METHOD FOR OPTIMIZING THE YIELD OF ELECTROEXTRACTION OF HEAVY METALS IN AQUEOUS SOLUTION WITH A HIGH SALT CONCENTRATION, AND DEVICE FOR THE IMPLEMENTATION THEREOF

Abstract

The invention relates to technical conditions of composition and use applied to the existing method and device for extracting heavy metals from an aqueous solution with a high salt concentration, with the single aim of adapting said method to technical, technological and ecological developments that have taken place since the protection thereof, and substantially optimising the results. To this end, the invention of the present patent application adds, to the device of the initial patent, an electronic control means (MC) that can manage three new actions. Disclosed are also modifications in the quality, function, destination and operation of certain elements of the device as well as the addition of a filter at the end of the electroplating operation, the purpose of which is to optimise the quality of the rejected effluent.

Claims

1. A method of optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration, wherein the method comprises: managing, controlling, and regulating operations linked to the extraction of heavy metals via electrolysis in an aqueous solution with a high salt concentration; adding one or more sensitive probes (SP) in order to be introduced into the solution to be treated between pairs of electrodes (6)(7), (8)(9) and (10)(11), and filtering the treated aqueous solution with a high salt concentration using an additional filter (EFF).

2. The method of optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration according to claim 1, wherein electronic control means (CM) in charge of providing for the management, control and regulation of the operations, control the interruption of the electrical power supply (PC) of the electrolysis device for successive limited durations and a periodicity determined according to the chemical composition of the solution to be treated and the texture of the electrodes used.

3. The method of optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration according to claim 1, wherein electronic control means (CM) in charge of providing for the management, control and regulation of the operations, control independently of the supply of the electrodes (6) to (11) of the device, the decoupling of the ground electrode for successive durations and a periodicity determined according to the different factors linked to the method.

4. The method of optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration as claimed in claim 1, wherein electronic control means (CM) in charge of providing for the management, control and regulation of the operations, control the control and the regulation of the optimum and constant voltage present in solution to be treated, throughout a entire electroplating operation and on information from the sensitive probes (SP) introduced into the solution to be treated, between the pairs of electrodes (6)(7), (8)(9) and (10)(11).

5. The method of optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration as claimed in claim 1, wherein the electrodes (6)(9)(10) (7)(8)(11) are confined when fixed polluting elements are of a radioactive nature and/or are eliminated by means adapted to fixed polluting elements and to the level of polluting effect thereof.

6. The method of optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration according to claim 1, wherein the operation can be carried out by alternating successive cycles or continuously, in this latter case, the supply of the solution to be treated is carried out through the bottom of the electrolysis tank and at slow speed and determined according to the chemical composition of the solution to be treated and the texture of the electrodes (6) to (11) of the device, with the evacuation of the treated solution being carried out in the top portion of the electroplating tank by a duct provided for this purpose.

7. Device for the implementation of the method according to claim 1, wherein the device comprises: a) electronic control means (CM) for the management, control and regulation of the operations linked to the extraction of the heavy metals via electrolysis in an aqueous solution with a high salt concentration; b) immersed electrodes (6) to (11) constituted of anodes (6) (9) (10) and of cathodes (7) (8) (11); c) a ground electrode in order to be introduced into the solution to be treated and increase the rapidity of the ionic degreasing of the electrodes (6) to (11); d) sensitive probes (SP) in order to be introduced into the solution to be treated between the pairs of electrodes (6)(7), (8)(9) and (10)(11); and e) at least one electrofiltration filter (EFF) in order to fix the residual elements with a weak electromotive force that are still present in the solution after the differential electroplating operation.

8. The device for the implementation of the method according to claim 7, wherein the immersed anode electrodes (6) (9) (10) are of a material and texture that are different from those of the immersed cathode electrodes (7) (8) (11), according to the chemical and radiochemical composition of the solution to be treated.

9. The device for the implementation of the method according to claim 7, wherein the ground electrode introduced into the solution to be treated inside an insulating tube in order to prevent an electronic distortion and connected to the ground (G) of the electric generator, is of a material and texture that are different from those of the other electrodes.

10. The device for the implementation of the method according to claim 7, wherein the sensitive probes (SP) introduced into the solution to be treated, between the pairs of electrodes (6) (7), (8) (9) and (10) (11), are of a chemically neutral texture and for example made of glass.

11. The device for the implementation of the method according to claim 7, wherein the electrofiltration filter (EFF) that is independent and associated with the electrolysis tank in order to fix the residual elements with a weak electromotive force that are still present in the solution after the differential electroplating operation, is mainly consisted of a cylindrical container (C) containing a neutral filtering material (FM) wherein are plunged two electrodes (EC), of which one is thrust on the inside peripheral plane of the container (C) and the other is thrust on an axial support tube (ST) located at the center of the inner surface of the lower plane of the container (C), with the electric current passing through the filtering material (FM) being regulated according to the chemical composition of the solution exiting from the electrolytic treatment container and adapted to the resistivity of the whole knowing that the conductivity of the filtering material (FM) varies according to the more or less aqueous liquid that it contains, with the solution filtered by its passing through the electrofiltration filter (EFF) then having an optimum quality allowing for the discharge thereof into the environment or for example the reuse thereof in another method of manufacturing.

12. The device for the implementation of the method according to claim 7, wherein the immersed anode electrodes (6) (9) (10) are of a material and texture that are different from those of the immersed cathode electrodes (7) (8) (11), according to the chemical and radiochemical composition of the solution to be treated and are constituted in the form of plates, of a composition, material, configuration and arrangement that are compatible with the operation and the performance of the device.

Description

[0036] FIG. 1 is a median diagrammatical cross-section view of the main element of the device of the initial patent, constituted by an electrolysis tank that is for example cylindrical, provided with electrodes and means of supplying with electrical energy and with solution to be treated.

[0037] FIG. 2 is a diagrammatical cross-section view of the main element of the device of the initial patent modified according to the technical elements claimed by this patent.

[0038] FIG. 3 is a median diagrammatical cross-section view of the electrofiltration filter of this invention.

[0039] This invention follows a patent filed by the same author in May 1995 and published on 8 Nov. 1996 under U.S. Pat. No. 2,733,748, concerning a method for extracting heavy metals from an aqueous solution having a high salt concentration, by means of electrolysis. This patent is designated hereinafter by the mention initial patent.

[0040] For a better understanding of this patent application, the determining elements of the main claims of said initial patent are repeated hereinbelow in reference with FIG. 1 of this patent.

[0041] The method and the device for extracting heavy metals from an aqueous solution having a high salt concentration object of the initial patent claim an electrolysis tank (2) of cylindrical shape and with axis (14) containing an aqueous solution (3) with a high salt concentration, into which at least one pair of electrodes is plunged. In the diagram FIG. 1 of this patent, three pairs of electrodes are shown for example the anode (6) and the cathode (7), the anode (9) and the cathode (8) and the anode (10) and the cathode (11), powered at the corresponding terminals of an electric generator (4) and a ground electrode (22) connected preferably to the ground (G) of said generator (4). The ground electrode (22) is separated from the electrode (11) by a polyamide screen (23) in order to prevent any electrolytic interaction between these two electrodes.

[0042] The method and the device for extracting heavy metals from an aqueous solution having a high salt concentration object of the initial patent claim a mixing in the closed circuit during the electrolysis cycle, driven by a pump (not shown) carrying out the displacement of the solution (3), by emptying the tank (2) of the solution (3) via the suction channel (24) taking the solution in the bottom portion of the tank and near the bottom (5) of the latter, in order to simultaneously reintroduce it into the same tank (2) and between the electrodes via the channel (28) under the action of a pump outside of the tank (2). (See FIG. 1).

[0043] The method and the device for extracting heavy metals from an aqueous solution having a high salt concentration object of the initial patent claim the filtration by intermittence of the treated solution (3), during the operation of electrolysis and by means of an independent filter (32) (not shown) and annexed to the tank (2) comprising a filtering material, for example clay granules.

[0044] The device for extracting heavy metals from an aqueous solution with a high salt concentration object of the initial patent claims a common material and a common texture for the electrodes for example the anodes (6) (9) 10), the cathodes (7) (8) (11) and the ground electrode (22).

[0045] The device for extracting heavy metals from an aqueous solution with a high salt concentration object of the initial patent claims the characteristics of the shape and of the position of the electrodes (6) (9) (10) (7) (8) (11), namely: that each electrode has a coaxial and generally cylindrical shape and that the device comprises at least one neutral support, in FIG. 1 two neutral supports (16) (17) of cylindrical shape and of an inert material, having an inner face and an outer face each covered by an electrode, with the electrodes covering the faces of the same support belonging to different pairs of electrodes.

[0046] The device for extracting heavy metals from an aqueous solution with a high salt concentration object of the initial patent, claims for example the presence of at least three pairs of electrodes the anode (6) and the cathode (7), the anode (9) and the cathode (8) and the anode (10) and the cathode (11), and at least two inert supports (16) and (17), with the electrodes covering the faces of the same support being connected to the same terminal of the electric generator (4).

[0047] The device for extracting heavy metals from an aqueous solution with a high salt concentration object of the initial patent, claims the characteristic consisting in that at least one electrode of each pair has a continuous axial opening (not shown) extending from one edge to the other of the electrode for example the electrodes (8) and (10) and/or the electrodes (7) and (9).

[0048] Said device for extracting heavy metals from an aqueous solution with a high salt concentration object of the initial patent claims the presence of means for emptying (24) the treatment tank (2) and means for filling (28) said tank (2) that communicate in a closed circuit.

[0049] The device for extracting heavy metals from an aqueous solution with a high salt concentration object of the initial patent claims the presence of at least two filters (not shown), a production filter (32a) and a finishing filter (32b) annexed to the tank (2) and comprising clay granules.

[0050] This invention relates to the technical conditions of composition and of use, added to the method for extracting heavy metals from an aqueous solution having a high salt concentration object of the initial patent filed by the inventor in 1995 and published on 8 Nov. 1996 under U.S. Pat. No. 2,733,748, with the sole purpose of adapting said method to the technical, technological and ecological developments that have taken place since the filing of said patent and to substantially optimize the results of said method.

[0051] With this objective, the inventor provides in this patent the adding to the device of the initial patent an electronic control means (CM) that can manage three new actions. Disclosed are also modifications in the quality, function, destination and operation of certain elements of the device of the invention as well as the adding of a particular electronic filter at the end of the electroplating operation, of which the purpose is to optimize the quality of the discharged effluent by fixing the components with a weak electromotive force driven by the residual ionic movements. (See FIG. 2).

[0052] According to a preferred embodiment of the invention, the device for optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration, has electronic control means (CM) allowing for successive cut-offs of the electrical power of the device (PC), according to durations and a periodicity determined according to the chemical composition of the solution to be treated (3) and the texture of the immersed electrodes (6) to (11).

[0053] This action is of great importance because the temporary stoppage of the supply results in an interaction between the elements in the solution (3) and the electrodes (6) to (11), caused by an exchange between the ions contained in the solution (3) and said electrodes. The consequence is therefore a return to electronic equilibrium that gives back to the electrodes (6) to (11) all of their capacity without loss of material deposited before the power cut-off.

[0054] According to a preferred embodiment of the invention, the device for optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration, has electronic control means (CM) allowing for decouplings (CM) of the ground electrode (22) provided in the method of the initial U.S. Pat. No. 2,733,748 in order to increase the rapidity of the ionic descaling of the electrodes (6) to (11).

[0055] This decoupling action of the ground electrode (22) has for purpose to disorganize the ionic system in such a way that the free electrons return to the path of their respective electrode and the ions are again deposited where they have to be.

[0056] According to a preferred embodiment of the invention, the device for optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration, has electronic control means (CM) allowing for permanent control and optimum regulation of the voltage in the treated solution (3) and during the entire duration of the treatment, by means of sensitive probes (SP) introduced between the pairs of electrodes (6)(7), (8)(9), (10)(11) of the device. These means also allow for all of the functions concerning the control, regulation and communication of information allowing for the proper management of the device. (See FIG. 2)

[0057] According to a preferred embodiment of the invention, the device for optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration involves a ground electrode (22) of a material and/or texture that are different from those of the other anode (6) (9) (10) and cathode (7) (8) (11) electrodes. As the ground constituted by the ground electrode (22) has to remain unique in the system, all of the other constituents of the device in contact with the liquid (3) and for example tank, filters, tubes, pipes, pumps, etc. are in no case conductors of electricity and consequently manufactured from suitable insulating materials. (See FIG. 2).

[0058] According to a preferred embodiment of the invention, the device for optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration, involves electrodes, anodes (6)(9)(10) and cathode (7)(8)(11) of materials and texture that are different according to a chemical and radiochemical composition (radioactive effluents) of the liquid (3) to be treated. (See FIG. 2).

[0059] According to a preferred embodiment of the invention, the device for optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration, involves sensitive probes (SP) with a chemically neutral texture and for example made of glass, in order to allow for the control and the regulation of the voltage in the solution to be treated (3), throughout the entire duration of the operation. (See FIG. 2).

[0060] According to a preferred embodiment of the invention, the device for optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration involves the recovery at the end of the cycle, of the confined electrodes (6) to (11) (radioactive elements) and/or the elimination thereof according to the fixed polluting elements, by means that are adapted to the elements thereof and to the level of the polluting effect thereof (See FIG. 2).

[0061] According to a preferred embodiment of the invention, the device for optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration, provides that the electrodes (6) to (11) plunged into the differential electroplating tank (2), provided in cylindrical shape and coaxial in the initial patent, be of a different shape and in particular in the form of a plate. In such a case, the initial principle remains unchanged, with the electrodes being applied on the opposite faces of neutral supports in plates, with the differential ground (22) being placed in an insulating tube in order to prevent any electronic distortion.

[0062] According to a preferred embodiment of the invention, the device for optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration, provides that the device allows for use in alternating successive cycles or as continuous operation. In this latter case, the supply of the solution to be treated is carried out through the bottom (5) of the tank (2) for example by the duct (24) and at slow speed and determined according to the chemical composition and the texture of the solution to be treated (3), with the evacuation of the treated solution (3) being carried out in the top portion of the tank by a duct (28) provided for this purpose. (See FIG. 2).

[0063] According to a preferred embodiment of the invention, the device for optimizing the yield of the electroextraction of heavy metals in an aqueous solution with a high salt concentration, comprises more preferably in the circuit for the circulation of the solution being treated (3) and more preferably at the end of the circuit, at least one electrofiltration filter (EFF) intended mainly to fix the residual elements with a weak electromotive force that are still present in the solution (3) after the differential electroplating operation. (See FIG. 3)

[0064] The electrofiltration filter (EFF) is mainly comprised of a cylindrical container (C) for example made from a plastic material that is compatible with its operation and its performance. It is preferably of dimensions (Height/Diameter) that are compatible with its operation and its optimum performance and has two electrodes (EC1) and (EC2) plunged into a neutral filtering material (FM), of which one for example the anode, (EC1) is preferably thrust on the inside peripheral plane of the container (C) and the other for example the cathode (EC2) is thrust on an axial support tube (ST) located at the center of the inner surface of the lower plane of the container, which itself is provided at a short distance with a grille (GR). The electric current passing through the filtering material (FM) is regulated according to the chemical composition of the solution (3) exiting from the electrolytic treatment container (2) and adapted to the resistivity of the whole knowing that the conductivity of the filtering material (FM) varies according to the more or less aqueous liquid that it contains (See FIG. 3).

[0065] The solution (3) filtered by its passing through the electrofiltration filter (EFF) of the invention then has an optimum quality allowing the discharge thereof into the environment or for example the reuse thereof in another method of manufacturing.

[0066] In a nuclear application, the radioactive elements are practically extracted from the effluent (3) which can then be eliminated into the environment without risk, with the radioactive elements being however confined according to known methods.