Method and plant for treating a flow of an aqueous solution by means of a particulate medium activated by bipolar electrochemistry

Abstract

The present invention relates to a method (200) for treating a flow of an aqueous solution, the method comprising: a) activating (205) a particulate medium (20) to be activated, which medium comprises a material having a non-zero electrical conductivity; b) dispensing (210) the thus activated particulate medium (20) into a treatment volume (15); and c) circulating (215) a flow of an aqueous solution to be treated (25) in the treatment volume (15) through the activated particulate medium (20), in order to form a flow of treated aqueous solution (45), which activation takes place using a bipolar electrochemical process, the bipolar electrochemical process comprising the application, using at least two electrodes (95), of an electrical potential difference to an activation compartment (70) containing the particulate medium (20), in the presence of an electrolyte (90), without direct contact between the particulate medium (20) and the electrodes (95).

Description

[0001] TITLE: Process and installation for treating a stream of aqueous solution using a particulate medium activated by bipolar electrochemistry

[0002] The present invention relates to a method for treating a stream of aqueous solution using a particulate medium activated by bipolar electrochemistry and to an installation for treating a stream of aqueous solution using such a method.

[0003] In the field of water treatment, for example for the production of drinking water or the purification of wastewater, it is known to implement a filtration or separation step of a water stream to be treated on a particulate medium chosen to adsorb one or more compounds to be removed.

[0004] The particulate medium is, for example, activated carbon, in powder form (CAP) or in granules (CAG).

[0005] The adsorption performance of activated carbon depends on many parameters, including the specific surface area and pore size distribution of the carbon, as well as the nature and concentration of the functional groups present on its surface.

[0006] It is known to activate or regenerate powdered or granular coal by physical processes, such as heating to a temperature of around 1000°C under a controlled atmosphere, in order to increase the specific surface area of ​​the pores and / or to desorb molecules that would already be adsorbed on these pores.

[0007] Due to the emergence of new micropollutants with increasingly diverse chemical structures, the adsorption spectrum of activated carbons obtained by current physical processes is not always sufficient to eliminate undesirable molecules under conditions of implementation of activated carbon that are realistic or compatible with industrial practices, particularly in terms of dosage and lifespan of activated carbon.

[0008] In particular, the removal of small, poorly adsorbable polar molecules such as pesticide metabolites, per- and polyfluoroalkyl substances (PFAS) or certain drug residues still needs improvement.

[0009] The adsorption properties of activated carbon can be modified by chemical processes, either alternatively or in addition to physical processes. Document EP 765 840 describes, in particular, a chemical process for treating activated carbon with trimethylchlorosilane to increase its hydrophobic character.

[0010] Such a chemical process has the disadvantage of uniformly increasing the hydrophobic character of activated carbon, thus reducing its affinity for any hydrophilic molecules which would also have to be eliminated from the water stream to be treated.

[0011] Furthermore, trimethylchlorosilane is toxic and harmful to the environment, so it is not desirable to implement this compound for water treatment, especially for the production of drinking water.

[0012] One aim of the invention is therefore to provide a method for treating an aqueous solution by means of a particulate medium allowing the adsorption of a wider range of compounds, particularly in terms of hydrophilic / hydrophobic character, than prior art treatments, while having a limited environmental impact.

[0013] To this end, the invention relates to a process for treating a stream of aqueous solution comprising: a) the activation of a particulate medium to be activated comprising a material having non-zero electrical conductivity, b) the distribution of the particulate medium thus activated in a treatment volume, and c) the circulation of a stream of aqueous solution to be treated in the treatment volume through the activated particulate medium, to form a stream of treated aqueous solution, characterized in that the activation is carried out by a bipolar electrochemical process, the bipolar electrochemical process comprising the application of an electrical potential difference by means of at least two electrodes to an activation compartment containing the particulate medium in the presence of an electrolyte, without direct contact between the particulate medium and the electrodes.

[0014] Activation of the particulate medium comprising a material having non-zero electrical conductivity, such as a semiconductor or electrically conductive material, including a metallic or carbon-based material, by a bipolar electrochemical process makes it possible to modify the surface state of this material and in particular to obtain a hydrophilic / hydrophobic affinity gradient on the macroscopic scale along a dimension in which the shaped particulate medium extends, for example at the scale of the height of a filtration column, and possibly at the scale of each particle.

[0015] The activated particulate medium can then adsorb not only the same molecules as before activation, but also molecules that are more hydrophobic and / or more hydrophilic than the latter, in a spectrum that depends on the physicochemical parameters of implementation of the bipolar electrochemistry process.

[0016] In particular, the choice of the potential difference between source electrodes, the electrolyte and / or the duration for which the potential difference is applied allows the hydrophilic / hydrophobic affinity gradient to be modulated according to the needs of the application, depending on the nature of the particulate medium before activation.

[0017] This activation step has the advantage of not involving toxic and / or polluting chemical solvents.

[0018] This activation step also has the advantage of being relatively energy-efficient.

[0019] According to other advantageous aspects of the invention, the process for treating a stream of aqueous solution comprises one or more of the following features, taken individually or in any technically possible combination:

[0020] - the bipolar electrochemistry process includes the circulation of the electrolyte through the particulate medium;

[0021] - the process of treating a stream of an aqueous solution includes between the activation a) and the distribution b) of the particulate medium: d) the separation of the activated particulate medium from the electrolyte in a separator connected to the activation compartment and the treatment volume;

[0022] - the electrolyte has an electrical conductivity of less than 100 mS.cm- 1 ;

[0023] - the particulate medium to be activated includes charcoal;

[0024] - the activation compartment is delimited by at least one wall permeable to fluids and impermeable to the particulate medium;

[0025] - the activation compartment extends between a first fluidic contact end placed in a first compartment of an electrolyte reservoir and a second fluidic contact end placed in a second compartment of the electrolyte reservoir, the activation compartment thus forming a first fluidic communication between the first and second compartments of the electrolyte reservoir;

[0026] - the second compartment of the electrolyte reservoir is placed at a higher altitude than the first compartment of the electrolyte reservoir so as to allow the electrolyte to flow spontaneously from the second compartment of the electrolyte reservoir to the first compartment of the electrolyte reservoir through the activation compartment, the process including a recirculation from the first compartment of the electrolyte reservoir to the second compartment of the electrolyte reservoir during activation (a). The invention also relates to an installation for treating a stream of an aqueous solution comprising: (i) a treatment volume intended to receive a particulate medium and a stream of aqueous solution to be treated, the treatment volume comprising:

[0027] * an inlet for the aqueous solution stream to be treated and an outlet for a treated aqueous solution stream, and

[0028] * an inlet for introducing the particulate media and an outlet for extracting the particulate media, the installation being characterized in that it comprises: ii) a bipolar electrochemical activation cell comprising:

[0029] - a source of particulate media,

[0030] - an activation compartment comprising an injection inlet for the particulate media to be activated connected to the source and an outlet for distributing the activated particulate media to the introduction inlet of the treatment volume,

[0031] - an electrolyte reservoir connected to the activation compartment, and

[0032] - at least two electrodes, configured to apply an electrical potential difference to the activation compartment, without direct contact with the particulate medium.

[0033] According to other advantageous aspects of the invention, the installation comprises one or more of the following features, taken individually or in all technically possible combinations:

[0034] - The installation includes a separator comprising:

[0035] *a separator inlet, connected to the distribution outlet and configured to receive a flow comprising the activated particulate media and the electrolyte,

[0036] * a first output of an electrolyte flow, and

[0037] * a second output of a drained particulate media stream, the second output being connected to the inlet of the processing volume;

[0038] - the installation includes an electrolyte recycling circuit from the first outlet of the separator to the electrochemical activation cell;

[0039] - the electrolyte reservoir comprises at least a first compartment and a second compartment in fluidic communication via the activation compartment;

[0040] - the installation includes an electrolyte recirculation system between the first and second compartments of the electrolyte tank;

[0041] - The installation includes a particulate media recycling circuit from the extraction outlet to the injection inlet. The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0042] Figure 1 is a schematic representation of a first installation for treating an aqueous solution according to the invention;

[0043] Figure 2 is a flowchart representation of a water treatment process according to the invention implemented using the installation of Figure 1;

[0044] Figure 3 is an observational snapshot of a charcoal grain activated by the activation step of the process in Figure 2, showing the atomic percentage of oxygen atoms for different areas of the grain;

[0045] Figure 4 shows the statistical distribution of the atomic percentage of oxygen atoms obtained on a sample of activated carbon by the activation step of the process in Figure 2, for different values ​​of the electrical voltage applied by the electrical voltage source, compared to an untreated sample (REF); and

[0046] Figure 5 shows a second embodiment of the activation cell of an installation similar to that of Figure 1.

[0047] A first embodiment of an installation 10 for treating a stream of an aqueous solution is described with reference to Figure 1.

[0048] The installation 10 includes a treatment volume 15, containing a particulate medium 20 comprising a material having electrical conductivity and receiving a flow of aqueous solution to be treated 25, and an activation cell 30 by bipolar electrochemistry, for the activation of the particulate medium 20 upstream of the treatment volume 15.

[0049] The treatment volume 15 includes an inlet 35 of the aqueous solution stream to be treated 25 and an outlet 40 of a treated aqueous solution stream 45, as well as an introduction inlet 50 of the particulate media 20 and an extraction outlet 55 of the particulate media 20, optionally connected to a storage tank 60.

[0050] The aqueous solution stream to be treated 25 received at the inlet 35 includes water, as well as molecular and / or ionic solutes and / or suspended solid particles.

[0051] The aqueous solution flow to be treated 25 is, for example, a flow of wastewater, industrial water, seawater, or even drinking water or water being treated for drinking.

[0052] The aqueous solution stream 25 must be treated, for example, before its release into the environment, its subsequent use or its reuse.

[0053] Ionic solutes include, for example, calcium, magnesium, sodium, carbonate, bicarbonate, sulfate, and / or chloride ions. Molecular solutes include, for example, organic molecules such as organic matter, hydrocarbons, or micropollutants, including pesticides, drug residues, or industrial waste.

[0054] In particular, micropollutants may include pesticide metabolites and / or per- and polyfluoroalkyl compounds (hereafter referred to as PFAS).

[0055] At least some of these solutes and / or suspended solid particles are to be removed at least partially during treatment, this part being referred to hereafter by the generic expression "at least one compound to be removed".

[0056] The treated aqueous solution stream 45 can therefore have a concentration in at least one compound to be removed lower than that of the treated aqueous solution stream 25.

[0057] The particulate medium 20 is configured to be brought into contact with the aqueous solution stream to be treated 25 in the treatment volume 15, so as to allow at least partial adsorption of at least one compound to be removed.

[0058] To this end, the particulate medium 20 is in the form of particles, so as to present a large contact surface with the flow of aqueous solution to be treated 25, and thus allow efficient adsorption of at least one compound to be removed.

[0059] The particulate medium 20 may include granular and / or microgranular particles and / or a powder.

[0060] In this application, the term "grains" means particles with an equivalent diameter between 0.5 mm and 4.0 mm inclusive, in particular between 0.5 mm and 2.0 mm.

[0061] In this application, micro-grains are defined as particles with an equivalent diameter between 100 pm and 0.5 mm, inclusive.

[0062] For the purposes of this application, powder means particles whose equivalent diameter is strictly less than 100 pm, in particular between 20 pm and 100 pm, excluding the upper limit.

[0063] The equivalent diameter of the particles, when it is greater than 80 pm, can be determined by sieving according to ISO 8130-1:2019 of 8 May 2019 or according to NF P94-056.

[0064] The equivalent diameter of particles, when it is between 5 pm and strictly less than 80 pm, can be determined according to ISO 14232-1:2017, i.e. by sieving, by sieving in an air jet or by laser diffraction as appropriate.

[0065] The particulate medium 20 comprises a material having a non-zero electrical conductivity.

[0066] In this application, non-zero electrical conductivity is defined as an electrical conductivity greater than or equal to 10 -6 S / cm at 298K. The material exhibiting non-zero electrical conductivity may notably include a semiconductor material, i.e., one exhibiting an electrical conductivity between 10 -6 S / cm and 103 S / cm at 298K and / or a material that conducts electricity, i.e., has an electrical conductivity between 10 3 S / cm and 10 6 S / cm at 298K.

[0067] In one particular embodiment, the particulate medium 20 comprises charcoal, alone or in a mixture, for example with silica.

[0068] The coal may have undergone prior activation by a process known in the prior art, in particular a process described in the introductory part of this application, so as to form activated carbon.

[0069] Activated charcoal can then be, for example, in the form of granular activated charcoal (GAC) or powdered activated charcoal (PAC).

[0070] Activated carbon can be new, meaning it has never been in contact with a stream of aqueous solution to be treated, or it can come from a regeneration step according to a process known in the prior art.

[0071] In general, the material exhibiting non-zero electrical conductivity can be chosen based on its electrical properties and its adsorption properties for one or more compounds to be removed.

[0072] The activation cell 30 is configured for the activation of the particulate medium 20 by bipolar electrochemistry upstream of the treatment volume 15.

[0073] The bipolar electrochemical activation cell 30 comprises a source 65 of the particulate medium 20, an activation compartment 70 of the particulate medium 20 including an injection inlet 75 of the particulate medium 20 to be activated connected to the source 65 and a distribution outlet 80 of the activated particulate medium 20 to the introduction inlet 50 of the treatment volume 15, as well as an electrolyte reservoir 85 90 connected to the activation compartment 70. The activation cell 30 includes at least two electrodes 95, configured to apply an electrical potential difference to the activation compartment 70, without direct contact with the particulate medium 20.

[0074] Source 65 therefore includes particulate medium 20 before its activation by bipolar electrochemistry.

[0075] The particulate medium 20 which is found in the source 65 is referred to as "particulate medium 20 to be activated" in this application.

[0076] The particulate medium 20 to be activated may have already undergone a process to modify its surface properties by a physical or chemical process known in the prior art, that is to say, a process other than a bipolar electrochemical process according to the invention. This is, for example, the case with CAP or CAG carbon. In a particular embodiment, the particulate medium 20 to be activated has at least partially already been previously activated within the meaning of the invention, that is to say, by a bipolar electrochemical process according to the invention, but has also already been implemented in the treatment volume 15.

[0077] In this case, the extraction outlet 55 of the treatment volume 15 can be connected by a recycling circuit 96 of the particulate media 20 from the extraction outlet 55 to the injection inlet 75.

[0078] The recycling circuit 96 includes, for example, as shown in Figure 1, a pump 97 for recycling the particulate media 20 from the storage tank 60 to the source 65.

[0079] This provision allows at least partial recycling of the particulate media 20 after its use in the treatment volume 15.

[0080] The activation compartment 70 is connected to the source 65 at the injection inlet 75 of the particulate media 20 to be activated via a pipe 100, equipped with a valve 105.

[0081] The activation compartment 70 is configured for the activation of the particulate medium 20 to be activated by the implementation of a bipolar electrochemical process.

[0082] Bipolar electrochemistry means the exposure of the particulate medium 20 to an electric field, so as to induce a temporary or permanent polarization at the scale of the individual particles of the particulate medium 20 and / or at the scale of a fictitious macroscopic volume in which the particulate medium 20 is contained.

[0083] For such polarization to be obtained, the particulate medium 20 to be activated has a non-zero electrical conductivity in the sense of the definition provided above.

[0084] Furthermore, the particulate medium 20 is not in direct contact with either of the electrodes 95 in the activation cell 30, since such contact would impose a uniform electrical potential on the whole of the particulate medium 20, incompatible with a polarization of this medium.

[0085] The general principle of bipolar electrochemistry, recalled above, is described in particular in the article by Fosdick SE et al., "Bipolar electrochemistry," Angewandte Chemie International Edition, September 2013, pages 10438-10456. Diagram 2, on page 10441 of this article, illustrates the polarization phenomenon of a so-called bipolar electrode (BPE) placed in an electrolyte between two control electrodes, which are not in direct contact with the bipolar electrode. It is clear from this figure that direct contact between the bipolar electrode and either of the control electrodes would impose a uniform potential on the bipolar electrode. In the absence of such direct contact, each section of the bipolar electrode has an electrical potential equal to the potential of the surrounding solution, so that the electrical potential varies continuously from one end of the bipolar electrode to the other.

[0086] In the present invention, the particulate medium 20 is to be polarized by the bipolar electrochemical process and is therefore not in direct contact with any of the electrodes 95 in the activation cell 30.

[0087] To achieve this, the activation compartment 70 is delimited by at least one wall permeable to fluids and impermeable to the particulate medium 20.

[0088] In the example in Figure 1, the activation compartment 70 is cylindrical. The bases and / or the side wall of the cylinder are permeable to fluids and impermeable to the particulate media 20.

[0089] At least one fluid-permeable and particulate-impermeable wall 20 is for example formed in a material chosen from electrical insulating materials, for example sintered glass or a plastic material such as polypropylene or polytetrafluoroethylene (PTFE).

[0090] The activation compartment 70 is connected to the electrolyte reservoir 90, 85.

[0091] In the first embodiment, the activation compartment 70 is directly immersed in the reservoir 85.

[0092] The reservoir 85 includes an inlet 110 for the electrolyte 90.

[0093] The supply inlet 110 can be connected to an electrolyte source 115 via a pipe 120 fitted with a valve 125 and optionally a pump 127.

[0094] Electrolyte 90, for example, is an aqueous solution comprising at least one anionic solute and at least one cationic solute.

[0095] The anion and the cation can be chosen according to the nature of the particulate medium 20 and / or the nature of the electrodes 95.

[0096] As an example, electrolyte 90 includes one or more cations chosen from among the sodium ion, the potassium ion, and the oxonium ion.

[0097] As an example, electrolyte 90 comprises one or more anions chosen from the sulfate ion, the nitrate ion and the chloride ion.

[0098] The concentrations of anions and cations are advantageously chosen so as to promote the bipolar current, that is to say the fraction of the electric current flowing through the electric dipoles (also called bipolar electrodes) in the particulate medium 20, as opposed to the ionic current, associated with the macroscopic movement of the ions present in the electrolyte 90.

[0099] To this end, electrolyte 90 may, in particular, have an ionic conductivity of less than 100 mS / cm. For example, electrolyte 90 is an aqueous solution of sulfuric acid with a concentration of less than 10 -3 mol / L, specifically on the order of 10 -4 mol / L.

[0100] Such concentrations are generally insufficient for electrochemical processes of the electrolysis type, but perfectly suited for the bipolar electrochemical process according to the invention.

[0101] The electrolyte 90 allows the circulation of a bipolar electric current through the particulate medium 20 present in the activation compartment 70 when an electrical potential difference is applied to it by means of the electrodes 95.

[0102] The electrodes 95 are positioned relative to the activation compartment 70 in such a way as to permit the application of such an electrical potential difference.

[0103] In the example in Figure 1, the electrodes 95 are partially immersed in the reservoir 85, so that each of the electrodes 95 faces a respective base of the activation compartment 70, without direct contact with that base.

[0104] In general, the position of the electrodes 95, the number of electrodes 95, their surface area, their chemical composition and / or their distance from the activation compartment 70 can be adapted according to the nature of the particulate medium 20, its particle size, the electrolyte 90, and / or the geometric characteristics of the activation compartment 70.

[0105] Electrodes 95 can be formed from an electrically conductive material, such as a noble metal, steel, or titanium. Gold and platinum are preferred materials if the electrode 95 is an anode-source.

[0106] The electrodes 95 are electrically connected to an external electrical voltage source 130 or integrated into the activation cell.

[0107] The electrical voltage source 130 is, for example, a DC voltage source.

[0108] The electrical voltage source 130 is configured to generate a potential difference of at least 10 V, in particular between 10 V and 1000 V between the electrodes 95.

[0109] The activation of the electrical voltage source 130 enables the particulate medium 20 to be activated, to form a particulate medium 20 said to be "activated".

[0110] The activation compartment 70 includes the distribution outlet 80 of the activated particulate media 20 to the introduction inlet 50 of the treatment volume 15.

[0111] The distribution outlet 80 is connected to the inlet 50 via an inlet pipe 135 equipped with a valve 140 and a pump 142. Optionally, as shown in Figure 1, the installation 10 includes a separator 145 downstream of the distribution outlet 80 and upstream of the inlet 50.

[0112] The separator 145 is configured to allow the separation of the activated particulate media 20 from a fraction 150 of the electrolyte 90 carried along with the activated particulate media 20 through the distribution outlet 80.

[0113] The separator 145 includes, for example, a draining surface 155 permeable to the electrolyte 90 and impermeable to the particulate media 20.

[0114] The draining surface 155 separates a circulation volume 160 of the particulate media 20 coming from the distribution outlet 80 and received on a separator inlet 145A, towards the introduction inlet 50 through a first outlet 145B, and a draining volume 165 allowing the formation of the fraction 150 of the electrolyte 90 alone, so as to recover a flow of electrolyte 90 alone on a second outlet 145C.

[0115] A stream of activated particulate media 20, at least partially drained, is supplied on the first outlet 145B.

[0116] In a particular embodiment, represented in Figure 1, the second outlet 145C is in fluidic communication with the electrolyte source 115. This arrangement allows at least partial recycling of the electrolyte 90.

[0117] We will now describe a treatment process 200 of the aqueous solution stream to be treated 25 using the installation 10 with reference to figure 2.

[0118] The treatment process 200 comprises: a) the activation 205 of the particulate medium 20 to be activated by a bipolar electrochemical process, the bipolar electrochemical process comprising the application of an electrical potential difference, by means of the electrodes 95, to the activation compartment 70 containing the particulate medium 20 in the presence of the electrolyte 90, without direct contact between the particulate medium 20 and the electrodes 95; b) the distribution 210 of the particulate medium 20 thus activated in the treatment volume 15; and c) the circulation 215 of the flow of aqueous solution to be treated 25 in the treatment volume 15 through the activated particulate medium 20, to form the treated aqueous solution flow 45.

[0119] Before activation 205, the treatment process 200 includes, if necessary, an introduction step 235, during which the particulate media 20 is introduced into the activation compartment 70 from the source 65 by opening the valve 105. The introduction 235 may be passive, for example by gravity, or active. In the latter case, the installation 10 may include a suitable pumping device, not shown.

[0120] Then valve 105 is closed.

[0121] The particulate medium 20 can be more or less compacted after the introduction 235.

[0122] Low compaction helps to reduce subsequent gas releases at the wall of the activation compartment 70 and thus limit the energy consumption of the activation 205. An accumulation of gas bubbles in the activation compartment can in particular restrict or even block the circulation of the electrolyte 90.

[0123] Simultaneously or not with the introduction 235, the treatment process 200 includes, if necessary, a filling step 240 of the tank 85.

[0124] Filling 240 is for example carried out from the electrolyte source 115, by opening the valve 125 and possibly activating the pump 127. The valve 125 is closed after filling 240.

[0125] For activation 205, the electrical voltage source 130 is activated.

[0126] The electrical voltage across the terminals of the electrical voltage source 130 can be chosen so that the intensity of the electric field to which the particulate medium 20 is subjected is between 0 and 100 V.cm- 1 .

[0127] It is essential that the electrodes 95 not be in direct contact with the particulate medium 20, in order to avoid the formation of a short circuit and the uniformization of the electrical potential within the particulate medium 20.

[0128] The electrical voltage across the terminals of the electrical voltage source 130 is, for example, between 40V and 100V, in particular in the order of 50V or 60V.

[0129] The application of this electrical voltage makes it possible to induce a temporary polarization at the scale of individual particles of the particulate medium 20 and / or at the scale of a fictitious macroscopic volume in which the particulate medium 20 is contained.

[0130] Temporary polarization induces a temporary or permanent modification of the physico-chemical properties of the surface of individual particles of the particulate medium 20 so that a variation of these physico-chemical properties can be observed at the scale of the particles and / or at the scale of said fictitious macroscopic volume.

[0131] A temporary modification of a given physicochemical property is understood to mean a duration of maintenance, or equivalently of persistence, of this modification such that the modification persists at the time of the introduction of the particulate medium 20 into the treatment volume 15. The duration of persistence of a physicochemical modification may depend on the conditions to which the particulate medium 20 is subjected after its activation 205 and before its distribution 210 in the treatment volume 15.

[0132] The electrical voltage source 130 is kept activated for an activation period which can be on the order of a few minutes, or even on the order of a few tens of minutes.

[0133] The activation time is then, for example, between 5 minutes and 120 minutes, preferably between 10 minutes and 30 minutes.

[0134] The activation time can be chosen according to the intensity of the electric current flowing in the circuit formed by the electrical voltage source 130, the electrodes 95 and the activation compartment 70.

[0135] For example, for an electrical current intensity between 10 mA and 100 mA, particularly between 20 mA and 50 mA, and for an electrical voltage between 40 V and 80 V, the activation time can be between 10 minutes and 30 minutes, particularly around 15 minutes, for a cylindrical activation compartment 70 with a height of 7 cm and a diameter of 2 cm filled with activated carbon.

[0136] The electrical consumption for the activation step 205 per kilogram of activated particulate media 20 produced can be on the order of 1 kWh, or even on the order of 0.1 kWh. This consumption is very low and therefore results in low operating costs for the process.

[0137] Activation 205 results in a modification of the surface properties of the particles of the particulate medium 20. In particular, a polarization gradient inducing a gradient of modification of the surface chemistry of the particles is established at the scale of each particle, so that at the end of activation 205, each particle is able to interact with a range of molecules of more varied polarities and / or polarizabilities than before activation 205.

[0138] This is particularly evident in Figure 3, showing a photograph of a grain of Filtrasorb® 400 activated carbon supplied by Calgon Carbon, which has undergone an activation step 205 in an activation compartment 70 in the form of a 5 cm long cylinder, according to the embodiment of Figure 5 described later, subjected to a voltage of 80V for 20 minutes in the presence of an electrolyte 90 consisting of a sulfuric acid solution with a concentration of 1.0 x 10⁻³ -4mol / L. This image was obtained using a TESCAN Vega 3 scanning electron microscope equipped with a Bruker EDX probe. Analysis with the EDX probe allows access to the local atomic concentration of oxygen atoms. Figure 3 shows that part 1 of the grain, which was on the cathode-source side during activation 205, comprises 7.39% oxygen atoms, zone 2 comprises 7.33% oxygen atoms, zone 3 comprises 11.41% oxygen atoms and zone 4, which was on the anode-source side during activation 205, comprises 13.98% oxygen atoms, so that an oxidation gradient and therefore hydrophilicity gradient was formed on the surface of the grain, from the cathode-source to the anode-source (i.e. from left to right in this figure).

[0139] In comparison, the oxygen atom content of a grain of the same coal but which has not undergone 205 activation is equal to 5% + / - 1% over the entire surface of the grain, as seen on the REF reference in Figure 4.

[0140] We therefore observe a broadening of the range of oxidation states at the grain scale, as well as a shift in the median value of this range towards higher oxygen percentages, following activation 205.

[0141] Figure 4 represents the statistical distribution of the atomic oxygen content %at(O) of unactivated (REF) coal grains, after activation under the conditions described for Figure 3 under a voltage of 40 V, under a voltage of 60 V and under a voltage of 60 V, cathodic side (hatching) and anodic side (dots) for these three cases.

[0142] We can see from this figure that the shift in the median value as well as the amplitude of the widening of the range of atomic content of oxygen atoms can be controlled in particular by the choice of the voltage applied by the electrical voltage source 130, and therefore of the intensity of the electric field to which the particulate medium 20 is exposed.

[0143] We can also see in figures 3 and 4 that a gradient is obtained not only at the scale of each particle, as seen in figure 3, but also at the scale of compartment 70 since the effect obtained on the side of the activation compartment 70 closest to the cathode-source is not the same as that obtained on the side of the activation compartment 70 closest to the anode-source.

[0144] Following activation 205, the particulate media 20 is distributed at the distribution stage 210 to the treatment volume 15 by opening the valve 140 and the pump 142.

[0145] The distribution step 210 includes the spontaneous flow by gravity and / or pumping of the activated particulate media 20 through at least one conduit and / or over at least one guiding surface extending between the activation compartment 70 and the treatment volume 15. This distribution is carried out without drying or packaging of the particulate material 20 from the activation compartment 70 to the treatment volume 15. Where applicable, the treatment process 200 includes a separation step 245 between the activation 205 and the distribution 210.

[0146] For the separation step 245, the activated particulate media 20 exiting the activation compartment 70 through the distribution outlet 80, possibly carrying the fraction 150 of electrolyte 90, circulates in the circulation volume 160 of the separator 145. The fraction 150 of electrolyte 90 is recovered in the draining volume 165 after passing through the draining surface 155.

[0147] As a result, the amount of electrolyte 90 carried with the particulate media 20 activated at the inlet 50 may be less than that carried with the particulate media 20 at the outlet 80.

[0148] In a particular embodiment, the duration of the separation 245 is chosen to allow the drainage of at least 90%, at least 95% or even at least 99% of the quantity of electrolyte 90 carried along at the distribution outlet 80.

[0149] The separation step 245 is not essential, particularly when the concentration of anions and cations in the electrolyte is low, for example less than 1.0 x 10⁻¹⁰. 3mol / L for cations and anions resulting from the dissolution of salts such as potassium chloride or potassium nitrate, or from the dissolution of acids such as sulfuric acid or hydrochloric acid. Such a concentration does not, in fact, have a significant impact on the efficiency of the subsequent circulation step 215.

[0150] Optionally, possibly during or after the separation step 245, or before the distribution step 210, the treatment process 200 may include a rinsing step 250, not shown in detail.

[0151] The rinsing 250 includes the circulation of a flow of rinsing water (not shown) through the activated particulate media 20, so as to decrease the concentration of the ions present in the electrolyte 90 and carried along with the activated particulate media 20.

[0152] At the end of the distribution step 210, the particulate media 20 forms at least a fraction of at least one layer 180 of a filtration bed present in the treatment volume 15.

[0153] In a particular embodiment, the filtration bed consists of the particulate medium 20.

[0154] During the circulation step 215, the flow of aqueous solution to be treated 25 is introduced into the treatment volume 15 through the inlet 50, for example by means of a pump 185.

[0155] The aqueous solution to be treated 25 flows through the filtration bed and is thus brought into contact with the activated particulate media 20. As a result, any compound(s) to be removed are partially or totally adsorbed onto the particulate media 20.

[0156] The treated aqueous solution stream 45 recovered at the outlet 40 therefore has, where applicable, a reduced concentration of the possible compound(s) to be eliminated compared to that(s) of the aqueous solution stream to be treated 25 and reduced compared to that(s) of an aqueous solution stream treated by the same particulate medium 20 but without activation.

[0157] As an example, from the same Filtrasorb® 400 activated carbon supplied by Calgon Carbon, 8 batches were created: a reference batch REF2 which did not undergo an activation step, and 7 batches CAG1 to CAG7 which underwent an activation step 205 in an activation compartment 70 in the form of a cylinder of revolution 7 cm long and 2 cm in diameter in a vertical and closed configuration, subjected to an electrical voltage specified in Table 1 below for 20 minutes in the presence of an electrolyte 90 consisting of an aqueous solution of sulfuric acid with a concentration of 1.0 x 10⁻³ 2 mol / L.

[0158] The batches of so-called "reduced" compactness were compacted during the filling of the activation compartment 70, so that the batches of reduced compactness have, in the activation compartment 70, a higher density than the batches of standard compactness.

[0159] [Table]

[0160] Table 1: Activation parameters for batches CAG1 to CAG7

[0161] The eight batches, after their possible activation 205, are implemented to each treat a respective fraction of an aqueous solution stream to be treated 25 in a treatment volume of 1 litre

[0162] Tables 2 and 3 below show the relative difference, with respect to the treated aqueous solution flow 45 with the reference batch REF2, of the reduction in different micropollutants obtained in the respective treated aqueous solution flows 45 compared to the aqueous solution flow to be treated 25.

[0163] Micropollutant concentrations were measured by:

[0164] - gas chromatography with headspace injection mass spectrometry with regard to 1,4-dioxane;

[0165] - High-performance liquid chromatography with tandem mass spectrometry for dimetachlor and metolachlor; and

[0166] - by gas chromatography with tandem mass spectrometry and solid-phase extraction with regard to acetochlore, alachlor and metazachlore.

[0167] [Table 2]

[0168] Table 2: Relative differences between the micropollutant reductions obtained with batches CAG1 to CAG7 and those obtained with batch REF2

[0169] [Table 3]

[0170] Table 3: Relative differences between the micropollutant reductions obtained with batches CAG1 to CAG7 and those obtained with batch REF2

[0171] Tables 2 and 3 show that activation step 205 increases the adsorption efficiency of most of the micropollutants tested during circulation 215, with the loss of performance in dissolved organic carbon remaining moderate in parallel (on the order of 5%), the adsorption performance depending on the conditions chosen for activation step 205.

[0172] The activation conditions 205 can be chosen according to a range of target values ​​or an upper threshold for one or more desired concentrations of compounds to be removed from the treated aqueous solution stream 45, and / or one or more concentrations of compounds to be removed from the treated aqueous solution stream 25 and / or a flow rate of the treated aqueous solution stream 25, in connection with what has been observed in Figures 3 and 4.

[0173] The distribution 210 can be carried out in such a way as to maintain or not for the circulation 215 in the treatment volume 15 the electronegativity gradient created at the macroscopic scale, i.e. at the scale of the activation compartment 70, during the activation 205.

[0174] In one particular embodiment, the treatment process 200 is implemented sequentially (in English, "batch").

[0175] Alternatively, the 200 treatment process is implemented in a semi-sequential (in English "semi-batch") or continuous manner.

[0176] The activated particulate media 20 can be renewed more or less frequently after its use for circulation 215, in particular depending on the flow rate of the aqueous solution stream to be treated 25 and / or the composition of the aqueous solution stream to be treated 25.

[0177] For this purpose, the particulate media 20 present in the treatment volume 15 is extracted in part or in whole through the extraction outlet 55 to the storage reservoir 60.

[0178] Preferably, less than 50% by volume, in particular less than 20% by volume of the particulate media 20 is extracted and renewed by sequence or semi-sequence.

[0179] Optionally, at least part, or even all, of the particulate media 20 thus extracted is recycled during a recycling step 255 via the recycling circuit 96 and reintroduced into the activation compartment 70 via the injection inlet 75 to undergo a new activation 205.

[0180] Alternatively or in addition, the particulate medium 20 can undergo a regeneration step 255 by a process known in the prior art at the outlet of the storage tank 60.

[0181] Regeneration may include a chemical treatment step, for example with caustic soda.

[0182] A second embodiment of the installation 10 is described with reference to Figure 5, with only the differences with the first embodiment being highlighted in what follows.

[0183] In this second embodiment, the electrolyte 90 reservoir 85 is separated into a first compartment 190 and a second compartment 195 configured to receive each a respective fraction of the electrolyte 90.

[0184] In this embodiment, the activation compartment 70 is not totally immersed in the electrolyte 90. In particular, a portion 70C of the activation compartment 70 is not immersed in the electrolyte 90.

[0185] A first fluidic contact end 70A of the activation compartment 70 is positioned in the first compartment 190 and is immersed in the electrolyte 90.

[0186] A second fluidic contact end 70B of the activation compartment 70 opposite the first end 70B relative to portion 70C is positioned in the first second compartment 195, and is immersed in the electrolyte 90.

[0187] The activation compartment 70 therefore ensures a first fluidic communication between the first and second compartments 190, 195 via the first and second fluidic contact ends 70A, 70B.

[0188] In this case, a side wall of the activation compartment 70 delimiting the portion 70C is fluid-tight, the first ends 70A and 70B each having at least one wall permeable to fluids and impermeable to the particulate medium 20.

[0189] In a particular embodiment, the activation cell 30 includes a recirculation system 196 of the electrolyte 90 between the first and second compartments 190, 195.

[0190] The activation 205 then includes the active or passive recirculation of the electrolyte 90 from one of the first and second compartments 190, 195 to the other of these compartments 190, 195 by means of the recirculation system 196.

[0191] For example, the recirculation system 196 includes a pump 197 allowing the recirculation of the electrolyte 90 from the first compartment 190 to the second compartment 195 through a pipe 198. In this case, the second compartment 195 is, in a particular embodiment not shown, placed at a higher altitude than the first compartment 190, so as to allow the electrolyte 90 to flow spontaneously from the second compartment 195 to the first compartment 190 through the activation compartment 70.

[0192] The activation 205 then includes the active recirculation of the electrolyte 90 from the first compartment 190 to the second compartment 195, for example by means of the pump 197.

[0193] This embodiment promotes the evacuation of any gas bubbles that may form during activation 205 and thus reduces the energy consumption of this step.

[0194] Regardless of the embodiment chosen, the treatment process 200 according to the invention is simple to implement and energy-efficient.

[0195] The activation cell 30 implements simple elements, and can be easily connected, for example in post-editing, to a pre-existing processing volume 15.

[0196] The choice of conditions for the activation step 205 allows the particulate medium 20 to be activated in a flexible manner, largely adaptable to the types of compounds to be eliminated.

[0197] In particular, it may be envisaged to form a filtration bed with several layers of activated particulate media 20, each layer being obtained by activation 205 under specific conditions.

[0198] The activation conditions 205 can, for example, be determined and controlled, possibly continuously, based on information on the composition and / or flow rate of the aqueous solution to be treated 25.

[0199] The frequency of distribution 210 and / or the frequency of recycling 255 of the particulate media 20 can be adapted, possibly continuously, according to information on the composition and / or flow rate of the aqueous solution flow to be treated 25.

Claims

DEMANDS 1. A process for treating (200) a stream of an aqueous solution, the process comprising: a) the activation (205) of a particulate medium (20) to be activated comprising a material having non-zero electrical conductivity, b) the distribution (210) of the particulate medium (20) thus activated in a treatment volume (15), and c) the circulation (215) of a stream of aqueous solution to be treated (25) in the treatment volume (15) through the activated particulate medium (20), to form a treated aqueous solution stream (45), characterized in that the activation is carried out by a bipolar electrochemical process, the bipolar electrochemical process comprising the application of an electrical potential difference by means of at least two electrodes (95) to an activation compartment (70) containing the particulate medium (20) in the presence of an electrolyte (90), without direct contact between the particulate medium (20) and the electrodes. (95).

2. Process for treating (200) a stream of an aqueous solution according to claim 1, wherein the bipolar electrochemistry process comprises the circulation of the electrolyte (90) through the particulate medium (20).

3. Process of treating (200) a stream of aqueous solution according to any one of the preceding claims, comprising between the activation (205) a) and the distribution (210) b) of the particulate medium (20): d) the separation of the activated particulate medium (20) from the electrolyte (90) in a separator (145) connected to the activation compartment (70) and the treatment volume (15).

4. A process for treating (200) a stream of an aqueous solution according to any one of the preceding claims, wherein the electrolyte (90) has an electrical conductivity of less than 100 mS.cnr 1 .

5. Process for treating (200) a stream of an aqueous solution according to any one of the preceding claims, wherein the particulate medium (20) to be activated comprises charcoal.

6. Process for treating (200) a stream of an aqueous solution according to any one of the preceding claims, wherein the activation compartment (70) is delimited by at least one wall permeable to fluids and impermeable to the particulate medium (20).

7. A process for treating (200) a stream of an aqueous solution according to any one of the preceding claims, wherein the activation compartment (70) extends between a first fluidic contact end (70A) placed in a first compartment (190) of an electrolyte (90) reservoir (85) and a second fluidic contact end (70B) placed in a second compartment (195) of the electrolyte (90) reservoir (85), the activation compartment (70) thus forming a first fluidic communication between the first and second compartments (190, 195) of the electrolyte (90) reservoir (85).

8. A process for treating (200) a stream of aqueous solution according to the preceding claim, wherein the second compartment (195) of the electrolyte (90) reservoir (85) is placed at an altitude higher than the first compartment (190) of the electrolyte (90) reservoir (85) so as to allow the electrolyte (90) to flow spontaneously from the second compartment (195) of the electrolyte (90) reservoir (85) to the first compartment (190) of the electrolyte (90) reservoir (85) through the activation compartment (70), the process comprising a recirculation of the first compartment (190) of the electrolyte (90) reservoir (85) to the second compartment (195) of the electrolyte (90) reservoir (85) during the activation (205) a).

9. Installation (10) for treating an aqueous solution comprising: i) a treatment volume (15) intended to receive a particulate medium (20) and a stream of aqueous solution to be treated (25), the treatment volume (15) comprising: * an inlet (35) of the aqueous solution stream to be treated (25) and an outlet of a treated aqueous solution stream (45), and * an inlet (50) for the particulate medium (20) and an outlet (55) for the particulate medium (20), the installation (10) being characterized in that it comprises: ii) a bipolar electrochemical activation cell (30) comprising: - a source (65) of particulate media (20), - an activation compartment (70) comprising an injection inlet (75) of the particulate media (20) to be activated connected to the source (65) and a distribution outlet (80) of the activated particulate media (20) to the introduction inlet (50) of the treatment volume (15), - an electrolyte reservoir (85) (90) connected to the activation compartment (70), and - at least two electrodes (95), configured to apply an electrical potential difference to the activation compartment (70), without direct contact with the particulate medium (20).

10. Installation (10) for treating an aqueous solution according to the preceding claim, further comprising a separator (145) comprising: - a separator input (145A), connected to the distribution output (80) and configured to receive a flow comprising the activated particulate media (20) and the electrolyte (90), - a first outlet (145C) of an electrolyte flow (90), and - a second output (145B) of a stream of drained particulate media (20), the second output (145B) being connected to the inlet (35) of the processing volume (15).

11. Installation (10) for treating an aqueous solution according to the preceding claim, comprising an electrolyte recycling circuit (90) from the first outlet (145C) of the separator (145) to the electrochemical activation cell (30).

12. Installation (10) for treating an aqueous solution according to any one of claims 9 to 11, in which the electrolyte (90) reservoir (85) comprises at least a first compartment (190) and a second compartment (195) in fluidic communication via the activation compartment (70).

13. Installation (10) for treating an aqueous solution according to the preceding claim, comprising a recirculation system (196) of the electrolyte (90) between the first and second compartments (190, 195) of the electrolyte (90) reservoir (85).

14. Installation (10) for processing a stream of an aqueous solution according to any one of claims 9 to 13, comprising a recycling circuit (96) of the particulate media (20) from the extraction outlet (55) to the injection inlet (75).

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