Aqueous Solutions Of NaNO3 Research Articles

Effects of concentration and temperature on molar volumes of L-serine, L-isoleucine, and L-glutamine in aqueous NaCl and NaNO3 solutions

Densities of L-serine, L-isoleucine, L-glutamine in 1.5 mol kg−1 aqueous NaCl, and NaNO3 solutions have been measured for several molal concentrations of amino acids at temperatures from 298.15 to 323.15 K. The partial molar volumes (ϕv0) of L-serine, L-isoleucine, and L-glutamine in 1.5 mol kg−1 aqueous NaCl/NaNO3 solutions have been computed using density data. The transfer partial molar volumes (Δtrϕv0) of L-serine, L-isoleucine, and L-glutamine from water to 1.5 mol kg−1 aqueous NaCl/1.5 mol kg−1 aqueous NaNO3 solutions have been determined at 298.15 K. The trends of variation of ϕv0 and Δtrϕv0 with change in temperature have been discussed in terms of ion-ion, ion-hydrophilic, and ion-hydrophobic interactions operative in solutions.

Fast sodiation/desodiation reactions of electrochemically delithiated olivine LiFePO4 in aerated aqueous NaNO3 solution

By potentiodynamic polarization in saturated aqueous NaNO3 solution, the composite LiFePO4/C was transformed completely to NaFePO4/C composite. The voltammograms of sodiated olivine were successfully recorded at the rate for two order of magnitude higher than reported for the same material in organic electrolyte. A high storage capacity amounting to 118 mAh g−1 at a scan rate of 10 mV s−1 was measured. The diffusion coefficients have been calculated via cyclic voltammetry and faster diffusion of sodium in comparison to lithium was found. This finding was confirmed also with the impedance measurements. The presence of dissolved oxygen in the electrolyte did not disturb the electrochemical behaviour of this composite material.

Preparation and electrochemical properties of polyaniline/α-RuCl3 .x H2 O composites for supercapacitor

Polyaniline/α-RuCl3.xH2O composites were successfully synthesized by an in-situ chemical polymerization and employed as new electrode materials in supercapacitors. The synthesized composites were characterized physically by scanning electronic microscope (SEM). The electrochemical capacitance performance of these composites was investigated by cyclic voltammetry, galvanostatic charge–discharge tests and AC impedance spectroscopy with a three-electrode system in 1 mol l−1 NaNO3 aqueous solution electrolyte. The polyaniline/α-RuCl3.xH2O composites electrodes showed much higher specific capacitance, better power characteristics and were more promising for application in capacitor than pure polyaniline electrode. The effect and role of α-RuCl3.xH2O in the composite electrode were also discussed in detail. POLYM. COMPOS., 34:2142–2147, 2013. © 2013 Society of Plastics Engineers

Rapid carbon activation via microwave irradiation of nongraphitic carbon doped with metallic potassium and tetrahydrofuran (THF)

We report here a rapid process to synthesize microporous carbon from nongraphitic carbon source through microwave-assisted exfoliation in a non-inert environment. A ternary compound of potassium-nongraphitic carbon-tetrahydrofuran (THF) was prepared and then heating by microwave irradiation for 2 min widens the interstices between adjacent graphene layers in ternary compound, inducing microporous texture with a large amount of ultramicropores. Exploiting microwave heating allows for efficient and rapid synthesis of activated carbon compared with commonly used chemical activation process. After microwave irradiation on nongraphitic carbon, the constituent stacked graphene layers were broken and the specific surface area of 563 m2 g−1 was developed. The feasibility of an electrode material for supercapacitor was estimated by cyclic voltammetry and galvanostatic charge/discharge cycling. The specific areal capacitance reveals as high as 16.4 μF cm−2 in 1 M NaNO3 aqueous solution, which is significantly larger than values found in traditional activated carbons made for use in electrochemical double layer capacitors. Without restrictive processing conditions of chemical activation, microporous structure carbon can be efficiently and rapidly synthesized via microwave irradiation for possible electrochemical capacitor electrode.

Enhancement of Hydrolysis through the Formation of Mixed Heterometal Species: Al3+/CH3Sn3+ Mixtures

The hydrolysis of mixed-metal cations (Al3+/CH3Sn3+) was studied in aqueous solutions of NaNO3, at I = 1.00 ± 0.05 mol·dm–3 and T = 298.15 K, by potentiometric technique. Several hydrolytic mixed species are formed in this mixed system, namely, Alp(CH3Sn)q(OH)r with (p, q, r) = (1, 1, 4), (1, 1, 5), (1, 1, 6), (2, 1, 4), (1, 2, 5), (1, 4, 11), (1, 3, 8), and (7, 6, 32). The stability of these species, expressed by the equilibrium: pAl3+ + qCH3Sn3+ + rOH– = Alp(CH3Sn)q(OH)r3(p+q)–r, βpqrOH, can be modeled by the empirical relationship: log βpqrOH = −3.34 + 2.67p + 9.23(q + r). By using the equilibrium constant Xpqr relative to the formation reaction: pAl(p+q)(OH)r + q(CH3Sn)(p+q)(OH)r = (p + q)Alp(CH3Sn)q(OH)r, it was found that the formation of heterometal mixed species is thermodynamically favored, and the extra stability can be expressed as a function of the difference in the stability of parent homometal species. This leads, in turn, to a significant enhancement of hydrolysis and solubility.

Verification of Solvation Theory of Dilute to Concentrated Solutions of Some Strong 1–1 Electrolytes

Density, ultrasonic velocity and isobaric heat capacity data have been used to study solvation parameters of aqueous solutions of NaCl, NaNO3, and KI. Using correct thermodynamic relations, quantitative solvation parameters have been determined at temperatures from 278.15 to 323.15 K: the hydration numbers h, the molar isentropic compressibilities of the solvation complexes $$ \beta_{S,h} V_{h} , $$ the volume V 1h , the coefficient of isentropic compressibility β 1h of water in the solvation shells of ions, and others. It has been shown that h is independent of the temperature in the range of the investigated conditions, $$ \beta_{S,h} V_{h} $$ is dependent both on the temperature and concentration, whereas the electrostriction compression in the vicinity of ions has a greater effect on its structure than that due to the mere change of pressure.

Influence of ECM Pulse Conditions on WC Alloy Micro-Pin Fabrication

M icro-pins with a large aspect ratio are required for micro tools and micro parts. We have proposed to use a neutral and less harmful electrolyte, NaNO3 aqueous solution to fabricate tungsten-carbide (WC) alloy micro-pins with ECM. The workpiece rotation and ultrasonic flushing were adopted during processing in order to obtain a higher machining accuracy and removal rate. However, it was found that oxidized substances adhered to the pin surface, which decreased the removal rate and machining accuracy. In order to reduce the oxidized substance adhesion to the WC alloy surface under the NaNO3 aqueous solution condition, bipolar pulses was then used, since it has been reported that a negative current has the effect to generate NaOH which can dissolve the oxide. Experiments were carried out by changing the pulse condition to investigate the influence of the positive and negative pulse width on the machining characteristics. The results show that a micro-pin with the diameter about 20μm was obtained in a very short time of 2.5min. It is also found that using the bipolar pulse power supply is an effective way to reduce the adhesion of oxidized substances to the pin surface, and there exists an optimized pulse period for the micro-pin fabrication.

ChemInform Abstract: Novel Blue‐Emitting NaxCa1‐xAl2‐xSi2+xO8 :Eu2+ (x = 0.34) Phosphor with High Luminescent Efficiency for UV‐Pumped Light‐Emitting Diodes.

AbstractThe new blue‐emitting phosphor Na0.34Ca0.66Al1.66Si2.34 O8:Eu2+ (I) is synthesized by addition of an EtOH solution of Si(OEt)4 to an aqueous solution of NaNO3, EuCl2, Ca(NO3)2, and Al(NO3)3 followed by solvent evaporation (120 °C, 24 h) and firing of the dry powder in a 5%H2/N2 atmosphere (1400 °C, 3 h).

Impact of metallic ions on electrohydrodynamics of soft colloidal polysaccharides

Electrostatic and hydrodynamic properties of carboxymethyldextran (CMD), a charged and well-defined polysaccharide, were evaluated in the presence and in the absence of divalent cations (calcium and cadmium) in aqueous NaNO3 solution. For that purpose, size, electrophoretic mobility and protolytic features of CMD macromolecules were derived from dynamic light scattering, electrophoresis and proton titration measurements. Electrokinetic properties evaluated in the absence of metal ions clearly reflect the permeable nature of CMD particles to ions and water. Size measurements further reveal CMD swelling with decreasing solution ionic strength. Binding of divalent ions with CMD was examined by measuring adsorption isotherm and protolytic titrations under conditions where particle charge is entirely screened. Results evidenced that complexation is the main mechanism underlying the interaction of Cd2+ and Ca2+ with CMD colloidal ligand. Finally, we investigated the effect of such metal ions on the intertwined conformational and electrostatic properties of CMD macromolecule. At high electrolyte background concentration where electrostatic effects are minimized, the presence of metal ions leads to a slight shrinking of the coiled macromolecules. This collapse of the CMD structure is accompanied by an increase in volume charge density and a decrease in particle permeability, as found from analysis of the decrease of CMD electrophoretic mobility in the presence of divalent ions. This result points out a structural modification and stiffening of CMD polymer segments following complexation of metal ions with CMD carboxylic reactive sites.

Electrochemical machining of tungsten carbide alloy micro-pin with NaNO3 solution

In this study, the fabrication of micro-pins made of tungsten carbide (WC) alloy with the electrochemical machining (ECM) using a neutral electrolyte, NaNO3 aqueous solution, was proposed and the machining conditions were investigated. The micro-pin fabrication was carried out by changing the electrolyte concentration, the current value and the machining time. The effect of the by-product removal by means of ultrasonic washing was investigated experimentally. The micro-pin with the diameter about 20 µm, the length about 2 mm and the aspect ratio about 100 was obtained under the constant current 400 mA in a very short time of 2.5 min.

Sequestering Ability of Phytate toward Biologically and Environmentally Relevant Trivalent Metal Cations

Quantitative parameters for the interactions between phytate (Phy) and Al(3+), Fe(3+), and Cr(3+) were determined potentiometrically in NaNO(3) aqueous solutions at I = 0.10 mol L(-1) and T = 298.15 K. Different complex species were found in a wide pH range. The various species are partially protonated, depending on the pH in which they are formed, and are indicated with the general formula MH(q)Phy (with 0 ≤ q ≤ 6). In all cases, the stability of the FeH(q)Phy species is several log K units higher than that of the analogous AlH(q)Phy and CrH(q)Phy species. For example, for the MH(2)Phy species, the stability trend is log K(2) = 15.81, 20.61, and 16.70 for Al(3+), Fe(3+), and Cr(3+), respectively. The sequestering ability of phytate toward the considered metal cations was evaluated by calculating the pL(0.5) values (i.e., the total ligand concentration necessary to bind 50% of the cation present in trace in solution) at different pH values. In general, phytate results in a quite good sequestering agent toward all three cations in the whole investigated pH range, but the order of pL(0.5) depends on it. For example, at pH 5.0 it is pL(0.5) = 5.33, 5.44, and 5.75 for Fe(3+), Cr(3+), and Al(3+), respectively (Fe(3+) < Cr(3+) < Al(3+)); at pH 7.4 it is pL(0.5) = 9.94, 9.23, and 8.71 (Al(3+) < Cr(3+) < Fe(3+)), whereas at pH 9.0 it is pL(0.5) = 10.42, 10.87, and 8.34 (Al(3+) < Fe(3+) < Cr(3+)). All of the pL(0.5) values, and therefore the sequestering ability, regularly increase with increasing pH, and the dependence of pL(0.5) on pH was modeled using some empirical equations.

Effect of NaCl and NaNO3 on the Partial Molar Volumes and Partial Molar Isentropic Compressibilities of Some Amino Acids at Several Different Temperatures (298.15–328.15) K

The partial molar volumes, \(\varphi_{v}^{\mathrm{o}}\), and partial molar isentropic compressibilities, \(\varphi_{k}^{\mathrm{o}}\), values have been computed using density and speed of sound values of L-phenylalanine/ L-leucine/L-glutamic acid/L-proline in 2 mol ⋅ L−1 aqueous NaCl or NaNO3 solutions, measured as a function of the amino acid concentration at temperatures of 298.15, 303.15, 308.15, 313.15, 318.15, 323.15 and 328.15 K. The variation of \(\varphi_{v}^{\mathrm{o}}\) values among the amino acids studied was found to follow the order proline < glutamic acid < leucine < phenylalanine. The increase in the partial molar volume of an amino acid with increasing in temperature has been attributed to the volume expansion of the hydrated zwitterions. The \(\varphi_{v}^{\mathrm{o}}\) and \(\varphi_{k}^{\mathrm{o}}\) values of L-phenylalanine, L-leucine, L-glutamic acid, and L-proline in 2 mol ⋅ L−1 aqueous NaCl and NaNO3 solutions have been found to be larger than the corresponding values in water. The larger partial molar volumes of L-phenylalanine, L-leucine, L-glutamic acid, and L-proline in 2 mol ⋅ L−1 aqueous NaCl and NaNO3 solutions have been ascribed to the possible formation of ‘zwitterion–\(\mbox{Na}^{+}/\mbox{Cl}^{-}/\mathrm{NO}_{3}^{ -}\)’ and ‘\(\mbox{Na}^{+}/\mbox{Cl}^{-}/\mathrm{NO}_{3}^{ -}\)–water dipole’ entities in solutions. The formation of these entities in solutions causes the release of water associated with zwitterions to the bulk water. The larger partial molar compressibilities of L-phenylalanine, L-leucine, L-glutamic acid and L-proline in 2 mol ⋅ L−1 aqueous NaCl NaNO3 solutions compared to the corresponding values in water has been attributed to the formation of these ‘zwitterion–ion’ and ‘ion–water dipole’ entities.

Hygroscopic behavior of wet dispersed and dry deposited NaNO3 particles

Previous controversial studies on the hygroscopic behavior of NaNO3 aerosol particles and our frequent observation of crystalline NaNO3-containing ambient particles prompted this hygroscopic study on NaNO3 particles. In this work, the hygroscopic behavior of individual NaNO3 particles of 2.5–4.0 μm in diameter is investigated on a single-particle basis using an optical microscopic technique. Quite different hygroscopic behavior between particles wet dispersed by the nebulization of aqueous NaNO3 solutions and dry deposited powdery particles was observed; i.e., most of wet dispersed particles continuously grew and shrank during humidifying and dehydration processes, respectively, and yet all the dry deposited particles had reproducible deliquescence and efflorescence relative humidities (DRHs and ERHs). The different behavior of the two NaNO3 systems is due to the different nucleation mechanisms. Our hygroscopic study of wet deposited NaNO3 particles indicates that they nucleate via homogeneous nucleation, but the time scale for the nucleation to occur is too long to be atmospherically relevant. And thus no efflorescence of the particles has been observed in the laboratory measurements. However, when chemical species acting as heterogeneous nuclei are present, then efflorescence occurs which can explain the observation of ambient crystalline NaNO3 particles. It is imperative to work with heterogeneous nucleation systems which are more relevant to the real world.

Direct fabrication and nitridation of a high-quality NaTaO3 crystal layer onto a tantalum substrate

High-quality nano-/microtextured NaTaO3 crystal layers were successfully fabricated on Ta substrates at a relatively low temperature using molten NaNO3 as the starting material. Ta substrates coated with an aqueous NaNO3 solution were heated at 500 °C in an infrared heating furnace, whereupon Ta reacted with NaNO3 (which acted as both the Na source and the flux) to afford a layer of densely packed cubic NaTaO3 crystals that adhered readily onto the substrate. Nitridation of the NaTaO3 crystal layer by heating at 850 °C under an NH3 flow yielded a Ta3N5 crystal layer. The crystals retained their original size and shape but became highly porous after nitridation. TEM observations clearly indicated that the porous cubic crystals consisted of highly crystalline nanoparticles.

Solvation of Electrolytes and Nonelectrolytes in Aqueous Solutions

A new theory of electrolyte and nonelectrolyte solutions has been developed which, unlike the Debye-Hückel method applicable for small concentrations only, makes it possible to estimate thermodynamic properties of a solution in a wide range of state parameters. One of the main novelties of the proposed theory is that it takes into account the dependence of solvation numbers upon the concentration of solution, and all changes occurring in the solution are connected with solvation of the stoichiometric mixture of electrolyte ions or molecules. The present paper proposes a rigorous thermodynamic analysis of hydration parameters of solutions. Ultrasound and densimetric measurements in combination with data on isobaric heat capacity have been used to study aqueous solutions of electrolytes NaNO3, KI, NaCl, KCl, MgCl2, and MgSO4 and of nonelectrolytes urea, urotropine, and acetonitrile. Structural characteristics of hydration complexes have been analyzed: hydration numbers h, the proper volume of the stoichiometric mixture of ions without hydration shells V(2h), compressibility β(1h), and the molar volume of water in hydration shells V(1h), their dependencies on concentration and temperature. It has been shown that for aqueous solutions the electric field of ions and molecules of nonelectrolytes has a greater influence on the temperature dependence of the molar volume of solution in hydration shells than a simple change of pressure. The cause of this effect may be due to the change in the dielectric permeability of water in the immediate vicinity of hydrated ions or molecules. The most studied compounds (NaCl, KCl, KI, MgCl2) have been studied in a wider range of solute concentrations of up to 4-5 mol/kg. Up to the complete solvation limit (CSL), the functions V(1h) = f(T) and β(1h) = f(T) are linear with a high correlation factor, and the dependence Y(K,S) = f(β1V1*) at all investigated concentrations of electrolytes and nonelectrolytes up to the CSL enables h and β(h)V(h) to be determined on the basis of relationships obtained in the study. The behavior of nonelectrolyte solutions is no different from that of electrolyte solutions, although it is possible to trace the difference between hydrophobic and hydrophilic interactions.

Hydrolysis of Monomethyl-, Dimethyl-, and Trimethyltin(IV) Cations in Fairly Concentrated Aqueous Solutions atI= 1 mol·L−1(NaNO3) andT= 298.15 K. Evidence for the Predominance of Polynuclear Species

The hydrolysis of methyltin(IV) cations at fairly high concentrations was investigated to evaluate the formation of polynuclear species in aqueous solution. The hydrolysis of monomethyltin(IV), dimethyltin(IV), and trimethyltin(IV) was studied by potentiometry at T = 298.15 K and at I = 1 mol·L−1 in NaNO3 aqueous solutions. The results obtained gave evidence for the formation of the following polynuclear species, in addition to the mononuclear species already reported, which were also considered in the models proposed for the three systems investigated: [(CH3)Sn(OH)3]0, [(CH3)Sn(OH)4]−, [((CH3)Sn)2(OH)4]2+, [((CH3)Sn)2(OH)5]+, [((CH3)Sn)2(OH)7]−, [((CH3)Sn)3(OH)5]4+, [((CH3)Sn)3(OH)7]2+, [((CH3)Sn)5(OH)9]6+, and [((CH3)Sn)5(OH)11]4+ for the monomethyltin(IV) system; [((CH3)2Sn)(OH)]+, [((CH3)2Sn)(OH)2]0, [((CH3)2Sn)(OH)3]−, [((CH3)2Sn)2(OH)2]2+, [((CH3)2Sn)2(OH)3]+, [((CH3)2Sn)3(OH)4]2+, and [((CH3)2Sn)4(OH)6]2+ for the dimethyltin(IV) system; [((CH3)3Sn)(OH)]0, [((CH3)3Sn)(OH)2]−, [((CH3)3Sn)2(OH)]+, [((CH3)3Sn)2(OH)2]0, and [((CH3)3Sn)2(OH)4]2− for the trimethyltin(IV) system. The formation constants βpqOH (relative to the equilibrium p(CH3)nSn(4−n)+ + qOH− = ((CH3)nSn)p(OH)q(p(4−n)−q)) can be expressed as a function of the cation charge z (z = 4 − n) by the general equation: log βpqOH/(p + q) = 1 + (2.50 ± 0.05)z, that allows the calculation of rough values of βpqOH for any (p,q) couple. The reliability of the proposed speciation models is discussed. As expected for a tricharged cation, by increasing the concentration of (CH3)Sn3+, the yield of polynuclear species becomes predominant; this behavior is less marked for (CH3)2Sn2+ and (CH3)3Sn+.

Sorption and desorption behavior of lead on a Chinese kaolin

The sorption and desorption of Pb on kaolin from Suzhou, China were investigated. The sorption experiment was conducted in a 0.01 M NaNO3 aqueous solution with respect to the effects of initial Pb concentration, pH, solid/solution ratio, and temperature. Langmuir and Freundlich models well described equilibrium isotherms of Pb sorption. Less than 5% of Pb sorbed was desorbed with 0.01 M NaNO3 extraction, suggesting a dominant specific sorption of Pb. As the initial pH increased, the sorption of Pb on the kaolin increased. More than 60% of Pb was sorbed at pH 2.69 far below the point of zero net charge of the kaolin at 4.2, indicating a mechanism of Pb inner-sphere complex or by chemisorption. Lead sorption decreased with increasing temperature, indicating a process of exothermic sorption.

Viscosities of l-Phenylalanine, l-Leucine, l-Glutamic Acid, or l-Proline + 2.0 mol·dm−3 Aqueous NaCl or 2.0 mol·dm−3 Aqueous NaNO3 Solutions at T = (298.15 to 328.15) K

Viscosity coefficients of l-phenylalanine, l-leucine, l-glutamic acid, or l-proline in 2.0 mol·dm−3 aqueous NaCl or 2.0 mol·dm−3 aqueous NaNO3 systems have been determined as a function of molal concentrations of amino acids at temperatures of (298.15, 303.15, 308.15, 313.15, 318.15, 323.15, and 328.15) K. Viscosity coefficients vary linearly with an increase in molal concentration of the amino acids. The trends of variation of viscosity values with an increase in molal concentration of l-phenylalanine, l-leucine, l-glutamic acid, and l-proline in 2.0 mol·dm−3 aqueous NaCl and 2.0 mol·dm−3 aqueous NaNO3 solutions and with an increase in temperature have been ascribed to the solute−solvent interactions operative in the solutions. The computed Jones−Dole B-coefficients have been also interpreted in terms of solute−solvent interactions.

Ultrasonic Velocities and Densities of l-Phenylalanine, l-Leucine, l-Glutamic Acid, and l-Proline + 2 mol·L−1 Aqueous NaCl and 2 mol·L−1 Aqueous NaNO3 Solutions from (298.15 to 328.15) K

Ultrasonic velocity and density values of l-phenylalanine, l-leucine, l-glutamic acid, and l-proline + 2 mol·L−1 aqueous NaCl and 2 mol·L−1 aqueous NaNO3 solutions have been measured for several molal concentrations of amino acids at different temperatures from T = (298.15 to 328.15) K. The isentropic compressibility values (κs) have been computed using the ultrasonic velocity and density data. The κs values decrease with an increase in the molal concentration of amino acids as well as with temperature. The trends of variation of κs with the variation in molal concentration of amino acids as well as with temperature have been discussed in terms of various interactions operative in solutions.

Solidification of binary aqueous solution cooled from above

AbstractFreezing and melting phenomena are important in many different fields, including crystal growth, casting, metallurgy, geophysics, and oceanography. Solidification of a multi‐component solution is the one often observed in nature. In order to investigate basic features of the freezing processes of binary systems, we conducted a series of laboratory experiments in a rectangular box cooled from above using aqueous NaNO3 solution. During the freezing, the solid phase always grows into many needle‐like crystals called the mushy layer. We measured the growth of the mushy layer thickness, the solid fraction, the temperature, and the concentration distributions. The average solid fraction is found to increase with time in the mushy layer. This causes a slow descent of the released solute in the mushy layer and its eventual fall into the liquid region below because of gravity. We propose a one‐dimensional model to explain the horizontally‐averaged mushy layer growth. In the model, the estimate of a heat flux at the mushy‐liquid interface due to natural convection is found essential for a correct prediction. The proposed theory predicts well the growth of the mushy‐layer and the average solid fraction, once the convective heat flux is properly given. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20278