Deposition measurement of particulate matter in connection with corrosion studies

A new passive particle collector (inert surrogate surface) that collects particles from all directions has been developed. It was used to measure particle deposition at 35 test sites as part of a project that examined corrosion of materials in order that variation in particulate material could be used in development of dose–response functions in a modern multi-pollutant environment. The project, MULTI-ASSESS, was funded by the EU to examine the effects of air pollution on cultural heritage. Passive samplers were mounted rain-protected, and both in wind-protected and wind-exposed positions, to match the exposure of the samples for corrosion studies. The particle mass and its chemical content (nitrate, ammonium, sulfate, calcium, sodium, chloride, magnesium and potassium) were analysed. The loss of light reflectance on the surrogate surface was also measured. Very little ammonium and potassium was found, and one or more anions are missing in the ion balance. There were many strong correlations between the analysed species. The mass of analysed water-soluble ions was fairly constant at 24% of the total mass. The particle mass deposited to the samplers in the wind-protected position was about 25% of the particles deposited to an openly exposed sampler. The Cl⁻/Na⁺ ratios indicate a reaction between HNO₃ and NaCl. The deposited nitrate flux corresponds to the missing chloride. The Ca²⁺ deposition equals the deposition and the anion deficiency. The deposition most likely originates from SO₂ that has reacted with basic calcium-containing particles either before or after they were deposited. The particle depositions at the urban sites were much higher than in nearby rural sites. The deposited mass correlated surprisingly well with the PM₁₀ concentration, except at sites very close to traffic.     

Chemical effects induced by γ-irradiated Na2SO4 in aqueous ammonium nitrate

It is well known that paramagnetic centers are formed when Na₂SO₄ crystals are exposed to -radiation. The dissolution of such crystals in aqueous ammonium nitrate results in reduction of nitrate to nitrite. Various factors which influence the yield of nitrite are investigated. The yield of nitrite is found to vary with the amount of irradiated Na₂SO₄ added, the dose absorbed by Na₂SO₄ crystals, the storing period of the irradiated salt, photoannealing time, concentration of aqueous ammonium nitrate and particle size of the Na₂SO₄ crystals. The G(NO ₂ ^– ) value under optimum conditions of the conversion of nitrate to nitrite by irradiated Na₂SO₄ in aqueous ammonium nitrate is 0.009. The efficiency of energy transfer is 1.5%. The mechanism of reduction is based on the reactions of paramagnetic centers with nitrate ions.     

δ 15N measurement of organic and inorganic substances by EA-IRMS: a speciation-dependent procedure

Little attention has been paid so far to the influence of the chemical nature of the substance when measuring δ ¹⁵N by elemental analysis (EA)–isotope ratio mass spectrometry (IRMS). Although the bulk nitrogen isotope analysis of organic material is not to be questioned, literature from different disciplines using IRMS provides hints that the quantitative conversion of nitrate into nitrogen presents difficulties. We observed abnormal series of δ ¹⁵N values of laboratory standards and nitrates. These unexpected results were shown to be related to the tailing of the nitrogen peak of nitrate-containing compounds. A series of experiments were set up to investigate the cause of this phenomenon, using ammonium nitrate (NH₄NO₃) and potassium nitrate (KNO₃) samples, two organic laboratory standards as well as the international secondary reference materials IAEA-N1, IAEA-N2—two ammonium sulphates [(NH₄)₂SO₄]—and IAEA-NO-3, a potassium nitrate. In experiment 1, we used graphite and vanadium pentoxide (V₂O₅) as additives to observe if they could enhance the decomposition (combustion) of nitrates. In experiment 2, we tested another elemental analyser configuration including an additional section of reduced copper in order to see whether or not the tailing could originate from an incomplete reduction process. Finally, we modified several parameters of the method and observed their influence on the peak shape, δ ¹⁵N value and nitrogen content in weight percent of nitrogen of the target substances. We found the best results using mere thermal decomposition in helium, under exclusion of any oxygen. We show that the analytical procedure used for organic samples should not be used for nitrates because of their different chemical nature. We present the best performance given one set of sample introduction parameters for the analysis of nitrates, as well as for the ammonium sulphate IAEA-N1 and IAEA-N2 reference materials. We discuss these results considering the thermochemistry of the substances and the analytical technique itself. The results emphasise the difference in chemical nature of inorganic and organic samples, which necessarily involves distinct thermochemistry when analysed by EA-IRMS. Therefore, they should not be processed using the same analytical procedure. This clearly impacts on the way international secondary reference materials should be used for the calibration of organic laboratory standards.

Efficiency of energy transfer from γ-irradiated ammonium halides in aqueous iodide and nitrate solutions

It is well known that ammonium halide (NH₄X) crystals, on -exposure, store energy in the form of primary and secondary radiolytic products. Such crystals on dissolution in aqueous iodide and nitrate solutions result in oxidation of iodide and reduction of nitrate, respectively. The yields of iodine and nitrite are determined by chemical methods under varying conditions of the amount, dose and particle size of the irradiated ammonium halide salts. The maximum values of the efficiency of energy transfer for oxidation and reduction processes for ammonium halide salts correspond to 40% and 10%, respectively. At low doses, an empirical relation proposed between the percent efficiency of energy transfer and the absorbed dose is valid. The concentrations of inherent oxidizing and reducing species initially present are 7.0×10¹⁸ and 1.0×10¹⁸ per mol of ammonium halide, respectively.     

Hot atom chemistry in oxyanion targets. Part IV1: Recoil isochronal annealing in permanganates

Investigations on isochronal annealing behaviour of /n, / activated⁵⁶Mn recoils in crystalline potassium and ammonium permanganates have given different results indicating a varying degree of sensitivity of the samples to recoil annealing. The presence of ammonium ion in ammonium permanganate shows the reduction of recoil species during annealing. Vand-Primak model has been utilized to deduce the kinetic behaviour by which the energy of activation is found to be 1.1 and 1.2 eV for KMnO₄ and NH₄MnO₄, respectively. Furthermore, the present work reveals the role of defects in the transient reactions of the lattice stable precursors and hence the mechanism of the recoil reactions.     

The thermodynamic properties and solvation of ammonium bromide,iodide, and nitrate in methylpyrrolidone at 298.15 K

The heat capacity and density of solutions of ammonium bromide, iodide, and nitrate in methylpyrrolidone (MP) were studied calorimetrically and densimetrically at 298.15 K. The standard partial molar heat capacities and volumes (\(\overline {C_{p_2 }^O } \) and \(\overline {V_2^O } \)) of the electrolytes in MP were calculated. The standard heat capacities \(\overline {C_{p_i }^O } \) and volumes \(\overline {V_i^O } \) of the nitrate and ammonium ions in MP were determined. The mean coordination numbers of the NH ₄ ⁺ and NO ₃ ^? ions in a solution in MP at 298.15 K were calculated.     

Study of copper complexes in saturated and unsaturated aqueous ammonium oxalate solutions containing Cu(II) impurity

The influence of Cu(II) impurity on chemical equilibria in unsaturated and saturated ammonium oxalate (AO) aqueous solutions was investigated as a function of concentration _ci$c_{\text{i}}$ of impurity. Using the computer programme “Hyss” the species present in the solutions were analysed. It was found that in the aqueous solutions of ammonium oxalate containing Cu(II) ions the following species are formed: Cu²⁺, Cu(OH)⁺, Cu(OH)₂, CuC₂O₄⁰ and Cu(C₂O₄)₂²⁻ in addition to C₂O₄²⁻, HC₂O₄⁻, H₂C₂O₄ and (NH₄)₂C₂O₄⁰ species, and their concentration depends on concentrations _ci$c_{\text{i}}$ of Cu(II) impurity and c of ammonium oxalate. The dependences of solution pH and of absorbance A   and the corresponding wavelength λ$\lambda$ for unsaturated aqueous solutions on ammonium oxalate concentration c   containing different concentrations _ci$c_{\text{i}}$ of Cu(II) ions showed three well-defined regions characterised by transition values of solution pH or solute concentration c. Speciation analysis revealed that Cu²⁺ and CuC₂O₄⁰, CuC₂O₄⁰ and Cu(C₂O₄₎₂²⁻, and Cu(C₂O₄)₂²⁻ complexes are predominantly present in the solute concentration intervals c≤0.01$c\le 0.01$ mol/dm³, 0.01 mol/dm³ <c<0.03$<c<0.03$ mol/dm³ and c≥0.03$c\ge 0.03$ mol/dm³, respectively. The concentration interval range 0.01 mol/dm³ <c<0.03$<c<0.03$ mol/dm³ corresponds to the pH interval where Cu(OH)₂ is precipitated. It was found that the solubility of ammonium oxalate at 30 °$°$C increases practically linearly with an increase in the concentration of Cu(II) impurity. Speciation analysis of saturated aqueous solutions of ammonium oxalate revealed that Cu(II) ions contained in AO saturated solutions exist mainly as Cu(C₂O₄)₂²⁻-type complexes, and the increase in the solubility of AO in the presence of Cu(II) impurity is essentially due to an increase in the ratio of the concentrations of CuC₂O₄⁰ and Cu(C₂O₄)₂²⁻ species.     

Chemical effects induced by γ-irradiated alkali halides in aqueous binary mixtures of nitrates and iodides

Dissolution of -irradiated chlorides of sodium and potassium in a solution of NaNO₃ and KI results in the formation of NO ₂ ^– and iodine as stable products. The variation in the yields of the products with the amount of irradiated salts is studied. The effect of photoannealing of the irradiated salts on the yields of nitrate and iodine in the mixture is discussed on the basis of photoannealing reactions of the colour centres.     

Ionic strength dependence of formation constants. Part 4. Potentiometric study of the system Cu2+-Ni2+-citrate

Summary The ternary Cu²⁺-Ni²⁺-citrate (cit^3–) system was investigated potentiometrically in aqueous solution, at different temperatures, 10t45°C, and ionic strengths, 0.03I0.8 mol dm^–3, using potassium nitrate or tetraethylammonium bromide as background salt. Since the citrate anion forms weak complexes with potassium, the stability constants here reported differ according to whether the potassium association is considered or not. In the presence of both Cu²⁺ and Ni²⁺, the mixed metal species, [CuNi(cit)₂H_–2]^4– is formed with citrate in solution, in addition to the various binary complexes. We have obtained the dependence for all the formation constants on ionic strength and temperature. The previous suggestions concerning a general equation for describing the dependence, log =f(I), are confirmed; from the study of log =f(T) we have obtained the values of thermodynamic parameters. The dependence of H on ionic strength is discussed.     

Standard thermodynamic functions of complexation between copper(II) and glycine and L-histidine in aqueous solutions

The Cu²⁺–glycine–L-histidine system is studied calorimetrically at 298.15 K and an ionic strength of 0.2, 0.5, and 1.0 in aqueous solutions containing potassium nitrate. The standard thermodynamic parameters (Δ_rH°, Δ_rG°, Δ_rS°) of complexation processes are determined.     

The state of Cu2+ ions in concentrated aqueous ammonia solutions of copper nitrate

Stabilization of Cu²⁺ ions in concentrated aqueous ammonia solutions of copper nitrate in a wide range of ammonium ion concentrations has been studied by EPR and electronic absorption spectroscopy. Three types of Cu²⁺ associates with different types of orbital ordering have been identified. The ammonium ion concentration in a solution has a decisive effect on the type of orbital ordering of Cu²⁺ ions in associates. In all cases, Cu²⁺ ordering in associates is caused by the existence of bridging OH groups in the axial and equatorial positions of [Cu(NH₃) _n (H₂O)_{6 ? n} ]²⁺ complexes (n < 6). At a high concentration of ammonium ions, weakly bound associates of tetramminecopper with the $d_{x^2 - y^2 }$ ground state are formed. In solutions with low ammonium concentrations, bulky associates with the $d_{y^2 }$ and $d_{x^2 - z^2 }$ ground states and associates of Cu²⁺ ions with the $d_{x^2 - y^2 }$ ground state with hydroxyl groups in the equatorial plane and axial water molecules are formed.     

Unusual Intercalation of Cationic Smectite Clays with Detergent‐Ranged Carboxylic Ions

Summary: The organic intercalation of cationic smectite clays is achieved by using alkali salts of alkyl carboxylic acids, instead of using conventional quaternary ammonium salts as ionic exchanging agents. Various organic acid salts, such as CH₃(CH₂)₁₆COO⁻Na⁺, can be incorporated into divalent montmorillonite (M²⁺‐MMT) with a 30–40 wt.‐% organic embedding and an X‐ray diffraction basal spacing of 43 Å from the pristine 10 Å. The intercalation is generalized for carboxylate salts of different alkyl lengths and for alkali metal ions, including sodium and potassium ions, but is specific for the divalent MMT clay. This new type of organic species for clay modification allows the preparation of organoclays in the absence of quaternary ammonium salts. It is proposed that the organic embedding is driven by the formation of a thermodynamically stable RCOO⁻/M²⁺/SiO⁻ complex.

Graphical illustration of the carboxylic acid salt complex with the divalent cations on silicate K10.     

Study of Cadmium Extraction with Aliquat 336 from Highly Saline Solutions

A large number of model solutions with high ionic strength were synthesised to mimic industrial conditions and were used as a first approach to study Cd extraction in the presence of chloride at high salinity, as experienced in real industrial solutions. The extractant used throughout in this work was Aliquat 336, a quaternary ammonium salt well known to the hydrometallurgical industry. The effects of some selected anions in addition to chloride (i.e., perchlorate, nitrate, and sulfate) were studied. The distribution of cadmium was measured using ¹⁰⁹Cd as a tracer. Liquid-scintillation spectroscopy quantified the concentration of ¹⁰⁹Cd in both phases. Raman and NMR spectroscopy were employed to gain further insight into the extraction chemistry. A careful analysis of all Cd extraction data showed that within specific windows of the reactant concentrations the chemical reactions could be represented by simplified equations, as discussed thoroughly in the text. Equilibrium constants for the extraction of \({\text{CdCl}}_{3}^{ - }\) from chloride and chloride/sulfate media were determined to be log₁₀K_ext?=?4.9?±?0.8 and log₁₀K_ext?=?5.7?±?0.5, respectively. For the nitrate environment, an exchange reaction involving a LiNO₃ ion pair is proposed and agrees with the experimental data, but was not proven. ¹⁴N-NMR and Raman spectroscopy confirmed that the relative affinity of Aliquat 336 for the relevant anions followed the order: perchlorate?>?nitrate?>?chloride?>?sulfate. Finally, ¹⁴N-NMR enabled the equilibrium constant of the exchange reaction between nitrate and chloride for Aliquat 336 to be determined.     

Chemical effects induced by γ-irradiated ammonium chloride in aqueous medium

Dissolution of -irradiated ammonium chloride in aqueous solutions of nitrate and iodide results in the formation of NO ₂ ^– and I₂ as products. Appropriate mechanisms have been suggested in the light of known stable radiolytic products formed in the salt during irradiation. The variation in the yields of products in the solution with the variation in -dose, amount, particle size is studied. The effect of thermal annealing on the yields of products is explained on the basis of annealing of radiolytic products.     

Development of a method for recovery of 233U from thorium oxalate cake in reconversion step of reprocessing of irradiated thorium rods

A method is developed for the selective leaching of ²³³U from a thorium oxalate cake. The leaching capacity of ammonium carbonate and nitric acid have been investigated, showing that (NH₄)₂CO₃ leads to higher recovery. The maximum leaching efficiency is obtained using 0.5% ammonium carbonate, with a minimal thorium pick-up. A uranium recovery of 94% is obtained after three consecutive contact experiments in carbonate media, with minimal thorium uptake in the leachate. This process was applied to an actual plant stream, allowing the reduction of the ²³³U -activity from 5.64 to 0.3 Ci/g of thorium oxalate cake.     

Polarographic behaviour of DL aspartic acid at the D.M.E.

dl Aspartic acid is reduced at the d.m.e. in 0.1M tetramethylammonium bromide, tetraethylammonium bromide, sodium chloride, potassium chloride, potassium nitrate, sodium perchlorate and lithium sulphate; in aqueous media. The waves are irreversible, diffusion controlled involving one electron transfer process determined by millicoulometry. The values of the kinetic parameters, transfer coefficient () and formal rate constant (k° _{f, h}) have been calculated byKoutecky's method and are 0.479 and 15.9×10^–16 respectively.With 1 Figure     

Processing of signals from an ion-elective electrode array by a neural network

Neural network software is described for processing the signals of arrays of ion-selective electrodes. The performance of the software was tested in the simultaneous determination of calcium and copper(II) ions in binary mixtures of copper(II) nitrate and calcium chloride and the simultaneous determination of potassium, calcium, nitrate and chloride in mixtures of potassium and calcium chlorides and ammonium nitrate. The measurements for the Ca²⁺/Cu²⁺ determinations were done with a pH-glass electrode and calcium and copper ion-selective electrodes; results were accurate to ±8%. For the K⁺/Ca²⁺NO^?₃/Cl^? determinations, the measurements were made with the relevant ion-selective electrodes and a glass electrode; the mean relative error was ±6%, and for the worst cases the error did not exceed 20%.     

Determination of oxygen impurity in high purity materials by charged particle activation analysis using alpha projectiles

40 MeV -particles have been used to determine oxygen impurity at ppm levels in silicon, copper, and stainless steel, through the radiochemical separation of¹⁸F from the matrix. The separation of¹⁸F has been carried out by two techniques, viz.(1) distillation of H₂SiF₆ and (2) precipitation of KBF₄ and some modification has been applied in the separation, depending on the nature of interferences from the matrix. Instrumental approach was also carried out to determine the oxygen impurity at 100 ppm in Si matrix because this approach is not possible in Cu and stainless steel samples due to matrix activity.     

The position of plutonium/III/ in the lanthanide series in respect to thermodynamic functions of complex formation with nitrates and thiocyanates

The position of Pu/III/ within lanthanides in respect to G⁰, H⁰ and S⁰ of complex formation with nitrate and thiocyanate ligands was determined by the extraction method. It was found that in respect to G⁰, Pu/III/ is a light pseudolanthanide for nitrate ligands and a heavy pseudolanthanide for thiocyanate ligands. A comparison of the positions of Pu/III/ and Am/III/ in respect to G⁰, H⁰ and S⁰ shows that the radius of plutonium is greater than that of americium in the An/NO₃/ ₅ ^2– complex and smaller in the An/NCS/₃/TBP/_n complex. The increase in the radii between plutonium and americium in the thiocyanate complex points out to a contribution from 5f orbitals to bonding.