Chemistry: electrical and wave energy – Apparatus – Electrophoretic or electro-osmotic apparatus
Patent
1995-03-16
1996-12-31
Phasge, Arun S.
Chemistry: electrical and wave energy
Apparatus
Electrophoretic or electro-osmotic apparatus
204633, B01D 6144, C02F 1469
Patent
active
055890504
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/GB93/0067 filed Mar. 31, 1993 and published as WO93/20012 Oct. 14, 1993.
TECHNICAL FIELD
The present invention relates to an electrodialyzer. That is a unit for electrolyte separation using selective membranes under action of an electromotive force created in solution. In particular, this invention relates to multichamber apparatus for desalting electrolyte aqueous solutions with ion-exchange membranes, and to a process for desalination.
BACKGROUND ART
Apparatus for desalting electrolyte aqueous solutions is known and in particular there are electrodialyzers which comprise a number of chambers formed in the housing of the apparatus by partitions of selective ion-exchange membranes through which solutions of salts are moved. In the end chambers there are electrodes connected up to the direct electric current supply. Applied across the membranes, the electric current makes the chambers in turn enriched and poorer with electrolyte. This process results in separation of the initial solution of electrolyte into desalted and concentrated solutions.
As described in U.S. Pat. No. 4,525,259, an electrodialyzer comprises a line of concentrating chambers between which are situated chambers with diluted solution. This line of chambers has a cathodic chamber with a cathode at one end of it and an anodic chamber with an anode at another end.
In the chambers adjacent to the chambers which contain electrodes, the diluted solution is maintained to prevent migration of ions from concentrated solutions in the concentration chambers into the chambers with the electrodes in them.
All the chambers of this electrodialyzer have input and output pipe branches for corresponding aqueous solutions. Also, the apparatus has two tanks for catholyte and anolyte collection which are in communication with corresponding electrode chambers. These tanks may be isolated from the electrode chambers during the process of solution recirculation between the chambers.
Another common electrodialyzer (F. N. Meller, "Electrodialysis--Electrodialysis Reversal Technology", IONICS, Incorporated, March 1984, p. 53-56) comprises a housing inside of which are set alternately with cation- and anion-exchange membranes arranged parallel with each other to form a line of chambers; a anodic chamber with an anode set at one end wall and a cathodic chamber with a cathode at another end wall with at least one pair of concentration/desalting chambers between them. The anodic chamber is formed by the internal surface of the housing walls and by one side of the first cation-exchange membrane, the other side of which, together with the internal surface of the housing walls and one side of the anion-exchange membrane, forms a concentration chamber which is adjacent to the anodic chamber. Another side of the anion-exchange membrane together with the internal surface of the housing walls and the next cation-exchange membrane form a desalting chamber.
The rest of the pairs of concentration/desalting chambers are formed in the same way. The last cation-exchange membrane, one side of which limited the adjacent desalting chamber, forms the cathodic chamber by its other side and the internal surface of the housing wall.
Each chamber of this known electrodialyzer has an input pipe branch for initial aqueous solution. What is more, anodic and cathodic chambers have input pipe branches for anolyte and catholyte respectively, while each concentration and desalting chamber has output pipe branches for concentrated and desalted solutions.
This known electrodialyzer is equipped with a relay unit for electrode polarity reversal and with a device for redirecting hydraulic flows from the desalting and concentration chambers.
The following describes the normal operation of the known electrodialyzer.
An aqueous solution of electrolyte is fed simultaneously into all chambers through the respective pipe branches, then a direct electric current is supplied to the electrodes.
The process of electrolysis takes place in anodic and cathodic chambers and res
REFERENCES:
patent: 3091583 (1963-05-01), Schufle
patent: 4354905 (1982-10-01), Yoshida et al.
patent: 4528077 (1985-07-01), Fair et al.
Medvedev Igor N.
Schogenov Klim A.
Aquamin Company Limited
Phasge Arun S,.
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