Mol Dm-3 HNO3 Research Articles

Mechanism of enhanced oxidation ability of dilute nitric acid and dissolution of pure gold in seawater with nitric acid

It has been discovered that dilute nitric acid in reversed micelle systems can oxidize the Br- ion to Br2 and we have proposed that the nitryl (or nitronium) ion NO2+ should be the active species in the oxidation process. Nitration of phenol in reversed micelle systems with dilute nitric acid, CHCl3/CTAC/H2O (2.0 mol dm-3 HNO3 in the 1.0% (v/v) H2O phase), has been performed at 35 oC to obtain 2- and 4-nitrophenols, where CTAC represents cetyltrimethylammonium chloride. In aqueous 2.0 mol dm-3 HNO3 solution accompanied by 4.0 mol dm-3 LiCl (and a small amount of LiBr as the bromide resource), trans-1,4-dibromo-2-butene was successfully brominated to 1,2,3,4-tetrabromobutane. This result is good evidence that the Br- ion can be oxidized to Br2 in dilute nitric acid (2.0 mol dm-3) providing it contains concentrated salts. For chloride salts, the cation effects increased as Et4N+ << Na+ < Li+ < Ca2+ < Mg2+. Even the evolution of Cl2 has been demonstrated from < 2.0 mol dm-3 HNO3 solution containing concentrated LiCl, MgCl2, and CaCl2 as well as AlCl3. The dissolution of precious metals (Au, Pt, and Pd), especially, of gold has been demonstrated in 0.1 - 2 mol dm-3 HNO3 accompanied by alkali metal, alkaline earth metal, and aluminum chlorides. The complete dissolution time of pure gold plate (20±2 mg, 0.1 mm thickness) in 2.0 mol dm-3 HNO3 accompanied by 1.0 mol dm-3 AlCl3 has been shortened remarkably with temperature increase from 15 to 80 oC. The dissolution rate constants, log (k /s-1), of a piece of gold wire (19.7±0.5 mg) in 20 mL of 2.0 mol dm-3 HNO3 accompanied by the metal chlorides, in general, increase with increasing salt concentrations at 40 and 60 oC. The gold can be dissolved in the solution of <1.0 mol dm-3 HNO3 and <1.0 mol dm-3 HCl, i.e. a “dilute aqua regia. We have achieved a total dissolution of five pieces of the gold wire (totally 0.10 g) in 100 mL of the 1:1 mixture between seawater and 2.0 mol dm-3 HNO3 at ca. 100 oC.

Plutonium and Americium Alpha Radiolysis of Nitric Acid Solutions.

The yield of HNO2, as a function of absorbed dose and HNO3 concentration, from the α-radiolysis of aerated HNO3 solutions containing plutonium or americium has been investigated. There are significant differences in the yields measured from solutions of the two different radionuclides. For 0.1 mol dm-3 HNO3 solutions, the radiolytic yield of HNO2 produced by americium α-decay is below the detection limit, whereas for plutonium α-decay the yield is considerably greater than that found previously for γ-radiolysis. The differences between the solutions of the two radionuclides are a consequence of redox reactions involving plutonium and the products of aqueous HNO3 radiolysis, in particular H2O2 and HNO2 and its precursors. This radiation chemical behavior is HNO3 concentration dependent with the differences between plutonium and americium α-radiolysis decreasing with increasing HNO3 concentration. This change may be interpreted as a combination of α-radiolysis direct effects and acidity influencing the plutonium oxidation state distribution, which in turn affects the radiation chemistry of the system.

Reevaluation of Neptunium-Nitric Acid Radiation Chemistry by Multiscale Modeling.

Multiscale modeling has been used to quantitatively reevaluate the radiation chemistry of neptunium in a range of aerated nitric acid solutions (0.1-6.0 mol dm-3). Exact calculation of initial radiolytic yields accounting for changes in radiation track chemistry was found to be crucial for reproducing experimental data. The γ irradiation induces changes in the Np(VI)/Np(V) oxidation-state distribution, predominantly driven by reactions involving HNO2, H2O2, NO2•, and NO3• from the radiolysis of aqueous nitric acid. Oxidation of Np(V) by NO3• (k = 8.1 × 108 dm3 mol-1 s-1) provides the initial increase in Np(VI) concentration, while also delaying net reduction of Np(VI) by consuming HNO2. Reduction of Np(VI) is dominated by thermal reactions with HNO2 (k = 0.7-73 dm3 mol-1 s-1) and H2O2 (k = 1.9 dm3 mol-1 s-1). A steady state is eventually established once the concentration of Np(V) is sufficiently high to be oxidized by NO2• (k = 2.4 × 102-3.1 × 104dm3mol-1 s-1). An additional thermal oxidation reaction between Np(V) and HNO3 (k = 2.0 × 103 dm3 mol-1 s-1) is required for nitric acid concentrations >4.0 mol dm-3. For 0.1 mol dm-3 HNO3, the rate of Np(VI) reduction is in excess of that which can be accounted for by radiolytic product mass balance, suggesting the existence of a catalytic-acid-dependent reduction process.

Effects of the Lorentz force and the gradient magnetic force on the anodic dissolution of nickel in HNO3 + NaCl solution

In this paper, the magnetic field perturbation method is used to study the effects of the Lorentz force and the gradient magnetic force on the anodic dissolution of Ni in 0.50mol dm-3 HNO3+5.0mmol dm-3 NaCl solution. During the anodic dissolution process, magnetic fields are applied in two directions: parallel (B//) and perpendicular (B⊥) to the surface of the electrode. Thus, the effects of different magnetic forces on the anodic dissolution can be analyzed. After the application of B//, the current may increase, decrease or remain stable under different potentials, while the peak potential, the oscillatory region and the passive potential shift positively. These are always caused by the Lorentz force, which enhances the mass-transport processes. However, after the application of B⊥, the peak potential, the oscillatory region and the passive potential shift negatively. The currents always tend to decrease under the different potentials, which can be explained as follows: the gradient magnetic force suppresses convection to increase the concentration of corrosion products, such as the paramagnetic Ni(II) species, in local positions at the electrode|electrolyte interface. However, neither B// nor B⊥ affects the anodic dissolution in the passive region for the oxide film on the electrode surface inhibits the MF effects. If Ni dissolves in 0.50mol dm-3 HNO3 with different chloride ions containing solution at the same potential, the effects caused by B// are different for it is in different regions and the rate-determining steps are different, however, the currents still tend to decrease with application of B⊥.

K-Ar Age Constraints on the Origin Of Micaceous Minerals in Savannah River Site Soils, South Carolina, USA

AbstractK-Ar measurements were used in this study of upland Savannah River Site soils to distinguish between sorbed K and the K remaining in remnants of primary minerals. Study of sorbed K contributes to understanding further the interaction of alkali metals (Cs in particular) with the soils. Primary mineral K and the associated radiogenic Ar were studied to characterize soil mica with respect to its provenance and its relationship to hydroxy-interlayered vermiculite. K-Ar age values of Na-saturated clay fractions from five samples of these soils range in age from 270 to 370 Ma. After a moderate acid treatment (6% HNO3 v/v, ~1 mol dm-3, 3 h, 80°C) of the clay fractions, K-Ar age values (270-325 Ma) were little changed on the whole, but they were more closely grouped near 300 Ma. Earlier work had shown that most of the K in these soils is found in material resistant to moderate acid extraction. The K-Ar age values show that this acid-resistant material is much older than any pedogenic minerals could be, even much older than the sedimentary parent rocks from which the soils were derived. These observations support earlier inferences by others that the K in these well leached soils is largely in remnants of primary muscovite from the parent sediments. Age values near 300 Ma suggest that the muscovite is largely from proximal Piedmont terranes of the Appalachian orogen, where the K-Ar relationship in most micas was set by Alleghanian tectonic processes late in the Paleozoic Era. The structural location of the K within mica, shown by the retention of the associated radiogenic Ar, is in contrast to the sorption-dominated behavior of the Cs and most of the Rb in these soils during pedogenesis. Stronger acid treatment (~6 mol dm-3 HNO3, 3 h, 100°C) extracted substantial fractions of both the K and the radiogenic Ar from bulk-soil portions, indicating destruction of some of the primary mica. K-Ar age values for the sand-rich bulk soils were not useful for this study because the sand contains excess radiogenic Ar, probably in sand-sized vein quartz.

Vertical Zinc Migration in Various Soil Types

Vertical Zinc Migration in Various Soil TypesIn this contribution the zinc content in selected soil types and soil reaction on zinc loading in kinetic model conditions with knock-down columns filled with soil samples are evaluated. The total zinc content after their draining, finish and decomposition by HF + HClO4mixture and its fractions content in extract of 2 mol dm-3HNO3, in extract of 0.05 mol dm-3EDTA and in extract of 0.01 mol dm-3CaCl2using atomic absorption spectrometry method were determined.The knock-down columns filled with soil samples in model kinetic conditions were used for observation of zinc sorption measure. The maximal water capacity of soils was determined and then solution of 280 mg zinc (ZnSO4.2H2O) per kilogram of soil was applied. The zinc contents in extraction solutions 2 mol dm-3HNO3, 0.05 mol dm-3EDTA and 0.01 mol dm-3CaCl2in drained 0.05 m high soil columns by atomic absorption spectrometry method were determined.The obtained results were evaluated by mathematical-statistical methods - multiple range analysis and linear regression. Achieved data were compared to allowed limit values.The results show different behavior of individual soil types against zinc loading. The soils showed different properties, where zinc migration to the lower column layers was determined. The accent is given to zinc dynamics in neutral and acid soils. The limit value A (140 mg kg-1) was observed in Luvic Cambisol. The limit value A1 (40 mg kg-1) was observed in Eutric Regosol and Luvic Cambisol in upper layer of soil in column. The obtained results show high mobility of zinc in tested soils and thus its risk for ecosystems.

Concentration of rhenium from dilute sodium chloride solutions

The conditions for the desorption of rhenium from the anion exchange resin Dowex 1-x8 by HNO3, HCl, H2SO4 and NaOH were determined. The solution (5.0?10-3 mol dm-3 Re in 0.15 mol dm-3 NaCl) was passed through a column containing 0.10 g of the resin. The total sorbed amount of rhenium was 0.20 g/g of the resin. It was then eluted by the corresponding eluent in the concentration range up to about 3.0 mol dm-3. The highest elution efficiency and the most favourable elution profile were found with 3.0 mol dm-3 HNO3. Over 77 % of the sorbed rhenium was found in the first 5 ml of the eluate. Practically all the rhenium was recovered with 20 ml of the acid. Under the given experimental conditions, HCl and H2SO4 were less favourable while NaOH was not applicable, due to very low efficiency of rhenium elution.

Cesium Ion-exchange Reaction in Inorganic Materials under Strongly Acidic Conditions

The cesium ion-exchange behavior of sodium difluorotetrasilicate (Na-TSM) and sodium taeniolite (Na-TAE), which belong to the mica family, in acidic media has been determined. Cs+ uptake in pH 1.0 decreased to about 30% to a neutral condition for Na-TSM. The amount of Cs+ exchange dropped dramatically for Na-TAE at pH 0.3, corresponding to about 0.5 mol dm-3 HNO3. After the ion-exchange reaction, scanning electron microscopy clearly showed that the layered structure was destroyed when the ion-exchange ratio decreased.

Protolytic Surface Reactions of a Fluorapatite−Maghemite Mixture in Aqueous Suspension

Synthetically prepared maghemite and fluorapatite, characterized with BET, SEM, XRD, FT-IR, and FT-Raman, are used to investigate the protolytic properties and surface characteristics in a mixed system of maghemite and fluorapatite by means of potentiometric titrations and surface complex modeling. Titrations were performed in the pH range of 7.3-10.5 at 25 +/- 0.2 degrees C in ionic media of 0.10 mol dm(-3) NaNO3 with 0.0100 mol dm(-3) HNO3 and 0.0100 mol dm(-3) NaOH used as titrants. The constant capacitance model (CCM) was applied to interpret the titration data. Two models with different surface equilibria were tested. In the first model, the mixed system was treated as a one-component system with a total surface area of 40.04 +/- 5.2 m2 g(-1) without any consideration to the subsystems. The surface equilibria, triple bond XOH + H+ <==> triple bond XOH2+, beta(s)(-11)(int) = 6.74 +/- 0.07; XOH <==> triple bond XO- + H+, beta(s)(-11)(int) = -7.75 +/- 0.07, were found to represent an accurate model for the system, and the specific capacitance was optimized to 2.0 F m(-2). The number of active surface sites N(s) was found to be 1.2 sites nm(-2). This model has, however, no relation to the subsystems of maghemite and fluorapatite. The second model is related to the subsystems and displays the surface equilibria, triple bond S2OH<==> triple bond S2O- + H+, beta(s)(-101)(int) = -9.12 +/- 0.01; triple bond FeOH + H+<==> triple bond FeOH2+, lg beta(s)(-11)(int) = 6.80 +/- 0.01; triple bond FeOH<==>FeO- + H+, beta(s)(-11)(int) = -7.77 +/- 0.01, where S2OH is related to fluorapatite and FeOH is representing maghemite. Fluorapatite corresponds to the dominating active surface in the system. The specific capacitance was optimized to 18 F m(-2). The N(s) values were found to be 2.27 sites nm(-2) for fluorapatite and 0.80 sites nm(-2) for maghemite. The N(s) values together with evidence from the FT-Raman and SEM investigations reveal that interactions between maghemite and fluorapatite surfaces occur during the titration. The acid-base properties and surface characteristics of the subsystems maghemite-H+ and fluorapatite-OH- using the CCM have been published earlier.

Separation of tungsten and rhenium on alumina

The conditions for the efficient separation of tungsten(VI) and rhenium (VII) on alumina were established. The distribution coefficients K d for tungstate and perrhenate anions, as well as the separation factors ?(? = KdWO42-/Kd ReO4-) were determined using hydrochloric or nitric acid as the aqueous media. Asolution of sodium chloride in the pH range 2?6 was also examined. Under all the tested experimental conditions, alumina is a much better adsorbent for tungsten than for rhenium. The obtained results indicated that the best separation of these two elements is achieved when 0.01? 0.1 mol dm-3HCl or 1.0mol dm-3 HNO3 are used as the aqueous media. If NaCl is used as the aqueous phase, the best separation is achieved with 0.20 mol dm-3 NaCl pH 4?6. Under these experimental conditions, the breakthrough and saturation capacities of alumina for tungsten at pH4 are 17 and 26 mg W/g Al2O3 respectively. With increasing pH, these values decrease. Thus, at pH 6 they are only 4 and 13 mg W/g Al2O3, respectively.

Extraction and separation studies of Ga(III), In(III) and Tl(III) using the neutral organophosphorous extractant, Cyanex-923

The neutral extractant, Cyanes-923 has been used for the extraction and separation of gallium(III), indium(III) and thallium(III) from acidic solution. These metal ions were found to be quantitatively extracted with Cyanex-923 in toluene in the pH range 4.5?5.5, 5.0?6.5 and 1.5?3.0 respectively, and from the organic phase they can be stripped with 2.0 mol dm-3 HNO3, 3.0 mol dm-3 HNO3 and 3.0 mol dm-3 HCl, respectively. The effect of pH equilibration period, diluents, diverse ions and stripping agents on the extraction of Ga(III), In(III) and Tl(III) has been studied. The stroichiometry of the extracted species of these metal ions was determined on the basis of the slope analysis method. The reaction proceed by solvation and the probable extracted species found were [MCl3. 3Cyanex-923]?[where M = Ga(III) or In(III)]?and [HTlCl4. 3Cyanex-923]. Based on these results a sequential procedure for the separation of Ga(III), In(III) and Tl(III) from each other was developed.

Extraction and separation studies of zinc(II) and copper(II) with D2EHPA and PC-88A from perchlorate media

The extraction behaviors of Zn(II) and Cu(II) from perchlorate media have been investigated using bis-2-ethylhexyl phosphoric acid (D2EHPA) and 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester, (PC-88A) in toluene. The extraction of Zn(II) was found to be quantitative in the pH range 2.5 to 3.0 and 3.0 to 4.0 using 1.0 x 10-1 moldm-3 D2EHPAand 1.0x10-2 mol dm-3 PC-88Ain toluene, respectively, while Cu(II) was extracted quantitatively in the pH range 6.0 to 8.0 and 5.5 to 7.0 with 1.0x10-2 mol dm-3 and 1.0 x 10-3 mol dm-3 D2EHPA and PC-88A in toluene, respectively. Zn(II) was stripped with 4.0 moldm-3 HCl, while Cu(II) with 2.0 moldm-3H2SO4 and 3.0 moldm-3 HNO3 from the organic phase containing D2EHPAand PC-88A respectively. The probable extracted species were ascertained by log D vs. log [HR] plot to be ZnR2.2HR and CuR2.2HR for both the reagents. These methods were used for the determination of Zn(II) and Cu(II) in real samples. The separation of Zn(II) and Cu(II) were carried out from each other and with associated metals.

Partial leaching as an aid to slurry nebulization for the analysis of soils by ICP-MS with flow injection and mixed-gas plasmas

Acid leaching (with 1 mol dm-3 HNO3) was combined with slurry nebulization in inductively coupled plasma mass spectrometry, with mixed-gas plasmas and flow injection, in an attempt to facilitate the quantitative analysis of heterogeneous materials such as soils. Matrices analyzed ranged from marine sediment to metal-contaminated soil, and were chosen for their variety in elemental composition and matrix structure. Slurries were prepared by first grinding the material to less than 3 μm in high-purity water and then diluting to 0.1% (w/v) with 1 mol dm-3 HNO3, which served as both a dispersing and a leaching agent. The resulting slurries were injected (0.25 cm3) into a deionized distilled water carrier. Under these conditions, the sensitivity was about 85% of that achieved by continuous nebulization. Multivariate optimization of the nitrogen percentage, forward torch power, and aerosol carrier gas flow rate was conducted to find conditions maintaining sensitivity constant between different slurries. Since no set of conditions was optimal for all elements, a compromise set was selected, which resulted in accurate results for La and Pb in a series of reference materials, by calibrating with aqueous standards. On the other hand, the results for V and Cr were almost systematically low, indicating that the compromise plasma conditions did not allow complete atomization/ionization of these elements.Key words: inductively coupled plasma mass spectrometry, slurry nebulization, flow injection, mixed-gas plasma.

Partial leaching as an aid to slurry nebulization for the analysis of soils by ICP-MS with flow injection and mixed-gas plasmas

Acid leaching (with 1 mol dm-3 HNO3) was combined with slurry nebulization in inductively coupled plasma mass spectrometry, with mixed-gas plasmas and flow injection, in an attempt to facilitate the quantitative analysis of heterogeneous materials such as soils. Matrices analyzed ranged from marine sediment to metal-contaminated soil, and were chosen for their variety in elemental composition and matrix structure. Slurries were prepared by first grinding the material to less than 3 μm in high-purity water and then diluting to 0.1% (w/v) with 1 mol dm-3 HNO3, which served as both a dispersing and a leaching agent. The resulting slurries were injected (0.25 cm3) into a deionized distilled water carrier. Under these conditions, the sensitivity was about 85% of that achieved by continuous nebulization. Multivariate optimization of the nitrogen percentage, forward torch power, and aerosol carrier gas flow rate was conducted to find conditions maintaining sensitivity constant between different slurries. Since no set of conditions was optimal for all elements, a compromise set was selected, which resulted in accurate results for La and Pb in a series of reference materials, by calibrating with aqueous standards. On the other hand, the results for V and Cr were almost systematically low, indicating that the compromise plasma conditions did not allow complete atomization/ionization of these elements.Key words: inductively coupled plasma mass spectrometry, slurry nebulization, flow injection, mixed-gas plasma.

Separation of a Multitracer from an Au Target Irradiated with High-Energy Heavy Ions by Means of a Supported Liquid Membrane.

The transport of Au(III) and 19 other metal ions through a tributyl phosphate (TBP)-decalin membrane supported on a microporous polytetrafluoroethylene sheet was studied in order to establish a procedure for removing Au(III) ions from acid solutions of a gold target irradiated by high-energy heavy ions, leaving a multitracer solution in a carrier- and salt-free state. Distilled water was used as a stripping agent. A feed solution of 3 mol dm-3 HCl gave the highest transport rate in the 0.1–8 mol dm-3 HCl range. The transport of carrier-free radioisotopes of Sc, Fe, Zr, Nb, Te, and Hf was observed for 8 mol dm-3 HCl and that of Fe, Zr, Nb, and Te for 5 and 6 mol dm3 HCl, while their transport was not detected for 0.1 and 1 mol dm-3 HCl feed solutions and was small with 3 mol dm-3 HCl. The 3 mol dm-3 HCl solution is considered to be the best feed solution for preparing a multitracer from an Au target, because of the large transport rate of Au(III) and the negligible transport of other elements. The transport rates of Au(III) ions from 0.2 - 2 mol dm-3 HNO3 solutions are smaller than those from 1 - 6 mol dm-3 HCl. On the basis of these observations, a practical procedure was established for preparing a multitracer solution from a heavy-ion-irradiated Au target.

Adsorption behavior of tungsten (VI) onto activated carbon.

The adsorption behavior of tungsten(VI) onto activated carbon was studied by using a column method. The result was compared with those of molybdenum(VI), chromium(VI) and other ions. The adsorption of tungsten(VI) shows remarkable pH-dependency, like that of molybdenum(VI) and chromium(VI). The adsorption-pH curves shift toward the higher pH in the following order: HClO4 <HNO3 < H2SO4< HCl. As much as 0.54 g of tungsten(VI) was adsorbed onto 5.0 g of activated carbon at pH 2.0, where the pH value was adjusted by using HNO3. The amount of tungsten(VI) adsorbed was one half as large as that of molybdenum(VI) and 100 times larger than those of other metal ions such as chromium(VI) and copper(II) under the optimum conditions. Tungsten(VI) may be adsorbed in the forms of polymerized species. The adsorption of tungsten(VI) onto activated carbon was remarkably affected by the addition of 0.2 mol dm-3 NaX( X = NO3-, ClO4-, Cl- and SO42-) solution. The amounts of tungsten (VI) adsorbed increased in the following order: NaClO4 <NaNO3 <Na2SO4 <NaCl at pH 2.0. The salt effect on the adsorption of tungsten(VI) may be ascribed to the effect of the anion on the equilibrium constant of the formation of the polymerized species and/or on the formation rate of the polymerized species. Ten percent of all the tungsten(VI) adsorbed was eluted by passing a 100 ml portion of 5.0 mol dm-3 HNO3 through the column packed with 5.0 g of activated carbon loaded with 0.41 g of tungsten(VI). The electron microscope photographs of activated carbon and activated carbon loaded with tungsten(VI) are also reported.