Nitrate Ions In Aqueous Solution Research Articles

Citric acid-modified pineapple leaves (Ananas comossus) for nitrate and chloride ions removal

Industrial developments have provided both positive and negative impacts for the environment. The environmental pollution caused by industrial activities discharge toxic waste such as chloride and nitrate. Therefore, recent research employed pineapple leaves (Ananas comossus) as a cellulose-based material to remove chloride and nitrate ion in aqueous solution. The pineapple leaf powder was modified using citric acid to enhance its performance. The optimum conditions were achieved at pH 2, contact time 90 minutes, concentration 100 mg/L for chloride removal meanwhile the removal of nitrate reached the peak at pH 3, contact time 150 minutes, and concentration 50 mg/L for pineapple leaves before modification. After citric acid modification, the optimum point was reached at pH 5, contact time 120 minutes, concentration 100 ppm for chloride. For nitrate adsorption, the optimums condition was at pH 4, contact time 150 minutes, and concentration 50 mg/L. The adsorption capacity of both adsorbents did not significantly change after three times adsorption/desorption cycles. Adsorption of pineapple leaf before and after modification followed the Langmuir isotherm model for chloride and nitrate removal. The obtained adsorbents were characterized using Fourier Transform Infra-Red (FTIR), Scanning Electron Microscopy (SEM) and Breuneur-Emmet-Teller (BET) indicating significant difference before and after adsorption onto pineapple leaves took place.

Real-Time Nitrate Ion Monitoring with Poly(3,4-ethylenedioxythiophene) (PEDOT) Materials.

Nitrate (NO3) pollution in groundwater, caused by various factors both natural and synthetic, contributes to the decline of human health and well-being. Current techniques used for nitrate detection include spectroscopic, electrochemical, chromatography, and capillary electrophoresis. It is highly desired to develop a simple cost-effective alternative to these complex methods for nitrate detection. Therefore, a real-time poly (3,4-ethylenedioxythiophene) (PEDOT)-based sensor for nitrate ion detection via electrical property change is introduced in this study. Vapor phase polymerization (VPP) is used to create a polymer thin film. Variations in specific parameters during the process are tested and compared to develop new insights into PEDOT sensitivity towards nitrate ions. Through this study, the optimal fabrication parameters that produce a sensor with the highest sensitivity toward nitrate ions are determined. With the optimized parameters, the electrical resistance response of the sensor to 1000 ppm nitrate solution is 41.79%. Furthermore, the sensors can detect nitrate ranging from 1 ppm to 1000 ppm. The proposed sensor demonstrates excellent potential to detect the overabundance of nitrate ions in aqueous solutions in real time.

Asymmetry of the Electrostatic Environment as the Origin of the Symmetry Breaking Effect of the Nitrate Ion in Aqueous Solution.

Elucidating the mechanism of how vibrational modes are affected by intermolecular interactions is important for a better understanding of the nature of the former as probes of the latter. Here, such an analysis is carried out for the N-O stretching modes of the nitrate ion interacting with water, with an emphasis on the symmetry breaking effect. On the basis of theoretical calculations on the structural, vibrational, and electrostatic properties of molecular clusters and spectral simulations for an aqueous solution, a transparent view is demonstrated on the mechanism that modulations of spatially local electrostatic environment give rise to structural and spectroscopic symmetry breaking effect. The electrostatic interaction model constructed here is a seven-parameter model; the use of a single electrostatic parameter, such as the electric field on a single atomic site, is found to be insufficient for quantitative evaluation. It is also shown that the frequency modulations of the N-O stretching modes in aqueous solution occur on a time scale much shorter than 0.1 ps.

Surface characterization of mesoporous biomass activated carbon modified by thermal chemical vapor deposition and adsorptive mechanism of nitrate ions in aqueous solution

The mesoporous activated carbon derived from moso biomass was selected to be modified to efficiently and rapidly remove aqueous phase nitrate ions. The bamboo was activated by H3PO4 and pyrolyzed at 500℃, marked as BAP6. Via various steps including thermal chemical vapor deposition (CVD), 7 types of surface modified biochar were obtained. Surface characterization of all the samples was investigated by Brunauer-Emmett-Teller method, elemental analyzer, and X-ray photoelectron spectroscopy. The quaternary nitrogen (N–Q) as strong adsorptive sites was deposited successfully on the surface of BAP6 (Davg = 6.8 nm, SBET = 1024 m2/g) by CVD doping nitrogen on it. The optimal modified mesoporous activated carbon BAP-8AN20-9.5HT30-8ST30 (Davg = 4.4 nm, SBET = 995 m2/g) owned nitrate adsorption capacity of 0.46 mmol/g in nitrate concentration of 200 mg/L at solution pH 3 and surface adsorption rate of 0.47 μmol/m2. The adsorption principle was also discussed. Adsorption kinetics were examined and analyzed by the pseudo-first-order and pseudo-second-order model. All powdery samples BAP6-8AN20-9.5HT30-8ST30 and reference samples KF-8ST10-8AN20-9.5HT30-8ST30 and HP555 were fitted by second-order model well (R2 = 0.995, 0.999 and 0.999). The results showed that BAP-8AN20-9.5HT30-8ST30 was the most rapid adsorbent to arrive at equilibrium, which took only 8 min with a Qe of 0.43 mmol/g.

Nitrate Removal from Waste-Water Using Silica Nanoparticles

This work presented the removal of nitrate ions in aqueous solution based on silica nanoparticles (SiNPs), which were extracted from rice husk ash. The optimal conditions for nitrate ion adsorption were studied including pH, contact time, adsorbate concentration, and amount of absorbance. The surface morphological analysis showed that the SiNPs extracted (purity of 98%) were around 50 nm with a surface area of 30 m2·g−1 and adsorption average pore width of 2.72 nm, offers possibility for high capability of nitrate ion removal. The experimental results showed that the nitrate ion capability of adsorption was obtained around 14.22 mg·g−1 with a concentration range from 0 to 25 mg·L−1 based on optimizing conditions including pH 6, contact time of 50 minutes, and SiNP dosage of 0.15 g vol−1. In addition, nitrate ion removal based on SiNPs will provide considerate benefits such as the reducing costly sample pretreatment steps, less time-consuming, and reliable methods for processing nitrate-polluted water.

Use of Raman spectroscopy to assess nitrate uptake by calcined LDH phases

Layered double hydroxides (LDHs) are natural or synthetic compounds with a layered structure that become mixed oxides of the metals that contain upon calcination at 450–700 °C. The resulting oxides have shown to be excellent solid sorbents for nitrate ions in aqueous solutions. The structure of the original LDH is recovered by rehydration as a result of the so-called “memory effect”. This process, which follows a Lagergren´s pseudo-first order kinetic model, is monitored via the NO stretching vibration band for nitrate ion at 1051 cm–1 in the Raman spectrum. The nitrate uptake is mainly governed by the temperature and the metal ratio in the initial LDH. At higher Mg/Al ratio, the nitrate adsorption rate was lower. Unlike, it was increased with the adsorption temperature with non-linear response, suggesting an endothermic process. The obtained results present Raman spectroscopy a reliable choice for monitoring nitrate uptake, overcoming to many existing alternatives in terms of accuracy and expeditiousness.

Surface modified mechanism of activated carbon fibers by thermal chemical vapor deposition and nitrate adsorption characteristics in aqueous solution

In this study, commercial activated carbon fibers (ACFs) KF1500 was modified by thermal chemical vapor deposition (CVD) method using acetonitrile and steam to adsorb nitrate ions in aqueous solution. Physical properties and surface chemical characteristics of each modified ACF were examined to reveal the surface modification mechanism of modified ACFs. Adsorption kinetics and influence of solution pH were also examined to investigate the adsorption properties. The sample of KF-8ST10-8AN20-9.5HT30-8ST30 showed maximal nitrate adsorption capacity of 0.74 mmol/g at solution pH 3, and surface area was calculated to be 1358 m2/g and 1483 m2/g by Brunauer-Emmett-Teller (BET) method and subtracting pore effect (SPE) method using αs plots, respectively. By means of modification, the quaternary N (or graphitic N) (N–Q) configuration, which is a strong site to adsorb nitrate ion, represented nearly 5 times greater value than that of KF1500. The N–Q configuration reached up to 1.86% in total elemental composition from 0.4% of KF1500. The adsorptive kinetic data of KF-8ST10-8AN20-9.5HT30-8ST30 ACFs were highly well described with pseudo-second-order (R2 = 0.998) model. The adsorption capacity of nitrate decreased rapidly with the increase of the alkalinity in nitrate solution, which indicated that hydroxyl groups rather than nitrate ions in the aqueous solution were more attractive and competitive to the N-Q and other adsorptive sites on the surface of ACFs.

Kinetics and Mechanism of Cathodic Reduction of Nitrate Ions in a Sulfuric Acid Solution

The cathodic reduction of nitrate ions in aqueous solutions of sulfuric acid in the presence of chromium(III) ions is studied via potentiometry. It is shown for the first time that nitrate ions are reduced to nitrogen in nitrate-containing solutions in the presence of chromium(III) ions.

A First-Principles Molecular Dynamics Study of the Solvation Shell Structure, Vibrational Spectra, Polarity, and Dynamics around a Nitrate Ion in Aqueous Solution.

A first-principles molecular dynamics study is presented for the structural, dynamical, vibrational, and dipolar properties of the solvation shell of a nitrate ion in deuterated water. A detailed description of the anisotropic structure of the solvation shell is presented through calculations of various structural distributions in different conical shells around the perpendicular axis of the ion. The nitrate ion-water dimer potential energies are also calculated for many different orientations of water. The average vibrational stretch frequency of OD modes in the solvation shell is found to be higher than that of other OD modes in the bulk, which signifies a weakening of hydrogen bonds in the hydration shell. A splitting of the NO stretch frequencies and an associated fast spectral diffusion of the solute are also observed in the current study. The dynamics of rotation and hydrogen bond relaxation are found to be faster in the hydration shell than that in the bulk water. The residence time of water in the hydration shell is, however, found to be rather long. The nitrate ion is found to have a dipole moment of 0.9 D in water which can be attributed to its fluctuating interactions with the surrounding water.

Nitration of pollen aeroallergens by nitrate ion in conditions simulating the liquid water phase of atmospheric particles

Pollen aeroallergens are present in atmospheric particulate matter (PM) where they can be found in coarse biological particles such as pollen grains (aerodynamic diameter dae>10μm), as well as fragments in the finest respirable particles (PM2.5; dae<2.5μm). Nitration of tyrosine residues in pollen allergenic proteins can occur in polluted air, and inhalation and deposition of these nitrated proteins in the human respiratory tract may lead to adverse health effects by enhancing the allergic response in population. Previous studies investigated protein nitration by atmospheric gaseous pollutants such as nitrogen dioxide and ozone. In this work we report, for the first time, a study on protein nitration by nitrate ion in aqueous solution, at nitrate concentrations and pH conditions simulating those occurring in the atmospheric aerosol liquid water phase. Experiments have been carried out on the Bovine serum albumin (BSA) protein and the recombinant Phleum pratense allergen (Phl p 2) both in the dark and under UV-A irradiation (range 4–90Wm−2) to take into account thermal and/or photochemical nitration processes. For the latter protein, modifications in the allergic response after treatment with nitrate solutions have been evaluated by immunoblot analyses using sera from grass-allergic patients. Experimental results in bulk solutions showed that protein nitration in the dark occurs only in dilute nitrate solutions and under very acidic conditions (pH<3 for BSA; pH<2.2 for Phl p 2), while nitration is always observed (at pH0.5–5) under UV-A irradiation, both in dilute and concentrated nitrate solutions, being significantly enhanced at the lowest pH values. In some cases, protein nitration resulted in an increase of the allergic response.

Enhancement of NO absorption in ammonium-based solution using heterogeneous Fenton reaction at low H2O2 consumption

A novel NO removal system is designed, where NO is initially oxidized by •OH radicals from the decomposition of hydrogen peroxide (H2O2) over hematite and then absorbed by ammonium-based solution. According to the high performance liquid chromatography (HPLC) profile and the isopropanol injection experiments, the •OH radicals are proved to play a critical role in NO removal. The NO removal efficiency primarily depends on H2O2 concentration, gas hourly space velocity (GHSV), H2O2 feeding rate and reaction temperature, while the flue gas temperature slightly affects the NO removal efficiency. The low H2O2 consumption makes this system a promising technique in NO removal process using wet-method. The evolution of catalyst in reaction is analyzed by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), Fourier Transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The nitrite ion and nitrate ion in aqueous solution are detected by the continuous phase flow analyzer. Finally, the macrokinetic parameters of the NO oxidation are obtained by using the initial rate method.

Effect of salting-out agents on nitric acid distribution between liquid and vapor in the course of evaporation of nitric acid radioactive waste

The database on the influence of concentrations of salting-out agents with different cation valence (Li+, Na+, K+, Cs+, NH4+, Mg2+, Ca2+, Cu2+, Zn2+, Al3+, Fe3+, La3+, Pu4+, UO22+ nitrates) and of H2SO4 on the HNO3 distribution between liquid and vapor at atmospheric pressure was verified and expanded by performing equilibrium evaporation experiments in an evaporator without reflux with circulation of the bottoms. This equilibrium can be described by the equation \(\log {\kern 1pt} {\alpha _H} = - 2.35 + 2\log \;{X_{\Sigma N{O_3}}}\) (where \({X_{\Sigma N{O_3}}}\) is the total concentration of nitrate ions in aqueous solution), taking into account partial binding of water due to hydration of the salting-out agent and apparent hydrolysis of polyvalent cations, and also incomplete dissociation of sulfuric acid. The suggested model is valid at \({X_{\Sigma N{O_3}}}\) from 3 to 16 M (azeotrope); at \({X_{\Sigma N{O_3}}}{\text{ < }}\;3\), Raoult’s law is observed (αH = const), which is confirmed by a number of examples. In this model, the additivity of the properties of the salting- out agents, taking into account the concentration of “free” water, is assumed, which allows calculation of the composition of the bottoms and distillate when evaporating waste of any composition from radiochemical plants.

Early processes in positron and positronium chemistry: possible scavenging of epithermal e+ by nitrate ion in aqueous solutions

Positron ionization slowing down, formation of the positron track, reactions of e+ with track species and its interaction with a scavenger on a subpicosecond timescale, including the process of the positronium formation process are discussed. Interpretation of the positron annihilation lifetime data on positronium formation in aqueous solutions of NO−3 anions, known as efficient scavengers of the presolvated track electrons, suggests that these ions may also capture epithermal (presolvated) positrons as well.

Vibrational relaxation of NO3−(aq)

The vibrational energy relaxation following UV excitation of nitrate ions in aqueous solution is investigated by infrared transient absorption spectroscopy. The experiments show that after their return to the electronic ground state the nitrate ions relax to the vibration ground state with a time constant of 2ps. The experimental data are compared to simulations of two relaxation scenarios in which the nitrate molecules either relax by intra-molecular vibrational redistribution or by inter-molecular energy transfer. The comparison suggests that the energy relaxation is dominated by the latter.

Formation of Nitrite- and Nitrate-Ions in Aqueous Solutions Treated with Pulsed Electric Discharges

The accumulation of nitrogen-containing ions formed in aqueous solutions dispersed in air and treated with pulsed corona, dielectric barrier and spark electric discharges, was studied dependent on electric conductivity and pH of treated solutions. The impact of conductivity to the spark and corona discharge is determined by the increased ohmic losses in the reactor. In contrast, the character of dielectric barrier discharge is significantly changed with growing conductivity resulted in increased nitrite-to-nitrate ratio. In alkaline solutions the production of nitrites is increased for the spark and the barrier discharge; the corona discharge produce only nitrates. The amount of nitrates produced in pulsed corona discharge at energy doses characteristic for potable water treatment is about 100 times lower than their maximum permissible concentration.

Platinum(IV) complexation with the nitrate ion in aqueous solutions according to 195Pt, 15N, 14N, and 17O NMR data

Solutions of platinum(IV) nitrate were studied by 195Pt, 15N, 14N, and 17O NMR and IR and Raman spectroscopy. It was found that in nitric acid, two interrelated systems of nitrate complexes, mono- and polynuclear ones, coexist. The complexes predominating in concentrated solutions are [Pt2(μ-OH)(μ-NO3)(NO3)2(H2O)6 − x(OH)x](4 − x)+, [Pt4(μ-OH)3(μ-NO3)3(NO3)3(H2O)9 − x(OH)x](7 − x)+, [Pt4(μ-OH)4(μ-NO3)2(NO3)4(H2O)8 − x(OH)x](6 − x)+, and [Pt4(μ-OH)6(NO3)3(H2O)16 − x(OH)x](7 − x)+.

Experimental investigation of the chemical reduction of nitrate ion in aqueous solution by Mg/Cu bimetallic particles

Bimetallic particles have recently been used as a new means of contaminant reduction from water. Comparing with Fe0 and Mg0 alone, synthesized magnesium/copper (Mg/Cu) bimetallic particles have been determined to be potential and efficient agents for nitrate reduction from aqueous solutions. This study suggests that the reductive denitrification of nitrate by Mg/Cu bimetallic particles was dependent on a number of parameters including reductant dose, solution temperature, initial nitrate concentration and contact time. The 1% Mg/Cu (Cu loading of 1 wt.%) bimetallic particles removed the majority of the various nitrate concentrations tested (50, 100, 150, 200 and 300 mg/L) within a short period. The time required for the removal of 90.6% of the NO3 − from a 100-mg/L solution was about 20 min using 2 g/L bimetallic Mg/Cu at an initial solution pH of 6. The activation energy (E a) for the nitrate reduction by 1% Mg/Cu over the temperature range of 5–60 °C was 12.77 kJ/mol. The experimental results of the kinetic analysis from batch studies indicated that a higher initial nitrate concentration yielded a greater reaction rate constant and the denitrification rate increased with increasing 1% Mg/Cu dosage. The effects of mixing rate on the denitrification rate suggested that the reaction rate increases linearly at mixing rate <100 rpm and remained almost constant at rates over that.

Nitrate-selective membrane electrode based on bis(2-hydroxyanil)acetylacetone lead(II) neutral carrier.

A nitrate-selective electrode based on a recently synthesized bis(2-hydroxyanil)acetylacetone lead(II) complex [(haacac)Pb] has been developed. Among different compositions studied, a membrane containing 30.7% poly(vinyl chloride) (PVC), 61.3% dibutyl phthalate (DBP) as a plasticizer, 3% methyltrioctylammonium chloride (MTOAC) as a cationic additive and 5% ionophore (all w/w) exhibited the best potentiometric response toward nitrate ion in aqueous solutions. The potentiometric response of the electrode was linear with a Nernstian slope of -58.8 mV decade(-1) within the NO3- concentration range of 2 x 10(-5)-1 x 10(-1) mol dm(-3). The response time of the electrode was < or =10 s over the entire linear concentration range of the calibration plot. The electrode is suitable for use within the pH range of 5.3-11. The selectivity coefficients for the proposed electrode were improved for some interferences, when compared with those of commercially available nitrate-selective electrodes.

Pharmaceuticals in STP effluents and their solar photodegradation in aquatic environment

The presence of pharmaceutical compounds in surface waters is an emerging environmental issue. Sewage treatment plants (STPs) are recognized as being the main point discharge sources of these substances to the environment. A monitoring campaign of STP effluents was carried out in four European countries (Italy, France, Greece and Sweden). More than 20 individual pharmaceuticals belonging to different therapeutic classes were found. For six selected pharmaceuticals (carbamazepine, diclofenac, clofibric acid, ofloxacin, sulfamethoxazole and propranolol) present in the STP effluents, the persistence towards abiotic photodegradation was evaluated submitting them to solar experiments at 40° N latitude during spring and summer. Based on experimentally measured quantum yields for the direct photolysis in bi-distilled water, half-life times ( t 1/2) at varying seasons and latitude were predicted for each substance. In salt- and organic-free (bi-distilled) water carbamazepine and clofibric acid are characterized by calculated half-life times of the order of 100 days at the highest latitudes (50° N) in winter, whereas under the same conditions sulphamethoxazole, diclofenac, ofloxacin and propranolol undergo fast degradation with t 1/2 respectively of 2.4, 5.0, 10.6 and 16.8 days. For almost all studied compounds, except propranolol the presence of nitrate ions in aqueous solutions results in a reduction of t 1/2. When present, humic acids act as inner filters towards carbamazepine and diclofenac, and as photosensitizers towards sulphamethoxazole, clofibric acid, oflaxocin and propranolol.

Effect of dissolved oxygen on the radiolytic conversion of nitrate ions in aqueous solutions in the presence of formate

A dose higher than 2 kGy and a tenfold excess of formate over nitrate are required for the almost complete degradation of ~10–4 mol dm–3 nitrate in an aerated aqueous solution.