Adsorption of fission products onto soils using a fission multitracer

The adsorption behavior of fission products to various soils was studied using a multitracer. The multitracer was prepared by neutron irradiation of ²³⁵U. Distribution coefficients of fission products were obtained for seventeen kinds of Japanese soils. It was found that zirconium, niobium, and rare earth elements show high distribution coefficients for all soil samples, however, elements like alkali metals show varied values.     

Volatility of tellurium and various fission products in heated nitric acid solutions

The volatility of tellurium and some other fission products was radiochemically studied in heated nitric acid solutions. As tracers ¹²¹Te produced by bremsstrahlung of an electron LINAC and other fission products produced by neutron irradiation were used. The distribution rate of radionuclides between the mother solution and the condensate, was considered as volatility, and was determined. The volatility of tellurium was found to be small and close to that of cesium. Volatilization tests were also performed in the presence of large amounts of solutes.The authors wish to thank Mr. Roy Jacobus for his help in preparing this paper.     

Volatility of tellurium and various fission products in heated nitric acid solutions

The volatility of tellurium and some other fission products was radiochemically studied in heated nitric acid solutions. As tracers ¹²¹Te produced by bremsstrahlung of an electron LINAC and other fission products produced by neutron irradiation were used. The distribution rate of radionuclides between the mother solution and the condensate, was considered as volatility, and was determined. The volatility of tellurium was found to be small and close to that of cesium. Volatilization tests were also performed in the presence of large amounts of solutes.The authors wish to thank Mr. Roy Jacobus for his help in preparing this paper.     

Extraction of fission products with 1,2-dichloroethane solutions of hexabromo derivative of cobalt dicarbollide from nitric acid medium

The dependence of the distribution of Cs, Sr, Ba, Eu, Ce between nitric acid solutions and 0.06M hexabromo derivative of cobalt dicarbollide (H⁺BBr ₆ ^– ) in dichloroethane has been investigated upon the concentration of the acid, the extractant and the synergistic additive Slovafol 909. The back-extraction due to the presence of propanol, hydrazine, nitric acid and NH₄NO₃ has been studied. The results were similar to those observed in analogous systems using nitrobenzene as the solvent.     

Properties of nitric acid palladium solutions with a high metal concentration

Nitric acid solutions (c _Pd up to 3.2 M) with variable HNO₃ concentration were studied by electronic spectroscopy, ¹⁴N and ¹⁷O NMR, acid-base titration, gravimetry, and other methods. Solid phases that precipitated on storing these solutions were studied by X-ray phase analysis, thermogravimetry, and IR spectroscopy. The conditions for stability of particular Pd(II) species were determined, and specific features of aging of such highly concentrated palladium solutions were revealed. A procedure for palladium isolation as [Pd(NH₃)₄](NO₃)₂ from nitric acid solutions in 98% yield was developed.     

Model study of acid rain effect on adsorption of trace elements on soils using a multitracer

Using a radioactive multitracer and model acid rain (HCl or H₂SO₄ solution), batch experiments were performed to examine the pH effect on the adsorption-desorption equilibrium of 16 elements on soils as a model study of an acid rain effect. Kaolin, black soil (original and with organic matter almost removed) and Kureha soil (original and with organic matter almost removed) were used as adsorbents. Characteristic dependence on the pH value of the suspension was observed for the adsorption of the elements on kaolin and the soils. The results of this model study indicate that acid rain decreases the retention of cations, while it increases or does not change the adsorption of anions on soils. Organic matter in soils has a positive effect on the extent of adsorption of most elements investigated.     

Separation of zirconium from fission products in silica gel—nitric acid systems

A method for the separation of zirconium from fission products based on the system 100–200 mesh silica gel—2.0 M nitric acid is described. Decontamination factors are over 500 for ⁹⁵Nb, ¹⁰⁶Ru, ¹²⁴Sb, ¹³⁷Cs, molybdate and uranium(VI), and the yield of zirconium is 98 %.     

Adsorption of fission products on stainless steel and zirconium

Contamination of the structural materials of nuclear reactors is a crucial question in view of radiation protection, especially, if due to some leakage, uranium and its fission products appear in the cooling water. Since it is rather difficult to obtain in situ experimental data on the actual amount of adsorbed radioactive species, the surface contamination may be quantified by measuring bulk activity concentrations of the cooling water and by calculating the amount of adsorbed material on the surfaces by using a partition coefficient. To do this, the knowledge of an appropriate adsorption isotherm is needed. Thus, our paper presents results, based on electrochemical measurements, about the extent and effect of the adsorption of certain fission products—caesium and iodide—in their ionic forms on the surface of some alloys used in the nuclear industry. Our findings allow the conclusion that the adsorption of these ions can be described by a Langmuir-type isotherm, where the saturation values correspond to surface monolayers.     

Pressure effect on cation exchange distribution of some fission products on a strongly acidic cation exchanger of sulfonic acid type in nitric acid

Distribution coefficients of fission products on a cation exchanger in 1M nitirc acid were measured as a function of the pressure by means of the column method. The distribution coefficients were found to decrease with the pressure, and this became more pronounced with increasing charge of the ions. The distribution coefficients of yttrium and RuNO³⁺ decreased with the pressure to a relatively greter extent than lighter lanthanides, and RuNO³⁺ appeared at a separate peak from europium in the elution chromatogram as the pressure was increased up to 900 kg/cm².     

Separation of fission and corrosion products from boric acid solutions by solvent extraction

Extractive purification of boric acid from radioactive corrosion and fission products dissolved in aqueous solutions modelling nuclear reactor coolants has been studied. Aliphatic 1,3-diols containing 8 and 9 carbon atoms per molecule were used as extractants fro boric acid. The behaviour of some representative corrosion and fission products as well as various factors affecting their distribution between the organic and aqueous phases have been investigated under the conditions of boric acid extraction. Conditions for the effective separation of boric acid from most of the radioactive contaminants are presented.     

Adsorption of metal halides from ethanol solutions by a 3-n-propylpyridiniumsilsesquioxane chloride-coated silica gel surface

3-n-propylpyridiniumsilsesquioxane chloride polymer, abbreviated as SiPy+Cl-, was used to coat a porous silica gel, SiO2, surface to form the chemically modified solid SiO2/SiPy+Cl-. The resulting polymer film was well adhered to the surface and presented an ion exchange capacity of 0.74 mmol g(-1). Metal halides, MClz [M=Fe(III), Cu(II), and Zn(II)], were adsorbed by the modified solid from ethanol solutions as neutral species by forming the surface anionic complexes described by the equation: mSiO2/SiPy+Cl-+ MClz <=> (SiO2/SiPy+)m[MCl(z+m)]m-, where the [MCl(z+m)]m- species adsorbed on the surface are FeCl4-, ZnCl4(2-), and CuCl4(2-). Accurate estimates of the specific sorption capacities and the heterogeneous stability constants of the immobilized metal complexes were determined with the aid of computational procedures.     

Analysis of aqueous nitric acid solutions using secondary-ion mass spectrometry

The results of model experiments on the qualitative and quantitative determination of HNO₃ in aqueous solutions by secondary-ion mass spectrometry are presented. Characteristic lines were selected in the mass spectra of the analyzed samples, by the intensity of which the concentration of HNO₃ in solutions can be determined, even in the presence of other ionic components. The potential of this instrumental method for determining the composition of the samples of atmospheric aerosols and condensed atmospheric moisture is discussed.     

Ion flotation behaviour of thirty-one metal ions in mixed hydrochloric/nitric acid solutions

The ion flotation of 31 metal ions in hydrochloric/nitric acid solution with the cationic surfactant cetylpyridinium chloride was investigated. A 25-ml portion of 0.27-2.87 x 10(-4)M metal ion and 1.8-6.0 x 10(-4)M cetylpyridinium chloride solution in 0.17-3.4M acid mixture ([HCl]:[HNO(3)] = 2.4:1) was subjected to flotation in a cell, 22.5 cm high and 4.0 cm in diameter, for 5 min, with nitrogen bubbles. Ir(IV), Pt(IV), Ge(IV), Sn(IV), Bi(III), Au(III), Tl(III), Pd(II) and Sn(II) were floated from solution in 95-100% yield; Ru(III), Rh(III), Ir(III), Hg(II), Ag(I) and Tl(I) were partly floated, while Cr(VI), Ti(IV), Zr(IV), Ga(III), In(III), Fe(III), Sb(III), Al(III), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), CD(II) and Pb(II) were floated with less than 20% yield. The flotation behaviour of these metal ions in the mixed acid system was compared with that in hydrochloric acid. The flotation is more efficient in the mixed acid system.     

Extraction of actinides and fission products from salt solutions using polyethylene glycols (PEGs)

The extraction behavior of several metal ions viz., Am³⁺, Eu³⁺, UO₂ ²⁺, Th⁴⁺, Sr²⁺ and Cs⁺ was investigated from sulphate medium employing phosphotungstic acid (PTA) and polyethylene glycol (PEG). The influence of various parameters such as pH, PTA concentration, PEG concentration and salt concentration was studied. The order of extraction followed the trend: Am³⁺>Eu³⁺>>Th⁴⁺>UO₂ ²⁺>Sr²⁺>Cs⁺ which deviate significantly from the reported order with conventional solvents. The relatively poor extraction of UO₂ ²⁺, Sr²⁺ and Cs⁺ was ascribed to their lack of interaction with the phosphotungstate anion. The separation behaviour of Am³⁺ vis-a-vis Eu³⁺ was also investigated under different experimental conditions.     

Chemical behavior of antimony and tellurium fission products in aqueous solutions

The oxidation states of antimony and tellurium fission products formed in the aqueous solutions of²³³U and²³⁵U irradiated in a reactor were studied by means of anion exchange method. Results were corrected for the thermal reactions such as radiation induced reactions using double tracers for each element. In hot reactions, the isotopes formed independently by fission take their reduced states almost completely, whereas the isotopes formed by β-decay of their precursors favor their oxidized states. The fractions of the tellurium isotopes in the oxidized state depend on the β-decay energy of their precursors, whereas those of the antimony isotopes are nearly constant irrespective of the β-decay energy. The different behaviors between those two elements would reflect the chemical properties of their precursors.     

Reversed phase extraction chromatography using solutions of nitric acid as eluants

Approximately 40 ions have been chromatographed on thin layers of silica gel impregnated with Alamine 336-S, Alamine 336-S oxide, tri-n-octylarsine oxide, tri-n-octylphosphine oxide or tri-n-butyl phosphate, and on non-impregnated silica gel. Solutions of 0.2–15 N HNO₃ are used as eluants. R_F spectra and a number of separations are reported. The ions are classified into four groups according to their chromatographic behaviour, which is explained on the basis of anion exchange, solvation, hydrolysis and interaction with the support.Data on the extraction of HNO₃ and the co-extraction of water are reported. The behaviour of Alamine oxide and tri-n-octylarsine oxide parallels that of high-molecular-weight amines: extraction proceeds through anion exchange. Nitric acid taken up in excess of the stoichiometric amount is mainly present in the organic phase as part of the ion [O₂NO…HONO₂]⁻. On the other hand, with tri-n-octyl-phosphine oxide (TOPO) and tri-n-butyl phosphate (TBP), extraction proceeds through solvation; TOPO·HNO₃, TOPO·2HNO₃ and TBP·HNO₃ are the species present in the organic extracts.     

Theoretical study of the dissociation of nitric acid at a model aqueous surface

The issue of acid dissociation of nitric acid at an aqueous surface is relevant in various portions of the atmosphere in connection with ozone depletion. This proton-transfer reaction is studied here via electronic structure calculations at the HF/SBK+(d) level of theory on the HNO(3) x (H(2)O)(3) model reaction system embedded in clusters comprising 33, 40, 45, and 50 classical, polarizable waters with an increasing degree of solvation of the nitrate group. Free energy estimates for all the cases examined favor undissociated, molecular nitric acid over the 0-300 K temperature range, including that relevant for the upper troposphere, where it is connected to the issue of the mechanism of nitric acid uptake by water ice aerosols. The presence of molecular HNO(3) at 300 K at the surface is further supported by vibrational band assignments in good agreement with a very recent surface-sensitive vibrational spectroscopy study of diluted HNO(3)/H(2)O solutions.     

Separation of traces of silver in nitric acid solutions using mercury as collector

Summary Microgram quantities of silver are quantitatively deposited into mercury globules from nitric acid solutions (ca. 1N acidity), leaving large amounts of base metals (e. g., copper, lead, and bismuth) in solution. This separation method has been applied to the atomic absorption spectrometric determination of a few ppm of silver in copper or lead.

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Zusammenfassung Mikrogrammengen Silber werden aus salpetersaurer Lösung (ca. 1-n) quantitativ auf Quecksilbertröpfchen niedergeschlagen, wobei große Mengen unedle Metalle (z. B. Cu, Pb und Bi) in Lösung bleiben. Diese Trennmethode wurde bei der Bestimmung weniger ppm Silber in Kupfer oder Blei durch Atomarabsorption angewendet.

     

A study of palladium recovery with thiourea from nitric acid solutions

Interaction in the system Pd(II)-HNO₃-SC(NH₂)₂ was studied. It was shown that the precipitates formed, which have various compositions and solubilities, contain palladium(II) and thiourea conversion products. Elemental, X-ray diffraction, and atomic-adsorption analyses and IR and electronic absorption spectroscopies were applied to demonstrate the possibility of virtually quantitative precipitation of palladium(II) under certain conditions in the form of a poorly soluble precipitate Pd₂(CN)₄ · H₂O.     

Adsorption of two phenoxyacid compounds on a clay surface: a theoretical study

Using density functional theory methods, we studied the adsorption of (4-chloro-2-methylphenoxy)acetic acid (MCPA) and 2-(4-chlorophenoxy)-2-methylpropanoic acid, therapeutically used under the name of clofibric acid (CA), two commonly detected water pollutants, both in neutral and ionized form on a model surface of muscovite. We report the geometries of the adsorbed species and discuss their interaction with the surface. It was found that the ionized adsorbates interact more strongly with the surface than do their neutral forms particularly for MCPA when compared with CA, which points to the same direction of previous experimental findings. Changes on the electron density due to adsorption has been studied by means of Bader charges analysis and it was found that electronic density is transferred from the anions to the surface and less significantly from the surface to the neutral molecules on adsorption.