Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
1999-07-09
2001-05-01
Gorgos, Kathryn (Department: 1741)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S254000
Reexamination Certificate
active
06224720
ABSTRACT:
FIELD OF THE INVENTION DESCRIPTION
This invention relates to an electrolytic cell with an electrolyte and a plurality of bipolar electrodes surrounded by the electrolyte, which electrodes are electrically connected in series during the operation of the cell, where each of the bipolar electrodes has a cathode side and an anode side, between which an electrically conductive connection exists during the operation, and where at least one bipolar electrode has a cathode side and an anode side which are designed to be movable with respect to each other.
BACKGROUND OF THE INVENTION
Such cell is known from DE-A-23 55 876, where the cathode side and the anode side are held together by spring elements. The DE-A-44 38 692 (corresponding to U.S. application Ser. No. 08/549,014filed Oct. 27, 1995, now U.S. Pat. No. 5,720,867) and also the U.S. Pat. No. 5,248,398 disclose electrolytic cells by means of which metals are recovered from an electrolyte. What is disadvantageous in the known cells is the fact that each bipolar electrode can only completely be withdrawn from the cell, as the anode side is rigidly connected with the cathode side of the electrode. It is therefore the object underlying the invention to design one or several of the bipolar electrodes such that the desired electrode portion can be handled more or less independent of the other portion.
In the above-mentioned electrolytic cell the object is solved in accordance with the invention in that the bipolar electrode is designed to be separable, and the cathode side or the anode side is designed to be withdrawn from the electrolyte. The cathode side and the anode side are no longer inseparably coupled with each other mechanically, and one of the two electrode sides can be removed from the cell, whereas the other electrode side remains in the cell. One, several or all of the bipolar electrodes of the cell are thus designed to be separable.
SUMMARY OF THE INVENTION
The independent movability of an electrode side as well as the possibility to separate bipolar electrodes in themselves can be utilized in various ways. When the electrolytic cell is used for separating a solid, the solid is deposited on the cathode side or on the anode side during the operation of the cell, depending on the substance and the electrolyte. The electrode side with the deposited product can be withdrawn from the cell independent of the other electrode side, be ensured that the metal is deposited on a bipolar electrode only on the desired surface and not also on another surface of the same bipolar electrode. Metals which are extracted from the electrolyte and are deposited on the cathode side of the bipolar electrodes include for instance copper, zinc, cobalt or nickel. MnO
2
can for instance be deposited on the anode side, where a sulfuric-acid manganese(II) sulfate solution is used as electrolyte.
An advantageous aspect consists in that the electric connection between the cathode side and the anode side of the separable bipolar electrode has a touching contact. Through this touching contact an electric current flows during the operation of the cell inside the bipolar electrode between the cathode side and the anode side. Since the two electrode sides only touch each other at the contact and are not screwed together, for instance, the parts can easily be separated from each other mechanically. It is possible to increase the contact pressure of the contact surfaces by means of a clamping effect in the vicinity of the touching contact. In general it is, however, sufficient to utilize the weight of the movable electrode portion for the pressure in the vicinity of the touching contact. A good flow of current in the vicinity of the touching contact is generally ensured in that metals with a good electrical conductivity such as copper or silver touch each other at this point.
The touching contact of two electrode portions may be disposed outside the electrolyte or also in the electrolyte. The touching contact may for instance be disposed on or in the vicinity of the container rim of the cell, where it is easily accessible and can be monitored without difficulties. On the other hand, the touching contact may also be disposed in the electrolyte, e.g. in the vicinity of the bottom of the cell container. In this case, the electrolyte advantageously effects the cooling of the contact area.
The formation of the bipolar electrodes, where the cathode side or the anode side is designed movable and separable, may be effected in various ways. For the anode side there may in particular be used plates of lead, titanium or graphite, and there may also be used activated expanded metal. The anode side may also be designed as gas diffusion anode, where a gas supply is ensured. For the cathode there may likewise be used sheets or plates of e.g. titanium, stainless steel or graphite. The cathode side may have a network or grid structure. It may furthermore be designed as a box with perforated walls, which is filled for instance with carbon granules. A further possibility is to design the cathode side as a gas diffusion cathode and provide for a gas supply.
In the cell, the cathode and anode sides of the electrode may for instance be guided in vertical grooves of the inner walls of the container. Advantageously, it will be ensured that laterally between the inner wall of the container and the electrodes little or no electrolyte is flowing. The distance between the bottom of the container and the lower edge of the electrodes will usually lie in the range between 3 and 30 mm, and the lateral distance between the container wall and the electrodes mostly lies in the range between 0 and 5 mm.
During the metal deposition it is for instance possible by means of the bipolar electrode to specifically limit the area of the deposition in a simple way be merely aligning and influencing the electric field. One possibility of such influence is to provide a partition between the cathode side and the anode side of the separable bipolar electrode. This partition should, however, be designed and arranged such that it does not completely prevent the flow of the electrolyte.
REFERENCES:
patent: 4139447 (1979-02-01), Faron et al.
patent: 5225061 (1993-07-01), Westerlund
Anastasijevic Nikola
Cieslak Heinrich
Laibach Stefan
Langschied Holger
Nepper Jean-Paul
Dubno Herbert
Gorgos Kathryn
Metallgesellschaft Aktiengesellschaft
Nicolas Wesley A.
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