Nitrate Waste Research Articles

Photocatalytic Synthesis of Glycine from Methanol and Nitrate

AbstractPhotocatalytic utilization of methanol and nitrate as carbon and nitrogen sources for the direct synthesis of amino acids could provide a sustainable way for the valorization of green “liquid sunlight” and nitrate waste. In this study, we develop an efficient photochemical method to synthesize glycine directly from methanol and nitrate, which cascades the C−C coupling to form glycol, nitrate reduction to NH3, and finally C−N coupling to generate glycine. Interestingly, the involved photocatalytic tandem reactions show a synergistic effect, in which the presence of nitrate is the dominant factor to enable the overall reaction and reach high synthetic efficiency. Ba2+−TiO2 nanoparticles are confirmed as a feasible and efficient catalyst system for the photosynthesis of glycine with a remarkable glycine photosynthesis rate of 870 μmol gcat−1 h−1 under optimal conditions. This work establishes a novel catalytic system for amino acid synthesis from methanol and nitrate under mild conditions. These results also allow us to further suppose the formation pathways of amino acids on the primitive earth, as an extension to proposals based on the Miller‐Urey experiments.

Electrosynthesis of Amino Acids from Biomass and Nitrate at Industrial Current Densities Using Porous PbBi Electrodes.

Electrosynthesis is a rising and attractive method for efficient amino acid production. However, industrial-grade electrosynthesis of high-value amino acids from simple carbon and nitrogen substrates is confronted with a great challenge. Herein, we design a dual-site PbBi alloy catalyst for various amino acids' electrosynthesis from keto acids and nitrate. An alanine Faradaic efficiency of 59.7% is delivered at -1.5 V vs SCE, reaching the industrial current density of 570 mA cm-2 with high catalytic durability of the porous Pb1Bi0.1 catalyst. In the tandem reaction process, nitrate is first converted to NH2OH via electrochemical reduction mainly over the Bi site. Then the obtained NH2OH integrates with the α-keto acid to form the oxime intermediate. Lastly, the Pb site facilitates the electroreduction of oxime to the final amino acids. More importantly, over 10 kinds of α-amino acids can be successfully synthesized in excellent FE and high yield at high current density, indicating the superior catalytic activity and wide universality of our strategy. In short, this work opens up a novel approach to realize the one-pot electrosynthesis of various amino acids from renewable biomass feedstocks and nitrate waste industrially.

Enhanced solar urea synthesis from CO2 and nitrate waste via oxygen vacancy mediated-TiOx support lead-free perovskite

The nitrogen fertilizer industry, particularly urea production, notably contributes to greenhouse gas emissions and energy consumption. Urea synthesis via solar energy encounters several challenges. Specifically, solar urea synthesis methods often exhibit low efficiency and yield, primarily stemming from inefficient energy conversion processes and intricate reaction pathways. Moreover, the kinetics of the urea synthesis reaction may be sluggish, thereby impacting the overall production rate. Therefore, in this study, we introduce a novel electron-reserve-enhanced Cs2CuBr4/TiOx-Ar (CCBT-Ar) structure for the photocatalytic synthesis of urea from CO2 and nitrate waste. Theoretical calculations and spectroscopic analysis underscore the critical role of oxygen vacancies (Ov) within the amorphous TiOx shell, enhancing reactant adsorption and catalyzing the rate-determining step (*OCONH2→*HOCONH2). However, the presence of Ov also results in significant carrier recombination, acting as trapping centers and reducing urea production activity. Importantly, we demonstrate that in-situ-grown carbon nanosheets, in conjunction with TiOx, function as efficient electron reservoirs, markedly mitigating trapping-induced recombination and facilitating electron redistribution. These reserved electrons can then actively participate in the urea synthesis process. As a result, the electron-reserve-enhanced structure exhibits robust solar urea yield and selectivity, even in challenging wastewater conditions. This work provides a rational and innovative approach to catalyst development in complex solar synthesis, offering promising avenues for the sustainable production of value-added chemicals while concurrently reducing carbon emissions.

Photocatalytic Synthesis of Glycine from Methanol and Nitrate.

Photocatalytic utilization of methanol and nitrate as carbon and nitrogen sources for the direct synthesis of amino acids could provide a sustainable way for the valorization of green "liquid sunlight" and nitrate waste. In this study, we developed an efficient photochemical method to synthesize glycine directly from methanol and nitrate, which cascades the C-C coupling to form glycol, nitrate reduction to NH3, and finally C-N coupling to generate glycine. Interestingly, the involved photocatalytic tandem reactions show a synergistic effect, in which the presence of nitrate is the dominant factor to enable the overall reaction and reach high synthetic efficiency. Ba2+-TiO2 nanoparticles are confirmed as a feasible and efficient catalyst system for the photosynthesis of glycine with a remarkable glycine photosynthesis rate of 870 μmol gcat-1 h-1 under optimal conditions. This work establishes a novel catalytic system for amino acid synthesis from methanol and nitrate under mild conditions. These results also allow us to further suppose the formation pathways of amino acids on the primitive earth, as an extension to proposals based on the Miller-Urey experiments.

Electrosynthesis of Ammonia from Nitrate Using a Self-Activated Carbon Fiber Paper.

While electrochemically upcycling nitrate wastes to valuable ammonia is considered a very promising pathway for tackling the environmental and energy challenges underlying the nitrogen cycle, the effective catalysts involved are mainly limited to metal-based materials. Here, we report that commercial carbon fiber paper, which is a classical current collector and is typically assumed to be electrochemically inert, can be significantly activated during the reaction. As a result, it shows a high NH3 Faradaic efficiency of 87.39% at an industrial-level current density of 300 mA cm-2 for over 90 h of continuous operation, with a NH3 production rate of as high as 1.22 mmol cm-2 h-1. Through experimental and theoretical analysis, the in situ-formed oxygen functional groups are demonstrated to be responsible for the NO3RR performance. Among them, the C-O-C group is finally identified as the active center, which lowers the thermodynamic energy barrier and simultaneously improves the hydrogenation kinetics. Moreover, high-purity NH4Cl and NH3·H2O were obtained by coupling the NO3RR with an air-stripping approach, providing an effective way for converting nitrate waste into high-value-added NH3 products.

Phase-Regulated Active Hydrogen Behavior on Molybdenum Disulfide for Electrochemical Nitrate-to-Ammonia Conversion.

Electrochemical reduction of nitrate waste is promising for environmental remediation and ammonia preparation. This process includes multiple hydrogenation steps, and thus the active hydrogen behavior on the surface of the catalyst is crucial. The crystal phase referred to the atomic arrangements in crystals has a great effect on active hydrogen, but the influence of the crystal phase on nitrate reduction is still unclear. Herein, enzyme-mimicking MoS2 in different crystal phases (1T and 2H) are used as models. The Faradaic efficiency of ammonia reaches ≈90 % over 1T-MoS2 , obviously outperforming that of 2H-MoS2 (27.31 %). In situ Raman spectra and theoretical calculations reveal that 1T-MoS2 produces more active hydrogen on edge S sites at a more positive potential and conducts an effortless pathway from nitrate to ammonia instead of multiple energetically demanding hydrogenation steps (such as *HNO to *HNOH) performed on 2H-MoS2 .

Phase‐Regulated Active Hydrogen Behavior on Molybdenum Disulfide for Electrochemical Nitrate‐to‐Ammonia Conversion

AbstractElectrochemical reduction of nitrate waste is promising for environmental remediation and ammonia preparation. This process includes multiple hydrogenation steps, and thus the active hydrogen behavior on the surface of the catalyst is crucial. The crystal phase referred to the atomic arrangements in crystals has a great effect on active hydrogen, but the influence of the crystal phase on nitrate reduction is still unclear. Herein, enzyme‐mimicking MoS2 in different crystal phases (1T and 2H) are used as models. The Faradaic efficiency of ammonia reaches ≈90 % over 1T‐MoS2, obviously outperforming that of 2H‐MoS2 (27.31 %). In situ Raman spectra and theoretical calculations reveal that 1T‐MoS2 produces more active hydrogen on edge S sites at a more positive potential and conducts an effortless pathway from nitrate to ammonia instead of multiple energetically demanding hydrogenation steps (such as *HNO to *HNOH) performed on 2H‐MoS2.

A Universal Approach for Sustainable Urea Synthesis via Intermediate Assembly at the Electrode/Electrolyte Interface.

Electrocatalytic C-N coupling process is indeed a sustainable alternative for direct urea synthesis and co-upgrading of carbon dioxide and nitrate wastes. However, the main challenge lies in the unactivated C-N coupling process. Here, we proposed a strategy of intermediate assembly with alkali metal cations to activate C-N coupling at the electrode/electrolyte interface. Urea synthesis activity follows the trend of Li+ <Na+ <Cs+ <K+ . In the presence of K+ , a world-record performance was achieved with a urea yield rate of 212.8±10.6 mmol h-1 g-1 on a single-atom Co supported TiO2 catalyst at -0.80 V versus reversible hydrogen electrode. Theoretical calculations and operando synchrotron-radiation Fourier transform infrared measurements revealed that the energy barriers of C-N coupling were significantly decreased via K+ mediated intermediate assembly. By applying this strategy to various catalysts, we demonstrate that intermediate assembly at the electrode/electrolyte interface is a universal approach to boost sustainable urea synthesis.

A Universal Approach for Sustainable Urea Synthesis via Intermediate Assembly at the Electrode/Electrolyte Interface

AbstractElectrocatalytic C−N coupling process is indeed a sustainable alternative for direct urea synthesis and co‐upgrading of carbon dioxide and nitrate wastes. However, the main challenge lies in the unactivated C−N coupling process. Here, we proposed a strategy of intermediate assembly with alkali metal cations to activate C−N coupling at the electrode/electrolyte interface. Urea synthesis activity follows the trend of Li+&lt;Na+&lt;Cs+&lt;K+. In the presence of K+, a world‐record performance was achieved with a urea yield rate of 212.8±10.6 mmol h−1 g−1 on a single‐atom Co supported TiO2 catalyst at −0.80 V versus reversible hydrogen electrode. Theoretical calculations and operando synchrotron‐radiation Fourier transform infrared measurements revealed that the energy barriers of C−N coupling were significantly decreased via K+ mediated intermediate assembly. By applying this strategy to various catalysts, we demonstrate that intermediate assembly at the electrode/electrolyte interface is a universal approach to boost sustainable urea synthesis.

Accelerating multielectron reduction at CuxO nanograins interfaces with controlled local electric field

Regulating electron transport rate and ion concentrations in the local microenvironment of active site can overcome the slow kinetics and unfavorable thermodynamics of CO2 electroreduction. However, simultaneous optimization of both kinetics and thermodynamics is hindered by synthetic constraints and poor mechanistic understanding. Here we leverage laser-assisted manufacturing for synthesizing CuxO bipyramids with controlled tip angles and abundant nanograins, and elucidate the mechanism of the relationship between electron transport/ion concentrations and electrocatalytic performance. Potassium/OH− adsorption tests and finite element simulations corroborate the contributions from strong electric field at the sharp tip. In situ Fourier transform infrared spectrometry and differential electrochemical mass spectrometry unveil the dynamic evolution of critical *CO/*OCCOH intermediates and product profiles, complemented with theoretical calculations that elucidate the thermodynamic contributions from improved coupling at the Cu+/Cu2+ interfaces. Through modulating the electron transport and ion concentrations, we achieve high Faradaic efficiency of 81% at ~900 mA cm−2 for C2+ products via CO2RR. Similar enhancement is also observed for nitrate reduction reaction (NITRR), achieving 81.83 mg h−1 ammonia yield rate per milligram catalyst. Coupling the CO2RR and NITRR systems demonstrates the potential for valorizing flue gases and nitrate wastes, which suggests a practical approach for carbon-nitrogen cycling.

(Invited) Understanding Trends for Electrocatalytic and Catalytic Nitrate Reduction

Fixation of nitrogen such as for ammonia production through the Haber-Bosch process is imperative for feeding the world’s population, but is causing an imbalance in the nitrogen cycle as oxidized nitrogen species such as nitrate builds up. This build up of nitrate pollution from agricultural and industrial waste poses an immediate threat to environmental and human health. While separation of this nitrate is a method to produce clean water, it does not chemically address the issue of oxidized nitrate. In addition, it does not form nitrogen species in a valuable form. One method is to use nitrate waste as a feedstock for production of fertilizers such as ammonia or ammonium nitrate. In this work we discuss the use of electrocatalysis to convert nitrate to ammonia, where renewable electricity can be used to drive the reaction, minimizing carbon dioxide emissions from current methods to produce ammonia. In this talk we will discuss (1) trends in electrocatalytic nitrate reduction, (2) similarities and differences in electrocatalytic nitrate reduction and catalytic nitrate reduction (i.e., using molecular H2 rather than an applied potential), and (3) practical challenges in systems to commercially convert nitrate. Through the use of kinetic studies, in situ spectroscopy, microkinetic modeling, and density functional theory calculations, we show how the adsorption energetics of nitrate and hydrogen are descriptors for nitrate reduction on metals and alloy surfaces. We will discuss the importance of operando spectroscopy to understand the catalyst under reaction conditions. We will show how alloying Pt with Ru to increase the nitrate adsorption energy shows an increase in the rates of nitrate reduction at low Ru content. We will also show that the nitrate reduction rate is decreased when the Ru content is too high, because nitrate binds to the catalyst too strongly. We will compare the electrocatalytic results to thermal nitrate catalytic and show that while there are numerous similarities between electrocatalysis and thermal catalysis, there are also factors unique to electrocatalysis that impact the rate of reaction. These differences motivate a greater understanding of electrochemical steps and the effect of the applied potential, solvent, and ions. We will discuss how the best performing catalysts in batch systems translate to flow reactors more amenable to commercialized processes and other challenges in realistic nitrate streams containing potential catalyst poisons such as chlorides.

Simultaneous utilization of CO2 and nitrate wastes from compact recirculating aquaculture system for improving algal biomass (Scenedesmus armatus) production

Tilapia cultivation in an air-tight culture tank of a recirculating aquaculture system (RAS) was conducted for 8 days to produce CO2 for growing Scenedesmus armatus in bubble column photobioreactors. The average CO2 concentrations in the headspace of the culture tank were determined at 925 ± 73.4 and 1619 ± 197.7 ppm for fish stocking densities of 3 and 10 kg/m3, respectively. These CO2 concentrations were higher than CO2 concentrations at the tank inlet (496 ± 13.9 ppm) exposed to the atmosphere. Using the captured CO2 and nitrate from the effluent of a commercial tilapia farm for cultivating S. armatus yielded higher algal biomass concentration (621 ± 41.2 mg/L) than using ambient air (410 ± 30.1 mg/L). Insufficient nitrate in RAS effluent is the limiting factor for CO2 utilization and algal biomass production. In conclusion, this study demonstrates the possibility of repurposing CO2 from RAS to enhance algal cultivation.

EFEKTIFITAS SAYURAN SELADA (Lactuca sativa L.) DALAM MEREDUKSI KONSENTRASI NITRAT PADA LIMBAH HASIL BUDIDAYA IKAN PATIN (Pangasius pangasius) DENGAN SISTEM AKUAPONIK

Background: Water is a natural resource that has a very important function for human life and other living things. Aquaculture waste produces ammonia, nitrite and nitrate waste. Nitrates can have a negative impact on the environment, among others, by contaminating water sources for various purposes, one of which is drinking water and causing health problems for humans.&#x0D; Method: This research used quasi-experimental (Quasi experiment) with Non-Equivalent Control group design. The study involved two groups, the control and the treatment by supplying 108 lettuce planting holes in three times. Data analysis used univariate and bivariate analysis with Wilcoxon test.&#x0D; Result: The lettuce (Lactuca sativa L) had no effect in reduced nitrate concentrations in the posttreatment. The results of the Wilcoxon test showed a p-value of 0.068.&#x0D; Conclusion: There was no significant difference in nitrate concentration in catfish (Pangasius pangasius) culture water at the input and output of the lettuce (Lactuca sativa L) installation.

Disintegration of Partial Denitrification Granules at High Nitrate Concentration

It is well acknowledged that high nitrate concentration would negatively affect the biological denitrification activity, especially in the presence of nitrite accumulation. In this study, a novel granular partial denitrification (PD) process was developed, and the impact of nitrate concentration (120–960 mg N/L) on PD granules was investigated by close monitoring of the operational performance, physicochemical characteristics, and microbial community. Results indicated that the effluent nitrite increased with the nitrate concentration, with a maximum value of 492.4 mg N/L obtained. And the maximum denitrification activity in situ was found not to be decreased despite high nitrite accumulation; it was maintained at 0.24 g N/g VSS/h, suggesting the high tolerance of PD granules to the nitrite. The granule size increased with the influent nitrate, and the compact PD granules, however, were observed to be disintegrated at 960 mg N/L of nitrate, which was likely attributed to the substrate diffusion limitation in larger granules, with the cavity formed in its inner part. In addition, microbial analysis revealed that bacterial richness and the diversity of PD granules were decreased, and Gracilibacteria that was supposed to be responsible for maintaining the PD granule structure was largely reduced at a high nitrate concentration, which was likely to be another major reason for the disintegration. This study revealed the potential causes for the disintegration of PD granules, which offer theoretical support and technical guidance to ensure the stability of PD granules in treating high nitrate wastes for efficient nitrite production.

Electrochemical ammonia production from nitrates in agricultural tile drainage: Technoeconomic and global warming analysis

AbstractNitrates from agricultural wastewater are harmful to human health and result in eutrophication. Several emerging electrochemical technologies have been developed independently to enable efficient recovery and recycling of nitrate waste; however, it remains unclear whether the implementation of such combined technologies can be economically viable. Herein, we perform technoeconomic and global warming potential analyses on several hypothetical nitrate capture and conversion systems for the recovery of nitrates from agricultural wastewater and conversion of nitrate to ammonia. The energy efficient technologies incorporated include: electrodialysis for nitrate separation, electrocatalysis for ambient ammonia production, and agrophotovoltaics as a clean energy source. Our technoeconomic analysis reveals that despite advancements in nitrate separation and conversion, capital investments for system installation cannot be recovered by the financial benefit of on‐site fertilizer production. Our analysis highlights the necessity of government intervention to promote nitrate abatement technologies to ensure environmental compliance and protect public health.

Denitrification of nitrate in regeneration waste brine using hybrid cation exchanger supported nanoscale zero-valent iron with/without palladium nanoparticles

The Sustainable Development Goals require that reducing waste is a priority. This work described the application of an innovative zero-waste hybrid ion exchange nanotechnology that concurrently removed nitrate and induced denitrification to ammonia, with the ability to generate fertilizer for the agriculture sector from the recycled by-products. Herein, hybrid cation exchanger-supported zero-valent iron (Fe0), and bimetallic Fe0/Pd nanoparticles (HCIX-Fe0 and HCIX-Fe0/Pd) were synthesized and successfully validated for denitrification of nitrate in spent waste brine that contained nitrate. The kinetics of nitrate catalysis by both HCIX-Fe0 and HCIX-Fe0/Pd were compared and presented by six kinetic models, namely, zero-order, pseudo first- and second-order reaction, pseudo first- and second-order adsorption, and Elovich. HCIX-Fe0/Pd displayed a higher kinetic value than HCIX-Fe0, with k1 of 0.0019 and 0.0026 min−1, respectively. Nitrate was predominantly catalysed to NH4+ at a ratio of ammonia to other nitrogen compounds of around 80:20. Although HCIX-Fe0/Pd showed slightly better (14%) kinetic results, it was determined as unfavourable for real-life application due to low selectivity toward N2 gas and the need to use H2 gas. Based on practicability, the HCIX-Fe0 was further validated. The effect of salt (using NaCl) and the role of initial pH conditions were optimized and discussed. The recovery of nitrate removal was also calculated, and a recovery range of 91.42–99.14% was obtained for three consecutive runs. The sustainable, novel, zero waste hybrid ion exchange nanotechnology using the combination of two fixed-bed columns containing nitrate-selective resin for nitrate removal and novel HCIX-Fe0 for nitrate reduction to NH4+ may be a promising sustainable solution toward the goal of discharging zero nitrate waste to the environment.

Electrochemically reconstructed copper-polypyrrole nanofiber network for remediating nitrate-containing water at neutral pH

As the main nitrogen-containing pollutant of agricultural and industrial wastewater, nitrate (NO3−) is obtainable from the natural nitrogen cycle and industrial emission. Recovering nitrogen (N) from nitrate-polluted wastewater to produce ammonia (NH3) is a promising route to mitigate pollution risks and create economic values. Since nitrate polluted wastewater always exists in acidic or neutral form, electrocatalytic nitrate conversion in neutral electrolytes is convenient for following treatments. Herein, we report an in-situ electrochemical reconstructed nanofiber-like Polypyrrole-Copper (PPy-Cu-E) 3D network for high-efficient NO3− reduction to NH3 in the neutral electrolyte (pH =7.5). In the presence of NO3−, the electrochemical reconstruction process endowed PPy-Cu-E with compactly arranged Cu nanocrystals on its nanofibers and remarkably improved electrochemical active surface area. In flow cell, the PPy-Cu-E achieved a high NH3 yield rate (0.588 mmol mgcat h−1) at a relatively low overpotential (−0.61 V vs. RHE) with 91.95 ± 1% Faradaic efficiency. By employing authentic electroplating wastewater (pH = 7.4) as a catholyte, 93 % of NO3−-N could be converted in 10 h. This work demonstrated the feasibility of high-yield electrocatalytic conversion from nitrate to ammonia under relatively low overpotential in neutral electrolytes and provided a promising method for N-recovery from nitrate wastes.

Electrocatalytic conversion of nitrate waste into ammonia: a review

Electrocatalytic conversion of nitrate waste into ammonia: a review

Nitrate-to-Ammonia Conversion on Ru/Ni Hydroxide Hybrid through Zinc-Nitrate Fuel Cell.

The fuel cell is a basic device to generate electricity from chemical fuels. It is often operated with oxygen as the oxidizing agent, but its sluggish reduction has become a key challenge. Herein, a conceptual oxygen-free design is demonstrated, namely a zinc-nitrate fuel cell, which converts nitrate waste into valuable ammonia and generates electricity simultaneously. The cell is constructed with zinc foil as the anode and ruthenium (Ru) nanoparticles loaded on nickel foam as the cathode. Catalyzed by Ru/Ni hydroxide hybrid, the reaction rate of 384mmolh-1 mgRu-1 (1.4×10-6 ±0.1×10-6 mols-1 cm-2 ) and Faradic efficiency (FENH3 =97%±2%) at -0.6V versus reverse hydrogen electrode are achieved for nitrate-to-ammonia conversion. During ammonia production, such zinc-nitrate fuel cell can further deliver a maximum power density of 51.5mWcm-2 (0.25cm2 electrode) and 23.3mWcm-2 (1cm2 electrode), keeping ultrahigh Faradic efficiency (97%±4%at 40mAcm-2 ) after long tests.

Pu distribution among mixed waste components at the Hanford legacy site, USA and implications to long-term migration

Beginning in 1943, process wastes containing approximately 1.85 × 1015 Bq (200 kg) of plutonium (Pu) were released into unlined cribs, trenches, and field tiles at the Hanford Site, Washington, USA. The 216-Z-9 (Z-9) unlined trench received over 4 × 106 L of mixed Pu processing waste from the Plutonium Finishing Plant (PFP) consisting of high ionic strength (∼ 5 M nitrate, ∼ 0.6 M aluminum), acidic (pH ∼ 2.5) solutions, which also contained the organic solvents: tributyl phosphate (TBP), dibutyl butylphosphonate (DBBP), carbon tetrachloride (CCl4), and lard oil. A small fraction of Pu migrated deep into the subsurface vadose zone to depths of 37 m, but the mechanisms controlling Pu migration beneath the trench are unknown. In this study, we determined Pu partitioning behavior in a series of binary and ternary batch experiments containing aqueous, organic, and solid phases representative of the waste constituents and natural sediments of the Z-9 trench in order to develop a conceptual model for the transport of Pu in the subsurface. Our results show that Pu at equilibrium with low pH, high nitrate waste and in the presence of a TBP/organic phase can migrate as a Pu-TBP-nitrate complex in the organic phase as long as the low pH and high nitrate concentrations are maintained. Reducing the nitrate concentrations or increasing the pH will lead to Pu partitioning into the aqueous phase from the organic phase with subsequent sorption to native Hanford sediments. The results of this work suggest that Pu migration in the subsurface is likely driven by weak sorption of aqueous Pu under low pH conditions as well as the formation of Pu-TBP-nitrate complexes in the organic phase. Long-term Pu migration will be limited by the transient nature of the low pH conditions and the dispersion of the nitrate plume.