w o r t h Applicant: The Graver Co.
Cleaning spiral-wound cartridges These c a r t r i d g e s a r e widely used. They b e c o m e fouled by h a r d - w a t e r salts, which do n o t a l w a y s flush a w a y w h e n fluid flow is reversed. The logical s t e p t a k e n here is to remove the filter c a r t r i d g e from its c a s i n g a n d u n w i n d it to e x p o s e t h e whole s u r f a c e area. S u i t a b l e c h e m i c a l c o m p o u n d s c a n t h e n be u s e d to clean t h e whole of the m e m b r a n e ' s s u r f a c e s . The c a r t r i d g e is t h e n r e a s s e m b l e d for reuse. R e a s s e m b l y , or r a t h e r its difficulty, is a d d r e s s e d in t h i s p a t e n t . By specifying a m a t e r i a l with a ' m e m o r y ' - - t h a t is, a t e n d e n c y to r e a d o p t the s h a p e it held s o m e time earlier - - a n d by e n c o u r a g i n g the m e m o r y effect
M e m b r a n e T e c h n o l o g y No. 4 9
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Bipolar membrane stack
d u r i n g r e a s s e m b l y by d r a w i n g a v a c u u m on the c e n t r a l ' p r o d u c t ' tube, the c a r t r i d g e i n t e r n a l s a d o p t their former disposition. In this w a y the r i s k involved in t a k i n g a p a r t a tightly w o u n d m e m b r a n e p a c k is minimized.
Patent number: US 5250118 Date: 5 October 1993 Inventors & Applicants: C.L. Netwlg, D.L. Kronmiller
Electrochemical
cell membrane This m e m b r a n e , t h o u g h p o r o u s , is gastight w h e n s a t u r a t e d with electrolyte, b u t p o s s e s s e s good i o n - t r a n s f e r properties. It is m a d e by p r e p a r i n g a solution of a n organic b i n d e r s u c h a s a p o l y s u l p h o n e in a solvent s u c h a s N-methylpyrrolidone, a d d i n g a m e t a l h y d r o x i d e or oxide s u c h a s zinc oxide or z i r c o n i u m oxide, forming a m e m b r a n e , t h e n e x t r a c t i n g the solvent b y i m m e r s i o n in a liquid which is n o t a solvent for the binder. A p o r e - f o r m i n g m a t e r i a l , for e x a m p l e polyvinylpyrrolldone, is a d d e d to the m e t a l o x i d e - o r g a n i c binder suspension at a c o n c e n t r a t i o n of 0.5-2%. The m e t a l oxide c o n t e n t of the m e m b r a n e is 65-95%. The p a r t i c u l a r n o n - s o l v e n t u s e d in the e x t r a c t i o n step h a s b e e n f o u n d to affect the p r o p e r t i e s of the m e m b r a n e
significantly. I s o p r o p a n o l is t h e e x t r a c t a n t of choice in this process.
Patent number: WO 9 3 1 5 5 2 9 Date: 5 A u g u s t 1993 Inventors: P. Vermelren, W. Doyen, W. A d r l a n s e n s , R. L e y s e n Applicant V l a a m s e I n s t e n l n g voor Technologisch Onderzoek
Membrane washing aid Hollow-fibre m e m b r a n e s b e c o m e clogged over time, a n d c a n b e b a c k - w a s h e d b y r e v e r s i n g the flow of liquid t h r o u g h them. In this p r o c e s s the p r e s s u r e difference n e c e s s a r y to dislodge c o n t a m i n a n t s m a y c a u s e collapse of s o m e of t h e pores, l e a d i n g to d e g r a d a t i o n of t h e m e m b r a n e ' s separation properties. The i n v e n t i o n c l a i m e d here is to coat the o u t e r s u r f a c e a n d the p o r e s of the fibre with ceramics, p r e f e r a b l y iron oxides s u c h a s ferrite or m a g n e t i t e , In this w a y the a d h e s i o n of p a r t i c l e s to the fibre s u r f a c e is r e d u c e d a n d the pore walls, if t h e y collapse t e m p o r a r i l y , a r e p r e v e n t e d from f u s i n g by t h e m a g n e t i t e c o a t i n g i n s i d e them.
Patent number: J P 5 1 6 8 8 7 6 Date: 2 J u l y 1993 Inventor: N. Uetake Applicant: Hitachi Ltd
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Patent number: US 5 2 5 0 1 5 9 Date: 5 October 1993 Inventor: D.J. B u t t e r w o r t h Applicant: The Graver Co.
Cleaning spiral-wound cartridges These c a r t r i d g e s a r e widely used. They b e c o m e fouled by h a r d - w a t e r salts, which do n o t a l w a y s flush a w a y w h e n fluid flow is reversed. The logical s t e p t a k e n here is to remove the filter c a r t r i d g e from its c a s i n g a n d u n w i n d it to e x p o s e t h e whole s u r f a c e area. S u i t a b l e c h e m i c a l c o m p o u n d s c a n t h e n be u s e d to clean t h e whole of the m e m b r a n e ' s s u r f a c e s . The c a r t r i d g e is t h e n r e a s s e m b l e d for reuse. R e a s s e m b l y , or r a t h e r its difficulty, is a d d r e s s e d in t h i s p a t e n t . By specifying a m a t e r i a l with a ' m e m o r y ' - - t h a t is, a t e n d e n c y to r e a d o p t the s h a p e it held s o m e time earlier - - a n d by e n c o u r a g i n g the m e m o r y effect
M e m b r a n e T e c h n o l o g y No. 4 9
C
B
A
MC
C
8
4,
eatlcm-
MC
C
8
A
MC
C
B
A
MC
~Ive rnlrn~ne
n~mbrlne
Bipolar membrane stack
d u r i n g r e a s s e m b l y by d r a w i n g a v a c u u m on the c e n t r a l ' p r o d u c t ' tube, the c a r t r i d g e i n t e r n a l s a d o p t their former disposition. In this w a y the r i s k involved in t a k i n g a p a r t a tightly w o u n d m e m b r a n e p a c k is minimized.
Patent number: US 5250118 Date: 5 October 1993 Inventors & Applicants: C.L. Netwlg, D.L. Kronmiller
Electrochemical
cell membrane This m e m b r a n e , t h o u g h p o r o u s , is gastight w h e n s a t u r a t e d with electrolyte, b u t p o s s e s s e s good i o n - t r a n s f e r properties. It is m a d e by p r e p a r i n g a solution of a n organic b i n d e r s u c h a s a p o l y s u l p h o n e in a solvent s u c h a s N-methylpyrrolidone, a d d i n g a m e t a l h y d r o x i d e or oxide s u c h a s zinc oxide or z i r c o n i u m oxide, forming a m e m b r a n e , t h e n e x t r a c t i n g the solvent b y i m m e r s i o n in a liquid which is n o t a solvent for the binder. A p o r e - f o r m i n g m a t e r i a l , for e x a m p l e polyvinylpyrrolldone, is a d d e d to the m e t a l o x i d e - o r g a n i c binder suspension at a c o n c e n t r a t i o n of 0.5-2%. The m e t a l oxide c o n t e n t of the m e m b r a n e is 65-95%. The p a r t i c u l a r n o n - s o l v e n t u s e d in the e x t r a c t i o n step h a s b e e n f o u n d to affect the p r o p e r t i e s of the m e m b r a n e
significantly. I s o p r o p a n o l is t h e e x t r a c t a n t of choice in this process.
Patent number: WO 9 3 1 5 5 2 9 Date: 5 A u g u s t 1993 Inventors: P. Vermelren, W. Doyen, W. A d r l a n s e n s , R. L e y s e n Applicant V l a a m s e I n s t e n l n g voor Technologisch Onderzoek
Membrane washing aid Hollow-fibre m e m b r a n e s b e c o m e clogged over time, a n d c a n b e b a c k - w a s h e d b y r e v e r s i n g the flow of liquid t h r o u g h them. In this p r o c e s s the p r e s s u r e difference n e c e s s a r y to dislodge c o n t a m i n a n t s m a y c a u s e collapse of s o m e of t h e pores, l e a d i n g to d e g r a d a t i o n of t h e m e m b r a n e ' s separation properties. The i n v e n t i o n c l a i m e d here is to coat the o u t e r s u r f a c e a n d the p o r e s of the fibre with ceramics, p r e f e r a b l y iron oxides s u c h a s ferrite or m a g n e t i t e , In this w a y the a d h e s i o n of p a r t i c l e s to the fibre s u r f a c e is r e d u c e d a n d the pore walls, if t h e y collapse t e m p o r a r i l y , a r e p r e v e n t e d from f u s i n g by t h e m a g n e t i t e c o a t i n g i n s i d e them.
Patent number: J P 5 1 6 8 8 7 6 Date: 2 J u l y 1993 Inventor: N. Uetake Applicant: Hitachi Ltd
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