System and method for ammonia production from nitrogen pollutants

Abstract

Disclosed is a system and method for effectively converting nitrogen pollutants, including nitrates, into ammonia. The system includes an electrolyzer unit capable of facilitating conversion of nitrates to ammonia. The resulting mixture leaving the cathodic compartment, including ammonia and any unreacted nitrogen pollutants, is directed to an ammonia separator where ammonia is separated from any unreacted nitrogen pollutants of the stream. Residual nitrogen pollutants are then recirculated back to the electrolyzer unit, enabling the system to operate in a continuous loop.

Description

SYSTEM AND METHOD FOR AMMONIA PRODUCTION FROM NITROGEN POLLUTANTSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of United States Provisional Application No. 63 / 548,429, filed on November 14, 2023, and to United States Provisional Application No. 63 / 601,322, filed on November 21, 2023. Each of the foregoing applications is incorporated herein by reference in its entirety.BACKGROUND

[0002] Ammonia plays a pivotal role in supporting stable food production globally. In2021, approximately 80% of the world's ammonia was utilized as a fertilizer in industrial agriculture, with the remaining 20% employed in various chemical industries. The worldwide production of ammonia for that year was an estimated 185 million metric tons, with the United States as the leading importer at 2.5 million metric tons, accounting for 15% of global imports. In the same year, Russia was the largest exporter with 4.4 million metric tons.

[0003] Projections suggest that the global ammonia market could nearly triple by 2050, reaching an estimated value of 225 billion dollars from a 78-billion-dollar valuation in2022. This anticipated surge is largely attributed to emerging applications of ammonia in power generation, as a shipping fuel, and as a hydrogen energy carrier. However, the expected rapid market expansion necessitates a corresponding escalation in reliable production capabilities. This growth is challenged by global mandates to transition to reduced carbon emission processes, creating significant tension in ammonia production dynamics.

[0004] Currently, the primary method for synthesizing ammonia is the energy-intensive Haber-Bosch process, which operates at high temperatures (400-500°C) and pressures (200-300 atm), contributing to a substantial carbon footprint that accounts for 1% of global annual CO2 emissions. An alternative for producing more environmentally friendly ammonia involves the use of “green” hydrogen, derived from water electrolysis powered by renewable energy sources as opposed to conventional hydrogen obtained from methane via steam methane reforming. However, the high cost of green hydrogen production — exceeding $5 / kg-H2 — poses a significant economic challenge. Moreover, additional carbon emissions from nitrogen separation and compression stages in the Haber-Bosch process, which contribute approximately 25% to its CO2 footprint, remain unresolved.

[0005] Beyond ammonia production, nitrogen pollution poses a significant environmental issue in both water and air. Nitrate (NOf) pollution, primarily from agricultural runoff, is a major source of contamination in surface water and groundwater. Approximately two- thirds of fertilizer nitrogen is not absorbed by crops, and instead becomes a pollutant in rivers and lakes. This leads to eutrophication, threatening aquatic ecosystems and public health. Nitrate-contaminated groundwater has been linked to health issues such as blue baby syndrome and certain cancers, prompting the United States Environmental Protection Agency (EP A) to establish a maximum contaminant level (MCL) for nitrates at 10 ppm.

[0006] Traditional nitrate removal technologies in water, such as reverse osmosis (RO) and ion exchange (IX), are challenged by the problem of disposing concentrated nitrate brines. Biological nitrate destruction is another option. However, such processes are temperature-sensitive and ineffective in colder or less sunny climates, making it unsuitable for large portions of the year.

[0007] Other nitrogen pollutants include nitrite (NO2 ) in water and nitrogen oxides (NO and NO2) in gas emissions. Nitrite, a reduction product of nitrate, is highly toxic, with an MCL of 1 ppm for public health protection. NO and NO2, collectively known as NOx gases, are primarily emitted from fuel combustion, with the EPA setting a limit for NO2 below 100 ppb.

[0008] Common techniques for mitigating NOx emissions include wet scrubbers and selective catalytic converters. Wet scrubbers effectively remove NOx by creating a gasliquid interface, where pollutants are absorbed by a liquid medium. This method is adaptable to various types of gas streams and is relatively inexpensive to install and operate. However, this method produces a highly concentrated wastewater byproduct, resulting in significant disposal costs. Selective catalytic converters, on the other hand, reduce NOx to nitrogen by using ammonia or urea as a reducing agent. This approach is effective for hot gas streams, but the expense of the reducing agent constitutes more than half of the operating costs, limiting its economic viability.

[0009] Accordingly, there is an ongoing need for improved ammonia production processes and for improved nitrogen pollution mitigation processes.SUMMARY

[0010] As noted above, there is an ongoing need for improved ammonia production processes and for improved nitrogen pollution mitigation processes. In 2022, nitrate compounds constituted 90% of the total Toxics Release Inventory (TRI) chemicals discharged into U.S. water systems, with the primary sources being the food, chemicals,petroleum, and primary metals industries. Additionally, annual NOx emissions in the U.S. exceeded 6.8 million tons. If fully converted, this amount would yield approximately 2.5 million tons of ammonia, surpassing the amount of ammonia imported into the U.S. that same year.

[0011] Disclosed herein is a system and method for converting nitrogen pollutants into ammonia. Converting nitrogen pollutants into ammonia can provide significant cost savings across various industries by reducing expenses associated with water treatment, chemical disposal, and operating chemicals. Additionally, the ammonia produced can serve as a locally sourced supply, classified as green ammonia when powered by renewable energy, benefiting the agriculture and power sectors as an additional resource. Overall, the disclosed embodiments can provide an efficient solution for mitigating nitrogen pollution while fostering a circular economy that supports both industry and community needs.

[0012] The present disclosure relates to the production of ammonia via an electrolytic process. The disclosed ammonia generation system can enhance the conversion efficiency of nitrogen pollutants into ammonia, with potential applications in the field of decentralized agricultural fertilizer production and energy storage, for example.

[0013] An example electrolyzer of the disclosed ammonia generation system includes an anode and a cathode, and can include an optimally thin gap between respective catalytic components (e.g., between the catalytic gas diffusion layers) to improve reaction kinetics. The anode includes an oxidation catalyst, and the cathode includes a reduction catalyst, to facilitate the respective oxidation and reduction reactions of the electrolyzer.

[0014] The electrolyzer unit includes anodic and cathodic compartments separated by a membrane electrode assembly (MEA). The MEA can include the anodic and cathodic catalysts separated by a selectively permeable membrane (e.g., a proton exchange membrane). Anodic and cathodic gas diffusion layers (GDLs) can also be disposed on opposite respective sides of the MEA.

[0015] In operation, the anodic compartment receives water, which is oxidized to produce oxygen, while the cathodic compartment receives a nitrogen pollutant-enriched feedstock and is where the reduction of nitrogen pollutants to ammonia takes place.

[0016] The disclosed electrolyzer can be utilized in a system that promotes separation of the product, ammonia, from remaining ions or pollutants, such as by using a bipolar electrodialysis unit and / or ammonia stripping unit. The separated ammonia can be stored,and the unconverted nitrates can be recirculated back to the cathodic compartment for further reaction.

[0017] An advantageous aspect of the disclosed system is compatibility with renewable energy sources, which allows for the sustainable production of green ammonia. Additionally, the materials selected for the gas diffusion layers — mesh, felt, or foam construction including carbon and metals, for example — can contribute to high efficiency, robustness, and longevity of the system.

[0018] The system as disclosed is particularly suited for integration with existing infrastructure in water treatment facilities or power utilities, allowing for the simultaneous treatment of nitrogen pollution and production of valuable ammonia, effectively turning a waste product into a resource.

[0019] The disclosed system can benefit ammonia production by providing a greener, more efficient, and cost-effective method, leveraging the principles of electrochemistry in effective ways to address both environmental concerns and the growing global demand for ammonia.

[0020] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an indication of the scope of the claimed subject matter.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Various objects, features, characteristics, and advantages of the disclosure will become apparent and more readily appreciated from the following description, taken in conjunction with the accompanying drawings and the appended claims, all of which form a part of this specification. In the Drawings, like reference numerals may be utilized to designate corresponding or similar parts in the various Figures, and the various elements depicted are not necessarily drawn to scale, wherein:

[0022] Figure 1 A illustrates an example electrolyzer unit in exploded view.

[0023] Figures 2A and 2B illustrate example configurations of a membrane, electrode, and gas diffusion layer (GDL) assembly.

[0024] Figure 3A-3C illustrate another example of the electrolyzer unit, showing the oxidation and reduction reactions using a nitrogen pollutant-containing fluid as feedstock.

[0025] Figure 4 illustrates an example ammonia generation system that integrate the electrolyzer unit and includes additional components to aid in ammonia separation and collection.

[0026] Figures 5A and 5B show SEM images of the surfaces of an example GDL before and after chemical treatment, respectively.

[0027] Figure 5C compares the performance of an untreated (bare) GDL and the acid treated GDL.

[0028] Figures 6A and 6B present the results of nitrate-to-ammonia conversion tests that omitted and included a pH buffer, respectively.

[0029] Figure 7A shows nitrate reduction results across seven different runs, where nitrate was mixed with high levels of other ions to simulate a nitrate-rich brine from an ion exchange process.

[0030] Figure 7B shows ion chromatography spectra before and after the conversion process, indicating that nitrate-to-ammonia conversion was unaffected by high levels of other ions.

[0031] Figure 8A illustrates an application of the ammonia generation system in an ion exchange process designed for nitrate removal.

[0032] Figure 8B illustrates an application of the ammonia generation system within a hydrogen combustion system.

[0033] Figure 8C illustrates an application of the ammonia generation system in an ammonia combustion system.DETAILED DESCRIPTIONIntroduction

[0034] As discussed above, there is an ongoing need for systems and methods that can efficiently remove nitrogen pollutants from water while circumventing the brine management issues inherent in current technologies. The production of ammonia from these pollutants offers a decentralized supply solution for the burgeoning ammonia economy, supporting compliance with environmental regulations, providing easy access to fertilizers for the agricultural industry, and alleviating production pressure from conventional processes.

[0035] Electrochemical processes offer a promising avenue for converting these nitrogen pollutants into ammonia. Some example reduction reactions are as follows:NOL + 8H++ 6e- NH4++ 2H2O E° = 0.89V (vs. NHE)2NO + 5H++ 5e~ NH3+ H2O E° = 0.71V (vs. NHE)

[0036] The conversion of nitrogen pollutants into ammonia can be achieved through such electrochemical reduction reactions. The reduction reaction occurs at the electrocatalytic surface, and the nitrogen pollutants can be present in a liquid or a gas. The electrocatalyst facilitates electron transfer between the nitrogen pollutants (i.e., the reactants) and the electrode, thus enabling the chemical transformation of nitrogen pollutants into ammonia.

[0037] A major practical limitation to effective conversion of nitrogen pollutants to ammonia has been determining configurations that work in real-world applications where various other anions and cations (e.g., sulfate and chloride ions) are present in the feed streams. Beneficially, the disclosed system demonstrated effective conversion of nitrate to ammonia even in the presence of relatively high levels of other ions.

[0038] Faradaic efficiency refers to the effectiveness with which electrical charge is transferred in a system to facilitate an electrochemical reaction. The Faradaic efficiency of the nitrogen reduction reaction has traditionally been suboptimal for commercial application due to issues like non-selective reactions, competing hydrogen evolution reactions at the cathode, interference from other ions, electrode stability, and low product yield. Beneficially, the disclosed system can exhibit effective selectivity, electrode stability, Faradaic efficiency, and product yield.

[0039] Another prevalent challenge in converting nitrogen pollutants to ammonia relates to device configuration. Whether utilizing a continuous flow or a batch-type process, there is a risk of destabilization of the catalyst-electrode interaction. This instability adversely affects the selective reduction process, leading to diminished efficiency in nitrate-to- ammonia conversion, increased power consumption, and augmented hydrogen gas evolution. The disclosed system can minimize or overcome such limitations through the described configuration and operation. In some embodiments, the oxidation catalyst and / or reduction catalyst are applied to the respective substrates (e.g., electrodes and / or gas diffusion layers) via electroplating, such that the catalyst forms metallic bonds with the underlying surfaces. This contrasts with conventional catalyst spraying processes, which result in relatively weak physical binding with the electrodes. The electrochemical reduction process can also help to re-deposit (recover) metallic catalyst that is lost within the electrolytes.Example Electrolyzer Unit

[0040] Figure 1A illustrates an example electrolyzer unit 100 in exploded view. The electrolyzer unit 100 includes a membrane-electrode assembly (MEA) 102, with the anodic gas diffusion layer (GDL) 104a and cathodic GDL 104b adjacent to it on oppositerespective sides. An anodic flow path plate 108a is positioned adjacent the corresponding anodic GDL 104a. The anodic flow path plate 108a includes an electrolyte flow path and defines an anodic compartment. On the opposite side, a cathodic flow path plate 108b is positioned adjacent the corresponding cathodic GDL 104b. The cathodic flow path plate 108b includes an electrolyte flow path and defines a cathodic compartment. The anodic flow path plate 108a and / or cathodic flow path plate 108b can be formed from suitable materials known in the art such as graphite, for example.

[0041] Current collectors 110 can be disposed on outer sides of respective flow path plates 108a and 108b. Gaskets 106 and external plates 112 can be included to aid in holding the assembly together and to minimize gaps and leaks between layers.

[0042] Figures 2A and 2B illustrate example configurations of the MEA 102 and GDLs 104a, 104b (collectively shown as MEA / GDL assembly 107). As shown, the MEA / GDL assembly 107 includes a proton exchange membrane 103. The proton exchange membrane can include an ion-conducting material such as a fluoropolymer-copolymer, such as a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer, such as those available under the trade name Nafion. In some embodiments, the proton exchange membrane conducts cations but not anions.

[0043] The proton exchange membrane 103 preferably has a thickness of 200 pm or less to minimize the distance between the electrodes and improve reaction kinetics. For example, the proton exchange membrane 103 can have a thickness of 200 pm or less, 180 pm or less, 160 pm or less, 140 pm or less, 120 pm or less, or 100 pm or less, or have a thickness within a range with endpoints selected from any two of the foregoing values.

[0044] In the configuration of Figure 2A, an anode layer 105a and a cathode layer 105b can be contacted to opposite sides of the proton exchange membrane 103. The anodic GDL 104a is contacted to the anode layer 105a, and the cathodic GDL is contacted to the cathode layer 105b. While preferred embodiments dispose the oxidation catalyst on the anode layer 105a and not the anodic GDL 104a, in other embodiments the anode layer 105a and / or the anodic GDL 104a can be coated with an oxidation catalyst. On the cathode side, the cathode layer 105b and / or the cathodic GDL 104b can be coated with a reduction catalyst.

[0045] The configuration of the MEA / GDL assembly 107 of Figure 2B differs from the configuration of Figure 2A by omitting a cathode layer 105b. In this configuration, a reduction catalyst is directly coated on the cathodic GDL 104b, and the cathodic GDL 104b functions as the cathode itself. This configuration has been found to reduce manufacturing complexity and overall device cost, without sacrificing performance.Indeed, the configuration of Figure 2B has been found to provide improved diffusion, reaction kinetics, and overall efficiency and yields.

[0046] Catalyst materials can be coated on the substrate materials using techniques such as chemical deposition, electrochemical deposition, electroless deposition, atomic layer deposition, or combinations thereof.

[0047] Figure 3A-3C illustrate another example of the electrolyzer unit 100. Figure 3A is an exploded sideview of the unit, and Figures 3B and 3C present front views of the anode flow path plate 108a and cathode flow path plate 108b, respectively. Figures 3A-3C also depict the corresponding oxidation and reduction reactions using a nitrogen pollutantcontaining fluid as feedstock.

[0048] In operation, a cathode-side fluid stream including water is fed to the anodic compartment (defined by flow path plate 108a), where it is oxidized into protons and oxygen at the interface between the oxidative side of the MEA 102 and the anodic GDL 104a. The protons then migrate through the proton exchange membrane 103 to the cathode side. In the cathodic compartment (defined by flow path plate 108b), protons facilitate reduction reactions with nitrogen pollutants in the anode-side fluid stream, resulting in the formation of ammonia. Consequently, a mixture comprising lean nitrogen pollutants (i.e., the unreacted nitrogen pollutants) and ammonia exits through an outlet of the cathodic compartment.

[0049] Nitrogen compounds that can be converted by the electrolyzer unit 100 include, but are not limited to, nitrates, nitrites, and / or nitrogen oxides. The one or more nitrogen pollutants can comprise, for example, ionic and / or non-ionic forms of NxOyspecies, such as NOT, NCh’, NO2+, NO2, NO, and / or N2O. These pollutants are commonly found in waste brines from ion exchange and reverse osmosis processes, as well as in wastewater from nuclear plants, aquaculture, agriculture, and industries such as fertilizer production, food processing, chemical manufacturing, semiconductor manufacturing, textile industry, munitions and explosives manufacturing, pharmaceuticals, and the combustion of fuels, including natural gas, hydrogen and ammonia. Mixed streams that include multiple types and / or sources of nitrogen pollution can also be utilized.

[0050] As shown in Figure 3D, multiple electrolyzer units can be arranged in a stacked configuration 150. In such a configuration, the multiple electrolyzer units can be electrically connected with one another and in fluidic communication with one another. The multiple electrolyzer units can be electrically connected in series, in parallel, or in more complex configurations with a combination of series and parallel electricalconnections. Each electrolyzer unit of the stacked configuration 150 can include base plates with designated inlets and outlets, bipolar electrodes, MEAs and GDLs as described herein. Incorporating multiple cell stacks increases capacity, facilitating a higher conversion rate. The number of cells in a stack can be adjusted to meet specific capacity requirements.

[0051] The fluidic connections between the multiple electrolyzer units can also be made in series, in parallel, or in configurations including both series and parallel connections. For example, in a series fluidic arrangement, the cathode-side fluid stream passes through multiple cathodic compartments of the multiple electrolyzer units in series while the anode-side fluid stream passes through multiple anodic compartments of the multiple electrolyzer units in series. In a parallel fluidic arrangement, the cathode-side fluid stream can be split into multiple sub-streams that are passed, in parallel, through respective cathodic compartments of the multiple electrolyzer units, and the anode-side fluid stream can be split into multiple sub-streams that are passed, in parallel, through respective anodic compartment of the multiple electrolyzer units.Example Electrolyzer Component Materials

[0052] Suitable electrocatalysts for the oxidation electrode (anode layer 105a) and / or the anodic GDL 104a include nickel, copper, iron, iridium, manganese, ruthenium, cobalt, titanium, or combinations thereof. These may independently be in various forms, including oxides, nitrides, phosphides, sulfides, or combinations thereof. In some embodiments, the electrocatalyst for the oxidation electrode (anode layer 105a) and / or the anodic GDL 104a include nickel, copper, iron, iridium, ruthenium, cobalt, titanium, or combinations thereof. These may independently be in various forms, including oxides, nitrides, phosphides, sulfides, or combinations thereof.

[0053] Suitable electrocatalysts for the reduction electrode (cathode layer 105b) and / or the cathodic GDL 104b include silver, gold, titanium, palladium, indium, iron, copper, nickel, ruthenium, platinum, bismuth, vanadium, iridium, chromium, tungsten, cobalt, manganese, rhodium, or combinations thereof. These may independently be in the form of oxides, nitrides, phosphides, sulfides, or combinations thereof. In some embodiments, the electrocatalyst for the reduction electrode (cathode layer 105b) and / or the cathodic GDL 104b include gold, palladium, indium, iron, copper, nickel, ruthenium, platinum, bismuth, vanadium, iridium, cobalt, rhodium, or combinations thereof. These may independently be in the form of oxides, nitrides, phosphides, sulfides, or combinations thereof.

[0054] In some embodiments, the oxidation catalyst and / or reduction catalyst comprise a bimetallic catalyst.

[0055] The electrodes (i.e., anode layer 105a, cathode layer 105b) and / or GDLs 104a, 104b can be constructed in various structural forms, such as mesh, felt, and / or foam. The electrodes and / or GDLs can utilize carbon and / or one or more metals such as gold, stainless steel, iron, cobalt, silver, palladium, titanium, gallium, tungsten, nickel, copper, chromium, zinc, magnesium, alloys of any of the foregoing, or combinations thereof. In some embodiments, the electrodes and / or GDLs can include stainless steel, iron, cobalt, titanium, tungsten, nickel, copper, alloys of any of the foregoing, or combinations thereof. Example Ammonia Generation System

[0056] Figure 4 illustrates an example ammonia generation system 200 that integrate the disclosed electrolyzer unit 100 and can include additional components to aid in ammonia separation and collection, fluid management, and recirculation. The disclosed configuration can promote the separation of ammonia products and the maintenance of a continuous loop production process.

[0057] As shown, two separate circulation streams are utilized: an anode-side fluid stream 214 comprising water that passes through the anode side of the electrolyzer unit 100 (through anodic flow path plate 208a) and is recirculated back to the anode compartment of the electrolyzer 100 after oxygen gas is separated (e.g., in phase separator 212), and a cathode-side fluid stream 204 comprising a nitrogen pollutant-containing fluid that passes through the cathode compartment of the electrolyzer unit 100 (through cathodic flow path plate 208b) and from which ammonia is generated. Fluid movement can be maintained using pumps 206 and 216, and / or other fluid control mechanisms known in the art. The paths through the electrolyzer unit 100 are shown as having a winding, tortuous shape, though other fluid paths can be utilized so long as sufficient residence time within the electrolyzer unit 100 is maintained.

[0058] The cathode compartment receives the nitrogen pollutant-containing fluid at its inlet and discharges a mixture of lean nitrogen pollutants (unreacted nitrogen pollutants) and ammonia at its outlet. An ammonia separator 208 is configured to receive the cathodeside fluid stream 204 and to separate ammonia therefrom. The ammonia separator can utilize bipolar electrodialysis, gas stripping, and / or distillation, for example. The collected concentrated ammonia can be stored (e.g., in ammonia storage tank 210) for further distribution and / or further downstream processing, while unreacted nitrogen pollutants can be recirculated back to the feed tank 202, ensuring a continuous conversion reaction loop.

[0059] The nitrogen pollutant-containing fluid feed tank 202 may include a pH buffer unit 210. As demonstrated in the disclosed working examples, controlling the pH of the cathode-side fluid stream 204 (e.g., to a pH of 4 or below) before passing into the cathodic compartment can beneficially improve conversion efficiencies.

[0060] In some embodiments, pH buffering promotes ammonium species that remain dissolved in water. This can enhance safety and can also facilitate the production of aqueous ammonia (e.g., via bipolar electrodialysis) at concentration levels of about 20-30 weight percent (w / w), which corresponds to concentrations commonly used in ammonia fertilization.

[0061] In alternative embodiments, the pH is not adjusted. Such embodiments can include the collection of anhydrous ammonia through the direct separation and compression or condensation of gaseous ammonia.

[0062] The collected concentrated ammonia and / or anhydrous ammonia may be distributed as fertilizers, clean fuel for hydrogen fuel cells, for ammonia combustion, and / or as reducing agent in selective catalytic converter systems, for example.

[0063] In some embodiments, the electrolyzer unit can be operated in a nitrate reduction mode for a first time period to generate ammonium ions in the cathodic compartment, and the polarity of the applied voltage can then be reversed to switch to an ammonia recovery mode in which ammonium ions pass across the proton exchange membrane toward the negative charge now present in the opposite compartment. This approach can separate the ammonium ions from the nitrogen-pollutant-containing fluid stream and collect the ammonium ions in the water stream, where further downstream processing or removal is easier.Working Examples

[0064] Figures 5A and 5B show SEM images of the surfaces of an example GDL before and after chemical treatment, respectively. The GDL of this example was a titanium felt, though similar results are expected with other GDL materials disclosed herein, including nickel and copper GDLs.

[0065] The GDL was initially cleaned by sonication for 20 minutes in acetone, isopropanol, and water, sequentially. After cleaning, the GDL was air-dried and then immersed in an acidic bath (hydrochloric acid, sulfuric acid, and / or nitric acid have been utilized), at a temperature of 40-60°C. The GDL remained in the acidic solution for 15 minutes and was then rinsed in water.

[0066] As shown, the acid treatment created a tortuous, hierarchical surface on the GDL, which was subsequently coated with a metallic catalyst. The acid treatment beneficially increased surface area of the substrate (the GDL, in this case), and improved the conductivity, wettability, and interfacial properties between the substrate and the catalyst. These changes can collectively contribute to enhanced nitrate-to-ammonia conversion. Although this example treated a GDL, the same process may be applied to other substrates intended for receiving a catalyst coating, such as in embodiments where the electrode receives the catalyst coating rather than the GDL.

[0067] Figure 5C compares the performance of an untreated (bare) GDL and the acid treated GDL. Nitrate reduction was significantly faster with the treated GDL, reducing nitrate concentrations from over 500 mg / L to below the safe level of 10 mg / L within 60 minutes. In contrast, the bare GDL exhibited a much slower reduction rate, failing to reach below 220 mg / L after 90 minutes of operation.

[0068] Figures 6A and 6B present the results of nitrate-to-ammonia conversion tests that omitted and included a pH buffer, respectively. In Figure 6A, nitrate and nitrite intermediates were rapidly reduced, leading to a progressive increase in ammonia formation. However, the selectivity for converting nitrate / ni trite to ammonia was approximately 50% (note the difference in scale of the y axes). Figure 6B, in contrast, shows that maintaining pH at acidic levels below pH of 4 enhanced the nitrate-to-ammonia conversion selectivity to over 85%.

[0069] Figure 7A shows nitrate reduction results across seven different runs, where nitrate (500 mg / L) was mixed with other ions including sulfate (2700 mg / L) and chloride (10,000 mg / L), simulating a nitrate-rich brine from an ion exchange process designed for nitrate removal. The results indicate consistent nitrate reduction, even in the presence of high concentrations of sulfate and chloride. Figure 7B shows ion chromatography spectra before and after the conversion process. Prior to conversion, initial peaks for CP, SOP , and NO3 confirm the presence of these ions. After conversion, the NO3 peak disappears, confirming complete conversion of nitrate, while the SOP and CP peaks remain nearly identical, indicating that sulfate and chloride concentrations were unaffected by the conversion process. This result confirms that sulfate and chloride ions do not interfere with the nitrate conversion process.Example Applications

[0070] Figure 8A illustrates an application of the ammonia generation system 200 in an ion exchange process designed for nitrate removal. In this process, the ion exchange resinsadsorb nitrate anions, replacing previously adsorbed chloride ions. Once the resins are saturated with nitrate, they are regenerated using a solution typically containing 10% sodium chloride (NaCl). During regeneration, chloride ions displace the nitrate ions, resulting in a concentrated brine containing both nitrate and chloride ions. This approach incurs two primary costs: disposal of nitrate-laden brine and the use of regeneration chemicals. With the integration of the system 200, the nitrate in the brine may be selectively converted to ammonia and separated from the chloride, enabling the recycling of the chloride solution for further ion exchange regeneration cycles while also collecting ammonia. This application could significantly reduce operating costs associated with waste disposal and regeneration chemicals in ion exchange applications while also providing potential revenue from ammonia production, including from green ammonia production when powered by renewable energy.

[0071] Figure 8B illustrates an application of the ammonia generation system 200 within a hydrogen combustion system. Hydrogen is a clean fuel that emits only water upon combustion. However, when air is used to supply oxygen for the combustion process, nitrogen present in the air can react with oxygen at high temperatures, leading to the formation of NOx in the hydrogen flame, which reaches over 2000°C. This thermal NOx formation is unavoidable in flames with temperatures exceeding 1300°C. A common method for mitigating such NOx emissions is the use of a wet scrubber, which captures NOx but produces wastewater with nitrate concentrations often exceeding 2000 ppm. By integrating the ammonia generation system 200 with the NOx scrubber, the highly concentrated nitrate compounds in the wastewater can be converted to ammonia, which is then collected as a valuable product. This approach not only reduces costs associated with wastewater disposal and solvent use through recycling but also provides potential revenue from ammonia, including revenue from green ammonia when powered by renewable energy. This approach may be applicable to various other types of combustion systems, such as ammonia and natural gas-based combustion systems.

[0072] Figure 8C illustrates an application of the ammonia generation system 200 in an ammonia combustion system. The ammonia flame reaches temperatures around 1800°C, exceeding the threshold for thermal NOx formation. NOx emissions from the combustion system can be directly fed into the electrolyzer, where gaseous nitrogen species pass through a high-surface-area GDL that instantly reduces these species to ammonia. The GDL may be wetted with liquid, and multiple electrolyzer units can be connected (e.g., in series) to convert unreacted nitrogen species. A moisture entrapment system may beintegrated within the line. The produced ammonia can then be recirculated back into the fuel feedstock, enhancing overall efficiency of the system. This process can be utilized with ammonia combustion engines in motor vehicles.Additional Terms & Definitions

[0073] The term “electrolyzer” and “electrolyzer unit” are used interchangeably herein. Terms such as “anode layer”, “anode”, and “oxidation electrode” are used interchangeably herein. Similarly, terms such as “cathode layer”, “cathode”, and “reduction electrode” are used interchangeably herein.

[0074] The terms anode, anodic, and the like, when used as modifiers, may be used interchangeably with the terms oxidative, oxidation, and the like. For example, the anode layer can also be referred to as the oxidation electrode layer, the anodic compartment can also be referred to as the oxidative compartment, and the anodic GDL can be referred to as the oxidation GDL. Similarly, the terms cathode, cathodic, and the like, when used as modifiers, may be used interchangeably with the terms reductive, reduction, and the like. For example, the cathode layer can also be referred to as the reduction electrode layer, the cathodic compartment can also be referred to as the reduction compartment, and the cathodic GDL can be referred to as the reduction GDL.

[0075] The term “fluid”, as used herein, follows the standard definition to those of skill in the art and is inclusive of both liquids, gases, and mixtures thereof. A fluid can also include solid components when the fluid acts as a carrier for one or more solid components, such as when one or more solid components are dispersed or otherwise mixed within the fluid.

[0076] While most of the examples disclosed herein refer to the generation of ammonia, it will be understood that the generated product can include ammonia, ammonium, or a combination of both. Thus, references to generation of ammonia in the above description and claims should be understood to include any combination of ammonia and ammonium. Ammonia / ammonium ratios are primarily dependent on pH and can be controlled accordingly, as known to those of skill in the art.

[0077] While certain embodiments of the present disclosure have been described in detail, with reference to specific configurations, parameters, components, elements, etcetera, the descriptions are illustrative and are not to be construed as limiting the scope of the claimed invention.

[0078] For any given element of component of a described embodiment, any of the possible alternatives listed for that element or component may generally be usedindividually or in combination with one another, unless implicitly or explicitly stated otherwise.

[0079] The various features of a given embodiment can be combined with and / or incorporated into other embodiments disclosed herein. Thus, disclosure of certain features relative to a specific embodiment of the present disclosure should not be construed as limiting application or inclusion of said features to the specific embodiment. Rather, it will be appreciated that other embodiments can also include such features.

[0080] Numeric values disclosed herein can optionally be modified by adding the term “about.” When the terms “about,” “approximately,” “substantially,” or the like are used in conjunction with a stated amount, value, or condition, it may be taken to mean an amount, value or condition that deviates by less than 10%, less than 5%, less than 1%, less than 0.1%, or less than 0.01% of the stated amount, value, or condition.

[0081] Any headings and subheadings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims.

[0082] As used in this specification and the appended claims, the singular forms “a,” “an” and “the” do not exclude plural referents unless the context clearly dictates otherwise. Thus, for example, an embodiment referencing a singular referent (e.g., “electrolyzer unit”) may also include two or more such referents.

[0083] The embodiments disclosed herein should be understood as comprising / including disclosed components, and may therefore include additional components not specifically described. Optionally, the embodiments disclosed herein are essentially free or completely free of components that are not specifically described. That is, non-disclosed components may optionally be completely omitted or essentially omitted from the disclosed embodiments. For example, catalyst materials, electrode materials, and / or gas diffusion layer materials that are not specifically disclosed herein can optionally be essentially omitted or completely omitted.

[0084] Also, any component that is disclosed herein can optionally be essentially omitted or completely omitted.

[0085] An embodiment that “essentially omits” or is “essentially free of’ a component may include trace amounts and / or non-functional amounts of the component. For example, an “essentially omitted” component may be included in an amount no more than 1%, no more than 0.1%, or no more than 0.01% by total weight of the composition.

[0086] A composition that “completely omits” or is “completely free of’ a component does not include a detectable amount of the component (i.e., does not include an amountabove any inherent background signal associated with the testing instrument) when analyzed using standard compositional analysis techniques such as, for example, chromatographic techniques (e.g., thin-layer chromatography (TLC), gas chromatography (GC), liquid chromatography (LC)), or spectroscopy techniques (e.g., Fourier transform infrared (FTIR) spectroscopy).Example Aspects

[0087] The following clauses represent a non-exhaustive list of example features of the present disclosure:

[0088] Clause 1. An ammonia generation system comprising an electrolyzer unit, the electrolyzer unit comprising: a proton exchange membrane that includes an ion-conductive material, the proton exchange membrane defining an anode side and a cathode side; an anode layer contacted to the anode side of the proton exchange membrane, the anode layer coated with an oxidation catalyst; an anodic gas diffusion layer adjacent the anode layer; a cathodic gas diffusion layer disposed on the cathode side of the proton exchange membrane, the cathodic gas diffusion layer coated with a reduction catalyst; an anode flow path plate disposed adjacent the anodic gas diffusion layer and comprising one or more flow channels defining an anodic compartment for receiving an anode-side fluid stream and bringing the anode-side fluid stream into contact with the anodic gas diffusion layer; and a cathode flow path plate disposed adjacent the cathodic gas diffusion layer and comprising one or more flow channels defining a cathodic compartment for receiving a cathode-side fluid stream and bringing the cathode-side fluid stream into contact with the cathodic gas diffusion layer, wherein the anode-side fluid stream comprises water that is substantially free of nitrogen pollutants and generates protons and oxygen through oxidation, and wherein the cathode-side fluid stream comprises a nitrogen pollutantcontaining fluid and generates ammonia through reduction of one or more nitrogen pollutants.

[0089] Clause 2. The system of clause 1, further comprising an anode-side phase separator configured to receive the anode-side fluid stream from an outlet of the anodic compartment, to separate oxygen from the anode-side fluid stream, and to recirculate the anode-side fluid stream to an inlet of the anodic compartment.

[0090] Clause 3. The system of any preceding clause, further comprising an ammonia separator configured to receive the cathode-side fluid stream from an outlet of the cathodic compartment and to separate ammonia from the cathode-side fluid stream.

[0091] Clause 4. The system of clause 3, wherein the ammonia separator comprises a bipolar electrodialysis unit, ammonia stripper unit, and / or ammonia distillation unit.

[0092] Clause 5. The system of clause 3 or claim 4, further comprising a pH buffer unit configured to control pH of the cathode-side fluid stream before passing into the cathodic compartment, such as being configured to maintain a pH of 4 or below.

[0093] Clause 6. The system of any preceding clause, wherein the proton-exchange membrane has a thickness of 200 pm or less.

[0094] Clause 7. The system of any preceding clause, wherein the cathodic gas diffusion layer directly contacts the proton exchange membrane and functions as the cathode.

[0095] Clause 8. The system of any one of clauses 1-6, further comprising a cathode layer contacted to the cathode side of the proton exchange membrane and disposed between the proton exchange membrane and the cathodic gas diffusion layer, the cathode layer optionally also coated with the reduction catalyst.

[0096] Clause 9. The system of any preceding clause, wherein the anodic gas diffusion layer is also coated with the oxidation catalyst.

[0097] Clause 10. The system of any preceding clause, wherein the oxidation catalyst comprises one or more of nickel, copper, iron, iridium, manganese, ruthenium, cobalt, titanium, oxides thereof, nitrides thereof, phosphides thereof, or sulfides thereof.

[0098] Clause 11. The system of clause 10, wherein the oxidation catalyst comprises one or more of nickel, copper, iron, iridium, ruthenium, cobalt, titanium, oxides thereof, nitrides thereof, phosphides thereof, or sulfides thereof.

[0099] Clause 12. The system of any preceding clause, wherein the reduction catalyst comprises one or more of silver, gold, titanium, palladium, indium, iron, copper, nickel, ruthenium, platinum, bismuth, vanadium, iridium, chromium, tungsten, cobalt, manganese, rhodium, oxides thereof, nitrides thereof, phosphides thereof, or sulfides thereof.

[0100] Clause 13. The system of clause 12, wherein the reduction catalyst comprises one or more of gold, palladium, indium, iron, copper, nickel, ruthenium, platinum, bismuth, vanadium, iridium, cobalt, rhodium, oxides thereof, nitrides thereof, phosphides thereof, or sulfides thereof.

[0101] Clause 14. The system of any preceding clause, wherein the oxidation catalyst and / or reduction catalyst comprise a bimetallic catalyst.

[0102] Clause 15. The system of any preceding clause, wherein the anode layer, cathode layer, anodic gas diffusion layer, and / or cathodic gas diffusion layer independently comprise a mesh, felt, and / or foam construction.

[0103] Clause 16. The system of any preceding clause, wherein the anode layer, cathode layer, anodic gas diffusion layer, and / or cathodic gas diffusion layer comprise carbon and / or metal, such as one or more of gold, stainless steel, iron, cobalt, silver, palladium, titanium, gallium, tungsten, nickel, copper, chromium, zinc, magnesium, or alloys thereof.

[0104] Clause 17. The system of clause 16, wherein the anode layer, cathode layer, anodic gas diffusion layer, and / or cathodic gas diffusion layer comprise one or more of stainless steel, iron, cobalt, titanium, tungsten, nickel, copper, or alloys thereof.

[0105] Clause 18. The system of any preceding clause, comprising one or more additional electrolyzer units electrically connected with and in fluidic communication with the first electrolyzer unit.

[0106] Clause 19. The system of clause 18, when the multiple electrolyzer units are electrically connected in series.

[0107] Clause 20. The system of clause 18, when the multiple electrolyzer units are electrically connected in parallel.

[0108] Clause 21. The system of any one of clauses 18-20, wherein the cathode-side fluid stream passes through multiple cathodic compartments of the multiple electrolyzer units in series, and wherein the anode-side fluid stream passes through multiple anodic compartments of the multiple electrolyzer units in series.

[0109] Clause 22. The system of any one of clauses 18-20, wherein the cathode-side fluid stream is split into multiple sub-streams that are passed, in parallel, through respective cathodic compartments of the multiple electrolyzer units, and wherein the anode-side fluid stream is split into multiple sub-streams that are passed, in parallel, through respective anodic compartment of the multiple electrolyzer units.

[0110] Clause 23. The system of any preceding clause, wherein the anodic gas diffusion layer and / or cathodic gas diffusion layer comprise a tortuous, hierarchical outer surface resulting from acid-treatment.[OHl] Clause 24. The system of any preceding clause, wherein the oxidation catalyst and / or reduction catalyst are applied via electroplating and form metallic bonds with underlying surfaces.

[0112] Clause 25. A method of generating ammonia, optionally utilizing a system as in any preceding clause, the method comprising: introducing the anode-side fluid stream tothe anodic compartment, the anode-side fluid stream comprising water; introducing the cathode-side fluid stream to the cathodic compartment, the cathode-side fluid stream comprising the nitrogen pollutant-containing fluid ; and applying a voltage to the electrolyzer unit to drive oxidation of water in the anodic compartment and reduction of the one or more nitrogen pollutants in the cathodic compartment.

[0113] Clause 26. The method of clause 25, further comprising: passing the anode-side fluid stream from an outlet of the anodic compartment to a phase separator to separate oxygen therefrom, and recirculating the anode-side fluid stream back to an inlet of the anodic compartment; and passing the cathode-side fluid stream from an outlet of the cathodic compartment to a separation unit to separate ammonia therefrom, and recirculating the cathode-side fluid stream back to an inlet of the cathodic compartment.

[0114] Clause 27. The method of any one of clauses 25-26, wherein the separation unit comprises a bipolar electrodialysis unit, ammonia stripper unit, and / or ammonia distillation unit.

[0115] Clause 28. The method of any one of clauses 25-27, wherein the bipolar electrodialysis process unit is configured to separate ammonia from remaining nitrogen pollutants using a bipolar membrane disposed inside an electrodialysis unit and configured for separating positively charged ammonia / ammonium ions from negatively charged nitrogen pollutant ions, such as nitrate and / or nitrite, while allowing recirculation of the unreacted nitrogen pollutant ions back to the cathodic compartment, optionally wherein the process operates at a voltage that minimizes ion recombination.

[0116] Clause 29. The method of any one of clauses 25-28, wherein the pH of the cathodeside fluid stream entering the cathodic compartment is controlled via addition of acidic or basic agents and / or through electrochemical modulation, such as controlled to a pH of 4 or below.

[0117] Clause 30. The method of any one of clauses 25-29, wherein the method is powered by a renewable energy source comprising solar power, wind power, hydroelectric power, and / or geothermal energy.

[0118] Clause 31. The method of any one of clauses 25-30, wherein the nitrogen pollutantcontaining fluid comprises a gas that includes NOx and / or a liquid that includes ionic and / or non-ionic nitrogen pollutants.

[0119] Clause 32. The method of any one of clauses 25-31, wherein the nitrogen pollutantcontaining fluid comprises an ion exchange brine, a reverse osmosis brine, and / or wastewater from a nuclear plant, aquaculture, agriculture, fertilizer production, foodprocessing, chemical manufacturing, semiconductor manufacturing, textile operation, munitions and explosives manufacturing, and / or pharmaceutical manufacturing.

[0120] Clause 33. The method of any one of clauses 25-32, further comprising separating the ammonia using the separation unit and storing the ammonia in an ammonia storage tank.

[0121] Clause 34. The method of any one of clauses 25-33, wherein the ammonia at least partially comprises ammonium.

[0122] Clause 35. The method of any one of clauses 25-34, wherein the system is operated in a continuous loop, enabling continuous production of ammonia.

[0123] Clause 36. The method of any one of clauses 25-35, wherein the nitrogen pollutant comprises ionic and / or non-ionic forms of NxOy species, such as NO3-, NO2-, NO2+, NO2, NO, and / or N2O.

[0124] Clause 37. The method of any one of clauses 25-36, further comprising: operating the electrolyzer unit in a nitrate reduction mode for a first time period to generate ammonium ions in the cathodic compartment; and reversing the polarity of the applied voltage to operate the electrolyzer in an ammonia recovery mode in which ammonium ions pass across the proton exchange membrane toward the negative charge now present in the opposite compartment.

Claims

CLAIMS1. An ammonia generation system comprising an electrolyzer unit, the electrolyzer unit comprising: a proton exchange membrane that includes an ion-conductive material, the proton exchange membrane defining an anode side and a cathode side; an anode layer contacted to the anode side of the proton exchange membrane, the anode layer coated with an oxidation catalyst; an anodic gas diffusion layer adjacent the anode layer; a cathodic gas diffusion layer disposed on the cathode side of the proton exchange membrane, the cathodic gas diffusion layer coated with a reduction catalyst; an anode flow path plate disposed adjacent the anodic gas diffusion layer and comprising one or more flow channels defining an anodic compartment for receiving an anode-side fluid stream and bringing the anode-side fluid stream into contact with the anodic gas diffusion layer; and a cathode flow path plate disposed adjacent the cathodic gas diffusion layer and comprising one or more flow channels defining a cathodic compartment for receiving a cathode-side fluid stream and bringing the cathode-side fluid stream into contact with the cathodic gas diffusion layer, wherein the anode-side fluid stream comprises water that is substantially free of nitrogen pollutants and generates protons and oxygen through oxidation, and wherein the cathode-side fluid stream comprises a nitrogen pollutant-containing fluid and generates ammonia through reduction of one or more nitrogen pollutants.

2. The system of claim 1, further comprising an anode-side phase separator configured to receive the anode-side fluid stream from an outlet of the anodic compartment, to separate oxygen from the anode-side fluid stream, and to recirculate the anode-side fluid stream to an inlet of the anodic compartment.

3. The system of claim 1, further comprising an ammonia separator configured to receive the cathode-side fluid stream from an outlet of the cathodic compartment and to separate ammonia from the cathode-side fluid stream.

4. The system of claim 3, wherein the ammonia separator comprises a bipolar electrodialysis unit, ammonia stripper unit, and / or ammonia distillation unit.

5. The system of claim 3, further comprising a pH buffer unit configured to control pH of the cathode-side fluid stream before passing into the cathodic compartment, such as being configured to maintain a pH of 4 or below.

6. The system of claim 1, wherein the proton-exchange membrane has a thickness of 200 pm or less.

7. The system of claim 1, wherein the cathodic gas diffusion layer directly contacts the proton exchange membrane and functions as the cathode.

8. The system of claim 1, further comprising a cathode layer contacted to the cathode side of the proton exchange membrane and disposed between the proton exchange membrane and the cathodic gas diffusion layer, the cathode layer optionally also coated with the reduction catalyst.

9. The system of claim 1, wherein the anodic gas diffusion layer is also coated with the oxidation catalyst.

10. The system of claim 1, wherein the oxidation catalyst comprises one or more of nickel, copper, iron, iridium, manganese, ruthenium, cobalt, titanium, oxides thereof, nitrides thereof, phosphides thereof, or sulfides thereof.

11. The system of claim 10, wherein the oxidation catalyst comprises one or more of nickel, copper, iron, iridium, ruthenium, cobalt, titanium, oxides thereof, nitrides thereof, phosphides thereof, or sulfides thereof.

12. The system of claim 1, wherein the reduction catalyst comprises one or more of silver, gold, titanium, palladium, indium, iron, copper, nickel, ruthenium, platinum, bismuth, vanadium, iridium, chromium, tungsten, cobalt, manganese, rhodium, oxides thereof, nitrides thereof, phosphides thereof, or sulfides thereof.

13. The system of claim 12, wherein the reduction catalyst comprises one or more of gold, palladium, indium, iron, copper, nickel, ruthenium, platinum, bismuth, vanadium, iridium, cobalt, rhodium, oxides thereof, nitrides thereof, phosphides thereof, or sulfides thereof.

14. The system of claim 1, wherein the oxidation catalyst and / or reduction catalyst comprise a bimetallic catalyst.

15. The system of claim 1 , wherein the anode layer, cathode layer, anodic gas diffusion layer, and / or cathodic gas diffusion layer independently comprise a mesh, felt, and / or foam construction.

16. The system of claim 1, wherein the anode layer, cathode layer, anodic gas diffusion layer, and / or cathodic gas diffusion layer comprise carbon and / or metal, such as one or more of gold, stainless steel, iron, cobalt, silver, palladium, titanium, gallium, tungsten, nickel, copper, chromium, zinc, magnesium, or alloys thereof.

17. The system of claim 16, wherein the anode layer, cathode layer, anodic gas diffusion layer, and / or cathodic gas diffusion layer comprise one or more of stainless steel, iron, cobalt, titanium, tungsten, nickel, copper, or alloys thereof.

18. The system of claim 1, comprising one or more additional electrolyzer units electrically connected with and in fluidic communication with the first electrolyzer unit.

19. The system of claim 18, when the multiple electrolyzer units are electrically connected in series.

20. The system of claim 18, when the multiple electrolyzer units are electrically connected in parallel.

21. The system of claim 18, wherein the cathode-side fluid stream passes through multiple cathodic compartments of the multiple electrolyzer units in series, and wherein the anode-side fluid stream passes through multiple anodic compartments of the multiple electrolyzer units in series.

22. The system of claim 18, wherein the cathode-side fluid stream is split into multiple sub-streams that are passed, in parallel, through respective cathodic compartments of the multiple electrolyzer units, and wherein the anode-side fluid stream is split into multiple sub-streams that are passed, in parallel, through respective anodic compartment of the multiple electrolyzer units.

23. The system of claim 1, wherein the anodic gas diffusion layer and / or cathodic gas diffusion layer comprise a tortuous, hierarchical outer surface resulting from acidtreatment.

24. The system of claim 1, wherein the oxidation catalyst and / or reduction catalyst are applied via electroplating and form metallic bonds with underlying surfaces.

25. A method of generating ammonia, utilizing a system as in any preceding claim, the method comprising: introducing the anode-side fluid stream to the anodic compartment, the anode-side fluid stream comprising water; introducing the cathode-side fluid stream to the cathodic compartment, the cathode-side fluid stream comprising the nitrogen pollutant-containing fluid; and applying a voltage to the electrolyzer unit to drive oxidation of water in the anodic compartment and reduction of the one or more nitrogen pollutants in the cathodic compartment.

26. The method of claim 25, further comprising:passing the anode-side fluid stream from an outlet of the anodic compartment to a phase separator to separate oxygen therefrom, and recirculating the anode-side fluid stream back to an inlet of the anodic compartment; and passing the cathode-side fluid stream from an outlet of the cathodic compartment to a separation unit to separate ammonia therefrom, and recirculating the cathode-side fluid stream back to an inlet of the cathodic compartment.

27. The method of claim 25, wherein the separation unit comprises a bipolar electrodialysis unit, ammonia stripper unit, and / or ammonia distillation unit.

28. The method of claim 25, wherein the bipolar electrodialysis process unit is configured to separate ammonia from remaining nitrogen pollutants using a bipolar membrane disposed inside an electrodialysis unit and configured for separating positively charged ammonia / ammonium ions from negatively charged nitrogen pollutant ions, such as nitrate and / or nitrite, while allowing recirculation of the unreacted nitrogen pollutant ions back to the cathodic compartment, optionally wherein the process operates at a voltage that minimizes ion recombination.

29. The method of claim 25, wherein the pH of the cathode-side fluid stream entering the cathodic compartment is controlled via addition of acidic or basic agents and / or through electrochemical modulation, such as controlled to a pH of 4 or below.

30. The method of claim 25, wherein the method is powered by a renewable energy source comprising solar power, wind power, hydroelectric power, and / or geothermal energy.

31. The method of claim 25, wherein the nitrogen pollutant-containing fluid comprises a gas that includes NOx and / or a liquid that includes ionic and / or non-ionic nitrogen pollutants.

32. The method of claim 25, wherein the nitrogen pollutant-containing fluid comprises an ion exchange brine, a reverse osmosis brine, and / or wastewater from a nuclear plant, aquaculture, agriculture, fertilizer production, food processing, chemical manufacturing, semiconductor manufacturing, textile operation, munitions and explosives manufacturing, and / or pharmaceutical manufacturing.

33. The method of claim 25, further comprising separating the ammonia using the separation unit and storing the ammonia in an ammonia storage tank.

34. The method of claim 25, wherein the ammonia at least partially comprises ammonium.

35. The method of claim 25, wherein the system is operated in a continuous loop, enabling continuous production of ammonia.

36. The method of claim 25, wherein the nitrogen pollutant comprises ionic and / or non-ionic forms of NxOyspecies, such as NCK, NCh’, NO2+, NCh, NO, and / or N2O.

37. The method of claim 25, further comprising: operating the electrolyzer unit in a nitrate reduction mode for a first time period to generate ammonium ions in the cathodic compartment; and reversing the polarity of the applied voltage to operate the electrolyzer in an ammonia recovery mode in which ammonium ions pass across the proton exchange membrane toward the negative charge now present in the opposite compartment.

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