Effect of transition metal chloride additives on the radiolysis of aqueous sodium nitrate

Radiolysis of aqueous sodium nitrate solution was studied as a function of concentration in the range 10^–4M to 1M NaNO₃. The radiolytic yield of nitrite was found to be linear with dose and concentration. The effect of transition metal chloride additives on the radiolysis of 0.01M NaNO₃ resulted in higher and lower yields of nitrite in the presence of cobalt and nickel chlorides, respectively, than that obtained in the pure nitrate system. The reduction of nitrate to nitrite is totally quenched even at very low concentration of copper chloride in the binary mixture. The results are explained on the basis of oxidizing and reducing properties of transition metal ions.     

Spectroscopy at very high pressures: Part 27. Raman study of the second-order phase transitions in sodium nitrite and sodium nitrate

Raman spectra of NaNO₂ have been studied as a function of hydrostatic pressure to 40 kbar at 295 and 348 K. Slight changes in slope of mode frequency versus pressure plots support the view that a structural anomaly exists at 9 ± 1 kbar. The absence of qualitative changes in the Raman spectra allow the space group of NaNO₂ IV to be specified as one of P1, P2, B2, Pm or Bm. The Raman spectrum of NaNO₃ has been studied to 87 kbar. The changes observed are fully consistent with a second-order transition to a phase with symmetry C⁶_3v, as indicated by previous X-ray work, although the transition is sluggish.     

Activity coefficients of sodium,potassium, and nitrate ions in aqueous solutions of NaNO3, KNO3, and NaNO3+KNO3 at 25°C

Ion selective electrodes have been used to measure the activity coefficients at 25°C of individual ions in aqueous solutions of NaNO₃ up to 3.5 molal, KNO₃ up to 3.5 molal and mixtures of NaNO₃ and KNO₃ up to 2.4 molal total nitrate ion concentration. The experimental results confirm that the activity coefficient of anion and cation in aqueous single electrolyte solutions of NaNO₃ and KNO₃ were different from each other over the whole range of concentrations studied. These effects are attributed to the ion-ion and ion-solvent interactions. The results also show that the activity coefficients of nitrate ions in the presence of sodium and potassium counterions do not depend significantly on the nature of the counterions present in the solution. The experimental data obtained in this study were correlated by a model proposed previously.     

Extraction of Eu(III) by dinonylnaphthalenesulfonic acid and synergistic effects of crown ethers and trioctylphosphine oxide

The extraction of Eu(III) by dinonylnaphthalenesulfonic acid (HDNNS) in benzene from nitrate and perchlorate solutions has been investigated. For nitrate solutions the ionic strength of the aqueous phase was kept constant at 0.1M using NaNO₃–HNO₃ mixtures. The Eu distribution was measured at different temperatures. The following stoichiometric formulae for the Eu species in benzene were derived: Eu(NO₃) (H_n–1 (DNNS)_n)₂ and Eu(H_n–1 (DNNS)_n)₃, from the nitrate and perchlorate medium respectively (n being a small number, e.g. 1, 2 or 3). The equilibrium constants were calculated and the thermodynamic parameters of the system were determined. When adding dibenzo-24-crown-8, dicyclohexyl-18-crown-6 or trioctylphosphine oxide, no synergism, but rather antagonism was observed.     

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 (? _v ⁰ ) 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 (Δ_tr? _v ⁰ ) 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 ? _v ⁰ and Δ_tr? _v ⁰ with change in temperature have been discussed in terms of ion-ion, ion-hydrophilic, and ion-hydrophobic interactions operative in solutions.     

Lanthanide-nitrate interaction in anhydrous acetonitrile and coordination numbers of the lanthanide ions: FT‒IR study

The interaction between lanthanide ions Ln^III (Ln = La, Nd, Sm–Dy, Er, Yb) and nitrate ions is investigated by FT-IR spectroscopy in dilute anhydrous MeCN solution. The work is performed for ratios R = [NO]_t/[Ln^III]_t ranging from 0 to 8 and for solutions generally 0.05M in Ln^III, prepared from anhydrous lanthanide perchlorates Ln(ClO₄)₃. When nitrate is progressively added to the Ln(ClO₄)₃ solutions, the formation of [Ln(NO₃)_n]^(3?n)+ species is clearly evidenced by the FT-IR spectra. All the NO₃^? ions are coordinated and bidentate. A quantitative study was performed using the v₁ and v₆ vibrational modes for coordinated NO ions. The average coordination numbers estimated for Nd, Eu, Tb, and Er in solutions of trinitrates are 9.0, 9.1, 8.3 and 8.2, respectively (±0.3 unit). In presence of an excess NO, these numbers become 9.8, 10.2, 10.0, 9.8, 9.9, and 9.9 (±0.3 unit) for La, Nd, Eu, Tb, Er, and Yb, respectively. No hexanitrato species forms under the experimental conditions used (R up to 8). The structural aspect of the various nitrato species is also investigated. In the pentanitrato species, all the ligands appear to be equivalent, while large inequivalences are observed for Ln(NO₃)₃ solutions. Since for the latter most of the absorption bands assigned to nitrate vibrations contain several components, a curve-fitting procedure has been used for decomposing the v₂, v₄ and v₆ vibrations. There is a considerable difference between Ln^III ions, the nitrate inequivalences being larger in the middle of the series.     

14N NMR studies of thallium nitrate solutions in liquid ammonia

¹⁴N chemical shifts and linewidths were determined for NO ₃ ^– and NH₃ in liquid ammonia solutions of thallium nitrate at concentrations between 0.07 and 10 M. The concentration dependences of the¹⁴NO ₃ ^– shift and linewidth are consistent with the presence of C_2v ion pairs at a 2:1 mole ratio of NH₃ to TINO₃ and C_3v ion pairs at mole ratios of 3:1 or higher. Previous studies had indicated the formation of ion pairs at low concentrations. The small value of the¹⁴NO ₃ ^– linewidth below 1 M suggests that these are contact ion pairs. Studies of the¹⁴NH₃ linewidth as a function of thallium salt concentration indicate slow solvent exchange at very high concentrations.¹⁴NH₃ exhibits a downfield shift upon incorporation into the solvation sphere of the Tl⁺NO ₃ ^– ion pair, in constrast to upfield shifts reported for complexation with transition metal cations.     

Durable Electrocatalytic Reduction of Nitrate to Ammonia over Defective Pseudobrookite Fe2TiO5 Nanofibers with Abundant Oxygen Vacancies

We propose the pseudobrookite Fe₂TiO₅ nanofiber with abundant oxygen vacancies as a new electrocatalyst to ambiently reduce nitrate to ammonia. Such catalyst achieves a large NH₃ yield of 0.73 mmol h⁻¹ mg⁻¹_cat. and a high Faradaic Efficiency (FE) of 87.6 % in phosphate buffer saline solution with 0.1 M NaNO₃, which is lifted to 1.36 mmol h⁻¹ mg⁻¹_cat. and 96.06 % at −0.9 V vs. RHE for nitrite conversion to ammonia in 0.1 M NaNO₂. It also shows excellent electrochemical durability and structural stability. Theoretical calculation reveals the enhanced conductivity of this catalyst and an extremely low free energy of −0.28 eV for nitrate adsorption at the presence of vacant oxygen.     

Vibrational relaxation of liquid dichloromethane at high pressure

The Raman spectra of two symmetric bands ν₁ and ν₃ of CH₂Cl₂ have been measured as a function of pressure to 300 MPa (3 kbar) and over the temperature range 303–363 K. For all bands the isotropic width increases with inreasing pressure and temperature. The experimental vibrational relaxation times are compared with the predictions of different combination of mass factors using the Fischer—Laubereau vibrational dephasing model.     

Densities,Apparent Molar Volumes and Viscosities of Concentrated Aqueous NaNO<Subscript>3</Subscript> Solutions at Temperatures from 298 to 607 K and at Pressures up to 30 MPa

Densities of four (2.124, 2.953, 5.015 and 6.271 mol-kg⁻¹) and viscosities of eight (0.265, 0.503, 0.665, 1.412, 2.106, 2.977, 5.015 and 6.271 mol-kg⁻¹) NaNO₃(aq) solutions have been measured with a constant-volume piezometer immersed in a precision liquid thermostat and using capillary flow techniques, respectively. Measurements were made at pressures up to 30 MPa. The temperature range was 298–607 K for the density measurements and 298–576 K for the viscosity measurements. The total uncertainty of density, viscosity, pressure, temperature and composition measurements were estimated to be less than 0.06%, 1.6%, 0.05%, 15 mK and 0.02%, respectively. The temperature, pressure and concentration dependence of density and viscosity of NaNO₃(aq) solutions were studied. The measured values of density and viscosity of NaNO₃(aq) were compared with data and correlations reported in the literature. Apparent molar volumes were derived using the measured density values. The viscosity data have been interpreted in terms of the extended Jones–Dole equation for strong electrolytes. The values of the viscosity A-, B-, D- and F-coefficients of the extended Jones–Dole equation for the relative viscosity (η/η₀) of NaNO₃(aq) solutions were evaluated as a function of temperature. The derived values of the viscosity A- and B-coefficients were compared with the results predicted by Falkenhagen–Dole theory of electrolyte solutions and calculated with the ionic B-coefficient data.     

Separation of iodine species by adsorption chromatography

Based on the different properties of iodide and iodate species in somesorption materials a new chromatographic method was developed to study thespeciation of iodine in a mangrove system. Two sorption materials, aluminaand silica, were investigated and several distribution coefficients for iodideand iodate were determined at different concentrations of NaOH, NaNO₃ and NaHCO₃ solutions. The best separation results wereobtained percolating sea water samples, containing iodine species, througha glass column filled with alumina. The iodide passed through the column afterwashing the column with 0.1M sodium nitrate solution, and the iodate was elutedwith a 0.5M sodium bicarbonate solution.     

Application of derivative UV spectrophotometry to the simultaneous determination of nitrate and nitrite ions in bath solutions for alkaline black-oxidation of steel

Second order derivative spectrophotometry was applied to the determination of nitrite and nitrate ions in bath solutions for alkaline black-oxidation of steel. The measurements were directly taken after dilution of the samples at λ = 336.4 nm for NO₃ ^– and λ = 390 nm for NO₂ ^–. The method was checked on artificial mixtures and applied to real samples containing approximately 5.5% NaNO₂ and 6% NaNO₃. The results agree well with those obtained by the standard manganometric method. Received: 8 July 1996 / Revised: 24 September 1996 / Accepted: 28 September 1996     

Partial Saturated Vapor Pressure of Sodium Nitrite Over the System NaNO2-KNO3

The partial pressure of sodium nitrite in the system NaNO₂-KNO₃ was measured at 798, 823, and 848 K. The dependence of the logarithm of the NaNO₂ pressure on inverse temperature is presented. Coefficients A and B of the Clausius-Clapeyron equation and the partial molar heats of vaporization are calculated. The activity and activity coefficient of sodium nitrite are determined. The dependences of ac- tivity and activity coefficient of sodium nitrite and potassium nitrate are presented as functions of composition of the NaNO₂-KNO₃ system. The consistency of the activity coefficients is verified using the Redlich-Kister integral.     

Interactions in L-phenylalanine/L-leucine/L-glutamic Acid/L-proline + 2 M aqueous NaCl/2 M NaNO3 systems at different temperatures

Density (ρ) and speed of sound (u) in 2 M aqueous NaCl and 2 M NaNO₃ solutions of amino acids: L-phenylalanine, L-leucine, L-glutamic acid, and L-proline have been measured for several molal concentrations of amino acids at different temperatures. The ρ and u data have been used to calculate the values of isothermal compressibility and internal pressure at different temperatures. The trends of variations of κ _T and P _i with an increase in molal concentration of amino acid and temperature have been discussed in terms of solute-solvent and solute-solute interactions in the systems.     

Vibrational relaxation in neat crystals of naphthalene by picosecond cars

Picosecond delayed CARS experiments on totally symmetric modes in naphthalene at 1.5 K are reported. The Raman lineshape of the vibrational excitons is lorentzian and vibrational relaxation can be surprisingly slow. The Raman lineshape of the A_g exciton level of the 766 cm^?1 vibrational mode reveals that the low-temperature lorentzian lineshape occurs by motional narrowing At higher temperature the exciton is trapped by interaction with lattice phonons.     

The Raman active internal vibrational modes of potassium nitrate

The Raman active internal vibrational modes of single crystal orthorhombic potassium nitrate have been studied in various polarizations. The full multiplet structure predicted by factor group analysis for the v₂ and v₃ regions has been observed for the first time. The expected site group splitting of the v₄ mode was not observed and can be assumed to be less than 0.5 cm^?1.     

Extraction chromatographic study on the separation of Am<Superscript>3+</Superscript> and Eu<Superscript>3+</Superscript> using ethyl-BTP as the extractant

Ethyl-substituted bis-triazinylpyridine (Et-BTP), a nitrogen containing soft-donor extractant, was used in investigations pertaining to the separation of Am³⁺ and Eu³⁺ from dilute nitric acid feed solutions by extraction chromatography using XAD-4 as the inert support, chlorinated dicarbollide as the modifier and 2-nitrophenyloctylether (NPOE) as the diluent. After carrying out a series of experiments, the optimum composition of the extractant mixture for the resin was found out to be 0.1 M Et-BTP and 0.025 M CCD in NPOE. Separation factor values were encouraging to carry out subsequent batch uptake studies at varying nitrate ion concentration which indicated favourable separation behaviour up to NaNO₃ concentration of 2 M. Column studies have been carried out and conditions for elution and separation of Am³⁺ from Eu³⁺ have been found out. Long term stability of the resin was also investigated.     

Electrosurface properties of microcrystalline cellulose dispersions in aqueous solutions of aluminum chloride, nitrate, and sulfate

The method of microelectrophoresis is employed to study the dependence of the ζ-potential of microcrystalline cellulose particles on the concentration (10^?6–10^?3 M) and pH (2–11) of aqueous aluminum chloride, nitrate, and sulfate solutions. It is shown that, in the absence of aluminum salts, the isoelectric point (IEP) of the particles is independent on the nature of acid anions and is observed at pH 3.2. The addition of aluminum salts in concentrations as low as 2 × 10 ^?6 M for chloride and nitrate and 1 × 10^?5 M for sulfate causes a shift of IEP to a less acidic region (pH 3.8), the value of which is virtually independent of the nature of the salt. As the concentration of salts is increased, the ζ-potential becomes positive, rises with an increase in pH to a maximum magnitude at pH 5.0–6.0, and decreases further until the second IEP (pH ～ 6.5–7.0) is reached. At higher pH values, the ζ-potential becomes negative again. The observed ζ(pH) dependences are explained by the formation of hydrolyzed aluminum species exhibiting different adsorbabilities on microcrystalline cellulose particles. It is shown that positively charged hydroxocomplexes formed in aluminum sulfate solutions are characterized by a lower adsorbability than hydroxocomplexes formed in chloride and nitrate solutions.     

Differential scanning calorimetry of sodium and potassium nitrates and nitrites

Differential scanning calorimetry (DSC) experiments were performed with NaNO₃, KNO₃, (Na,K)NO₃, NaNO₂ and KNO₂ over the temperature range 350–990 K. Endothermic peaks, indicative of decomposition reactions, were observed to occur in the single salts above their melting points. The equimolar mixture of sodium and potassium nitrate did not decompose in the temperature range specified. The nitrites began to decompose at 800±10 K. Sodium nitrate began to decompose at 840±10 K and potassium nitrate began to decompose at 820±20 K. These results were compared with previously reported differential thermal analysis investigations of NaNO₃ and KNO₃.     

Extraction from mixed HCl−H2C2O4 solutions purification of some actinides

Carrier-free⁹⁰Y isotope was used to study the distribution between the aqueous solution of nitric acid and sodium nitrate and HDOP in cyclohexane. The distribution coefficients (D) were measured as a function of the acidity and the nitrate concentration (M_{NO 3}) in the aqueous phase. The acid dependence was studied in a HNO₃ concentration range of 1–14M. The curve IgD vs. lgM_{HNO 3} in the range of 1–4 gives a slope of 3. The anion effect of nitrate ions shows a complexing influence on the yttrium ions changing its distribution between the two phases. The results can be useful in hydrometallurgical processes in which the solutions are highly acidic and contain a large amount of the dissolved materials as nitrate salts.