Adsorption Of Nitrate Ions Research Articles

Single Atom Catalyst for Nitrate-to-Ammonia Electrochemistry.

Various life forms suffer from the negative effects of nitrate when it accumulates in water bodies, which is a major concern in the present day. The removal of nitrate from water bodies is a critical challenge, and the most effective method to achieve that is to change it into ammonia. Ammonia is a clean energy source and a vital input for the fertilizer industry. The Haber-Bosch process, which dominates the industrial production of ammonia, requires a lot of energy. A more sustainable way to produce ammonia is to use nitrate-contaminated water and reduce it to ammonia through electrocatalysis. This review is constituted of amalgamated articles featuring unique conditions that affect the productivity and activity of the transition metal single atom catalyst (TNMSAC) for the electrocatalytic nitrate reduction to ammonia (NRA) reaction. It explores factors such as nitrate ion adsorption, the characteristics of the central electroactive transition metal, the type of coordinating atoms, the impact of potential on stability, and the interplay among single atoms on the selectivity and yield of ammonia gas. In addition, this review also covers advanced concepts such as dual-atom catalysts, dual single atom catalysts, and single atom alloys. The review will provide valuable guidance for enhanced comprehension and strategic designing of TNMSAC for the electrocatalytic conversion of NRA, which will contribute to achieving a green ammonia economy.

Synthesis of gamma aluminum oxide nano-powder for adsorptive removal of nitrate from aqueous solutions

Nitrate pollution of surface and groundwater could be a worldwide issue resulting in the threat to the environment and public health. The removal of nitrate from water was carried out using gamma aluminum oxide (γ-Al2O3) nano powder. The nano powder was synthesized from aluminum oxide powder using the aqueous-based reflux method and applied for nitrate removal. The surface properties of the activated γ-Al2O3 were characterized using FTIR, XRD, and BET surface area analysis. Analysis of variance (ANOVA) was used to analyze nitrate removal to determine the appropriate regression model, which was found to be the quadratic model with a coefficient of determination (R2 = 0.99). The adsorption process was observed to be dependent on initial nitrate concentration, adsorbent dose, and time. The optimized nitrate removal efficiencies were 97.01% using a dose of 2.26 gL−1, an initial nitrate concentration of 10 mgL−1, and a contact time of 45 min. Additionally, the kinetics of nitrate ion adsorption was discussed based on pseudo-first order and pseudo-second order kinetic models. The experimental data fitted well with the pseudo-second order kinetic model, indicating that the adsorption mechanism is chemisorption. The equilibrium adsorption of nitrate experimental data followed the both Freundlich and Langmuir isotherm (R2 = 0.95), implying a homogeneous nature of the γ-Al2O3 surface sites. These results suggest further consideration of the practical application of γ-Al2O3 for nitrate treatment for domestic purposes.

Adsorption of nitrate and phosphate ions using ZnCl2-activated biochars from phytoremediation biomasses

Adsorption of nitrate and phosphate ions using ZnCl2-activated biochars from phytoremediation biomasses

Biosorptive removal of toxic nitrate ion from wastewater using Albizia lebbeck seed pods: Isotherm and equilibrium studies

A major environmental issue that contaminates drinking water and endangers human health is nitrate pollution. In this study, goethite, citric acid, tartaric acid was employed to modify Albizia lebbeck seed pod for the biosorption of nitrate ion. The developed unmodified Albizia lebbeck (UALB), citric acid modified Albizia lebbeck (CALB), tartaric acid modified Albizia lebbeck (TALB), and goethite acid modified Albizia lebbeck (GALB) were characterized using scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), and point of zero charge (pHpzc) to determine the structural morphology, functional group, and adsorbent surface charge. The adsorption nitrate ion onto the biosorbents was found to be dependent on the operating parameters. The findings revealed that the maximum percentage removal of nitrate ion was 80.8 % at pH 7 for UALB, 80.3 % at pH = 4.0 for CALB, 70.30 % at pH = 3.0 for TALB and 76 % at pH 7 for GALB. The adsorption experimental data for nitrate ion adsorption onto ULAB, CALB, TALB, and GALB were best described by the Langmuir isotherm model. The UALB exhibited the highest Langmuir monolayer adsorption capacities with a value of 344.827 mg/g. Therefore, the unmodified form of Albizia lebbeck (UALB) which is economical, and sustainable provides an efficient alternative method for nitrate removal in aqueous environment.

Probing interfacial stress on Au cathode in DMSO electrolyte during electrochemical polarization in aprotic Li-O2 batteries

The practical performance of Li-O2 batteries suffers from interfacial instabilities associated with the reaction intermediates. These instabilities on the cathode-electrolyte interface dictate the direction of the oxygen evolution and reduction reactions (OER/ORR) in Li-O2 batteries. Despite intensive research on chemical instabilities in the reaction intermediates, there is limited work on understanding the importance of stress on the interfacial dynamics. To address this gap, in-situ curvature measurements were conducted to probe interfacial stress generation during electrochemical polarization on Au cathode in DMSO electrolytes. Charge accumulation induces tensile stress, whereas compressive stress generation is associated with the adsorbate-induced stress and mismatch strain between reaction intermediates and the Au surface. Abrupt stress relaxation on the onset of discharge presents evidence for a contribution of electrostriction stress. Adsorption of redox mediator nitrate ions induces compressive stress before ORR. Unique findings demonstrate the impact of interfacial stress on the OER/ORR in Li-O2 batteries.

Application of TiO2 Supported on Nickel Foam for Limitation of NOx in the Air via Photocatalytic Processes.

TiO2 was loaded on the porous nickel foam from the suspended ethanol solution and used for the photocatalytic removal of NOx. Such prepared material was heat-treated at various temperatures (400-600 °C) to increase the adhesion of TiO2 with the support. Obtained TiO2/nickel foam samples were characterized by XRD, UV-Vis/DR, FTIR, XPS, AFM, SEM, and nitrogen adsorption at 77 K. Photocatalytic tests of NO abatement were performed in the rectangular shape quartz reactor, irradiated from the top by UV LED light with an intensity of 10 W/m2. For these studies, a laminar flow of NO in the air (1 ppm) was applied under a relative humidity of 50% and a temperature of 28 °C. Concentrations of both NO and NO2 were monitored by a chemiluminescence NO analyzer. The adsorption of nitrogen species on the TiO2 surface was determined by FTIR spectroscopy. Performed studies revealed that increased temperature of heat treatment improves adhesion of TiO2 to the nickel foam substrate, decreases surface porosity, and causes removal of hydroxyl and alcohol groups from the titania surface. The less hydroxylated surface of TiO2 is more vulnerable to the adsorption of NO2 species, whereas the presence of OH groups on TiO2 enhances the adsorption of nitrate ions. Adsorbed nitrate species upon UV irradiation and moisture undergo photolysis to NO2. As a consequence, NO2 is released into the atmosphere, and the efficiency of NOx removal is decreasing. Photocatalytic conversion of NO to NO2 was higher for the sample heated at 400 °C than for that at 600 °C, although coverage of nickel foam by TiO2 was lower for the former one. It is stated that the presence of titania defects (Ti3+) at low temperatures of its heating enhances the adsorption of hydroxyl groups and the formation of hydroxyl radicals, which take part in NO oxidation. Contrary to that, the presence of titania defects in TiO2 through the formation of ilmenite structure (NiTiO3) in TiO2/nickel foam heated at 600 °C inhibits its photocatalytic activity. No less, the sample obtained at 600 °C indicated the highest abatement of NOx due to the high and stable adsorption of NO2 species on its surface.

Characteristics of Nitrate Ion Adsorption onto N-doped Activated Carbon Derived from Pinecone and Urea

Characteristics of Nitrate Ion Adsorption onto N-doped Activated Carbon Derived from Pinecone and Urea

Breaking Local Charge Symmetry of Iron Single Atoms for Efficient Electrocatalytic Nitrate Reduction to Ammonia.

The electrochemical conversion of nitrate pollutants into value-added ammonia is a feasible way to achieve artificial nitrogen cycle. However, the development of electrocatalytic nitrate-to-ammonia reduction reaction (NO3-RR) has been hampered by high overpotential and low Faradaic efficiency. Here we develop an iron single-atom catalyst coordinated with nitrogen and phosphorus on hollow carbon polyhedron (denoted as Fe-N/P-C) as a NO3-RR catalyst electrode. Owing to the tuning effect of phosphorus atoms on breaking local charge symmetry of the single-Fe-atom catalyst, it facilitates the adsorption of nitrate ions and enrichment of some key reaction intermediates during the NO3-RR process. The Fe-N/P-C catalyst exhibits 90.3% ammonia Faradaic efficiency with a yield rate of 17980 μg h-1 mgcat-1, greatly outperforming the reported Fe-based catalysts. Furthermore, operando SR-FTIR spectroscopy measurements reveal the reaction pathway based on key intermediates observed under different applied potentials and reaction durations. Density functional theory calculations demonstrate that the optimized free energy of NO3-RR intermediates is ascribed to the asymmetric atomic interface configuration, which achieves the optimal electron density distribution. This work demonstrates the enhanced function of heteroatom doping on single atoms for NO3-RR, and provides an effective strategy for improving the catalytic performance of single atom catalysts in different electrochemical reactions.

Breaking Local Charge Symmetry of Iron Single Atoms for Efficient Electrocatalytic Nitrate Reduction to Ammonia

AbstractThe electrochemical conversion of nitrate pollutants into value‐added ammonia is a feasible way to achieve artificial nitrogen cycle. However, the development of electrocatalytic nitrate‐to‐ammonia reduction reaction (NO3−RR) has been hampered by high overpotential and low Faradaic efficiency. Here we develop an iron single‐atom catalyst coordinated with nitrogen and phosphorus on hollow carbon polyhedron (denoted as Fe−N/P−C) as a NO3−RR electrocatalyst. Owing to the tuning effect of phosphorus atoms on breaking local charge symmetry of the single‐Fe‐atom catalyst, it facilitates the adsorption of nitrate ions and enrichment of some key reaction intermediates during the NO3−RR process. The Fe−N/P−C catalyst exhibits 90.3 % ammonia Faradaic efficiency with a yield rate of 17980 μg h−1 mgcat−1, greatly outperforming the reported Fe‐based catalysts. Furthermore, operando SR‐FTIR spectroscopy measurements reveal the reaction pathway based on key intermediates observed under different applied potentials and reaction durations. Density functional theory calculations demonstrate that the optimized free energy of NO3−RR intermediates is ascribed to the asymmetric atomic interface configuration, which achieves the optimal electron density distribution. This work demonstrates the critical role of atomic‐level precision modulation by heteroatom doping for the NO3−RR, providing an effective strategy for improving the catalytic performance of single atom catalysts in different electrochemical reactions.

Herbs carbonization and activation for fast sorption of nitrate ions: a new challenge for a full treatment of groundwater pollution.

The evolution of low-cost ecotechnologies in water treatment and purification is highly increased. Face to the growing global demand for eco-friendly water treatment materials, the non-valorized herb-based biomass covering a large area could be a promising alternative. Herbs (HB) are currently one of the cheapest biomasses. Therefore, the utilization of HB for environmental applications is relevant. HB was treated and activated in this work to produce an eco-friendly adsorbent for nitrate removal from groundwater. HB was treated with modified carbonization at 220 °C to produce highly reactive biochar (BCH). Ammonium groups (AM) are immobilized covalently over the BCH surface, and then, the resulting materials BCH-AM are fully characterized. Results showed that ammonium is successfully grafted at the BCH surface, producing a highly stable material. Measurements on nitrate ion adsorption revealed that BCH-AM are of great interest as 80% of nitrate ions (NO3-) were removed. Importantly, the eco-friendly BCH-AM demonstrated the ability to easily desorb the nitrate ions using Na2CO3 as a green eluent. Parametric studies confirmed the effectiveness of the prepared adsorbent and approved that the adsorption occurred by electrostatic interactions. To demonstrate the performance of the adsorbent, BCH-AM was evaluated to remove NO3- from groundwater upstream in a water treatment plant. This work opens an immense perspective for herb biomass to be the actual challenge to resolve environmental problems.

Volcanic Soils: Their Characteristics, Management Practices, and Potential Sollution for Water Pollution

Volcanic soils are formed from materials originating from volcanic eruptions, and with various pedogenic processes occurring, volcanic soils have unique physical, chemical, and biological characteristics. This paper aims to review the characteristics of volcanic soils, constraints, management practices, and their potential as adsorbents for contaminants. The paper was based on secondary information using a systematic review. The studies carried out include identifying manuscripts, analyzing report data, critically assessing the topic, and combining the results of relevant published manuscripts. The issues raised include data on volcanic soils, management practices, water pollution, and using volcanic soils as an environmentally friendly adsorbent. Colloidal compounds in the clay fraction of volcanic soils generally contain active Al and Fe compounds, allophane, imogolite, ferrihydrite, or Al/Fe-humus complex, and together with opaline silica. The volcanic soil material produces a pool of Al and Fe solid phases with high reactivity, which contributes to the unique physicochemical properties of Andisol. The main problem chemically is the high adsorption of phosphate and nitrate ions which causes the fertilization process to be inefficient. The main problem affects the adsorption of phosphate and nitrate on agricultural lands, so fertilization becomes inefficient. However, the high reactivity of volcanic soils can be used as a basic pollutant adsorbent. This is quite a promising opportunity, given the wide distribution of volcanic soils, so this resource is a very prospective candidate as an adsorbent material in water purification.

Adsorption characteristics of nitrate ion by sodium carbonate activated PAN-based activated carbon fiber

In this study, polyacrylonitrile (PAN)-based carbon fiber with high nitrogen content was activated at 800 °C with sodium carbonate and heat-treated at 950 °C to prepare activated carbon fiber (ACF), and the results of nitrate ion adsorption on the prepared ACF are presented. CHN elemental analysis, XPS measurement, and Boehm titration were used to determine the nitrogen content and surface functional groups of ACF. It is discussed that the total amount of nitrogen decreases, whereas quaternary nitrogen (N-Q) increases upon heat treatment. The decrease in adsorption capacity of the prepared activated carbon under different storage conditions is shown. It is observed that the adsorption capacity of nitrate ion at equilibrium pH (pHe) 5 is halved after 5 weeks, and the decrease in adsorption capacity at pHe 3 is suppressed. The adsorption isotherms of the prepared ACF are shown using the Langmuir equation. The effect of pH on the adsorption capacity of the prepared ACF is compared with that of ACF before heat treatment and zinc chloride-activated powdered activated carbon. The adsorption capacity of ACF without heat treatment at 950 °C decreases as the pHe of the solution increases, and the pH of the nitrate solution including ACF after heat treatment is stable at pHe 4–5.

Electronic Metal-Support Interaction Triggering Interfacial Charge Polarization over CuPd/N-Doped-C Nanohybrids Drives Selectively Electrocatalytic Conversion of Nitrate to Ammonia.

Selective electrocatalytic nitrate-to-ammonia conversion holds significant potential in treatment of nitrate wastewater and simultaneously produces high-value-added ammonia. However, today's development of nitrate-to-ammonia technology remains hindered by the lack of electrocatalysts with high activity and selectivity. In this work, metal-organic framework-derived CuPd bimetallic nanoparticles/nitrogen-doped carbon (CuPd/CN) hybrid nanoarrays for efficient ammonia electrosynthesis from nitrate are designed and synthesized. Systematic characterization reveals that the electronic metal-support interaction between the CuPd nanoparticles and N-doped nanocarbon matrix could trigger interfacial charge polarization over the CuPd/CN composite and make Cu sites electron deficient, which is conducive to the adsorption of nitrate ions. Moreover, the Pd atom sites separate by Cu atoms and could catalyze the dissociation of H2 O molecules to form adsorbed H species, which evolves into hydrogen radicals and behaves as the dominant reactive species in accelerating nitrate-to-ammonia electrocatalysis. These advantages endow the CuPd/CN nanoarrays with high faradaic efficiency (96.16%), selectivity (92.08%) as well as excellent catalytic stability for electroreduction of nitrate to ammonia.

Acidic layer-enhanced nanoconfinement of anions in cylindrical pore of single-walled carbon nanotube

The adsorption of the nitrate ion by the cylindrical pore of single-walled carbon nanotubes (SWCNT) was found to be aided by an acidic adsorbed layer. Adsorbed water in the vicinity of the pore wall can supply protons through ionization, forming the acidic layer, according to Raman spectra and results of solution pH fluctuations caused by ion species adsorption. Such an acidic adsorbed layer leads to surplus adsorption of anionic species where the adsorbed amount of nitrate ions is much larger than that of cations. Also, we could observe the Raman bands being assignable to the symmetrical stretching mode at an extremely high-frequency region for nano-restricted nitrate ions compared to any other bulk phases. The abnormal band shift of adsorbed nitrate ions indicates that the nitrate ions are confined in the pore under the effects of nanoconfinement by the pore and the strong interaction with the acidic layer in the pore. Our results warn that we have to construct the adsorption model of aqueous electrolytes confined in carbon pores by deliberating the acid layer formed by the adsorbed water.

Adsorption of Phosphate and Nitrate Ions on Oxidic Substrates Prepared with a Variable-Charge Lithological Material

This work evaluates phosphate and nitrate ion adsorption from aqueous solutions on calcined adsorbent substrates of variable charge, prepared from three granulometric fractions of an oxidic lithological material. The adsorbent material was chemically characterized, and N2 gas adsorption (BET), X-ray diffraction, and DTA techniques were applied. The experimental conditions included the protonation of the beds with HCl and H2SO4 and the study of adsorption isotherms and kinetics. The lithological material was moderately acidic (pH 5) with very little solubility (electrical conductivity 0.013 dS m−1) and a low cation exchange capacity (53.67 cmol (+) kg−1). The protonation reaction was more efficient with HCl averaging 0.745 mmol versus 0.306 mmol with H2SO4. Likewise, the HCl-treated bed showed a better adsorption of PO4−3 ions (3.296 mg/100 g bed) compared to the H2SO4-treated bed (2.579 mg/100 g bed). The isotherms showed great affinity of the PO4−3 ions with the oxide surface, and the data fit satisfactorily to the Freundlich model, suggesting a specific type of adsorption, confirmed by the pseudo-second-order kinetic model. In contrast, the nitrate ions showed no affinity for the substrate (89.7 µg/100 g for the HCl-treated bed and 29.3 µg/100 g bed for the H2SO4-treated bed). Amphoteric iron and aluminum oxides of variable charges present in the lithological material studied allow for their use as adsorbent beds as an alternative technique to eliminate phosphates and other ions dissolved in natural water.

Exclusive nitrate to ammonia conversion via boron-doped carbon dots induced surface Lewis acid sites

Electrocatalytic nitrate reduction represents a very promising route for ammonia synthesis under ambient conditions. However, for most nitrate-to-ammonia electrocatalysts developed to date, the Faradaic efficiency (FE) to ammonia is modest due to the competitive hydrogen evolution reaction (HER). Here, we report that the decoration of vertically aligned NiCo2O4 pillars with boron-doped carbon dots (BCDs) enables electrocatalytic nitrate reduction to ammonia with ∼100% FE. A BCDs/NiCo2O4/carbon cloth cathode delivers a NH3 production rate of 173.9 μmol h−1 cm−2 at −0.55 V versus reversible hydrogen electrode (RHE). This state-of-the-art performance is linked to the BCDs, which provide an abundance of Lewis acid sites on the electrocatalyst surface for the adsorption of nitrate ions (simultaneously suppressing the competitive HER). This work reveals that highly selective NH3 electrosynthesis can be achieved under ambient conditions by regulating the surface acidity/basicity properties of metal-oxide-based catalysts, paving the way toward more sustainable NH3-production technologies.

Surface Reconstruction on Uniform Cu Nanodisks Boosted Electrochemical Nitrate Reduction to Ammonia

The Haber–Bosch (HB) process has provided most of commercial ammonia at the expense of high energy consumption and high CO2 emission. Nitrate electroreduction is showing great potential as an alternative route for the green and scale-up synthesis of ammonia at ambient conditions. However, the performance has lagged due to lack of efficient electrocatalysts. In this work, we present the facile synthesis of uniform Cu nanodisks with exposed (111) facets as highly active electrocatalyst for electrochemical ammonia synthesis, delivering a high ammonia yield of 2.16 mg mg–1cat h–1 and a maximum Faradaic efficiency of 81.1% at −0.5 V versus a reversible hydrogen electrode (RHE). The remarkable activity is originated from the surface reconstructed triatomic Cu clusters due to the cathodic deoxygenation process. As a result, the reconstructed surface shows enhanced affinity to the adsorption of nitrate ions which undergo successive break of three N–O bonds, followed by subsequent formation of three N–H bonds to finally form NH3. The present study provides the feasible preparation of Cu based advanced catalysts and a unique insight into the mechanism of nitrate electroreduction.

Removal of Nitrate Ions Using Thermally and Chemically Modified Bioadsorbents

Nitrate ions are one of the causes of surface water eutrophication. In the present research, the effective adsorption of nitrate ions (NO3) on bioadsorbents prepared from yam skins (Dioscorea alata) was evaluated. The yam skin was chemically modified with ammonium chloride (NH4Cl), and biochar was prepared from the thermally modified biomass. The results were compared with commercial coal (CC). The bioadsorbents were characterized by SEM-EDS analysis, which showed that the synthesized adsorbents have a heterogeneous surface with pores. The batch adsorption tests showed that the pH has the most significant effect on the NO3 adsorption capacity when using the modified yam skin (MYP), obtaining as best conditions pH 12 and a 0.5 mm particle size with an adsorption capacity of 25.75 mg/g; the best adsorption capacity when using the carbon synthesized from yam skin (CYP) and CC was obtained at pH 2, reaching values of 36 and 33.34 mg/g, respectively. The following performance in terms of adsorption capacity was found: CYP > CC > MYP, according to Langmuir’s model. The equilibrium isotherm of NO3 adsorption on MYP and CYP was adjusted by the Freundlich model, while the Langmuir model described adsorption on CC. The kinetics of all the systems studied showed a good fit to the pseudo-first-order, pseudo-second-order and Elovich models with R2 > 0.95, suggesting a mechanism of chemical adsorption by means of species exchange between the aqueous phase and the surface of the material, with the intervention of an intraparticle diffusion stage; based on these findings, the studied biomasses reached promising adsorption capacities in the removal of nitrate anions, showing that the carbon synthesized from yam skins and modified with ammonium chloride had a remarkable behavior in comparison with commercial carbon and NH4Cl-modified yam skins.

Development and tailoring of amino-functionalized activated carbon based Cucumerupsi manni Naudin seed shells for the removal of nitrate ions from aqueous solution

The removal of nitrate ions with ethylenediamine (EDA)-functionalized activated carbon (AC-NH2) was studied in this work. Activated carbon prepared from Cucumerupsi manni Naudin seed shells using ZnCl2 (ACZ) was functionalized with EDA via a nitric acid oxidation followed by acyl chlorination and amidation process. The effect of pH, contact time, initial concentration and co-existing ions on the adsorption of nitrate ions have been investigated. The FTIR and elemental analysis revealed that amino groups were successfully grafted onto the ACZ after functionalization. The surface area and average pore of ACZ were found to be 1008.99 m2/g and 2.02 nm respectively. However, it was noticed that, after functionalization (AC-NH2), its surface area decreases to 113.43 m2/g meanwhile, its pore diameter increases to 2.48 nm. The experimental results of adsorption showed that AC-NH2 exhibit excellent nitrate ions uptake performance compared to ACZ which is attributed to the presence of the grafted amino groups on the ACZ. Nitrate adsorption follows pseudo-first-order kinetic model while the equilibrium adsorption data was best fitted the Freundlich isotherm suggesting that the adsorption process was predominated by physisorption. This study demonstrates that the prepared AC-NH2 is a promising adsorbent for nitrate ions removal from aqueous media.

Anisotropic Growth of Silver Dendrites Regulated by Preferential Adsorption of Nitrate Ions on Crystal Facets

AbstractDendritic structures are widely present in nature, from snowflakes to dendritic cells. However, their formation mechanisms are unclear, which causes long unsolved engineering problems, such as lithium dendrites. Here a strategy to control the growth of dendritic structures by the selective adsorption of ions on crystal facets is reported. Silver particles are synthesized by galvanic replacement reaction and the growth anisotropy of crystals is regulated by changing the concentration of nitrate ions in silver nitrate precursor solution. At a low concentration of nitrate ions, messy branching particles are synthesized while symmetric dendrites are generated at a high concentration of nitrate ions. Molecular dynamics simulation suggests that the selective adsorption of abundant nitrate ions on low‐energy facets promotes the prior growth of the high‐energy facets, resulting in the symmetric dendritic structures. When the potassium nitrate is changed to sodium nitrate, similar phenomena are obtained, confirming the role of selective adsorption of additives in regulating the growth anisotropy of crystals.