Ni-mn LDH electrodes for organic pollutant degradation in wastewater

Abstract

The present invention relates to the field of water treatment technologies, specifically to the development of electrochemical electrodes for the removal and degradation of 5 organic pollutants from water. The invention particularly focuses on the use of nickel- manganese layered double hydroxide (NiMn-LDH) electrodes, modified with various carbon materials and supported on a porous material substrate, to enhance the efficiency and effectiveness of electrochemical oxidation processes in water purification.

Description

[0001] Ni-Mn LDH Electrodes for Organic Pollutant Degradation in wastewater

[0002] The present invention relates to the field of water treatment technologies, specifically to the development of electrochemical electrodes for the removal and degradation of organic pollutants from water. The invention particularly focuses on the use of nickelmanganese layered double hydroxide (NiMn-LDH) electrodes, modified with various carbon materials and supported on a porous material substrate, to enhance the efficiency and effectiveness of electrochemical oxidation processes in water purification.

[0003] BACKGROUND ART

[0004] The presence of organic pollutants in water sources represents a critical environmental and public health issue. These pollutants arise from diverse origins, including industrial discharges, agricultural runoff, pharmaceutical residues, and municipal wastewater. Common organic contaminants such as pesticides, pharmaceuticals, endocrine-disrupting compounds, and industrial chemicals are of particular concern. When introduced into water sources, these pollutants pose significant risks to both ecosystems and human health. Exposure to contaminated drinking water has been linked to a range of adverse health outcomes, including carcinogenesis, endocrine disruption, reproductive and developmental issues, neurological disorders, and other chronic health conditions. The persistence and bioaccumulative nature of these compounds necessitate the development of effective water treatment technologies capable of not only removing but also degrading these harmful substances to prevent their long-term impact. [A. Mandal, P. Senthil Kumar, C. S. Poorva, L. Srinivasa Raju, S. R. Balasubramani, and G. Rangasamy, “Research progress of persistent organic pollutants in water: classification, sources, potential risks, and treatment approaches,” Water Pract. Technol., vol. 19, no. 3, pp. 937-959, Mar. 2024, doi: 10.2166 / wpt.2024.031.].

[0005] Traditional water treatment methods — including physical processes like filtration and sedimentation, chemical methods such as chlorination and ozonation, and biological treatments like activated sludge — have demonstrated limited effectiveness in fully removing or degrading organic pollutants. [ G. Crini and E. Lichtfouse, “Advantages and disadvantages of techniques used for wastewater treatment,” Environ. Chem.Left, vol. 17, no. 1, pp. 145-155, Mar. 2019, doi: 10.1007 / s10311-018-0785-9] These methods primarily focus on separating contaminants from water rather than achieving complete mineralization, which can lead to the persistence of pollutants or the formation of harmful byproducts. The shortcomings of these conventional approaches underscore the need for more advanced treatment technologies.

[0006] Electrochemical Advanced Oxidation Processes (EAOPs) have emerged as a promising alternative for the degradation of organic pollutants in water. EAOPs operate by generating highly reactive species, such as hydroxyl radicals, at the surface of an electrode. These radicals are capable of breaking down a wide spectrum of organic contaminants into less harmful substances or fully mineralizing them to carbon dioxide and water. However, the effectiveness of EAOPs is often limited by poor mass transport of organic pollutants to the reactive vicinity of the electrode. This results in inefficient electrochemical oxidation, with much of the electrode area and electrical energy being expended on the electrolysis of water rather than the oxidation of contaminants. Given that oxidation occurs only at the electrode surface, the low concentration of pollutants in water (often in the parts-per-million range) requires that these species be within nanometers of the electrode to undergo oxidation. Moreover, hydroxyl radicals, despite their crucial role in oxidation, have an extremely short lifespan and reactive range, limiting their effectiveness in real-world applications. [ J. Radjenovic and D. L. Sedlak, “Challenges and Opportunities for Electrochemical Processes as Next-Generation Technologies for the Treatment of Contaminated Water,” Environ. Sci. Techno / ., vol. 49, no. 19, pp. 11292-11302, Oct. 2015, doi: 10.1021 / acs.est.5b02414],

[0007] In commercial electrochemical reactors, the efficiency of organic oxidation is typically less than 15% at pollutant concentrations ranging from 200 mg / L to trace levels. Although reducing the current density can somewhat improve current efficiency at higher pollutant concentrations (e.g., 1000 mg / L), this approach offers only marginal gains — a tenfold reduction in current density results in just a 5% increase in efficiency, which is still below 20%, and entails significant increases in capital costs. These challenges highlight the critical importance of electrode material selection in improving the efficiency and economic viability of EAOPs.Several electrode materials have been investigated fortheir potential to enhance the degradation of organic pollutants, each offering distinct advantages and limitations. Boron-Doped Diamond (BDD) electrodes are among the most advanced options in EAOPs. Known for their exceptional chemical and electrochemical stability, BDD electrodes possess a high overpotential for oxygen evolution and effectively generate hydroxyl radicals, making them highly efficient for organic pollutant degradation. Electrodes are typically produced using chemical vapor deposition (CVD) techniques. However, the CVD process is inherently slow and expensive, leading to low production rates and high costs. Additionally, producing high-surface-area BDD electrodes is challenging, necessitating the use of numerous expensive electrodes to meet treatment objectives. The high production costs and the relatively brittle nature of diamond materials have limited the widespread adoption of BDD electrodes in commercial water treatment applications. [S. J. Cobb, Z. J. Ayres, and J. V. Macpherson, “Boron Doped Diamond: A Designer Electrode Material for the Twenty-First Century,” Annu. Rev. Anal. Chem., vol. 11, no. 1, pp. 463-484, Jun. 2018],

[0008] Dimensionally Stable Anodes (DSA) represent another significant development in electrochemical oxidation technology. DSAs have become widely used in industrial processes, including chlor-alkali production and wastewater treatment. DSAs are characterized by their robust structure, long operational lifespan, and high efficiency in generating reactive oxygen species for pollutant degradation. Typically composed of a titanium substrate coated with mixed metal oxides (MMOs) such as ruthenium oxide (RUO2), iridium oxide (lrC>2), or other platinum group metals, DSAs offer excellent catalytic activity and corrosion resistance, making them suitable for longterm operation in harsh electrochemical environments. In water treatment, DSAs have demonstrated good performance in terms of pollutant degradation rates and energy efficiency. However, DSAs also face challenges, including the potential for catalyst deactivation and the formation of chlorinated byproducts in chloride-containing waters. Moreover, the metals used in DSAs, such as ruthenium and iridium, are not only expensive but also toxic, raising environmental and safety concerns regarding their use and disposal. [G. R. Pointer Malpass and A. de Jesus Motheo, “Recent advances on the use of active anodes in environmental electrochemistry,” Curr. Opin. Electrochem., vol. 27, p. 100689, Jun. 2021],Ti4C>7 electrodes have emerged as a comparable alternative to BDD electrodes in terms of organic compound oxidation efficiency. These electrodes can be synthesized at much lower costs, primarily due to their much higher specific surface area compared to BDD electrodes. The high specific surface area of porous Ti4O? electrodes enhances the availability of active sites for oxidation reactions, thereby improving overall treatment efficiency. Various synthesis techniques allow for the formation of high-surface-area Ti4O? structures more cost-effectively than the CVD methods used for BDD production. As a result, Ti4O? electrodes represent a promising alternative to BDD and DSA electrodes from both a technical and economic standpoint, potentially offering a more viable solution for electrochemical oxidation processes in water treatment applications. [H. Wang etal., “Comparison of Ti / Ti4O7, Ti / Ti4O7-PbO2-Ce, and Ti / Ti4O7 nanotube array anodes for electro-oxidation of p-nitrophenol and real wastewater,” Sep. Purif. Technol., vol. 266, p. 118600, Jul. 2021],

[0009] Therefore, existing technologies for the treatment of contaminated water, such as advanced filtration processes, chemical oxidation, and biological treatments, face several significant limitations and problems in terms of cost, efficiency, and the ability to fully degrade these contaminants. Specifically, many of these methods fail to fully decompose complex organic compounds and can generate potentially toxic byproducts or require a large amount of energy.

[0010] As previously indicated, alternatives such as boron-doped diamond electrodes, dimensionally stable anodes or titanium oxides offer certain advantages in generating reactive species for contaminant degradation but are costly to implement and often require high current densities, which increases energy consumption.

[0011] SUMMARY OF THE INVENTION

[0012] The present invention discloses a group of novel advanced materials based on lamellar double hydroxides of nickel and manganese (NiMn-LDH) modified with carbon support-additives such as carbon nanotubes (CNT). These materials, deposited on a substrate, are capable of carrying out electrochemical oxidation processes for the removal of organic pollutants from water.Utilizing nickel-manganese double hydroxides (NiMn-LDH) with carbon additives that exhibit a technical effect on their electrocatalytic behavior and stability allows their use in an innovative electrode design that facilitates the efficient generation and utilization of hydroxyl radicals for the electrochemical oxidation of pollutants. This synergistic effect is particularly advantageous as it allows the electrode system to operate efficiently even at very low current densities, significantly reducing energy consumption compared to existing technologies. This ability to operate at low current densities not only improves the sustainability of the treatment process, but also extends electrode life and reduces operating and maintenance costs. Additionally, this hydroxide-based technology allows syntheses to be performed at room temperature, in contrast to oxide-based solutions.

[0013] This approach provides a greener and economically viable solution for wastewater treatment, addressing the challenge of degrading complex organic pollutants efficiently without compromising environmental safety or economic viability.

[0014] A first aspect of the present invention related to an electrocatalytic material characterized in that it comprises:

[0015] • an oxidized conductive carbon material as an additive-support;

[0016] • a nickel-manganese layered double hydroxide deposited homogeneously over the support;

[0017] wherein the conductive carbon material additive-support is selected from oxidized graphene, oxidized carbon black, oxidized activated carbon, oxidized carbon nanonions, oxidized carbon dots, oxidized mesoporous carbon, oxidized CNTs, and oxidized CNTs with carboxylmethyl cellulose and any combination thereof;

[0018] wherein the amount of conductive carbon material as an additivesupport is between 1% and 40% in weight with respect to the nickel- manganese layered double hydroxide, preferably between 5% and 30%, more preferably between 10% and 20%, even more preferably between 10% and 15%;

[0019] and wherein the ratio of nickel with respect to the manganese in the layered double hydroxide is between 1:1 and 6:1, preferably 2:1 and 5:1, more preferably 2.5:1 and 4:1, even more preferably 2.8:1 and 3.2:1.NiMn-LDH is distinguished by the variable oxidation states of both nickel and manganese. Nickel cycles between Ni2+and Ni3+, while manganese can transition between Mn2+, Mn3+, and Mn4+states. This multiplicity of redox states makes NiMn-LDH a highly effective material for electrochemical applications where charge transfer processes dominate. These different oxidation states allow the material to store and release electrons through Faradaic processes, where Ni2+ / Ni3+and Mn2+ / Mn3+ / Mn4+undergo reversible redox reactions. This ability to participate in multiple electron transfers makes NiMn-LDH an ideal candidate for different applications such as electrocatalytic processes. The synergistic interaction between the oxidation states of Ni and Mn significantly enhances the generation of hydroxyl radicals, facilitating the effective removal of pollutants from wastewater. Ni2+ / Ni3+transitions are central to the electrocatalytic performance, providing active sites for the adsorption and desorption of oxygen-containing intermediates, such as *OH, *0, and *OOH. Mn oxidation states, particularly Mn3+and Mn4providing additional pathways for oxygen intermediates and improving the electron density around the Ni active sites. The multivalent nature of Mn also allows it to stabilize the catalyst during prolonged reactions, improving durability and resistance to catalyst degradation. This cooperative redox mechanism, where manganese stabilizes nickel in higher oxidation states and enhances the material’s overall redox capacity, makes NiMn-LDH highly effective as an electrode material. Furthermore, NiMn-LDH can accommodate ions within its layers, improving ion diffusion rates.

[0020] In a preferred embodiment of the electrocatalytic material the manganese oxidation state is exclusively Mn+2.

[0021] Oxidized carbon materials such as graphene, and carbon nanotubes (CNTs) provide conductive networks that facilitate electron transfer, thereby improving the overall efficiency of the material. According to all that has been discussed regarding the electrochemical properties, redox activity, and structural advantages of NiMn-LDH, particularly its enhanced performance when combined with carbon materials like graphene and carbon nanotubes. In addition, conclusion of the oxidation experiments on conductive carbon material is that the sample oxidizes between 0.1% and 2%, additional to the initial one, and it shows that the dispersibility of the sample oxidized is better than the unoxidized one. Such oxidation surprisingly leads to betterdispersibility of the generated LDH particles on the conductive carbonaceous support, causing less sample aggregation and exhibiting smaller aggregate particle sizes in both DLS and AFM leading to better electrochemistry as there is surprisingly more active surface area.

[0022] The term “conductive carbon material” as used herein refers to carbon-based materials with high electrical conductivity, which are used to facilitate electron transfer in various applications. These materials may include, but are not limited to CNTs, graphene, rGO, carbon black, activated carbon, carbon fibers, carbon nano-onions, carbon dots and mesoporous carbon.

[0023] The term “homogeneously” as used herein refers to a uniform and consistent distribution of the NiMn-LDH material across the entire surface of the support. The term “uniform” as used herein refers to arranged as a dispersed particulate phase and / or distributed without localized accumulation.

[0024] In another preferred embodiment of the present invention the conductive carbon material is selected from oxidized carbon nanotubes and oxidized carbon nanotubes with carboxylmethyl cellulose.

[0025] In another preferred embodiment the sample is oxidized to a value between 0.1% and 2%. Preferably, between 0.5 and 1.5%, more preferably 0.8% and 1.3%. This value is calculated from the controlled amount of oxidizing agent used in the process. At values higher than this controlled oxidation the condition of good electrical conduction starts to be lost so that not any oxidation can be used and the material could not be used for the intended function.

[0026] CNTs provide a similar advantage by acting as conductive backbones that support the NiMn-LDH nanosheets. The incorporation of CNTs enhances the overall conductivity and rate capability of the material, enabling it to perform better at higher current densities. NiMn-LDH with carbon nanotubes as a support composites have demonstrated significant improvements in the conductivity of the material and the available active surface area, resulting in higher efficiency compared to conventional materials.In another embodiment of the electrocatalytic material further comprise a a porous material substrate;

[0027] wherein the electrocatalytic material is arranged on the carbon material substrate.

[0028] A second aspect of the present invention a process for preparing an electrocatalytic material, comprising:

[0029] • modifying a conductive carbon material; and

[0030] • forming and depositing inorganic particles on the modified conductive carbon material.

[0031] In a preferably embodiment of the process for obtaining an electrocatalytic material, the process comprising:

[0032] 1. treating a conductive carbon material so as to modify its surface chemistry; 2. combining the treated conductive carbon material with metal precursors in a solvent to form a precursor mixture;

[0033] 3. converting the metal precursors into inorganic particles and depositing said particles onto the treated conductive carbon material;

[0034] 4. recovering the electrocatalytic material obtained.

[0035] In a more preferred embodiment of the process to obtain an electrocatalytic material described above characterized in that it comprises the following steps:

[0036] a) mixing a conductive carbon material with a 1.2 w / V% to 6 wA / % of H2O230% solution;

[0037] b) oxidizing the mixture obtained in step (a), filtering and drying the oxidized conductive carbon material obtained;

[0038] c) mixing in a solution of methanol, preferably dry methanol, the metal precursors of Ni and Mn in a stoichiometric ratio of between 1.5:1 and 6:1 respect to Ni:Mn, preferably between 2.0:1 and 5.0:1, more preferably 2.5:1 and 4:1, and then adding the oxidized conductive carbon material obtained in step (b) wherein the ratio of oxidized conductive carbon material is between 0.6:1 and 18:1 with respect to the nickel-manganese, preferably between 4:1 and 14:1, more preferably 6:1 and 10:1;d) preparing a NaOH solution in methanol with a concentration ranging from 0.1 M to 6 M and adding it slowly to the mixture, preferably by dropwise technique, obtained in step (c) over a period of 2 to 100 minutes, followed by stirring the mixture for a minimum of 48 hours and the obtained dispersion is filtering; and

[0039] e) drying the powder obtained in step (d), preferably in a temperature of between 15 °C and 80 °C.

[0040] The use of methanol in step (c) is a critical parameter to prevent the oxidation of manganese during the formation process, and it is even better with dry methanol. In addition, the slow addition of the hydroxide solution during step (d) is crucial to prevent manganese oxidation. The oxidation state of the Mn in the product of the present invention is 2+, thus Mn2+is the exclusive oxidation state of the manganese in the LDH.

[0041] In preferred embodiment the conductive carbon material is selected from carbon nanotubes, graphene, carbon black, activated carbon, carbon fibers, carbon nanoonions, carbon dots, mesoporous carbon, and carbon nanotubes with carboxymethyl cellulose, preferably the conductive carbon material is carbon nanotubes.

[0042] In another preferred embodiment the oxidizing of step (b) is a treatment using a microwave furnace at 450 W during 6 minutes.

[0043] In another preferred embodiment the metal precursors of step (c) are Ni and Mn in a stoichiometric ratio of between 2.8:1 and 3.2:1, preferably the precursor are halide salts, nitrate salts, sulfate salts.

[0044] In another preferred embodiment the ratio of oxidized conductive carbon material with respect to the nickel-manganese and the ratio of nickel-manganese is between 1 :6.8 and 1:7.8.

[0045] In another preferred embodiment of the process further comprises an additional step of preparing an ink solution dissolving the product obtained of step (e), preferably in a weight percentage of between 70% to 90% in an aprotic organic solvent, more preferably the solvent is N-methyl-2-pyrrolidone (NMP), and in combination with abinding agent in a weight percentage of between 1% to 10%, more preferably 2% to 8%, even more preferably 4% to 6%, more preferably wherein the binding agent is selected from Polyvinylidene fluoride (PVDF) and Nation. In a more preferred embodiment of the process it further comprises an additional step wherein the obtained ink impregnates by impregnation treatment a porous material substrate previously cleaned. In a preferred embodiment the porous material substrate is selected from graphite felt (GF), preferably GF with a thickness selected from 2.5, 4.6 and 6 mm, reticulated vitreous carbon (RVC), preferably RVC with a porosities selected from 10, 20, and 30 pores per inch (ppi), nickel foam (NF), aluminum foam (AF), carbon felt, carbon cloth, carbon paper, graphite foam, expanded graphite, glassy carbon, carbon fiber brush, carbon fibers, carbon nanonions. More preferably the carbon material support is graphite felt, defined as GF / NiMn-LDH with conductive carbon material.

[0046] In a more preferred embodiment the cleaned porous material increases the surface tension, preferably by corona treatment. In another more preferred embodiment the cleaned porous oxidizes the porous material substrate, preferably by immersing in H2O2 and irradiating for 3-6 minutes at 450W in a microwave. In an even more preferred embodiment the cleaned porous material firstly increases the surface tension, preferably by corona treatment, and second oxidizes the porous material substrate, preferably by immersing in H2O2 and irradiating for 3-6 minutes at450Win a microwave.

[0047] Another preferred embodiment during the preparation of the ink step comprises the addition of an additional conductive carbon supplement, preferably the conductive carbon additive is carbon black material.

[0048] Said carbon supplement is optionally added because it is observed that a carbon conductive layer appears as a support from the procedure carried out in stages (i) to (v) with the carbon material substrate without said further optional addition of such material, obtaining an improved conductivity, nevertheless it also works and such layer appears if said conductive carbon material is added additionally, although the conductivity is slightly lower than the most optimal one obtained without the addition of the material.A third aspect of the present invention is an anode electrode characterized in that it comprises:

[0049] • an electrocatalytic material as described above

[0050] • a porous material substrate;

[0051] wherein the electrocatalytic material is arranged on the carbon material substrate.

[0052] In a preferred embodiment the porous material substrate is selected from graphite felt (GF), preferably GF with a thickness selected from 2.5, 4.6 and 6 mm, reticulated vitreous carbon (RVC), preferably RVC with a porosities selected from 10, 20, and 30 pores per inch (ppi), nickel foam (NF), aluminum foam (AF), carbon felt, carbon cloth, carbon paper, graphite foam, expanded graphite, glassy carbon, carbon fiber brush, carbon fibers, carbon nanonions. More preferably the carbon material support is graphite felt, defined as GF / NiMn-LDH with conductive carbon material.

[0053] The above-listed porous-based materials substrates are interchangeable as electrode supports substrates, as they perform the same function of providing an electrically conductive and electrochemically stable interface between the power supply and the wastewater.

[0054] The enhanced performance of the GF / NiMn-LDH with conductive carbon material configured as a composite can be attributed to the synergistic effects of the CNTs (as example of the conductive carbon material) and NiMn-LDH. CNTs provide a highly conductive network that facilitates efficient electron transfer, enhancing the electrocatalytic activity of the NiMn-LDH. Additionally, the high surface area and the mesoporous structure of the CNTs increase the available active sites for phenol adsorption and degradation. This combination results in a more effective and faster removal of organic pollutants, as demonstrated in the experiments, underscoring the potential of GF / NiMn-LDH-CNT as an advanced electrode material for wastewater treatment applications.

[0055] A fourth aspect of the present invention is a process for obtainment of an electrocatalytic material deposited on a porous substrate characterized in that it comprises the following steps:

[0056] i. cleaning a porous material substrate;

[0057] ii. optionally, increasing the surface tension of the cleaned porous material substrate obtained in step (i);iii. optionally, oxidizing the porous material substrate obtained in step (i) or (ii); iv. impregnating the oxidized porous material substrate obtained in step (iii), with the electrocatalytic material described before in the first aspect of present invention, preferably in a weight percentage of between 70% to 90% in an aprotic organic solvent, more preferably the solvent is N-methyl-2-pyrrolidone (NMP), and in combination with a binding agent in a weight percentage of between 1% to 10%, more preferably 2% to 8%, even more preferably 4% to 6%, more preferably wherein the binding agent is selected from Polyvinylidene fluoride (PVDF) and Nation;

[0058] or

[0059] the metal salts precursors of Ni and Mn in a stoichiometric ratio of between 2.5:1 and 4:1, preferably metal salt precursors are selected from halide salts, nitrate salts, sulfate salts, and oxidized conductive carbon material that it is obtained by oxidizing, filtering and drying a mixture of a conductive carbon material with a 1.2 w / V% to 6 w / V% of H2O2 30% solution and adding the precipitating agent to the mixture obtained in step (iv) in an amount of at least 2 times the stoichiometric amount of the metals present in the mixture, preferably the precipitation agent is selected from NaOH and Glycidol; v. rinsing of excess powder obtained in step (v) with at least twice a volume of polar solvent, preferably water, with respect to the total volume obtained in step (v) and drying, preferably in a temperature of between 15 °C and 80 °C.

[0060] In a preferably embodiment after step (v) and before step (vi) adding an additional conductive carbon supplement, preferably the conductive carbon additive is carbon black material.

[0061] Said carbon supplement is optionally added because it is observed that a carbon conductive layer appears as a support from the procedure carried out in stages (i) to (v) with the carbon material substrate without said further optional addition of such material, obtaining an improved conductivity, nevertheless it also works and such layer appears if said conductive carbon material is added additionally, although the conductivity is slightly lower than the most optimal one obtained without the addition of the material.

[0062] In a preferably embodiment the cleaning of step (i) is by washing with a polar solvent selected from methanol or acetone.In another preferred embodiment increasing the surface tension of optionally step (ii) is carried out by a corona treatment.

[0063] In another preferred embodiment the oxidizing of optionally step (iii) is carried out by immersing in H2O2 and irradiating for 3-6 minutes at 450W in a microwave.

[0064] A fifth aspect of the present invention is the use of the electrocatalytic material described above or the electrode described above, as an anode in an electrochemical oxidation process of wastewater for the removal and degradation of their organic pollutants.

[0065] A preferred embodiment of the use of the electrode described above in wastewater treatment applications, preferably in the electrochemical oxidation of phenol in water.

[0066] A sixth aspect of the present invention is a method for wastewater treatment characterized in that it comprises the following steps:

[0067] 1) contacting the electrochemical device described above in a medium comprising waste water;

[0068] 2) applying a current density of between 5 and 20 mA cm2;

[0069] 3) sampling of the water to be treated for intervals between 2.5 and 20 min; 4) analyzing the evolution of the samples of step (3) of the phenol concentration and the chemical oxygen demand (COD); and

[0070] 5) optionally cleaning by keeping the device and the anode immersed in milliQ water for at least 1 h.

[0071] A seventh aspect of the present invention is a wastewater treatment device, comprising:

[0072] - a reaction tank configured to contain wastewater to be treated, the reaction tank comprising an inlet and an outlet arranged at upper ends of opposite side walls of the reaction tank;

[0073] - an electrolysis device comprising at least one positive electrode and at least one negative electrode arranged inside the reaction tank, and a power supply electrically connected to the positive electrode and the negative electrode;characterized in that the wastewater treatment system further comprises:

[0074] - an electrode as described before in the present invention arranged within an interior of the electrolysis device.

[0075] A preferred embodiment of the wastewater treatment device further comprises a hydraulic pumping system configured to circulate the electrolyte through the electrolyzer, thereby enhancing mass transfer to the anode and improving oxidation efficiency. The hydraulic pumping system is configured to provide controlled flow of the electrolyte across the anode surface, reducing concentration polarization and increasing electrochemical oxidation efficiency.

[0076] In another preferred embodiment of the wastewater treatment device, the catalytic material is arranged on the anode electrode, which is positioned adjacent to the positive electrode, and the membrane is arranged between the positive and negative electrodes.

[0077] In another preferred embodiment of the wastewater treatment device further include, but are not limited to, a stainless-steel (SS) sheet as the cathode and an aqueous supporting electrolyte.

[0078] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. Methods and materials similar or equivalent to those described herein can be used in the practice of the present invention. Throughout the description and claims the word "comprise" and its variations are not intended to exclude other technical features, additives, components, or steps. Additional objects, advantages and features of the invention will become apparent to those skilled in the art upon examination of the description or may be learned by practice of the invention. The following examples, drawings and sequence listing are provided by way of illustration and are not intended to be limiting of the present invention.

[0079] BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Fig. 1. XRD patterns of different synthesized NiMn-LDHs.Fig. 2. Raman spectra of different synthesized NiMn-LDHs with carbon nanotubes.

[0081] Fig. 3. XRD patterns of different synthesized NiMn-LDHs.

[0082] Fig. 4. N2adsorption-desorption isotherms of different NiMn-LDHs.

[0083] Fig. 5. SEM images of different NiMn-LDH-CNT electrode at various magnifications (25,000x, 30,000x, and 100,000x) and mapping of the different elements and Energy-Dispersive X-ray Spectroscopy (EDS) data of the selected area.

[0084] Fig. 6. TEM images of NiMn-LDH-CNT nanocomposite and Energy-Dispersive X-ray Spectroscopy (EDS) data of the selected area.

[0085] Fig. 7. Comparison of electroactive response of NiMn-LDH and NiMn-LDH-CNT

[0086] Fig. 8. Comparison of phenol degradation using anodes with different active materials.

[0087] Fig. 9. Electrode's potential for repeated use in water purification processes.

[0088] Fig. 10. Dynamic Light Scattering (DLS) particle size distribution of electrocatalytic materials prepared with oxidized and non-oxidized conductive carbon supports.

[0089] Fig. 11. Comparative Atomic Force Microscopy (AFM) analysis of surface morphology and particle dispersion in electrocatalytic materials prepared with oxidized (C-D) and non-oxidized conductive carbon supports (A-B).

[0090] Fig. 12. Comparative Transmission Electron Microscopy (TEM) analysis of particle size and dispersion in electrocatalytic materials prepared with oxidized (B) and nonoxidized (A) conductive carbon supports.

[0091] Examples

[0092] Example 1

[0093] Protocol for obtainment of NiMn-LDHs with CNTsPreparation of NiMn-LDH with CNTs Samples

[0094] Two types of CNTs were used in this study: Tuball CNTs stabilized with CMC and commercially available CNTs from Sigma-Aldrich. Both types underwent an oxidation treatment using a microwave furnace, during which the CNTs were mixed with a 60 g / L H2O2 solution. Following the oxidation, the CNTs were filtered and dried for subsequent use.

[0095] For the preparation of NiMn-LDH with CNTs, the CNTs were introduced into a metal solution of NiMn precursors salts (chloride salts) in the desired stoichiometry of the LDH compound (for example, 2.8:1 and 3.2:1 ratio of Ni:Mn) before the addition of NaOH, allowing the CNTs to interact with the metal precursors for a period of 1 to 24 hours. The NaOH solution was then slowly added over 2 to 3 minutes, and the mixture was stirred for 48 hours. In these samples, the metal-to-CNT ratio was maintained at 7:1.

[0096] Example 2. Electrode preparation.

[0097] Preparation of NiMn-LDH with CNTs on Graphite Felt directly

[0098] To obtain NiMn-LDH with CNTs directly on a carbon felt collector, a series of pretreatments were applied to the carbon felt. First, the felt was cleaned with methanol or acetone to remove surface polymers. Next, it underwent a corona treatment. Finally, the carbon felt was oxidized using a microwave process, where it was immersed in H2O2 and irradiated for 6 minutes at 400W. After oxidation, the carbon felt was soaked in a metal solution of NiMn precursors salts (chloride salts) in the desired stoichiometry of the LDH compound (for example, 2.8:1 and 3.2:1 ratio of Ni:Mn) in addition to the CNT oxidized (as described in example 1) for at least 2 hours, then the precipitation agent (NaOH or Glycidol) was added, and after 24 hours, the substrate with the catalyst layer was cleaned to remove any excess powder and subsequently dried.

[0099] Preparation of NiMn-LDH with CNTs on Graphite Felt by impregnation Graphite felt substrates (20 mm x 20 mm x 6 mm) were used as the anode support material. Prior to coating, the substrates were thoroughly cleaned, via ultrasonication in 0.1 M HCI, acetone, ethanol, and deionized water for 10 minutes each to remove impurities and enhance surface wettability. The catalyst ink for electrode coating was prepared by dispersing 85 wt.% of the material obtained as described in example 1, (10 wt.% carbon black as a conductive additive is added optionally), and 5 wt.%polyvinylidene fluoride (PVDF) as a binder in N-methyl-2-pyrrolidone (NMP) under continuous stirring until a homogeneous colloidal suspension was obtained. The pretreated graphite felt substrates were immersed in the catalyst ink and subjected to ultrasonication for 30 minutes to ensure uniform deposition of the active material. The coated electrodes were subsequently dried at 80 °C for 12 hours under vacuum. The mass loading of the deposited active material was consistently maintained at 200 ± 5 mg across all electrode samples to ensure comparability in electrochemical performance.

[0100] Example 3: Comparative examples

[0101] Synthesis of NiMn-LDH Powder (without CNT)

[0102] NiMn-LDH was synthesized using an alkoxide method. A 40 mM solution of metals (30 mM Ni and 10 mM Mn) was prepared in methanol, and separately, a 1 M NaOH solution was prepared in methanol as well. The NaOH solution was gradually added to the metal solution over a period of 2 to 3 minutes, followed by continuous stirring for 48 hours.

[0103] NiMn-LDH-Tris: NiMn-Tris LDH with a Ni / Mn = 3:1 ratio was synthesized using a modified hydrothermal method published by Kuroda et al. to obtain a functionalized LDH.

[0104] Synthesis of NiMn-LDH (without CNT) on Pretreated Graphite Felt

[0105] Two synthetic routes were employed to grow NiMn-LDH on the pretreated graphite felt (SGL CARBON: Thermally activated graphite felt GFD 4.6.)

[0106] Alkoxide Synthesis: A 40 mM solution of metals (30 mM Ni and 10 mM Mn) was prepared in methanol, and a 1 M NaOH solution was prepared separately in methanol. The NaOH solution was slowly added to the metal solution over 2 to 3 minutes, followed by stirring for 48 hours.

[0107] Epoxide Route: A metal solution with the same concentrations (30 mM Ni and 10 mM Mn) was prepared in water with a pH lower than 3 and a high NaCI concentration. An epoxide was then added to initiate the reaction, and the mixture was stirred for 48 hours.

[0108] Example 4. Characterization structural

[0109] The X-ray diffraction (XRD) analysis results for these materials are presented in Figure 1. The XRD results for NiMn-LDHs typically reveal the characteristic layeredstructure of LDHs, with reflections corresponding to the brucite-like layers of metal hydroxides. The XRD patterns commonly show sharp peaks at low angles, representing the (003), (006), and (009) planes, which are indicative of the ordered stacking of the hydroxide layers. The interlayer spacing between these planes, often calculated from the (003) reflection, provides insights into the intercalation of anions and the overall layer thickness. The presence of Ni and Mn within the layers usually does not significantly shift the basal reflections compared to other LDHs, but additional peaks at higher angles, corresponding to metal oxides or hydroxides, might appear depending on the degree of crystallinity and the presence of impurities or secondary phases. In composites where NiMn-LDH is coupled with materials like graphene or rGO, the XRD results often show broadened peaks, indicating a reduction in the crystallite size or layer order due to the exfoliation of the LDH sheets or the interaction with the carbon matrix. These XRD characteristics are essential for confirming the successful synthesis of NiMn-LDH and for understanding how structural modifications affect its electrochemical performance.

[0110] Raman spectroscopy was conducted on the samples NiMn-LDH-CMC and NiMn-LDH-CNT, as shown in Figure 2. In both samples, low-frequency vibrations corresponding to the metal-oxygen (M-O) signals were observed. These signals are related to the presence of both Ni-0 and Mn-O. Additionally, signals around 1250, 1600, and 2750 cm-1are observed, which correspond to the D, G, and 2D bands associated with carbon-based nanostructures. The D band, located around 1250-1300 cm-1is associated with the defects or the disorder in the carbon lattice. The G band, around 1550-1600 cm-1represents the in-plane vibrations of sp2 carbon atoms, and represents the graphiticity of the structure. Finally, the 2D band, which is observed c.a. 2500-2800 cm-1is a second-order resonance of the D band and its really sensitive to the number of layers in the material. A strong 2D signal is characteristic for single layered graphene, while it’s broadening suggest the presence of more layers. For the NiMn-LDH-CMC sample, a significant difference between the intensities of the D and G bands indicates that the pre-treatment process did not result in oxidation, thereby preserving the graphitic structure of the material. In contrast, for the NiMn-LDH-CNT sample, the increased intensity of the D band suggests that the oxidation pre-treatment was effective. This increase in the D band indicates a higher level of defects in the carbon component, consistent with the successful modificationof the nanotubes through oxidation. For both samples the 2D peak behaves similar, suggesting a few-layer conformation of nanotubes.

[0111] Additionally, X-ray Photoelectron Spectroscopy (XPS) was performed on the NiMn-LDH-CMC and NiMn-LDH-CNT samples. The resulting spectra were deconvoluted for carbon, nickel and manganese as depict in Figure 3. For the Carbon the spectrum shows signals at 284 eV which corresponds to the C sp2, which predominate, exhibiting the predomination of graphitic carbon on the surface. However, C-0 and O-C-0 signals are also observed. For the metallic environments, the spectrum of Ni exhibits a typical behaviour of Ni" while for Mn, the spectrum suggests the presence of both Mn" and Mn1".

[0112] The nitrogen adsorption-desorption isotherms depicted in Figure 4 provide insights into the surface properties of three different NiMn-LDH samples, showcasing their specific surface areas (SBET). The isotherms follow a Type IV curve with H3 hysteresis loops, which are typical for mesoporous materials. These loops suggest that the materials possess slit-shaped pores formed by the aggregation of plate-like particles, common in layered materials like LDHs.

[0113] The sample represented by the blue curve (NiMn-LDH-CNT) exhibits a significantly higher specific surface area (SBET = 71 m2g_1) compared to the other two, indicated by the grey (SBET = 12.91 m2g_1) and white (3.33 m2g_1) curves. This increased surface area can be attributed to a more open pore structure or smaller, more tightly packed nanosheets, which enhance the accessibility of active sites for adsorption processes. A higher surface area is generally advantageous for catalytic applications, including the electrocatalytic oxidation of organic pollutants in water treatment, as it allows for more extensive interaction between the catalyst and contaminants. Thus, the sample with a surface area of 71 m2g-1(NiMn-LDH-CNT) is expected to exhibit superior performance in applications requiring high surface reactivity.

[0114] The Scanning Electron Microscopy (SEM) images and corresponding energy-dispersive X-ray spectroscopy (EDX) data presented illustrate the morphological and compositional characteristics of the NiMn-LDH-CNT composite. The SEM images (Figure 5) at various magnifications (25,000x, 30,000x, and 100,000x) reveal a complex network of CNTs thoroughly interwoven with NiMn-LDH. The high-resolutionimage at 100,000x magnification clearly shows the ultrafine structure of the intertwined CNTs and the layered morphology of NiMn-LDH, suggesting a successful integration of the two components which is likely to provide a high surface area and enhance electron mobility.

[0115] The EDX spectrum confirms the presence of carbon (C), oxygen (O), nickel (Ni), and manganese (Mn) in the composite. The composition shows a high carbon content at 75.1% atomic percent, which is indicative of a substantial CNT presence, aligning with the observed dense networks in the SEM images. Nickel and manganese are detected at 2.6% and 0.8% atomic percent respectively, which supports the integration of NiMn-LDH into the carbon matrix.

[0116] The Transmission Electron Microscopy (TEM) images and Energy-Dispersive X-ray Spectroscopy (EDS) data provide a detailed insight into the ultrastructural composition and elemental distribution of the NiMn-LDH-CNT composite (Figure 6).

[0117] The TEM images at various scales clearly depict the intricate, web-like structure of the CNTs intertwined with finer particles and layers of NiMn-LDH. This arrangement suggests a highly porous network, favorable for enhancing surface-reactive properties due to the high accessibility of active sites. The EDS analysis confirms the elemental makeup of the composite, highlighting that nickel and manganese are present in amounts of 9% and 2.8% respectively, indicating their incorporation as active components within the predominantly carbon-based matrix. This composition is critical for the electrochemical functionality of the composite, as the metallic components (Ni and Mn) are essential for catalytic activity, while the carbon framework provides structural support and electrical conductivity. Additionally, the elemental mapping included in the EDS analysis visually demonstrates the homogeneity of the elemental distribution, which is crucial for consistent electrochemical performance across the material. The integration of NiMn-LDH with CNTs in this manner likely enhances both the electrical conductivity and the electrochemical activity, making this composite an excellent candidate for advanced electrode materials in applications such as energy storage and environmental remediation.

[0118] Example 5. Electrochemical response of NiMn-LDH based anode with and without CNTCyclic voltammetry (CV) characterization was conducted in a three-electrode cell setup, employing a platinum mesh as the counter electrode, an Ag / AgCI electrode as the reference electrode, and 0.1 M Na2SC>4 as the electrolyte. The working electrodes used were GF / NiMn-LDH (without CNT) and GF / NiMnLDH-CNT (with CNT), respectively. The results of this analysis are presented in Figure 7.

[0119] The redox activity of NiMn-LDH grown on CNTs is significantly enhanced, as evidenced in the graph where the black curve (GF / NiMn-LDH-CNT) exhibits higher current than the red curve (GF / NiMn-LDH) across a similar range of potentials. Both samples display two common redox peaks, the first appearing around 0.5 V and the second near 1.4 V. The first redox peak is attributed to the Ni2+ / Ni3+redox couple, while the second corresponds to the Mn3+ / Mn4+redox process. These redox peaks are indicative of the electrochemical activity of the NiMn-LDH material, with the redox behavior being more pronounced in the presence of CNTs. The enhancement observed in the GF / NiMn-LDH-CNT composite can be attributed to the unique properties of CNTs. Their excellent conductivity facilitates more efficient electron transport, thereby improving the utilization of active sites. Additionally, CNTs provide a high surface area and a strong structural support, which increases the availability of active sites and enhances the accessibility of reactants to these sites. The interaction between NiMn-LDH and CNTs results in a synergistic effect, reducing charge transfer resistance and promoting faster electrochemical kinetics.

[0120] Example 6. The efficiency of various NiMn-LDH-based anode materials in the electrochemical removal of phenol from water under different current densities (0 to 20 mA cm'2).

[0121] The results in terms of phenol are collected in Figure 8. The electrodes tested include GF, GF / NiMn-LDH-CNT, GF / NiMn-LDH-CMC, GF / NiMn-LDH-Tris, and GF / NiMnO3-rGO.

[0122] Across all the current densities, the GF / NiMn-LDH-CNT electrode exhibits superior performance in phenol removal efficiency. At 0 mA cm-2, the removal rates are relatively lower for all materials, indicating the limited spontaneous adsorption capacity of these electrodes. However, as the current density increases the GF / NiMn-LDH-CNT consistently achieves higher phenol removal percentages in a shorter time, reaching nearly 100% removal at 10 mA cm'2and maintaining this efficiency at 20 mA cm-2. In the experiments conducted at a current density of 20 mA cm-2, the GF / NiMn-LDH-CNT electrode notably excels in the rapid removal of phenol, achieving complete removal within just 30 minutes. This remarkable efficiency highlights the effectiveness of the electrode material under higher operational currents, where the increased electron flow likely enhances the oxidative processes at the electrode surface. The swift removal rate is particularly significant for practical applications, as it demonstrates the potential for achieving high treatment efficiencies within short operational times, making the GF / NiMn-LDH-CNT composite an exceptionally promising candidate for the electrochemical treatment of wastewater. This capability to quickly remove pollutants not only improves the overall process efficiency but also reduces the energy and operational costs associated with longer treatment cycles. The enhanced performance of the GF / NiMn-LDH-CNT composite can be attributed to the synergistic effects of the carbon nanotubes and NiMn-LDH. CNTs provide a highly conductive network that facilitates efficient electron transfer, enhancing the electrocatalytic activity of the NiMn-LDH. Additionally, the high surface area and the mesoporous structure of the CNTs increase the available active sites for phenol adsorption and degradation. This combination results in a more effective and faster removal of organic pollutants, as demonstrated in the experiments, underscoring the potential of GF / NiMn-LDH-CNT as an advanced electrode material for wastewater treatment applications.

[0123] In the present invention, the stability of the NiMn-LDH-CNT electrode was tested through its application in the electrochemical oxidation of phenol in water across five consecutive experiments. This approach aimed to evaluate the electrode's ability to consistently remove phenol, thereby providing insights into its practical applicability for water treatment. The experiments were designed to assess not only the efficiency of phenol removal in each cycle but also to observe any potential degradation or loss of activity in the electrode material after repeated use. This methodological approach is crucial for determining the durability and reusability of such electrodes in real-world environmental applications. NiMn-LDH-CNT exhibits slight variability but generally remains within a close range throughout the experiments (Figure 9).

[0124] Example 7. Comparative Example - Effect of Oxidation of the Conductive Carbon Additive-Support on Particle Dispersibility of the Electrocatalytic MaterialThis example describes a comparative study carried out with the aim of evaluating the effect of oxidizing a conductive carbon additive-support on the dispersibility and agglomeration behavior of an electrocatalytic material comprising inorganic particles supported on said conductive carbon additive-support.

[0125] Preparation of Oxidized conductive Carbon Additive-Support sample

[0126] A conductive carbon-based additive-support material, comprising commercially available CNTs from Sigma-Aldrich as described in Example 1, was subjected to an oxidation treatment prior to deposition of the inorganic electrocatalytic particles. The oxidation treatment was carried out by contacting the conductive carbon support with 60 g / L H2O2 solution. Following the oxidation, the CNTs were filtered and dried for subsequent use.

[0127] As a result of the oxidation treatment, oxygen-containing functional groups were introduced onto the surface of the conductive carbon additive-support.

[0128] Subsequently, the oxidized conductive carbon additive-support was used to prepare an electrocatalytic material according to Example 1 of the present invention, resulting in an inventive electrocatalytic sample.

[0129] Preparation of Non-Oxidized Carbon additive-Support sample (Comparative Sample)

[0130] For comparison, an electrocatalytic material was prepared following the same procedure as described above and in Example 1, with the exception that the conductive carbon additive-support was used in its non-oxidized form, i.e. without undergoing the oxidation treatment.

[0131] This resulted in a comparative electrocatalytic sample differing from the inventive sample only in that the conductive carbon additive-support was not oxidized.

[0132] Dynamic Light Scattering (DLS) Analysis

[0133] The dispersibility and particle size distribution of both the inventive sample and the comparative sample were analyzed by Dynamic Light Scattering (DLS). The DLS measurements were performed at room temperature with a Zetasizer Nano ZS instrument (Malvern Instruments Ltd.)The results of the DLS analysis are shown in Figure 10.

[0134] As illustrated in Figure 10, the electrocatalytic material obtained using the oxidized conductive carbon additive-support exhibits a smaller average particle size and a narrower particle size distribution compared to the electrocatalytic material prepared using the non-oxidized conductive carbon additive-support. In particular, the inventive sample shows a reduced degree of particle agglomeration and a more homogeneous distribution of the inorganic particles.

[0135] Atomic Force Microscopy (AFM) Analysis

[0136] Further comparative analysis of the surface morphology and particle dispersion was carried out by Atomic Force Microscopy (AFM). AFM measurements were performed using the multimode Scanning Probe Microscope Nanoscope IV (from Bruker, formerVeeco). The resolution of all the images was 512 x 512 pixels and theywere acquired in Non-Contact Mode over a 500 x 500 nm 2 area with ascan rate of 0.25 Hz lines per second. Thanks to the low surface rough-ness very similar feedback parameters during acquisition could be used, in tapping mode, with a scan area from 15 pm x 15 pm to 20 pm x 20 pm.

[0137] The AFM images of the inventive sample and the comparative sample are shown in Figure 11.

[0138] As can be seen from Figure 11, the electrocatalytic material prepared using the oxidized conductive carbon additive-support (C-D) exhibits a more uniform distribution of particles on the carbon additive-support surface, with significantly fewer large agglomerates than the comparative sample. In contrast, the non-oxidized sample (A-B) shows pronounced particle clustering and larger agglomerated domains.

[0139] Conclusion of Comparative Example

[0140] The comparative results demonstrate that oxidation of the conductive carbon additivesupport prior to deposition of the inorganic particles leads to a significant improvement in the dispersibility of the resulting electrocatalytic material. Without being bound by theory, it is believed that the presence of oxygen-containing functional groups on the oxidized carbon additive-support enhances the interaction between the additivesupport and the inorganic particles, thereby reducing particle agglomeration andpromoting a more homogeneous particle distribution as can be seen in the right TEM image of figure 12 (oxidized, B) on contrary to left TEM image of figure 12 (nonoxidized, A).

[0141] Accordingly, the oxidation of the conductive carbon additive-support provides a technical advantage over non-oxidized additive-supports, resulting in an electrocatalytic material with improved dispersion characteristics, as evidenced by both DLS and AFM analyses.

Claims

1. CLAIMS1. An electrocatalytic material characterized in that it comprises• an oxidized conductive carbon material as an additive-support;• a nickel-manganese layered double hydroxide deposited homogeneously over the support;wherein the conductive carbon material additive-support is selected from oxidized graphene, oxidized carbon black, oxidized activated carbon, oxidized carbon nanonions, oxidized carbon dots, oxidized mesoporous carbon, oxidized CNTs, and oxidized CNTs with carboxylmethyl cellulose and any combination thereof;wherein the amount of conductive carbon material as an additivesupport is between 1% and 40% in weight with respect to the nickelmanganese layered double hydroxide, preferably between 5% and 30%, more preferably between 10% and 20%, even more preferably between 10% and 15%;and wherein the ratio of nickel with respect to the manganese in the layered double hydroxide is between 1:1 and 6:1, preferably 2:1 and 5:1, more preferably 2.5:1 and 4:1, even more preferably 2.8:1 and 3.2:1.

2. Electrocatalytic material according to claim 1, wherein the conductive carbon material is oxidized carbon nanotubes and oxidized carbon nanotubes with carboxylmethyl cellulose.

3. A process to obtain the electrocatalytic material described in any claims 1 to 2, characterized in that it comprises the following steps:a) mixing a conductive carbon material with a 1.2 w / V% to 6 wA / % of H2O2 30% solution;b) oxidizing the mixture obtained in step (a), filtering and drying the oxidized conductive carbon material obtained;c) mixing in a solution of methanol, preferably dry methanol, the metal precursors of Ni and Mn in a stoichiometric ratio of between 1.5:1 and 6:1 respect to Ni:Mn, preferably between 2.0:1 and 5.0:1, more preferably 2.5:1 and 4:1, and then adding the oxidized conductive carbon material obtainedin step (b) wherein the ratio of oxidized conductive carbon material is between 0.6:1 and 18:1 with respect to the nickel-manganese, preferably between 4:1 and 14:1, more preferably 6:1 and 10:1;d) preparing a NaOH solution in methanol with a concentration ranging from 0.1 M to 6 M and adding it slowly to the mixture, preferably by dropwise technique, obtained in step (c) over a period of 2 to 100 minutes, followed by stirring the mixture for a minimum of 48 hours and the obtained dispersion is filtering; ande) drying the powder obtained in step (d), preferably in a temperature of between 15 °C and 80 °C.

4. Process according to claim 3, wherein the conductive carbon material is selected from carbon nanotubes, graphene, carbon black, activated carbon, carbon fibers, carbon nano-onions, carbon dots, mesoporous carbon, and carbon nanotubes with carboxymethyl cellulose, preferably the conductive carbon material is carbon nanotubes.

5. Process according to any of claims 3 or 4, wherein the oxidizing of step (b) is a treatment using a microwave furnace at 450 W during 6 minutes.

6. Process according to any claims 3 to 5, wherein the metal precursors of step (c) are Ni and Mn is in a stoichiometric ratio of between 2.8:1 and 3.2:1, preferably the precursor are halide salts, nitrate salts, sulfate salts.

7. Process according to any claims 3 to 6, wherein the ratio of oxidized conductive carbon material with respect to the nickel-manganese is between 6:1 and 8:1.

8. An anode or positive electrode for electrochemical oxidation process for wastewater treatment characterized in that it comprises:• an electrocatalytic material according to any of claims 1 to 2;• a carbon material substrate;wherein the electrocatalytic material is arranged on the porous material substrate.

9. Process for obtainment of an anode electrode described in claim 8 characterized in that it comprises the following steps:i. cleaning a porous material substrate;ii. optionally, increasing the surface tension of the cleaned porous material substrate obtained in step (i);iii. optionally, oxidizing the porous material substrate obtained in step (i) or (ii); iv. impregnating the oxidized porous material substrate obtained in step (iii), with the electrocatalytic material described before in the first aspect of present invention, preferably in a weight percentage of between 70% to 90% in an aprotic organic solvent, more preferably the solvent is N-methyl-2-pyrrolidone (NMP), and in combination with a binding agent in a weight percentage of between 1% to 10%, more preferably 2% to 8%, even more preferably 4% to 6%, more preferably wherein the binding agent is selected from Polyvinylidene fluoride (PVDF) and Nation;orthe metal salts precursors of Ni and Mn in a stoichiometric ratio of between 2.5:1 and 4:1, preferably metal salt precursors are selected from halide salts, nitrate salts, sulfate salts, and oxidized conductive carbon material that it is obtained by oxidizing, filtering and drying a mixture of a conductive carbon material with a 1.2 w / V% to 6 w / V% of H2O2 30% solution and adding the precipitating agent to the mixture obtained in step (iv) in an amount of at least 2 times the stoichiometric amount of the metals present in the mixture, preferably the precipitation agent is selected from NaOH and Glycidol; v. rinsing of excess powder obtained in step (v) with at least twice a volume of polar solvent, preferably water, with respect to the total volume obtained in step (v) and drying, preferably in a temperature of between 15 °C and 80 °C.

10. Process according to claim 9, wherein after step (iv) and before step (v) adding an additionally conductive carbon supplement, preferably the conductive carbon supplement is carbon black material.

11. Process according to any of claims 9 or 10, wherein the cleaning of step (i) is carried out by washing with a polar solvent selected from methanol or acetone.

12. Process according to any of claims 10 or 11, wherein increasing the surface tension of step (ii) is carried out by a corona treatment.

13. Process according to any of claims 10 to 12, wherein the oxidizing of step (iii) is carried out by immersing in H2O2 and irradiating for 3-6 minutes at 450W in a microwave.

14. Use of the electrocatalytic material described in any claims 1 to 2 or the electrode described in claim 8, as an anode in an electrochemical oxidation process of wastewater for the removal and degradation of their organic pollutants, preferably the organic pollutant is phenol.

15. Method for wastewater treatment characterized in that it comprises the following steps:1) contacting an electrochemical device that comprising the anode described in claim 8, in a medium comprising waste water;2) applying a current density of between 5 and 20 mA cm2;3) sampling of the water to be treated for intervals between 2.5 and 20 min; 4) analyzing the evolution of the samples of step (3) of the phenol concentration and the chemical oxygen demand (COD); and5) optionally cleaning by keeping the device and the anode immersed in mill iQ water for at least 1 h.

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