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Abstract  

The adsorption of Zn2+ ions on amorphous Fe(OH)3 and -Fe2O3, as a function of pH, has been investigated. In the pH region corresponding to the formation of positively charged Zn-hydroxy complexes, an abrupt increase in adsorption was observed. The influence of EDTA and glycine on the adsorption of Zn2+ by -Fe2O3 has also been investigated. Strong suppression of the adsorption of Zn2+ was observed for high [EDTA or Gly]/[Zn2+] concentration ratios. The results of the adsorption of Zn2+ in the presence of an organic ligand were explained by the formation of Zn-EDTA or Zn-glycine complexes and also by the occupation of adsorption sites by the free organic ligand.

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Abstract  

The adsorption of Ru on amorphous Fe(OH)3, -Fe2O3 and Fe3O4 have been measured as a function of the pH and the time of aging. The adsoprtion of Ru increases markedly in the 3–5.5 pH range. At higher pH values, -Fe2O3 shows different behaviour with respect to Ru adsorption. The influence of EDTA, citrate and oxalate on the adsorption of Ru on Fe3O4 has also been investigated. Possible mechanisms of the adsorption of Ru on hydrous iron oxides are discussed in the light of the results obtained in the course of this study and of those of other researchers.

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Abstract  

Factors that influence the adsorption of trace elements or radionuclides on hydrous iron oxides were investigated. The adsorption of monovalent cations (Cs+, Rb+) on hydrous iron oxides is not strongly pH-dependent and it can be regarded as nonspecific. On the other hand, the adsorption of Ag+, divalent cations (Zn2+, Cd2+, Mn2+, Sr2+) or trivalent cations (Cr3+, La3+, Ce3+, Eu3+, Gd3+, Er3+, Yb3+) is strongly pH-dependent. The regularities of the adsorption of these cations on hydrous iron oxides are discussed. Also, the differences in the adsorption behaviour of some divalent and trivalent cations are explained. Freshly precipitated iron(III) hydroxide can be used for the decontamination of radionuclides from low-level waste solutions. However, the efficacy of decontamination depends on the oxidation state and the chemical properties of radionuclides.

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Abstract  

Thermal decomposition of natural pyrite (cubic, FeS2) has been investigated using X-ray diffraction and57Fe Mössbauer spectroscopy. X-ray diffraction analysis of pyrite ore from different sources showed the presence of associated minerals, such as quartz, szomolnokite, stilbite or stellerite, micas and hematite. Hematite, maghemite and pyrrhotite were detected as thermal decomposition products of natural pyrite. The phase composition of the thermal decomposition products depends on the temperature, time of heating and starting size of pyrite crystals. Hematite is the end product of the thermal decomposition of natural pyrite.

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Abstract  

Thermal decomposition of iron(II) acetate, Fe(CH3COO)2, and iron(III) acetate hydroxide, FeOH(CH3COO)2, has been studied using57Fe Mössbauer spectroscopy and X-ray diffraction. Samples were thermally treated in air atmosphere between 150°C and 1000°C. The formation of maghemite '-Fe2O3, and hematite, -Fe2O3, is discussed. Hematite appears as the final decomposition product.

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Abstract  

The denitration of several chemical compositions of simulated HRLW (highly radioactive liquid waste) was performed using formic acid as reducing agent. Precipitates formed during the denitration of simulated HRLW were analyzed using X-ray diffraction and57Fe Mössbauer spectroscopy. Goethite and amorphous fraction were the principal phases in these precipitates. It was found that the chemical composition of simulated HRLW and the experimental conditions of denitration have more influence on the crystallinity and the particle size than on the phase composition of the precipitates. Thermal treatment of denitrated precipitates caused the solid state transformation of goethite+amorphous fraction into hematite. The values of hyperfine magnetic field (HMF) of hematite were decreased, thus indicating the substitution of Fe3+ ions with other metal cations.

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Abstract  

Glasses are suitable host matrices for the immobilization of high-level radioactive wastes. The corrosion behaviour of nuclear waste glass in water is of considerable importance, since a potential route for returning of radionuclides to the biosphere is their leaching from the waste form into groundwater and subsequent transport by the groundwater to the surface. In this study, the preparation and characterization of borosilicate glasses of different chemical composition were investigated. Borosilicate glasses were doped with simulated nuclear waste oxides. The chemical corrosion in water of these glasses was followed by measuring the leach rates (g·cm–2·day–1), as a function of time. It was found that a simulated nuclear waste glass with the chemical composition (weight %), 15.61% Na2O, 10.39% B2O3, 45.31% SiO2, 13.42% ZnO, 6.61% TiO2 and 8.66% waste oxides, is characterized by low melting temperature and with good corrosion resistance in water. Influence of passive layers on the leaching behaviour of nuclear waste glasses is discussed.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
M. Hadžišehović
,
D. Spasova
,
A. Milojević
,
K. Buraei
,
M. Župancić
,
V. Urosević
,
M. Ristić
, and
S. Pongrac

Abstract  

The investigated water samples were collected from rivers, underground waters and precipitations at different locations near Belgrade during the period 1976–1979. By preconcentration and scintillation counting, the individually and monthly collected samples were analyzed for3H contents. It has been found that the3H-concentration in monthly river water samples (Danube, Sava, Tisa) varies from 39 to 196 TU with a maximum in summer, between 0–192 TU in the underground water depending on the sampling depth and distance from river Sava and Danube, while values of 26 to 153 TU have been detected in the monthly precipitation samples attaining a maximum during the break-through of arctic and polar continental air masses. The results were used to calculate the3H quantity deposited per m2 (Bq/m2) of surface, due to precipitations and the flow per second (Bq/s) in the investigated locations in rivers. The interrelation between rivers, underground waters and precipitations is discussed. The3H-distributions obtained are correlated with the water level in rivers and with the precipitation quantities and are interpreted in light of the relevant meteorological parameters and other related phenomena.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
M. Hadžišehović
,
A. Milojević
,
K. Buraei
,
M. Ristić
,
N. Tončev
,
D. Spasova
, and
D. Paligorić

Abstract  

A study of the tritium content of precipitation and of river water samples, collected during a seasonal maximum of tritium concentration in 1976 is given. The measurements were made for precipitation in Belgrade from April to December 1976, and for river water from the Sava (in Belgrade), the Tisa at 137 km, and the Danube at 1425 km, 1174 km, 861 km from the confluence. The maximum monthly value of the tritium content of precipitation is 135 TU, and the Danube at 1425 km has a maximum of 196 TU (627 pCi/l). In general, there is no correlation between the amount of precipitation and river water with tritium content.

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Abstract  

Mössbauer, FTIR and XRD analyses showed that in aqueous medium in air in the presence of L-tryptophan (Trp) or indole-3-acetic acid (IAA) the ambient-temperature ageing of the precipitates formed from ferrous sulphate at pH7 gave composite phases with varying proportions of -FeOOH (a dominating crystalline phase), -FeOOH (both fine-grained, showing superparamagnetic behaviour at 298 K, and relatively better crystallized) and amorphous ferric hydroxide. The experimental data suggested a competition for adsorption sites at the oxyhydroxide surface in the suspension during phase transformations, as well as the transformation of -FeOOH (and/or amorphous ferric hydroxide) to -FeOOH via the dissolution-reprecipitation mechanism. The formation of certain ferric oxyhydroxide phases in the presence of Trp and IAA — released e.g., in the course of bacterial and plant metabolism — can contribute to the regulation of soil mineral composition.

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