System for the treatment of at least one reducing substance of mineral or organic origin in an aqueous medium and method for implementing it

Abstract

System for treating at least one reducing substance of mineral or organic origin in an aqueous medium and method for implementing it. The invention relates to a system for treating at least one reducing substance of mineral or organic origin in an effluent, characterized in that the system comprises at least: an electrochemical cell (1) comprising at least: two compartments, respectively anodic (12) and cathodic (14), separated by a cation or anion exchange membrane (13); a pair of electrodes, anodic (121) and cathodic (141), positioned at the level of the respective compartments (12, 14); an electrolyte in the cathodic compartment (14) in the form of at least one strong base; a circuit (2) for circulating the aqueous effluent to be treated, at least a portion of which constitutes the anodic compartment (12); an electrical circuit (3) for supplying power to each of the electrodes (121, 141) of the cell (1) electrochemical,the electrical circuit (3) involving a pulsed field generator (31) of which at least one parameter is controlled by a dedicated device. Figure to be published with the abbreviation: Fig. 1,

Description

Title of the invention: System for the treatment of at least one reducing substance of mineral or organic origin in an aqueous medium and method for implementing the same

[0001] The present invention relates to the field of mechanisms for treating reducing substances of mineral or organic origin in an aqueous medium and more particularly to the field of mechanisms allowing the treatment of reducing substances having a so-called hard or refractory chemical oxygen demand.

[0002] For ecological reasons, water of industrial origin cannot be discharged into natural environments when it contains certain more or less complex substances for which oxidation and / or biological degradation are particularly difficult, or even impossible. Indeed, such discharges would lead to a depletion of the oxygen available in aquatic environments and would harm ecosystems by affecting them through hypoxia and anoxia.

[0003] In order for water containing such substances known as hard COD, i.e. for which a chemical oxygen demand is particularly high, to be discharged into nature, it is therefore essential and imperative that they undergo prior treatment resulting in the oxidation of these substances. Different solutions for the oxidation of suspended substances have thus been developed which allow the discharge of treated aqueous solutions into natural environments while meeting the constraints of respecting ecosystems.

[0004] While treatment solutions exist and have been developed, such as the implementation of the so-called "Fenton" process or oxidation by H2O2 under ultraviolet catalysis, they are also the source of significant, if not negligible, waste production. Some developed solutions, such as treatment with ozone oxidation, are sometimes even dangerous. But more generally, the various solutions currently available, despite investments and implementation costs that are often particularly high, such as for example in the context of treatment by hypercritical oxygen oxidation, do not, however, adequately meet the performance requirements required in view of increasingly stringent environmental standards for the discharge of effluents.

[0005] The present invention aims to overcome these drawbacks by proposing a solution which allows effective treatment on an industrial scale of aqueous effluents comprising reducing substances known as hard or refractory COD with a view to their total or partial destruction, prior to their possible discharge into natural environments, while being, on the one hand, simple to implement and, on the other hand, capable of meet any compactness constraints.

[0006] The invention thus consists of a system for the treatment of at least one reducing substance of mineral or organic origin in an aqueous medium, characterized in that the system comprises at least: - an electrochemical cell involving at least: - two compartments, respectively anode and cathode, separated by a cationic or anionic exchange membrane, - a pair of electrodes, anodic and cathodic, positioned at the level of respective compartments, - an electrolyte in the cathode compartment in the form of at least one strong base, mineral or organic, - a circulation circuit for the water or aqueous medium to be treated, at least one portion of which forms the anode compartment, - an electrical circuit for supplying power to each of the electrodes of the electrochemical cell, the electrical circuit involving a pulsed field generator of which at least one parameter is controlled by a dedicated device.

[0007] The invention also relates to a method for treating at least one reducing substance of mineral or organic origin by a system comprising: - at least one electrochemical cell involving at least: - two compartments, respectively anode and cathode, separated by a cationic or anionic exchange membrane, - a pair of electrodes, anodic and cathodic, positioned at the level of respective compartments, - an electrical circuit supplying each of the electrodes of the electrochemical cell, characterized in that the method comprises at least one step of supplying the electrochemical cell with a pulsed field current.

[0008] The invention will be better understood from the following description, which relates to a preferred embodiment, given by way of non-limiting example, and explained with reference to the appended schematic drawings, in which:

[0009] [Fig-1] represents a schematic illustration of an example of a system according to the invention for the treatment of at least one reducing substance of mineral or organic origin in an aqueous medium,

[0010] [Fig.2] represents a graphic illustration of the comparison of the reaction dynamics of degradation of at least one reducing substance in an aqueous effluent for different types of electrical power supplies of the electrochemical cell of a system according to the invention.

[0011] The invention relates to a system for the treatment of at least one reducing substance of mineral or organic origin in an aqueous medium, characterized in that the system comprises at least: - an electrochemical cell 1 involving at least: - two compartments respectively anode 12 and cathode 14 separated by a cationic or anionic exchange membrane 13, - a pair of electrodes, anode 121 and cathode 141, positioned at the level of respective compartments 12, 14, - an electrolyte in the cathode compartment 14 in the form of at least one strong base, mineral or organic, - a circuit 2 for circulating the water or aqueous medium to be treated, at least one portion of which forms the anode compartment 12, - an electrical circuit 3 for supplying power to each of the electrodes 121, 141 of the electrochemical cell 1, the electrical circuit 3 involving a generator 31 of pulsed fields of which at least one parameter is controlled by a dedicated device.

[0012] The system of the invention is thus configured to allow the implementation of an electrochemical reaction resulting in an oxidation of certain of the components present in the aqueous medium to be treated with circulation in particular through the anode compartment 12 of the electrochemical cell 1. Within the electrochemical cell 1 forming a substantially sealed reaction volume, this electrochemical reaction results in particular in the displacement of a sodium ion in the anode compartment 12 through the exchange membrane 13 so as to operate, on the one hand, the oxidation of at least one substance in solution and / or in suspension in the water to be treated circulating in the anode compartment 12 and, on the other hand, the reduction of the anode electrode 121.This electrochemical reaction is activated in particular under the effect of a pulsed electric current between each of the electrodes 121, 141 causing, on the one hand, at the cathode electrode 141, a release of dihydrogen and, on the other hand, at the anodic electrode 121, a release of gases resulting from the reduction of certain substances called hard COD such as nitrogen, carbon dioxide or dioxygen.The coupling of the anodic 121 and cathodic 141 electrodes of the system to an electrical circuit 3 makes it possible, on the one hand, to maintain efficiency in the redox reactions implemented at the level of the anode compartment 12, in particular between the anodic electrode 121 and at least one substance called hard COD, and, on the other hand, to carry out a possible forcing of the redox reactions by coupling them to an electrolysis so as to carry out an effective oxidation of the reducing substances suspended in the flow of the aqueous medium or the water to be treated. The electrical circuit 3 thus maintains in . permanently the oxidation capacities of the anode electrode 121 so that it is able to react effectively with the reducing substances suspended in the flow of water to be treated.

[0013] The pulsed field generator 31 operates the power supply of the electrodes, anode 12 and cathode 14. The different pulsed fields are controlled so as to correspond to a signal which specifically responds to at least one parameter determined by the dedicated control device. These different parameters are thus likely to correspond to the voltage, the intensity, the frequency, the geometric profile of the signal or even the cycle percentage. This cycle percentage, also called the cycle ratio, thus defines the ratio between, on the one hand, the duration of the active signal of all the pulses during a cycle and, on the other hand, the total duration of the cycle.

[0014] It should be noted that the anode electrode 121 is likely to exhibit behavior, in particular in its variation of the electrical potential at the surface of the electrode 121 in contact with the aqueous medium to be treated, similar to the operation of a capacitor operating according to the electric double layer model.

[0015] According to an example of construction relating to an alternative embodiment of the system according to the invention, the system also comprises a circuit 4 for circulating at least one strong base, at least a portion of which forms the cathode compartment 14 of the electrochemical cell 1. The integration of such a circuit 4 for circulating at least one strong base in the system according to the invention makes it possible to carry out a regular, or even continuous, renewal of the strong base present in the cathode compartment 14 of the electrochemical cell 1. Also, the cathode compartment 14 is able to maintain the presence of a quality reagent to ensure the operating efficiency of the electrochemical cell 1 in the treatment of the flow of the aqueous medium to be treated in circulation of the dedicated circuit 2.

[0016] It should be noted that at least one of the circuits among circuit 2 for circulating the water or aqueous effluent to be treated and circuit 4 for circulating at least one strong base, involves a pump to ensure continuity of the respective flow circulating in each of the dedicated circuits.

[0017] According to another example of construction relating to an alternative embodiment of the system according to the invention capable of being combined with the different variants detailed previously, the electrochemical cell 1 is arranged so that: - the anode electrode 121 is positioned inside the anode compartment 12, and - the wall of the anode compartment 12 comprises at least two cation exchange membranes 13 respectively positioned at different portions of the wall of the compartment 12, each of the membranes 13 cation exchangers being arranged to achieve a separation of the anode compartment 12 with a respective cathode compartment 14. According to this exemplary implementation, the electrochemical cell 1 of the invention is configured to optimize the exchanges between the different compartments 12, 14 and in particular to facilitate the exchanges allowing redox reactions within the anode compartment 12. Indeed, the multiplication of the cationic exchange membranes 13 around the anode compartment 12 makes it possible to increase the exchange surface between the two types of compartment 12, 14 and, in particular, to prevent a portion of the reducing substances suspended in the flow of water in transit through the anode compartment 12 from escaping the electrochemical treatment that the cell 1 allows. It should be noted that, in the example illustrated schematically in the figures of this document, the anode compartment 12 is associated with two cathode compartments 14.However, a combination of an anode compartment 12 with a greater number, for example three or four, cathode compartments 14 is perfectly feasible within the framework of the construction of a system according to the invention.

[0018] According to another example of construction relating to an alternative embodiment of the system according to the invention capable of being combined with the technical characteristics of the previously detailed variant, at least one of the circulation circuits 2, 4 of the system comprises at least one branch configured to distribute at least two conduits associated with respective compartments 12, 14 of the electrochemical cell 1. According to this alternative construction, the supply of different compartments of the same type is operated by the same circuit so that the components and reagents present at the level of the respective compartments of the same type are strictly identical as well as the electrochemical reactions which result therefrom. Thus, an identical strong base with an identical concentration or an identical mixture of strong bases is distributed by branches 41 of the dedicated circuit 4 at the level of each of the cathode compartments 14 of the system.Similarly, although a construction of the system integrating a single anode compartment 12 associated with several cathode compartments is preferred, a variant of construction of the system according to the invention is likely to correspond to a treatment of the water or the aqueous medium to be treated distributed by the dedicated circuit 2 at the level of branches associated with several respective anode compartments 12 of the system to allow its circulation therein.

[0019] According to another example of construction relating to an alternative embodiment of the system according to the invention capable of being combined with different variants previously detailed, the circulation circuit 4 of at least one strong base comprising at least two branches 41 configured to distribute compartments ca respective cathodic compartments 14 positioned opposite different portions of the anode compartment 12, each cathodic compartment 14 incorporates at least one respective cathodic electrode 141. Thus, in the context of this variant embodiment, each of the cathodic compartments 14 which correspond to respective portions of the circulation circuit of the at least one strong base formed by branches 41 of the circuit 4, forms an autonomous compartment of the electrochemical cell 1 to operate, through an exchange membrane 13, with the anode compartment 12 and the associated anode electrode 121.

[0020] According to another example of construction relating to an alternative embodiment of the system according to the invention capable of being combined with different previously detailed variants, at least one of the compartments, anode 12 or cathode 14, has an arrangement such that the distance which separates the electrode, anode 121 or cathode 141, from the cation exchange membrane 13 along an axis perpendicular to the plane or to a tangent of the membrane 13 is of the order of at most 15 millimeters.The construction of a compartment 12, 14 with such a configuration allows the creation of a reaction space sufficiently narrow so that the majority, or even all, of the reagents or components intended to react present in the flow circulating at the level of this space, anodic or cathodic, are forced to circulate close to or as close as possible, on the one hand, to the electrode 121, 141 of the compartment 12, 14 and, on the other hand, to the exchange membrane 13 so as to support an electrochemical reaction within the framework of the operation of the cell 1. Preferably, the compartment, anodic 12 or cathodic 14, is arranged so that the flow circulating in the compartment 12, 14 passes entirely through the space which separates the electrode, anodic 121 or cathodic 141, from the cationic exchange membrane 13.A multiplication of the reaction compartments, anodic 12 and / or cathodic 14, which have narrow thicknesses of their respective internal volumes makes it possible to increase the treatment speed and the quantity of water or aqueous medium treated.

[0021] According to another example of construction relating to an alternative embodiment of the system according to the invention capable of being combined with different previously detailed variants, the electrolyte of the cathode compartment 14 also called catholyte comprises at least sodium hydroxide and / or another strong mineral and / or organic base. It should be noted that the electrolyte present in the cathode compartment 14 is a strong base or a mixture of strong bases and has a pH of at least 12. Also, although sodium hydroxide is preferred because it corresponds to a common inexpensive commercial reagent, any other electrolyte of the cathode compartment 14 which meets the characterization of a strong base or a mixture of strong bases, mineral and / or organic, is likely to be considered.

[0022] According to another example of construction relating to an alternative embodiment of the system according to the invention capable of being combined with different variants previously detailed, the cathode electrode 141 is made of graphite and / or graphene and / or stainless steel and / or conductive polymer. It should be noted that the cathode electrode 141 is also capable of being made by a structure formed from a mixture of these different components. As an example of construction, the cathode electrode 141 has a thickness of the order of 5 millimeters.

[0023] It should be noted that, geometrically, the electrodes and preferably the cathode electrode 141, are likely to be configured to have the shape of a three-dimensional structure, such as expanded metal so that the surfaces of each of the electrodes allowing the implementation of redox reactions are optimized, the shearing and the stretching of the structure of the electrode allowing an increase in the reactive surface with the components of the liquid flow circulating at the level of the compartment, anodic 12 or cathodic 14. Similarly, independently or in combination, the electrodes and preferably the anodic electrode 121, are likely to be configured so that the two respective faces of an electrode produce active surfaces for the implementation of redox reactions.Each of these construction geometries makes it possible to optimize the reactions between a liquid flow circulating at the level of the compartment, anodic 12 or cathodic 14, whether it is the strong base or mixture of strong bases or the aqueous medium to be treated in their dedicated circuits 2, 4.

[0024] According to another example of construction relating to an alternative embodiment of the system according to the invention capable of being combined with different variants previously detailed, the anode electrode 121 is of the boron-doped polycrystalline diamond type, also called BDD (boron-doped diamond), or of the vitrified carbon type or of the lead dioxide type or of the titanium dioxide type. The anode electrode 121 is also capable of being produced in the form of a fluidized bed containing fine particles of boron-doped polycrystalline diamond. It should be noted that the anode electrode 121 is still capable of being produced by a structure formed from a mixture of these different components. As an example of construction, the anode electrode 121 has a thickness of the order of 5 millimeters.

[0025] According to another example of construction relating to an alternative embodiment of the system according to the invention capable of being combined with different previously detailed variants, the electrochemical cell 1 uses a reaction measurement probe, the device for controlling the fields pulsed by the generator being connected to this measurement probe. This measurement probe thus makes it possible to carry out real-time monitoring of the different electrochemical reactions in the presence and expected in the different reaction compartments, anode(s) 12 and cathode(s) 14. The association of this probe with the control device then makes it possible to operate an adjustment accordingly of at least one of the parameters of the electric current which supplies the electrodes, anode 121 and cathode 141, of the system so as to optimize the operation of the electrochemical cell 1 and the treatment of the water or aqueous medium circulating at the level of the anode compartment 12.

[0026] According to another example of construction relating to an alternative to the previous variant of the system according to the invention and capable of being combined with different variants previously detailed, the device for controlling the fields pulsed by the generator is arranged to operate independently of the reaction mechanism operated at the level of the electrochemical cell.

[0027] According to another example of construction relating to an alternative embodiment of the system according to the invention capable of being combined with different previously detailed variants, the system also comprises a device for recovering at least one of the gases produced by one of the reactions implemented by the electrochemical cell 1. These gases are in particular, at the cathode electrode 141, dihydrogen and, at the anode electrode 121, dinitrogen, carbon dioxide and / or dioxygen. The device for recovering at least one of these gases is also capable of being associated with a purification mechanism for the purpose of its storage or its use at the level of a fuel cell.

[0028] The invention also relates to a method for treating at least one reducing substance of mineral or organic origin by a system comprising: - at least one electrochemical cell 1 involving at least: - two compartments, respectively anode 12 and cathode 14, separated by a cationic or anionic exchange membrane 13, - a pair of electrodes, anode 121 and cathode 141, positioned at the level of respective compartments 12, 14, - an electrical circuit 3 supplying each of the electrodes 121, 141 of the electrochemical cell 1, characterized in that the method comprises at least one step of supplying the electrochemical cell 1 with a pulsed field current.

[0029] In the context of the method according to the invention, the electrical supply of the electrochemical cell 1 is not continuous but is carried out by a succession of electrical pulses at one of the two electrodes, anodic 12 or cathodic 14. These electrical pulses at a first of the two electrodes 12, 14 are then spaced apart by a rest period during which the intensity is zero or, alternatively, an electrical pulse is generated at the second of the two electrodes 12, 14. Such a supply of the electrochemical cell 1 by current pulsed allows a reduction of the impedance at the level of the electrical circuit of the system by an operation of the electrochemical cell 1, not only as a simple resistance but as a device allowing a resonance phenomenon similar to that of an RLC type circuit to be achieved. Such operation of the electrochemical cell 1 allows energy savings to be made. Furthermore, in the context of a pulsed electrical supply at the level of the electrochemical cell 1, the management of the frequency of the electrical pulses allows the operation of the electrochemical cell 1 to be adjusted to the degradation of one or other of the components moving at the level of the cell 1.Thus, for example, a component incorporating sulfur is likely to be subject to targeted degradation by a determined pulse frequency which is higher than a lower frequency likely to be necessary against another component present in the aqueous medium to be treated and having slower kinetics.

[0030] In the context of implementing the method according to the invention, the anode electrode 121 is preferably of the boron-doped polycrystalline diamond type, also called BDD (boron-doped diamond), or of the vitrified carbon type or of the lead dioxide type or of the titanium dioxide type. Similarly, the cathode electrode 141 is preferably made of graphite and / or graphene and / or stainless steel and / or conductive polymer.

[0031] According to an example of construction relating to an alternative embodiment of the method according to the invention and capable of being combined with the characteristics of the different variants detailed above, the current pulses are bidirectional and / or superimposed. When the pulses generated are of the bidirectional type, that is to say when the electrical circuit 3 supplying each of the electrodes 121, 141 of the electrochemical cell 1 is crossed by a superposition of two electric currents circulating in opposite directions to each other, it is then possible to obtain as an effect an electrochemical phenomenon corresponding to a maximum of polarization.When the generated current pulses are of the superimposed type, several currents are applied simultaneously to the terminals of the electrochemical cell 1 with different respective electrical pulse frequencies so as to target a degradation of different components present in the aqueous medium to be treated. As an example of implementation, two currents are applied to the terminals of the electrochemical cell 1: a first current in the form of a direct current and a second current in the form of a pulsed current. This combination of currents superimposed on the terminals of the electrochemical cell 1 has the effect of optimizing the conduction in the aqueous medium to be treated.

[0032] According to another example of construction relating to a variant of implementation of the method according to the invention and capable of being combined with the characteristics characteristics of the different variants previously detailed, the pulsed field current has a sinusoidal, triangular or rectangular profile.

[0033] Furthermore, according to another example of construction relating to an alternative embodiment of the method according to the invention and capable of being combined with the characteristics of the different variants detailed above, the frequency of the current profile is determined or selected to be adapted to one or more of the reactions at the level of the electrochemical cell 1, or even synchronized with one or more of these electrochemical reactions. Synchronization of parameters of the profile with certain of the electrochemical reactions at the level of the cell 1 also makes it possible to select one or more electrochemical reactions to be implemented as a priority depending on one or other of the components present in the aqueous medium to be treated.Thus, for example, in the context of a targeted degradation of hydrogen sulfide (H2S), the production of high-frequency current pulses allows a reduction of the hydrogen sulfide (H2S) to the sulfur state so that it precipitates, while keeping the other molecules intact. After filtration of the precipitated sulfur, the filtered aqueous medium is likely to be treated at the level of another cell supplied by current pulses at a lower frequency and / or at a higher potential to degrade other components present in the aqueous medium. Alternatively and / or complementary, the filtered aqueous medium is also likely to be circularized by being reintroduced at the level of the same electrochemical cell 1 which is then supplied by different current pulses with a lower frequency and / or a higher potential.

[0034] According to another example of construction relating to an alternative implementation of the method according to the invention and capable of being combined with the characteristics of the different variants detailed above, the method comprises at least one step of parameterizing the electric current pulse at the level of the electrochemical cell 1 as a function of at least one reducing substance to be treated. This parameterization step consists of characterizing the electric current pulses generated as a function in particular of their frequency and their intensity as well as the rest phase which separates two successive pulses or even the generation period of these successions of pulses. Depending on the specific characteristics of the pulses generated during a sequence, the electrochemical cell 1 is able to carry out a targeted oxidation of a particular substance or a group of specific substances.For example, a pulse sequence with a frequency of around 400 kHz can be used to carry out targeted degradation by oxidation of hydrogen sulfide (H2S).

[0035] According to another example of construction relating to a variant of implementation of the method according to the invention and capable of being combined with the characteristics characteristics of the different variants previously detailed, the electrochemical cell 1 being associated with a probe for measuring at least one reaction at the level of the cell 1, the method comprises at least one step of parameterizing the current pulse as a function of the reaction speed at the level of the electrochemical cell 1. This step of the method thus makes it possible to adjust the electrical pulses supplied to the electrochemical cell 1 as a function of at least one reaction in the expected presence or of the degradation by oxidation of at least one particular targeted substance of the water or aqueous medium to be treated.

[0036] According to another example of construction relating to an alternative implementation of the method according to the invention and capable of being combined with the characteristics of the different variants detailed above, the method comprises at least one step of varying at least one parameter of the pulsed current during the treatment. By way of example, the variation of the at least one current parameter is triggered under the effect of a command associated with a signal coming from a probe for measuring at least one reaction at the level of the electrochemical cell 1. Due to variations of at least one parameter of the pulsed current, the electrical supply of the electrochemical cell 1 is carried out in the form of a succession of at least two sequences of pulses which differ from the variation of the at least one parameter. The treatment method according to the invention is thus capable of being carried out in the form of a succession of different sequences of pulses.Depending on the parameters specific to each of these successive pulse sequences, oxidations are more specifically directed towards one or other of the substances in the aqueous medium to be treated. Also, the treatment method according to the invention is likely to be carried out by a succession of pulse sequences respectively configured for degradation directed towards a substance or a group of substances specific to the aqueous medium to be treated. The management of these different sequences, in particular in terms of parameterization and programming, is likely to be implemented by dedicated software.

[0037] According to another example of construction relating to a specific variant of the previously detailed implementation variant of the method, the method comprises at least one step of variation of at least one parameter of the pulsed current during the treatment, during which the at least one parameter of the pulsed current corresponds to the voltage, the intensity, the frequency of the pulsed current and / or the percentage of cycle also called duty cycle ratio. Several steps of variations of one or more parameters of the pulsed current are likely to occur, successively or jointly when different currents are distributed in the electrical circuit 3 during the treatment. Also, the method is likely to have one or more windows corresponding to respective combinations of different parameters of the electrical signal for treatments respectively targeted towards one or more of the substances in the aqueous environment to be treated.

[0038] According to another example of construction relating to a specific variant of the two previously detailed implementation variants of the method, the method comprises at least one step of varying at least one parameter of the pulsed current during the treatment so that the variation of the at least one parameter is adjusted according to the progress of at least one electrochemical reaction at the level of the electrochemical cell 1. Also, during the treatment, the variation of at least one parameter of the electrical signal is likely to accentuate the degradation reaction(s) of one or more of the substances of the aqueous medium to be treated.Similarly, during the treatment and as the rate of depletion of one or more of the substances in the aqueous medium to be treated increases, the windows corresponding to respective combinations of different electrical signal parameters are likely to be readjusted so as to maintain conduction even when the oxidation reaction(s) are complete so that the slowdown in depletion is able to be abbreviated at the end of the depletion exponential.

[0039] According to another example of construction relating to a variant of implementation of the method according to the invention and capable of being combined with the characteristics of the different variants detailed previously, the pulsed field has a frequency between 0 and 2000 kHz, preferably between 100 kHz and 900 kHz, ideally between 200 kHz and 600 kHz and, optimally, of the order of 400 kHz.

[0040] According to an example of implementation of the method of the invention, a volume of one liter of effluent is prepared from a solution at pH 7.92 with a conductivity of the order of 11.1 mS / cm acidified with 1 mL of 96% sulfuric acid so as to obtain a final solution of pH 1.84 and final conductivity of the order of 16 mS / cm. In parallel, a volume of one liter of strong base is prepared from commercial sodium hydroxide of concentration IN. Each of the prepared solutions is circulated by a pump mechanism in a dedicated circuit of a system according to the invention with a circulation speed of the order of 15 liters per hour so that, on the one hand, the acid solution is in circulation at the level of the anode compartment 12 of the electrochemical cell 1 and, on the other hand, the strong base is in circulation at the level of the cathode compartment 14 of the electrochemical cell 1.The anode electrode 121 is then made of boron-doped polycrystalline diamond, also called BDD.

[0041] In the context of this example of implementation of the method of the invention, an oscilloscope is connected to the level of the electrochemical cell 1 so as to monitor different parameters of the electric fields pulsed by the generator 31 such as the type of current, the voltage, the intensity, the effective frequency, the percentage of cycle and the shape or geometry of the signal. At the same time, the reaction present at the electrochemical cell 1 is monitored by a chemical dosage at regular time intervals of the reducing substances called hard COD present. Furthermore, the gases resulting from the reactions present at the electrochemical cell 1, namely in particular the oxygen at the anode electrode 121 and the hydrogen at the cathode electrode 141 are channeled via dedicated breathing tubes.

[0042] Comparative tests of the degradation efficiencies of reducing substances known as hard COD as a function of different types of current, namely direct current, rectified current and pulsed current, were carried out and reported on the detailed graph in [Fig.2],

[0043] In the context of a test carried out with a direct current supply of the electrochemical cell 1 by the generator 31 with a voltage of 10 volts and a maximum intensity of 10 amperes and where the oscilloscope connected to the level of the electrochemical cell 1 measures a real current with an intensity of between 2 and 6 amperes, the evolution of the content of reducing substances called hard COD measured over time is represented by the curve referenced A of the detailed graph in [Fig.2]. From a concentration of reducing substances of the order of 2500 mg / L, this fell to 47.3 mg / L indicating an elimination rate of 98% after 730 minutes of treatment.

[0044] In the context of a test carried out with a power supply to the electrochemical cell 1 with rectified current by the generator 31 with a voltage of 12 volts and a maximum intensity of 30 amperes and where the oscilloscope connected to the level of the electrochemical cell 1 measures a real current with an intensity of between 3 and 15 amperes, the evolution of the content of reducing substances called hard COD measured over time is represented by the curve referenced B of the detailed graph in [Fig. 2]. From a concentration of reducing substances of the order of 2500 mg / L, this fell to 42 mg / L indicating an elimination rate of 98% after more than 950 minutes of treatment and according to a curve substantially similar to the degradation curve of hard COD in the context of a power supply to the electrochemical cell 1 with direct current.

[0045] In the context of a test carried out with a power supply of the electrochemical cell 1 with pulsed current from the generator 31 and where the oscilloscope connected to the level of the electrochemical cell 1 measures a real current with a voltage of the order of 23.6 volts, an intensity of 10 amperes, a frequency of 200 kHz and 80% of the cycle, the evolution of the content of reducing substances called hard COD measured over time is represented by the curve referenced C of the detailed graph in [Fig.2]. From a concentration of reducing substances of the order of 2082 mg / L at the start, this is of the order of 224 mg / L after 300 minutes of treatment, indicating an elimination rate of more than 89%. Unlike the degradation of hard COD in the context of a supply of electrochemical cell 1 by a direct current or by a rectified current, the degradation curve of hard COD in the context of a supply of electrochemical cell 1 by pulsed current is of an exponential nature with significant kinetics.

[0046] It should be noted that for each of the tests detailed above, at the start of treatment, a degassing phenomenon occurs demonstrating the start of the electrochemical reaction at the level of cell 1. The electrolyte of the cathode compartment 14, initially transparent and devoid of coloration, is likely to experience a progressive coloration, in particular an orange color, due to a reaction with the binder of the graphite cathode electrode 141. At the same time, the treated aqueous effluent experiences a discoloration during the oxidation of the reducing substances called hard COD present.

[0047] Of course, the invention is not limited to the embodiments described and shown in the attached drawings. Modifications remain possible, in particular from the point of view of the constitution of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims

Claims

1. System for the treatment of at least one reducing substance of mineral or organic origin in an aqueous medium, characterized in that the system comprises at least: - an electrochemical cell (1) involving at least: - two compartments, respectively anode (12) and cathode (14), separated by a cationic or anionic exchange membrane (13), - a pair of electrodes, anode (121) and cathode (141), positioned at the level of respective compartments (12, 14), - an electrolyte in the cathode compartment (14) in the form of at least one strong base, mineral or organic, - a circuit (2) for circulating the water or aqueous medium to be treated, at least a portion of which forms the anode compartment (12), - an electrical circuit (3) for supplying each of the electrodes (121, 141) of the electrochemical cell (1),the electrical circuit (3) involving a generator (31) of pulsed fields of which at least one parameter is controlled by a dedicated device.,

2. System according to claim 1, characterized in that the system also comprises a circulation circuit (4) of at least one strong base of which at least one portion forms the cathode compartment (14) of the electrochemical cell (1).

3. System according to one of the preceding claims, characterized in that the electrochemical cell (1) is arranged so that: - the anode electrode (121) is positioned inside the anode compartment (12), and - the wall of the anode compartment (12) comprises at least two cation exchange membranes (13) respectively positioned at different portions of the wall of the compartment (12), each of the cation exchange membranes (13) being arranged to achieve a separation of the anode compartment (12) with a respective cathode compartment (14).

4. System according to one of the preceding claims, characterized in that the circuit (2) for circulating the water or aqueous medium to be treated and / or, when the system also comprises a circuit (4) for circulating at least one strong base, the circuit (4) for circulating at least one strong base, comprises at least one branch configured to distribute at least two conduits associated with respective compartments (12, 14) of the electrochemical cell (1).

5. System according to claims 2, 3 and 4, characterized in that, the circulation circuit (4) of at least one strong base comprising at least two branches (41) configured to distribute respective cathode compartments (14) positioned opposite different portions of the anode compartment (12), each cathode compartment (14) integrates at least one respective cathode electrode (141).

6. System according to one of the preceding claims, characterized in that at least one of the compartments, anodic (12) or cathodic (14), has an arrangement such that the distance which separates the electrode, anodic (121) or cathodic (141), from the cation exchange membrane (13) along an axis perpendicular to the plane or to a tangent of the membrane (13) is of the order of at most 15 millimeters.

7. System according to one of the preceding claims, characterized in that the electrolyte of the cathode compartment (14) comprises at least sodium hydroxide and / or another strong mineral and / or organic base.

8. System according to one of the preceding claims, characterized in that the cathode electrode (141) is made of graphite and / or graphene and / or stainless steel and / or conductive polymer.

9. System according to one of the preceding claims, characterized in that the anode electrode (121) is of the boron-doped polycrystalline diamond type, also called BDD (boron-doped diamond), or of the vitrified carbon type or of the lead dioxide type or of the titanium dioxide type.

10. System according to one of claims 1 to 9, characterized in that the electrochemical cell (1) uses a reaction measurement probe, the device for controlling the fields pulsed by the generator being connected to this measurement probe.

11. System according to one of claims 1 to 9, characterized in that the The device for controlling the pulsed fields by the generator is arranged to operate independently of the reaction mechanism operated at the level of the electrochemical cell.

12. System according to one of claims 1 to 11, characterized in that the system also comprises a device for recovering at least one of the gases produced by one of the reactions carried out by the electrochemical cell (1).

13. Method for treating at least one reducing substance of mineral or organic origin by a system comprising: - at least one electrochemical cell involving at least: - two compartments, respectively anode and cathode, separated by a cationic or anionic exchange membrane, - a pair of electrodes, anode and cathode, positioned at the level of respective compartments, - an electrical circuit supplying each of the electrodes of the electrochemical cell, characterized in that the method comprises at least one step of supplying the electrochemical cell with a pulsed field current.

14. Method according to claim 13, characterized in that the current pulses are bidirectional and / or superimposed.

15. Method according to one of claims 13 to 14, characterized in that the method comprises at least one step of parameterizing the pulse of the electric current at the level of the electrochemical cell (1) as a function of at least one reducing substance to be treated.

16. Method according to one of claims 13 to 15, characterized in that, the electrochemical cell (1) being associated with a probe for measuring at least one reaction at the level of the cell (1), the method comprises at least one step of parameterizing the current pulse as a function of the reaction speed at the level of the electrochemical cell (1).

17. Method according to one of claims 13 to 16, characterized in that the method comprises at least one step of varying at least one parameter of the pulsed current during the treatment.

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