Chemistry: electrical and wave energy – Processes and products – Electrophoresis or electro-osmosis processes and electrolyte...
Patent
1997-01-06
1998-07-07
Phasge, Arun S.
Chemistry: electrical and wave energy
Processes and products
Electrophoresis or electro-osmosis processes and electrolyte...
204543, 204544, 204627, B01D 6144
Patent
active
057763259
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 continuation of PCT/NZ95/0006 filed on Jul. 6, 1995.
TECHNICAL FIELD
The invention relates to the mono-directional transport of ions through a conducting polymer membrane and to an apparatus for inducing such mono-directional transport.
BACKGROUND ART
Two approaches have been used to apply conducting polymers (CP's) to separation technology. The first involves coating the CP film onto the stationary phase of an ion chromatography medium. Separation was achieved by varying the redox state of the polymer during elution. Using this approach, Deinhammer et. al. (Anal. Chem. 1991, 63, 1884) successfully demonstrated the separation of the adenosine nucleotides, AMP and ATP. The second approach employs CP's as either free standing or composite membranes through which ion transport could be achieved. Transportation of ions was similarly induced by modifying the conductive state of the polymer matrix.
Mirmohseni et. al. (J Intelligent Material Systems and Structures, 1993, 4, 43) demonstrated the transport of Na.sup.+ and K.sup.+ ions through a free standing membrane of polypyrolle (PPy). The anion employed as the dopant within the membrane was p-toluene sulphonate (PTS.sup.-). The experimental setup used comprised a two compartment cell separated by a PPy membrane. A current was applied potentiostatically by a three-electrode system in one of the compartments, using the membrane as the working electrode. Transportation of ions was achieved by oscillating the membrane between anodic and cathodic potentials. The result was the selective transport of K.sup.+ ions over Na.sup.+, the extent of which depended on the pulse width employed.
Although the process described by Mirmohseni et. al. achieved continuous ion transport through the membrane, transport could not be maximised. The experimental setup dictated that ions absorbed selectively from one compartment of the cell, were desorbed simultaneously into both compartments. A mono-directional flow of ions could not be achieved.
It is therefore an object of the invention to provide a means capable of inducing mono-directional transport of ions through a conducting polymer membrane.
SUMMARY OF THE INVENTION
In broad terms the invention comprises a method of inducing mono-directional transport of ions between electrolyte solutions, the method comprising separating the electrolyte solutions with a conducting polymer membrane and creating a potential gradient across said membrane.
Preferably the potential gradient is created by using the conducting polymer membrane as a shared working electrode.
In broad terms the invention further comprises an apparatus for inducing mono-directional transport of ions between electrolyte solutions separated by a conducting polymer membrane by applying a potential gradient across the polymer membrane.
Preferably the potential gradient through the conducting polymer membrane is achieved by a three electrode system in each solution, the three electrode systems comprising a reference electrode, a counter electrode, and a shared working electrode and wherein the shared working electrode is the polymer membrane separating the solutions.
Preferably the conducting polymer membrane is free-standing.
Preferably the conducting polymer membrane is a composite membrane made of a conducting polymer incorporated into either a non-conductive or conductive media.
Preferably the potential gradient through the conducting polymer membrane remains constant.
Preferably the conducting polymer membrane is selected from polypyrrole, polythiophene, polyacetylene, polyfuran, polyaniline or polyphenylene or derivatives of these.
Preferably the apparatus further includes combination pH probes.
Preferably the electrolyte solutions are constantly stirred.
Preferably the counter electrodes are stainless steel, titanium, gold, platinum or carbon counter electrodes.
Preferably the reference electrode is an Ag/AgCl or SCE electrode.
Preferably the potential gradient across the conducting polymer membrane is varied.
Preferably the potential
REFERENCES:
patent: 4585536 (1986-04-01), Puetter et al.
patent: 5043048 (1991-08-01), Muralidhara
patent: 5064515 (1991-11-01), Harapanahalli
patent: 5085749 (1992-02-01), Grimshaw et al.
patent: 5094732 (1992-03-01), Oldani et al.
Industrial Research Limited
Mandragouras Amy E.
Monks Lawrence E.
Phasge Arun S,.
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