An electrochemical equipment and the relevant method for removing pollutants from water

Abstract

The invention refers to an electrochemical equipment (10, 10', 10", 10"', 10"") for the treatment of water contaminated by oxidizable pollutants (such as petroleum hydrocarbons and derivatives, herbicides, pesticides, PFAS and the like), reducible pollutants (such as halogenated organic solvents, perchlorate, nitrate and the like) and / or mixtures thereof. The equipment comprises an anode (1, 1', 1", 1'", 1"") and a cathode (2, 2', 2'", 2"", 2""), jointly referred to as electrodes (1, 1', 1", 1'", 1""; 2, 2', 2", 2"", 2""); the equipment also comprises a voltage or current generator (3, 3', 3", 3'", 3"") and a non- conductive separator (4, 4', 4'", 4"", 4"") placed between the electrodes. The anode (1, 1', 1", 1'", 1"") is preferably made of titanium coated with mixed oxides (preferably, Jr and Ru) and the cathode (2, 2', 2'", 2'", 2"") is preferably made of carbon material in granular form (preferably chosen from graphite, activated carbon and biochar) mixed with ferrous material (preferably chosen from zero-valent iron of millimetric dimensions and iron colloidal suspensions). According to the preferred embodiment of the invention, anode (1, 1') and cathode (2, 2') are concentrically arranged; according to an alternative embodiment of the invention, anode (1") and cathode (2") are made in superimposed modules. The invention also refers to a method that provides that, by applying a voltage (preferably between 0 V and 220 V, more preferably between 1 V and 20 V) or a current (preferably between 0 A and 50 A, more preferably between 0 A and 5 A) between the electrodes, Fenton reagents (i.e., H2O2 and Fe2+ ions) are generated in-situ, said reagents being able of completely oxidizing the pollutants contained in the water to be treated; furthermore, the ferrous material present in the cathode allows the simultaneous chemical reduction (i.e., reductive dehalogenation) of the substances contained in the water. Advantageously, the invention allows to treat waters polluted by toxic and recalcitrant substances without the need to continuously supply from the outside chemical conditioners (such as hydrogen peroxide or other chemical oxidants, iron, air, oxygen and the like). The invention is preferably and advantageously applied for the remediation of contaminated sites and for the treatment of wastewater; the invention is advantageously used both inside wells, piezometers or boreholes and in devices, pipes or reactors, in plug-in configuration.

Description

[0001] "An electrochemical equipment and the relevant method for removing pollutants from water"

[0002] DESCRIPTION

[0003] TECHNICAL FIELD

[0004] The present invention refers to the field of contaminated sites remediation and of wastewater treatment and, advantageously, allows to treat water polluted by toxic and recalcitrant substances without the need to continuously supply from the outside chemical conditioners (such as hydrogen peroxide or other chemical oxidants, iron, air, oxygen and the like).

[0005] More precisely, the present invention refers to an electrochemical equipment for the treatment of water contaminated by oxidizable pollutants (such as petroleum hydrocarbons and derivatives, herbicides, pesticides, PFAS and the like), reducible pollutants (such as halogenated organic solvents, perchlorate, nitrate and the like) and / or mixtures thereof.

[0006] Specifically, the electrochemical equipment of the present invention can be used both inside wells, piezometers or boreholes and in devices, pipes or reactors, in plug-in configuration.

[0007] Furthermore, the present invention refers to a method for treating water contaminated by oxidizable pollutants (such as petroleum hydrocarbons and derivatives, herbicides, pesticides, PFAS and the like), reducible pollutants (such as halogenated organic solvents, perchlorate, nitrate and the like) and / or their mixture by means of the aforementioned electrochemical equipment.

[0008] STATE OF THE ART

[0009] The remediation of contaminated sites and the treatment of wastewater are the subject of several research studies and subsequent technical solutions.

[0010] Petroleum hydrocarbons, PH, and chlorinated aliphatic hydrocarbons, CAH, are among the most frequent and dangerous soil and groundwater contaminants for humans and the environment; their presence in underground environments, typically caused by accidental spills, leaks from underground storage tanks and improper production or disposal practices, raises serious environmental and health problems due to the considerable toxicity and recalcitrance of these compounds.

[0011] With regard to the treatment of groundwater contaminated by petroleum hydrocarbons or other recalcitrant oxidizable substances such as herbicides, pesticides, pharmaceutical compounds, perfluorinated alkyl substances and polyfluorinated PFAS, the state of the art essentially considers physical-chemical processes, such as air stripping, adsorption on activated carbon and / or chemical or biological oxidation processes; such oxidation processes require the continuous addition of oxidizing substances with associated high operation, storage and transport costs.

[0012] With regard to groundwater contaminated by halogenated hydrocarbons, instead, these are preferably treated through a reductive process, often referred to as reductive dechlorination, which can also be of a chemical or biological nature; chemical reductive dechlorination typically requires the addition of chemical reducing agents, such as zero-valent iron; on the contrary, the biological reductive dechlorination process, catalysed by different types of bacteria, requires the addition of reducing substrates such as fermentable organic substrates or hydrogen.

[0013] One of the main challenges related to the remediation of sites containing mixtures of oxidizable and reducible pollutants is the fact that these substances are degraded through distinct processes, oxidative and reductive respectively, thus requiring different chemical conditioners and redox conditions.

[0014] Clearly, to minimize the establishment of competitive reactions that can negatively affect speed and efficiency of the remediation process, the supply of oxidizing substances (to perform the oxidation of PH) and reducing substances (to perform the reductive dechlorination of CAH) must occur in different locations or successive steps, thus complicating design, operation and control of the entire process and increasing the overall cost and time of the intervention.

[0015] Advanced oxidation processes AOP are extremely effective in rapidly removing recalcitrant contaminants from aqueous matrices, and are based on the generation of strong oxidizing agents such as the hydroxyl radical OH*; a very effective way to produce radicals is the use of Fenton reagents, i.e. hydrogen peroxide and Fe2+that, at acid pH between 2.5 and 4, develop a chain reaction propagated by the catalytic couple Fe2+ / Fe3+.

[0016] On the other hand, the hydrogen peroxide needed for the Fenton reaction can be constantly generated in the aqueous solution by electrochemical means, giving rise to the so-called "electro-Fenton" process (Brillas, 2022): it consists in the reduction of molecular oxygen to two electrons in an electrolytic cell; in the electro-Fenton process, O2 is typically supplied by blowing air while Fe2+ions are added in the form of an iron salt.

[0017] The electro-Fenton process has already been widely applied to the field of wastewater treatment, especially industrial wastewater, and sludges (Zhou et al., 2019).

[0018] On the other hand, its application to groundwater treatment is almost completely unexplored due to the lack of suitable reactor configurations that limit its in-situ implementation.

[0019] Furthermore, although zero-valent iron has been employed in previous studies, at laboratory scale, as a substrate capable of releasing, through corrosion reactions in water, the Fe2+ion necessary to catalyse the electro-Fenton process, no previous study has evaluated the possibility of combining the electro-Fenton process with zero-valent iron to obtain a simultaneous treatment of oxidizable and reducible contaminants.

[0020] Among the known and patented solutions, there are on-ground plants for pumping water and decontaminating pollutants, also using Fenton reagents, while few refer to compact devices to be directly introduced into wells for in-situ decontamination using Fenton reactions.

[0021] Document CN112661255 describes a system for the in-situ treatment of groundwater contaminated by halogenated hydrocarbons, consisting of concentric electrodes (a steel cathode and a carbon fibre anode) separated by a perforated PVC tube; the system can be positioned inside wells; by applying a modest voltage (about 1 V), a current flow is induced that allows, at the cathode, the reductive dehalogenation of halogenated compounds by specific bacteria mainly through the generation of hydrogen. This system, however, does not allow the in-situ generation of Fenton reagents; therefore, it can be exclusively used for the reductive treatment of halogenated hydrocarbons and only in the presence of specific bacteria in the aquifer capable of catalysing such a reaction.

[0022] On the contrary, the present invention allows the simultaneous treatment of hydrocarbons, PFAS and other oxidizable pollutants and reducible halogenated hydrocarbons, even in the absence of specific bacteria in the aquifer since the reaction is catalysed by the zero-valent iron present in the cathode.

[0023] Document TW201006768 describes an electrochemical system, integrable inside wells, for the monitoring and control of treatment processes of groundwater containing organic pollutants by means of the Fenton reaction; the system, specifically, uses a steel cathode, connected to a dimensionally stable DSA® anode, to regenerate Fe2+necessary for the Fenton reaction, preventing its natural oxidation to Fe3+and preventing the consequent formation of deposits (Fe3+oxides) that lead to the clogging of the wells; the system is also equipped with instruments for the real-time control of pH and redox potential that allow monitoring the Fenton reaction.

[0024] This system, however, does not provide the in-situ generation of Fenton reagents but only the electrochemical regeneration of Fe2+; in other words, contrary to the present invention, the system provides the continuous addition of Fenton reagents inside the well, where the treatment takes place (e.g. H2O2).

[0025] Document CN212076722U describes a system for the treatment of groundwater contaminated by organic contaminants, composed of a sedimentation tank and a reactor in which ultrasound and the electro-generation of Fenton reagents are combined; in the reactor there are an anode made of iron and platinum and a carbon felt cathode, connected to an electrical power supply; in addition, air is constantly blown into the reactor.

[0026] This system, however, due to the geometry and complexity of the set-up, cannot be used for the in-situ treatment of contaminants and cannot be applied inside a well.

[0027] Document WO202134580 describes an electro-coagulation system for the treatment of contaminated waters through the release of Fe(II) ions and / or the creation of oxidizing conditions; the reactor contains an anode and a cathode, made of iron wound in a spiral and separated by a perforated insulating material, to which a potential difference is applied.

[0028] This system, however, because of the complex set-up due to the spirally arranged electrodes, cannot be used for the in-situ treatment of contaminants; furthermore, it does not provide the generation of Fenton reagents for the advanced oxidation of contaminants and, on the contrary, an oxidant can be added to facilitate the release of Fe (II); finally, this system aims at promoting electrocoagulation, contrary to the present invention that encourages the complete oxidation of contaminants.

[0029] As it can be deduced from the above discussion, one of the main challenges related to the remediation of sites containing mixtures of oxidizable and reducible pollutants is linked to the fact that these substances are degraded through distinct processes, oxidative and reductive, thus requiring different chemical conditioners and redox conditions.

[0030] The present invention allows to treat in a single step ground waters and wastewaters contaminated by mixtures of oxidizable and reducible compounds, thanks to an electrochemical equipment operating in-situ, inside wells, piezometers or boreholes, or on the ground in plug-in mode, without adding chemical reagents.

[0031] In the current panorama, despite the considerable technological development and the variety of available technical solutions, it is still not possible to combine the simultaneous treatment of oxidizable contaminants and reducible contaminants, and / or their mixtures (these substances, as mentioned above, are degraded through distinct processes, oxidative and reductive) and to achieve the flexibility of in-situ and off-site treatment in plug-in mode.

[0032] In particular, although the electro-Fenton process is known for the treatment of wastewaters, specifically industrial wastewaters, and sludges, its application to the treatment of groundwaters is however almost completely unexplored due to the lack of suitable reactor configurations that allow its in-situ implementation.

[0033] Therefore, the need for an equipment, and for the relevant method, to treat groundwaters and wastewaters containing oxidizable and reducible pollutants, and / or their mixtures, remains unsatisfied.

[0034] In particular, the need for an equipment, and for the relevant method, capable of treating contaminated waters in a single step and without the use of chemical conditioners remains unsatisfied.

[0035] Furthermore, the need for an equipment, and for the relevant method, capable of being used both in-situ inside wells, piezometers or boreholes and in devices, pipes or reactors in plug-in mode remains unsatisfied.

[0036] Finally, the needs for an equipment, and for the relevant method, capable of working with low energy consumption, of allowing the generation of Fenton reagents directly inside the system and therefore not requiring the addition or dosage of chemical conditioners from sources external to the system, of being easily scalable and of having a high treatment capacity and electrochemical controllability remain unsatisfied.

[0037] The present invention aims at offering a solution that satisfies the currently unsatisfied needs.

[0038] OBJECTS AND SUMMARY OF THE INVENTION

[0039] It is the object of the present invention to overcome the drawbacks of the known art in the field of electrochemical equipments, and of the relevant methods, for treating polluted groundwaters or wastewaters.

[0040] More precisely, the present invention intends to solve the problem of having an equipment, and the relevant method, for treating groundwaters and wastewaters containing oxidizable and reducible pollutants, and / or mixtures thereof.

[0041] In particular, an object of the present invention is to provide an equipment, and the relevant method, capable of treating contaminated water in a single step and without the use of chemical conditioners.

[0042] Furthermore, an object of the present invention is to provide an equipment, and the relevant method, capable of being used both in-situ inside wells, piezometers or boreholes and in devices, pipes or reactors in plug-in mode.

[0043] Furthermore, an object of the present invention is to provide an equipment, and the relevant method, capable of operating with low energy consumption, of being easily scalable and of having a high electrochemical treatment capacity and controllability. The abovementioned and other objects and advantages of the invention, which will become apparent from the following description, are achieved with an electrochemical equipment according to claim 1 and with the relevant methods according to claims 12 and 13.

[0044] Preferred embodiments and variants of the electrochemical equipment of the present invention form the subject of the dependent claims.

[0045] In particular, in a first embodiment, the equipment according to the invention comprises electrodes, preferably cylindrical, positioned concentrically, and an electrically non-conductive and water-permeable separator that is interposed between the electrodes. In a preferred embodiment, the anode is positioned inside and the cathode is positioned outside. In a second embodiment, the equipment according to the invention comprises an ordered succession of anodes and cathodes, preferably disk-shaped, permeable to water; in particular, the anode and the cathode are superimposed to form a module and are intercalated with each other, and an electrically non-conductive and water-permeable separator is interposed between each module formed by the electrodes.

[0046] In a variant of the first or second embodiment, the equipment according to the invention is equipped with a pump suitable for inducing a forced flow of the water to be treated inside the equipment and / or a recirculation of the water inside the aquifer system, the reactor, the water basin or the water stream / pipe to be purified.

[0047] In a further variant of the first or second embodiment, the equipment according to the invention is equipped with a modular and removable cartridge containing ferrous material or a mixture of carbonaceous and ferrous material, suitable for the rapid replacement of the exhausted ferrous material. In a particular embodiment, the cartridge may coincide with one of the two electrodes. In a particular embodiment, the system may be equipped with a pump for the flow or recirculation of the fluid to be treated.

[0048] It is understood that all the appended claims form an integral part of the present description and that each of the technical features claimed therein is possibly independent and autonomously usable with respect to the other aspects of the invention.

[0049] It will be immediately evident that innumerable changes (for example related to shape, sizes, arrangements and parts with equivalent functionality) could be brought to what described, without departing from the scope of the invention as claimed in the appended claims.

[0050] Advantageously, the technical solution according to the present invention that provides an electrochemical equipment, and the relevant method, for the treatment of contaminated waters allows:

[0051] - the simultaneous treatment of oxidizable and reducible pollutants;

[0052] - the in-situ realization of the electro-Fenton reaction;

[0053] - to avoid the use of chemical conditioners introduced from the outside; a high treatment capacity guaranteed by the high surface development of the electrodes; a good electrochemical controllability linked to the possibility of directly manipulating the potential or the applied electric current; a low energy consumption, especially with the concentric arrangement of the two electrodes that minimizes the distance and therefore the over-voltages (i.e., the energy losses);

[0054] - low construction, operation and maintenance costs;

[0055] - the in-situ application inside wells, piezometers or boreholes;

[0056] - to also implement the on-ground variant in plug-in configuration and with standalone power supply (preferably with renewable energy systems such as the photovoltaic panels).

[0057] Further advantageous features will appear more evident from the following description of preferred but not exclusive embodiments, given by mere way of nonlimiting example.

[0058] BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The present invention will be described hereinafter by means of some preferred embodiments, given by way of non-limiting example, with reference to the attached drawings. These drawings illustrate different aspects and examples of the present invention and, where appropriate, similar structures, components, materials and / or elements in different figures are denoted by similar reference numbers.

[0060] FIG. 1 is a schematic representation of a first embodiment of the equipment according to the present invention;

[0061] FIG. 2 is a schematic representation of a variant of the first embodiment of the equipment according to the present invention, wherein a pump to induce a forced circulation of the water is also present;

[0062] FIG. 3 is a schematic representation of a preferred variant of the first embodiment of the equipment according to the present invention, wherein a cartridge for the rapid replacement of the exhausted material is also present;

[0063] FIG. 4 is a schematic representation of a second embodiment of the equipment according to the present invention;

[0064] FIG. 5 is a schematic representation of a variant of the second embodiment of the equipment according to the present invention, wherein a pump to induce a forced circulation of the water is also present;

[0065] FIG. 6 is a schematic representation of the Fenton reactions occurring in the equipment according to the present invention;

[0066] FIG. 7 is a graph showing the removal of toluene (oxidizable contaminant model) using the equipment according to the present invention;

[0067] FIG. 8 is a graph showing the removal of trichloroethylene TCE (reducible contaminant model) using the equipment according to the present invention;

[0068] FIG. 9 is a schematic representation of a third embodiment of the equipment according to the present invention, specifically designed for the in-situ remediation of contaminated aquifers, directly integrated into wells, piezometers or boreholes; and FIG. 10 is a schematic representation of a variant of the third embodiment of the equipment according to the present invention, wherein gaskets and / or shutters and a pump to induce water circulation are present.

[0069] DETAILED DESCRIPTION OF THE INVENTION

[0070] While the invention is susceptible to various modifications and alternative constructions, some preferred embodiments are shown in the drawings and will be described in detail hereinbelow.

[0071] It should be understood, however, that there is no intention to limit the invention to the specific embodiments illustrated, but, on the contrary, the invention is intended to cover all modifications, alternative constructions, and equivalents falling within the scope of the invention as defined in the claims.

[0072] In the following description, therefore, the use of "for example", "etc.", "or" denotes non-exclusive alternatives without any limitation, unless otherwise indicated; the use of "also" means "including, but not limited to" unless otherwise indicated; the use of "includes / comprises" means "includes / comprises, but not limited to" unless otherwise indicated.

[0073] The equipment of the present invention is an electrochemical device created starting from an in-depth study of the Fenton reaction and from the application thereof for the remediation of contaminated waters.

[0074] The object of this technical solution is the treatment of contaminated waters and its use is considered, with temporary or permanent introduction, inside underground perforations, wells, piezometers or boreholes, existing or newly built, or in underground or aboveground devices (such as pipes, tanks, reactors and the like).

[0075] With reference to FIGS. 1 - 5, which show the embodiments of the electrochemical equipment according to the present invention, it is observed that said electrochemical equipment 10, 10', 10" for the treatment of waters contaminated by oxidizable pollutants, reducible pollutants and / or mixtures thereof through the in-situ generation of Fenton reagents (H2O2 and Fe2+ions) comprises:

[0076] - at least one anode 1, T, 1",

[0077] - at least one cathode 2, 2', 2" , at least a voltage or current generator 3, 3', 3" capable of providing an electric current between said anode 1, T , 1" and said cathode 2, 2', 2" and at least a separator 4, 4', 4" not electrically conductive and permeable to the passage of the water to be treated. The anode 1, V, 1" and the cathode 2, 2', 2" are made of metallic, carbonaceous material or a mixture thereof.

[0078] Preferably, the anode 1, T, 1" is made of metallic material coated with mixed metal oxides and the cathode 2, 2', 2" is made of ferrous material.

[0079] Preferably, the ferrous material of the cathode 2, 2', 2" is in zero-valent or oxidized form or a mixture thereof, suitable for the dual function of inducing the direct chemical reduction of reductively degradable contaminants and generating Fe2+ions necessary for the Fenton reaction; more preferably, preferably the ferrous material of the cathode 2, 2', 2" is zero-valent iron of millimetric or micrometric or nanometric dimensions, or a mixture thereof.

[0080] The electrochemical equipment 10, 10', 10" may further comprise at least one granular carbonaceous material mixed with the ferrous material of the cathode 2, 2', 2".

[0081] In a preferred embodiment of the equipment, the system may comprise at least an adsorbent material, which may or may not coincide with the ferrous material and / or the carbonaceous material of the cathode 2, 2', 2", mixed with the materials that form the cathode 2, 2', 2". The adsorbent material has porosity and / or microporosity and / or surface charge and is capable of adsorbing contaminants by concentrating them and increasing their residence time inside the equipment to facilitate their removal by Fenton reagents; preferably, the adsorbent material is electrically conductive and, more preferably, it comprises one or more of the following materials: graphite, carbonaceous materials, activated carbon, biochar, conductive polymers, conductive fabrics.

[0082] The electrochemical equipment 10, 10', 10" may further comprise an inert material mixed with or in contact with the adsorbent material and / or with the ferrous material and / or with the carbonaceous material, said inert material being suitable for homogenizing the distribution of the Fenton reagents and the water to be treated inside the equipment.

[0083] With reference to FIGS. 1, 2 and 3, which represent a first embodiment of the invention, the cathode 2, 2' is arranged concentrically around the anode 1, 1' and the non- conductive separator 4, 4' is interposed between the electrodes 1, T; 2, 2'. With particular reference to FIG. 2, which illustrates a preferred variant of the first embodiment of the invention, the system is equipped with a pump 6 suitable for inducing a forced flow of the water to be treated inside the equipment and / or a recirculation of the water inside the aquifer system, the water basin or the water stream / pipe to be purified.

[0084] With particular reference to FIG. 3, which illustrates the preferred variant of the first embodiment of the invention, the electrochemical equipment 10' also comprises a modular and removable cartridge containing ferrous material 5', suitable for the rapid replacement of the exhausted ferrous material, and a pump 6' suitable for inducing a forced flow of the water to be treated inside the equipment.

[0085] With reference to FIG. 4, which represents a second embodiment of the invention, the anode 1" and the cathode 2" are superimposed to form a module and are intercalated with each other, and the non-conductive separator 4" is interposed between each module formed by the electrodes 1"; 2" . With particular reference to FIG. 5, which illustrates a preferred variant of the second embodiment of the invention, the system is equipped with a pump 6" suitable for inducing a forced flow of the water to be treated inside the equipment and / or a recirculation of the water inside the aquifer system, the water basin or the water stream / pipe to be purified.

[0086] Preferably, the distance between the anode 1, 1', 1" and the cathode 2, 2', 2" is less than 10 cm, in order to minimize the energy consumption of the equipment and maximize the effectiveness in the contaminants degradation.

[0087] Preferably, the voltage applied to the electrodes 1, 1', 1"; 2, 2', 2" ranges between 0 V and 220 V (more preferably between 1 V and 20 V) and the current circulating in the equipment ranges between 0 A and 50 A (more preferably between 0 A and 5 A).

[0088] The equipment according to the invention can be a hollow body equipped with suitable holes or doors, suitable for allowing the entry and exit of the water to be treated; optionally, the holes or doors comprise at least one non-return valve suitable for preventing a reflux or the leakage of the water to be treated and of the conductive, reducing and / or adsorbent materials present inside the equipment.

[0089] The equipment can be equipped with mechanical, hydraulic or pneumatic gaskets and / or shuters for fixing on the internal walls of a pipe or to ensure the hydraulic insulation of a portion of the pipe containing the water to be treated. The water to be treated can be in natural or forced flow, with a flowrate continuous or variable over time; in case, the equipment according to the invention can be equipped with a pump, placed inside or outside the equipment itself, suitable for inducing a forced flow of the water to be treated.

[0090] In an embodiment of the system, the voltage or current generator is powered by replaceable or rechargeable bateries or photovoltaic panels; as an alternative, the equipment can be equipped with a hydroelectric device suitable for converting the kinetic energy of the water under treatment, in natural or forced flow, into electrical energy to power the generator or recharge its batteries; optionally, the generator power supply and / or batery recharging is operated by a wireless device.

[0091] The equipment can be equipped with a monitoring and control system consisting of sensors for the periodic or continuous measurement of important process parameters, such as the applied voltage, current and power, the pH, the oxidation-reduction potential of the water present between the electrodes and the temperature and the electrical conductivity of the equipment itself, and by a control unit for the transmission, analysis and processing of the data; moreover, the control unit is programmed to autonomously manage and adjust the voltage / current generator on the basis of the monitoring data and to maintain the process parameters within optimal variation ranges.

[0092] An embodiment is specifically designed for the in-situ remediation of aquifer systems (FIG. 9) and provides a perforation 9"' made in an underground portion, a porous or fenestrated tube of electrically insulating material 4'", an electrically conductive material, containing at least a carbonaceous or ferrous material, possibly with adsorbent properties, or a mixture thereof, suitable for filling an interspace that is generated between an external wall of the insulating tube and an internal wall of the borehole and for acting as a cathode 2"' , an electrode placed inside the cavity of the insulating tube suitable for acting as an anode T" , a direct and / or alternating current generator or any other device capable of supplying an electric current to the two electrodes 3'".

[0093] In a variant of the embodiment specifically designed for the in-situ remediation of aquifer systems (FIG. 10), the equipment can be equipped with a pump 6"", to induce the forced circulation of the groundwater to be treated, and with mechanical, hydraulic or pneumatic gaskets and / or shutters 8"", for the hydraulic insulation of a portion of electrically insulating pipe 4"". The electrically insulating pipe 4"" can be provided with multiple porous / fenestrated sections interspersed with non-porous / fenestrated sections in order to connect two different underground portions and to induce a flow or recirculation of the groundwater between the two different underground portions. FIG. 6 schematically illustrates the Fenton reaction on which the operation of the electrochemical equipment 10, 10', 10'", 10'", 10"" according to the invention is based. The Fenton reaction is an Advanced Chemical Oxidation, AOP, treatment that uses a reagent consisting of hydrogen peroxide (H2O2) and iron salts (Fe2+ions): H2O2, in the presence of iron salts, dissociates generating hydroxyl radicals OH* .

[0094] As it can be observed, the mixture of hydrogen peroxide (H2O2) and iron salts (Fe+2ferrous ions) shows its oxidizing action towards organic substances, through the production of OH* radicals according to the chemical reaction reported in FIG. 6; like other metals, iron has special properties of transferring oxygen by improving the effectiveness of hydrogen peroxide through the formation of hydroxyl radicals OH* . The hydroxyl radicals can be treated, in turn, by reacting with other Fe+2; the Fe+3ions catalytically decompose H2O2 according to a mechanism that involves the formation of hydroxyl radicals. The Fenton reagent thus created is proved to be a powerful oxidizing agent.

[0095] The present invention also provides a method for the treatment of water contaminated by oxidizable pollutants, reducible pollutants and / or mixtures thereof by means of the electrochemical equipment described above.

[0096] The method according to the present invention provides that, by applying between the electrodes 1 ,T , 1", T" , 1""; 2, 2' , 2"' , 2"", 2"", a voltage (ranging between 0 V and 220 V, preferably between 1 V and 20 V) or a current (ranging between 0 A and 50 A, preferably between 0 A and 5 A), Fenton reagents (i.e., H2O2 and Fe2+ions) capable of completely oxidizing the pollutants contained in the water to be treated are generated in-situ; this method implicates that the ferrous material present in the cathode allows the simultaneous reductive dehalogenation of the halogenated substances contained in the water.

[0097] The present invention has been experimentally tested in the embodiment illustrated in FIG. 3, to verify the simultaneous removal of two model contaminants, one oxidizable (specifically, toluene) and one reducible (specifically, trichloroethylene TCE).

[0098] For the experimental test, a tubular reactor was used, having a volume of 250 mL, in which the anode consisted of a titanium mesh coated with mixed oxides (specifically, iridium and ruthenium oxides) and a cathode arranged concentrically around the anode and consisting of granular graphite.

[0099] Between the two electrodes there was an electrically non-conductive polyethylene mesh that allowed the passage of contaminated water avoiding the short circuit between the two electrodes.

[0100] The water was recirculated by a peristaltic pump, with a flowrate of 192 mL min-1, entering at the bottom of the reactor and exiting from the top.

[0101] Before entering the reactor, the water passed through an external cartridge, with a volume of 10 mL, containing sand mixed with zero-valent iron filings of millimetre dimensions.

[0102] A constant current of 5 mA was imposed between the electrodes by means of a potentiostat.

[0103] The experiment was carried out at 25 ± 3 °C.

[0104] The experiment was repeated with a completely identical configuration except that the two electrodes were disconnected from the potentiostat and left in open circuit (OCP). With reference to FIG. 7, a rapid degradation of toluene is observed in the configuration in which a current of 5 mA was applied, reaching almost complete removal of the contaminant (95.5%).

[0105] On the contrary, in the open circuit configuration the removal was much slower and stopped at a value equal to about half of the initial concentration (45.9%).

[0106] With reference to FIG. 8, it can be noted that also for TCE there is a large disparity in the removal speed in favour of the configuration in which a current was imposed, in which the removal was almost complete (91.8%).

[0107] On the contrary, in OCP the removal at the final time was 45.3% .

[0108] The results showed that the described equipment is able to simultaneously remove an oxidizable and a reducible contaminant.

[0109] The removal is mainly due to the imposition of a constant current, which allows the generation of H2O2 that, in combination with Fe2+ions released in the external cartridge, triggers the Fenton reaction.

[0110] The removal was almost total for toluene and TCE in the configuration in which a current was imposed, while in the open circuit the removal stopped around 45% .

[0111] As it can be deduced from the above disclosure, the innovative technical solution herein described has the following advantageous features: simultaneous treatment of oxidizable and reducible pollutants;

[0112] - in-situ realization of the electro-Fenton reaction; avoiding the use of chemical conditioners introduced from the outside;

[0113] - high treatment capacity guaranteed by the high surface development of the electrodes; good electrochemical controllability linked to the possibility of directly manipulating the potential or the applied electric current;

[0114] - low energy consumption, especially with the concentric arrangement of the two electrodes that minimizes the distance and therefore the over-voltages (i.e., the energy losses);

[0115] - low construction, operation and maintenance costs;

[0116] - in-situ application inside wells, piezometers or boreholes; on-ground variant in plug-in configuration and with stand-alone power supply (preferably with renewable energy systems such as the photovoltaic panels).

[0117] From the description reported hereinabove it is evident, therefore, how the disclosed present invention allows to achieve the proposed aims.

[0118] It is likewise evident, to a person skilled in the art, that it is possible to make modifications and variants to the solution described with reference to the attached drawings, without thereby departing from the teaching of the present invention and from the scope as defined in the appended claims.

[0119] Citations - Brillas E. 2022. Progress of homogeneous and heterogeneous electro-Fenton treatments of antibiotics in synthetic and real wastewaters. A critical review on the period 2017-2021. Sci. Total Environ. 819:153102.

[0120] - Zhou W, Meng X, Gao J, Alshawabkeh AN. 2019. Hydrogen peroxide generation from 02 electroreduction for environmental remediation: A state-of-the-art review. Chemosphere 225:588-607.

Claims

CLAIMS1. An electrochemical equipment (10, 10', 10", 10'", 10"") for the treatment of water contaminated by oxidisable pollutants, reducible pollutants and / or mixtures thereof through in-situ generation of Fenton reagents (H2O2 and Fe2+ions), the electrochemical equipment (10, 10', 10", 10'", 10"") comprising:- at least one anode (1, T, 1", 1'", 1""),- at least one cathode (2, 2', 2", 2'", 2""),- at least a voltage or current generator (3, 3', 3", 3'", 3"") capable of providing an electric current between said anode (1, 1', 1", 1'", 1"") and said cathode (2, 2', 2", 2'", 2"") and at least a separator (4, 4', 4", 4'", 4"") not electrically conductive and permeable to the passage of the water to be treated and characterised in that said anode (1, 1', 1", 1'", 1"") is made of metallic material coated with mixed metal oxides, capable of developing oxygen from the oxidation reaction of water, and said cathode (2, 2', 2", 2'", 2"") is made of granular carbonaceous material mixed with ferrous material, capable of developing H2O2 from the reduction of the oxygen generated at the anode and Fe2+ions.

2. The electrochemical equipment (10, 10', 10", 10'", 10"") according to claim 1, wherein the ferrous material of said cathode (2, 2', 2", 2'", 2"") is in zero-valent or oxidized form or a mixture thereof, suitable for the dual function of inducing the direct chemical reduction of reductively degradable contaminants and generating Fe2+ions necessary for the Fenton reaction; preferably the ferrous material of said cathode (2, 2', 2", 2"', 2"") is zero-valent iron of millimetric or micrometric or nanometric dimensions, or a mixture thereof.

3. The electrochemical equipment (10, 10', 10", 10'", 10"") according to claim 1 or 2, further comprising an adsorbent material mixed with the ferrous material of said cathode (2, 2', 2", 2'", 2""), said adsorbent material having porosity and / or microporosity and / or surface charge and being capable of adsorbing contaminants by concentrating them and increasing their residence time inside the equipment to facilitate their removal by Fenton reagents, said adsorbent material preferablybeing electrically conductive and, more preferably, comprising one or more of the following materials: graphite, carbonaceous materials, activated carbon, biochar, conductive polymers, conductive fabrics, ionic exchange resins, clays, zeolites.

4. The electrochemical equipment (10, 10', 10", 10'", 10"") according to any of the preceding claims, further comprising an inert material, electrically conductive or non-conductive, mixed with or in contact with the adsorbent material and / or with the granular material, said inert material being suitable for homogenizing the distribution of the Fenton reagents and the water to be treated inside the equipment.

5. The electrochemical equipment (10, 10') according to any of the preceding claims, wherein said cathode (2, 2') is arranged concentrically around said anode (1, 1') and said non-conductive separator (4, 4') is placed between said anode (1, 1') and said cathode (2, 2').

6. The electrochemical equipment (10, 10') according to any of the preceding claims, having the shape of a hollow body and having holes suitable to allow the entry and exit of the water to be treated.

7. The electrochemical equipment (10") according to any claim 1 to 4, wherein said anode (1") and said cathode (2") are superimposed to form a module and interleaved with each other and said non-conductive separator (4") is placed between each module formed by said anode (1") and said cathode (2").

8. The electrochemical equipment (10') according to claim 6 or 7, further comprising a modular and removable cartridge containing ferrous material (5'), suitable for the rapid replacement of the exhausted ferrous material, and a pump (6') suitable for inducing a forced flow of the water to be treated inside the equipment.

9. The electrochemical equipment (10, 10', 10", 10'", 10"") according to any of the preceding claims, wherein the distance between said anode (1, T , 1", T" , 1"") and said cathode (2, 2' , 2", 2'" , 2"") is less than 10 cm, in order to minimize the energy consumption of the equipment and maximize the effectiveness in the degradation of contaminants, and wherein the voltage applied to the electrodes (1, T , 1", T" , 1'"; 2, 2', 2", 2'", 2"") is between 0 V and 220 V, preferably between 1 V and 20 V,and the current circulating in the equipment is between 0 A and 50 A, preferably between 0 A and 5 A.

10. The electrochemical equipment (10"', 10"") according to any of the preceding claims, for use inside perforations (9'", 9"") made underground, inside wells, piezometers or boreholes, existing or newly built.

11. The electrochemical equipment (10"") according to claim 10, further comprising a pump (6""), suitable for inducing a forced flow of the water to be treated inside the equipment, and gaskets and / or shutters mechanical, hydraulic or pneumatic (8""), for the hydraulic insulation of a portion of electrically insulating pipe (4"").

12. A method for the treatment of water contaminated by oxidisable polluting substances, reducible polluting substances and / or mixtures thereof by means of the electrochemical equipment (10, 10', 10") according to any of the preceding claims, wherein, applying between the electrodes (1, T , 1"; 2, 2', 2") a voltage (preferably between 0 V and 220 V, more preferably between 1 V and 20 V) or a current (preferably between 0 A and 50 A, more preferably between 0 A and 5 A) Fenton reagents (i.e., H2O2 and Fe2+ions) are generated in-situ, which Fenton reagents are capable of completely oxidizing the polluting substances contained in the water to be treated, and wherein the ferrous material present in the cathode allows the simultaneous reductive dehalogenation of the halogenated substances contained in the water.

13. A method for in-situ remediation of aquifer systems contaminated by oxidisable pollutants, reducible pollutants and / or mixtures thereof using the electrochemical equipment (10'", 10"") according to any of the preceding claims, wherein said electrochemical equipment (10'", 10"") is inserted into a perforation (9'", 9"") built in a portion of the underground.

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