Aqueous Sodium Nitrate Solutions Research Articles

Adsorptive removal of a nitrate ion from the aqueous solution of sodium nitrate by application of double fixed-bed column

This study focuses on the removal of nitrate ions from aqueous solutions using rice husk activated carbon (RHAC). The RHAC was subjected to characterization via Fourier transform infrared (FTIR), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), and X-ray florescence (XRF) to ascertain its functional groups, surface morphology, and oxide/elemental composition, respectively. Batch experiments were conducted to assess the impact of nitrate concentration, bed height, and number of packing layers on removal efficiency. FTIR spectra revealed favorable sorption-related functional groups within RHAC, while SEM analysis indicated the presence of effective sorption sites on its surface. EDS analysis of the rice husk adsorbent before adsorption (RHBS) demonstrated a significant composition of Si (42.20%), O (35.30%), and Ca (12.33%). The batch study unveiled a concentration-dependent decrease in nitrate removal efficiency, alongside the enhanced performance with increased bed height and number of packing layers. Kinetic data fitting favored the Yoon–Nelson and Adams–Bohart models. Overall, RHAC exhibited efficient nitrate ion removal, with column performance notably improved by utilizing multiple packing layers. These results will enhance our understanding of the mechanisms involved in removing nitrate ions and highlight the potential effectiveness of RHAC, especially when utilized with multiple packing arrangements in column setups.

Exclusion liquid chromatography of carboxymethylchitin and carboxymethylchitosan from crustacean <i>Artemia Parthenogenetica</i> of the Aral Sea

The article deals with the synthesis of water-soluble derivatives of chitin and chitosan from cysts of crustaceans of the genus Artemia Parthenogenetica of the Aral Sea by carboxymethylation of OH and NH2 groups of their chains. The elution, viscosity and polyelectrolyte properties in size exclusion liquid chromatography of carboxymethylchitin and carboxymethylchitosan were studied. The suppression of electrostatic effects and the implementation of the exclusion mechanism for the separation of these polysaccharides were achieved by using an aqueous solution of sodium nitrate with a concentration of 0.1 mol/l as an eluent, which was recommended for determining molecular weight characteristics.

Particle Network Self-Assembly of Similar Size Sub-Micron Calcium Alginate and Polystyrene Particles Atop Glass.

Particle-mediated self-assembly, such as nanocomposites, microstructure formation in materials, and core-shell coating of biological particles, offers precise control over the properties of biological materials for applications in drug delivery, tissue engineering, and biosensing. The assembly of similar-sized calcium alginate (CAG) and polystyrene sub-micron particles is studied in an aqueous sodium nitrate solution as a model for particle-mediated self-assembly of biological and synthetic mixed particle species. The objective is to reinforce biological matrices by incorporating synthetic particles to form hybrid particulate networks with tailored properties. By varying the ionic strength of the suspension, the authorsalter the energy barriers for particle attachment to each other and to a glass substrate that result from colloidal surface forces. The particles do not show monotonic adsorption trend to glass with ionic strength. Hence, apart from DLVO theory-van der Waals and electrostatic interactions-the authors further consider solvation and bridging interactions in the analysis of the particulate adsorption-coagulation system. CAG particles, which support lower energy barriers to attachment relative to their counterpart polystyrene particles, accumulate as dense aggregates on the glass substrate. Polystyrene particles adsorb simultaneously as detached particles. At high electrolyte concentrations, where electrostatic repulsion is largely screened, the mixture of particles covers most of the glass substrate; the CAG particles form a continuous network throughout the glass substrate with pockets of polystyrene particles. The particulate structure is correlated with the adjustable energy barriers for particle attachment in thesuspension.

Gamma Radiation-Induced Degradation of Acetohydroxamic Acid (AHA) in Aqueous Nitrate and Nitric Acid Solutions Evaluated by Multiscale Modelling.

Acetohydroxamic acid (AHA) has been proposed for inclusion in advanced, single-cycle, used nuclear fuel reprocessing solvent systems for the reduction and complexation of plutonium and neptunium ions. For this application, a detailed description of the fundamental degradation of AHA in dilute aqueous nitric acid is required. To this end, we present a comprehensive, multiscale computer model for the coupled radiolytic and hydrolytic degradation of AHA in aqueous sodium nitrate and nitric acid solutions. Rate coefficients for the reactions of AHA and hydroxylamine (HA) with the oxidizing nitrate radical were measured for the first time using electron pulse radiolysis and used as inputs for the kinetic model. The computer model results are validated by comparison to experimental data from steady-state gamma ray irradiations, for which the agreement is excellent. The presented model accurately predicts the yields of the major degradation products of AHA: acetic acid, HA, nitrous oxide, and molecular hydrogen.

Study on ionic association behavior in sodium nitrate solution

Raman spectroscopy combined with component analysis and molecular dynamics simulation were used to study chemical species and their transformation in aqueous sodium solutions. Study shows that the characteristic vibrational frequency of nitrate ions (ν1-NO3-) blue-shifted from 1043.9 to 1046.9 cm−1, and the full width at half maximum increased from 6.8 to 10.8 cm−1 as the concentration increasing. When water/salt molar ratio (WSR) > 30, the relative concentration (RC) of free hydrated ions and solvent shared ion pair accounts for the vast majority, and there is almost no contact ion pair in solution. When WSR less than 30, due to the continuous reduction of the number of water molecules, the hydrated water molecules around the sodium ions and nitrate ions begin to decrease, and solvent shared ion pair or contact ion pair gradually forms. Sodium ions and nitrate ions mainly exist in a monodentate coordination. When WSR > 160, both the relative concentration of contact ion pair and complex structure is close to 0. This work proves that a lower RC of complex structure in solution, a smaller supersaturation of the solution is achieved, meaning aqueous sodium nitrate solution is easier to nucleate crystals.

On altering the wetting behaviour and corrosion resistance of a large metallic surface area by wire electrochemical texturing

This paper presents a novel and practically applicable method for a quick fabrication of uniform surface patterns (periodic micro-pillars with rectangular and square cross-section) on a large surface area of any conducting or semi-conducting material using Wire Electrochemical Micromachining (Wire-ECMM). Micro pillars with a rectangular cross-section are generated by machining mutually perpendicular micro channels. The depth, spacing, and cross-sectional area of pillars are controlled by varying the process parameters and tool travel distance. Primary pillars (level-1 texture) are machined with a constant Direct Current (DC) voltage and secondary pillars (level-2 texture) are machined with a pulsed DC voltage using a tungsten wire of diameter 100 μm. An aqueous solution of sodium nitrate (NaNO 3 ) is selected as an electrolyte having a pH of about 7.01. A good repeatability in the geometrical parameters of a pillar profile is observed on analysing 3D profilometer micrographs of the textured surfaces. Wetting behaviour of textured surfaces with different geometrical parameters is observed using drop shape analyser. A surface with two levels of textures offers highest contact angle of 147.3° with deionized water. Corrosion current and resistance of the textured surfaces are obtained using Linear Sweep Voltammetry (LSV) and Electrochemical Impedance Spectroscopy (EIS), respectively. Results suggest that corrosion resistance depends upon the area of texture and is highest for the sample with the largest textured area. Also, a sample with the smallest value of area factor (ratio of total area of the top surface of all the pillars in a region to the total projected area of a region) offers highest resistance to corrosion. • A novel approach for large area texturing on any conducting and semi-conducting surface using Wire Electrochemical Micromachining (Wire-ECMM). • A study of the influence of different process parameters on various geometrical features of a textured surface. • A detailed characterization of different textured surfaces using SEM imaging and surface topography. • In depth analysis of the wetting and corrosion behaviour of the textured surfaces using drop shape analyser and Electrochemical Impedance Spectroscopy (EIS).

Determination of bioactive properties of protein and pigments obtained from Spirulina platensis

Microalgae have a great potential for usage in functional foods or ingredients. The amount of the pigments obtained with different solvents from Spirulina platensis and their antioxidant activities, Angiotensin Converting Enzyme (ACE) inhibition of S. platensis and dried phycocyanin powder were investigated. The highest Chlorophyll-a and phycocyanin pigment contents were 9.26 mg chlorophyll-a/g dry spirulina and 78.57 mg phycocyanin/g dry spirulina using sequentially extraction, respectively. It was found that Chlorophyll extracts have higher antioxidant activity (14.62–16.19 mg FeSO4·7H2O/g dry spirulina) than phycocyanin extracts (10.87–12.34 mg FeSO4·7H2O/g dry spirulina). Single extraction was preferred due to increased pigment concentration and antioxidant activity. The percent ACE inhibition values of 10% S. platensis powder and phycocyanin powder suspensions were found as 92.40% and 89.50%, respectively. The necessary protein concentration of S. platensis and phycocyanin powder samples to inhibit 50% of the ACE activity (IC50 values) were 2.93 and 3.96 mg protein/ml, respectively. It was concluded that S. platensis suspension could be more effective than the pure phycocyanin on ACE inhibition. Practical applications Microalgae itself can be considered as functional food or food ingredient because of the bioactive contents such as polyunsaturated fatty acids, sterols, pigments, proteins and enzymes, vitamins, and other bioactive substances. In this study, the quantities and the antioxidant activities of phycocyanin and chlorophyll-a pigments obtained from Spirulina platensis by sequential extraction of methanol and aqueous sodium nitrate solutions were determined. Also, protein contents and ACE inhibition of residual protein rich fraction were determined after the pigment extraction. The results showed that pigment fractions and residual protein content after pigment extraction have antioxidative and antihypertensive health promoting potential.

Suppression of self-induced thermal lensing in stimulated Raman scattering of liquids

Stimulated Raman scattering (SRS), due to the interaction of intense laser beams with Raman active media, provides an effective operational mode for frequency conversion, downgraded (primarily in liquids) by self-induced thermal lensing (TL). Here, a unique setup, including a pump laser beam [green (532 nm), 10 Hz, 5 ns] passing through a rotating cell, filled with a saturated aqueous solution of sodium nitrate ( N a N O 3 ) was tested, for conversion to a yellow (564 nm) beam. This distinct geometry allowed each pump pulse to pass through a “fresh” solution, practically eliminating TL. A sharp enhancement in SRS generation ( ∼ 20 % ) and observation of unexpanded beams’ cross sections at the cell exit verified TL removal. The results and the obtained physical insight from the N a N O 3 model system point to the promise of this approach for suppression of impeding TL in frequency conversion by SRS in liquids.

Implications of thermal lensing and four-wave mixing on stimulated Raman scattering in an aqueous solution of sodium nitrate

Stimulated Raman scattering (SRS) is an effective technique for imaging, spectroscopy and for frequency conversion of lasers in all states of matter. Yet, controlling SRS frequency conversion efficacy is a great challenge, due to ensuing competing scattering processes and laser-induced thermal lensing (TL). Here, we focus on both SRS and the associated processes occurring during frequency conversion in an aqueous solution of sodium nitrate. It is demonstrated that SRS efficiently converts 532 nm nanosecond laser pulses, via a single pass through the solution. In this light-matter interaction, SRS along with four-wave mixing (FWM) converted the pump beam to collinear beams of the 1st [yellow (564 nm)] and 2nd [orange (599 nm)] Stokes of the NO3− ion symmetric stretch. The experimental results were well reproduced by a newly developed numerical model. Based on the experimental and numerical results, it was found that the 1st Stokes is generated through SRS of the pump laser, while the onset and growth of the 2nd Stokes were obtained through FWM. The results also reveal the significant role played by SRS induced TL, growing over many laser pulses, suggesting its substantial contribution and importance.

Drying kinetics and nucleation in evaporating sodium nitrate aerosols.

A quantitative understanding of the evaporative drying kinetics and nucleation rates of aqueous based aerosol droplets is important for a wide range of applications, from atmospheric aerosols to industrial processes such as spray drying. Here, we introduce a numerical model for interpreting measurements of the evaporation rate and phase change of drying free droplets made using a single particle approach. We explore the evaporation of aqueous sodium chloride and sodium nitrate solution droplets. Although the chloride salt is observed to reproducibly crystallize at all drying rates, the nitrate salt solution can lose virtually all of its water content without crystallizing. The latter phenomenon has implications for our understanding of the competition between the drying rate and nucleation kinetics in these two systems. The nucleation model is used in combination with the measurements of crystallization events to infer nucleation rates at varying equilibrium state points, showing that classical nucleation theory provides a good description of the crystallization of the chloride salt but not the nitrate salt solution droplets. The reasons for this difference are considered.

Enhancing Double-Beam Laser Tweezers Raman Spectroscopy (LTRS) for the Photochemical Study of Individual Airborne Microdroplets.

A new device and methodology for vertically coupling confocal Raman microscopy with optical tweezers for the in situ physico- and photochemical studies of individual microdroplets (Ø ≤ 10 µm) levitated in air is presented. The coupling expands the spectrum of studies performed with individual particles using laser tweezers Raman spectroscopy (LTRS) to photochemical processes and spatially resolved Raman microspectroscopy on airborne aerosols. This is the first study to demonstrate photochemical studies and Raman mapping on optically levitated droplets. By using this configuration, photochemical reactions in aerosols of atmospheric interest can be studied on a laboratory scale under realistic conditions of gas-phase composition and relative humidity. Likewise, the distribution of photoproducts within the drop can also be observed with this setup. The applicability of the coupling system was tested by studying the photochemical behavior of microdroplets (5 µm < Ø < 8 µm) containing an aqueous solution of sodium nitrate levitated in air and exposed to narrowed UV radiation (254 ± 25 nm). Photolysis of the levitated NaNO3 microdroplets presented photochemical kinetic differences in comparison with larger NaNO3 droplets (40 µm < Ø < 80 µm), previously photolyzed using acoustic traps, and heterogeneity in the distribution of the photoproducts within the drop.

Electrolytic Effect on the Solubility and Solvation Thermodynamics of l-Serine and l-Isoleucine in Aqueous Media

By the analytical gravimetric technique, the equilibrium saturated solubilities of l-serine and l-isoleucine in aqueous solutions of sodium nitrate (NaNO3) and potassium nitrate (KNO3) were measure...

Thermodynamic Properties of Aqueous Sodium Nitrate Solutions Under Superambient Conditions

Use has been made of the Pitzer ion-interaction or virial coefficient approach to estimate the pressure dependence of the osmotic and activity coefficients of aqueous solutions of sodium nitrate (NaNO3) up to 423.15 K and 6.0 mol·kg−1 using published volumetric data on NaNO3(aq). In particular, volumetric Pitzer ion-interaction parameters have been evaluated from a mathematical fit of published apparent molar volume data with the appropriate Pitzer equation. The Pitzer parameters were then fitted as a function of temperature and pressure. These results were then used to calculate the change in the osmotic and activity coefficients in going from the state of an initial pressure p1 to one of a final pressure p2. These pressure dependences have been combined with the osmotic and activity coefficient values of NaNO3(aq) at 0.1 MPa or vapor-saturation pressures (psat) obtained from the model of Archer to yield a comprehensive set of thermodynamic parameters for NaNO3(aq) at temperatures from 293.15 K through 423.15 K, at pressures of (5, 10, 15, 20) MPa, and molalities to 6.0 mol·kg−1.

Viscometric, thermodynamic and theoretical DFT studies of dl-2-aminobutyric acid in aqueous sodium nitrate solutions at different temperatures

The dynamic viscosities of six pseudobinary systems consisting of dl-2-aminobutyric acid + pseudo-unary solvent (aqueous sodium nitrate solutions) were determined, in the temperature range of 283.15–318.15 K, each 5 K under pressure of 101.1 kPa, using a microviscometer automatic Anton Paar (AMVn). Absolute viscosities, relative viscosities, solvation numbers, viscosity coefficients A and B, the slope (dB/dT), activation free energy per mole of solute, the enthalpy of partial molar activation, and zwitterionic partial molar activation entropy were calculated at infinitesimal concentration. Also, the intermolecular structures and interactions of several water-sodium nitrate-dl-2-aminobutyric acid molecular complexes were theoretically modeled from DFT electronic calculations by using the B3LYP/6-31G(d) chemical model. It was found that the forces between zwitterion-pseudo-unary solvent species dominate the viscosimetric behavior of the six systems studied at all concentrations and temperatures. We also analyzed the activation parameters of the viscous flow with respect to the solute, and it was found that the zwitterion is more ordered in the transition state at the expense of a process of viscous endothermic flow and by predominance of zwitterion-solvent interactions.

Kinetics and Mechanism of Silver Dissolution in Aqueous Sodium Nitrate

The kinetics of the electrochemical oxidation–reduction of silver in aqueous solutions of sodium nitrate was studied by potentiometry. The effect of the electrolyte concentration and temperature and sweep rate on the electrochemical behavior of silver was studied. To characterize the mechanism of silver electrooxidation, the following kinetic parameters were calculated: ion transport number (αn), diffusion coefficient (D), heterogeneous rate constant of the electrode process (Ks), and effective activation energy of the process (Eef). The data obtained may be of interest to specialists in the field of electrochemistry.

Dielectric measurement of low-concentration aqueous solutions: assessment of uncertainty and ion-specific responses

Excessive amounts of chemicals and ions flowing into water sources cause serious environmental and human-health related concerns. The lack of affordable and real-time monitoring systems for these contaminants limits effective conservation and management strategies. To establish a basis for developing an effective, fast, real-time, and affordable sensing system, a dielectric spectroscopy method has been employed to characterize aqueous solutions of sodium chloride (NaCl), sodium nitrate (NaNO3), and sodium sulphate (Na2SO4) at environmentally-relevant (low) concentrations. Dielectric spectra were measured over a frequency range of 200 MHz to 20 GHz, at a temperature of 25.00 °C ± 0.01 °C and for concentrations 0–20 mmol l−1. The measured spectra were fitted with a Debye model using a non-linear, weighted, least-squares analysis. A method of judiciously exploiting the resulting fitting parameters is proposed, that allows the concentration and type of ions to be uniquely determined. Uncertainties due to random and systematic errors that contribute to the measured dielectric spectra and become critical in the context of low concentration aqueous solutions have been assessed. Furthermore, two methods of calculating associated uncertainties of the indicator parameters, viz. covariance matrix and Monte Carlo methods have been performed. The results show the numerical approach taken by a Monte Carlo method, while yielding the same estimates, reduces the tediousness accompanied by the analytical covariance matrix method.

Synthesis and crystal structure of N,N-dimethylformamide solvate of thiocyanuric acid

Considerable attention has been paid recently to crystal engineering; which involves the design and preparation of new crystalline molecular solids with desired properties [1–4]. Crystalline materials with specific properties find applications in petrochemical industry for separation and purification. Moreover, crystal engineering provides products designed for manufacturing catalysts and high-valued chemicals for specific purposes. Recently, crystalline materials find application in pharmaceutical, food and microelectronic industries [5]. The main two strategies that are used for crystal engineering are based on hydrogen bonding and coordination bonding [6]. Since the hydrogen bonding is usually stronger and more directional than the other methods, more new crystal materials have been prepared based on this method. We are here able to design crystalline materials based on hydrogen bonding and study their solid state structures. N, N-dimethylformamide (DMF)-solvate of thiocyanuric acid (TCUA) and dimethyl sulfoxide (DMSO)-solvate of thiocyanuric acid (TCUA) were successfully prepared at room temperature in the presence of aqueous solution of sodium nitrate (NaNO3). To the best of our knowledge, this study presents the easy, modest, and rapid method to prepare co-crystal formation based on thiocyanuric acid (TCUA) and solvent-containing hydrogen bonding functionality. In this paper, we present the most effective method to synthesize the co-crystals of (TCUA), and as evidence, the crystal structure of (TCUA) in DMF is fully studied and presented in this paper. The N,N-dimethylformamide (DMF)-solvate of thiocyanuric acid (TCUA) was successfully prepared at room temperature, and was characterized spectroscopically by nuclear magnetic resonance (NMR) and single-crystal X-ray diffraction (SXRD). The asymmetric unit of the title compound contains one molecule of thiocyanuric acid (TCUA) features an almost planar six-membered ring having exocyclic C-S thione double bonds and one molecule of N,N-dimethylformamide (DMF). It was crystallized in the monoclinic, P21/c with unit cell parameters of a = 9.6255 (4) Å, b = 12.6864 (5) Å, c = 9.1367 (4) Å, β = 90.095 (2)°, V = 1115.71 (8) Å3, Z = 4. The structure is composed of 1-D TCUA ribbons formed via N–H–S hydrogen bonds. The ribbons are separated by DMF molecules, which are bridged to the ribbons by N–H–O hydrogen bonds. The ribbons and their DMF molecules form 2-D sheets which are in turn π-stacked to build up a layered, 3-D structure. The proton and carbon-13 NMR studies confirmed the formation of such solvate between DMF and TCUA.

Effect of temperature on compressibility properties of 0.1, 0.5 and 1.0 molal solutions of alkali metal nitrates. Part 2. Aqueous solutions of lithium nitrate, sodium nitrate and potassium nitrate in the 278.15 K to 353.15 K temperature range

Sound velocities in aqueous solutions of LiNO3, NaNO3 and KNO3 were measured at 1K intervals from T=(278.15 to 353.15)K, in the 0.1mol·kg−1 0.5mol·kg−1 and 1.0mol·kg−1 solutions. Determined sound velocities and densities served to determine the isentropic and isothermal compressibilities, the apparent molar compressibilities, the apparent molar volumes, the isochoric thermal pressure coefficients, cubic expansion coefficients, changes of heat capacities with volume and with pressure, and the hydration numbers. In addition were evaluated the ultrasonic relaxation times and corresponding thermodynamic functions of the activation of the viscous process. Determined parameters are qualitatively correlated with changes in the structure of water when alkali metal nitrates are dissolved in it.

COMPORTAMIENTO VOLUMÉTRICO DE LA DL-VALINA EN SOLUCIONES ACUOSAS DE NITRATO DE SODIO A DIFERENTES TEMPERATURAS

Densities of DL-valine (2-amino-3-methylbutanoic acid) in aqueous solutions of sodium nitrate were determined at temperatures ranging from 283.15 to 318.15 K using an Anton Paar DMA 5000 vibrating tube densitometer. The apparent molar volume, infinite dilution apparent molar volume, second derivative of the infinite dilution partial molar volume with respect to temperature, partial molar volume of transfer at infinite dilution and the number of hydration were calculated. The results obtained were discussed in terms of the dominant interactions in solution, it was found that the DL-valine has a disruptor effect in the structure of the solvent and that at infinite dilution solute-solvent interactions are dominant between isopropyl group the amino acid and sodium and nitrate ions.

Insights into electrochemical behavior and anodic oxidation processing of graphite matrix in aqueous solutions of sodium nitrate

The electrochemical oxidation of graphite matrix from the simulative fuel elements for high-temperature gas-cooled reactor was investigated experimentally using NaNO3 solution as an electrolyte. The intercalation and oxidation reactions of graphite were investigated by means of cyclic voltammetry. In addition, the morphological changes of the graphite anodes at predetermined intervals of time during the electro-oxidation process were examined by scanning electron microscopy. The structural transformation of graphite was systematically characterized by different methods. Results showed that the electro-oxidation process induced oxygen-containing groups (i.e., hydroxyl, epoxide, carbonyl/ketone, and carboxyl groups) into the graphite backbone. Electrolytic graphite oxide presented a heterogeneous, indeterminate, and disordered system composed of crystalline and amorphous phases. The structure and microstructure of nuclear graphite, particularly its cracks and defects, primarily determined its destruction pathway during the electrolytic process. The mechanism of graphite lattice destruction could be attributed to the complicated interplay of water electrolysis, anionic intercalation, and gas evolution. The mechanical force caused by gas eruptions among the graphite lattice is the most important and essential factor favoring disintegration.