Band 101, Heft 1 -

Apparent formation constants of pentavalent Np with fulvic acid (FA) were determined in 0.1 M NaClO 4 , at 25 ºC using a solvent extraction technique with thenoyltrifluoroacetone (TTA) and phenanthroline (phen) in an isoamyl alcohol solution. The metal concentration was set constant to a tracer level of 10 15  M Np(V), relevant for the far field safety assessment of a nuclear waste disposal site. The impact of several solution conditions, namely pH, ionic strength, the initial fulvic acid concentration and the presence of Ca 2+ , on the complex formation were studied. Similar to the sodium system, the divalent calcium ion effectively prevents complexation of the neptunyl ion with fulvic acid. Furthermore, the derived apparent formation constants were comparatively discussed with literature values obtained at very similar solution conditions.

The stability constant for Tc(IV)/EDTA complexes were determined using a solvent extraction technique at varying ionic strength (NaCl) and the specific ion interaction theory model allowed for calculating stability constants at zero ionic strength. The stability constants at zero ionic strength for the formation of the TcOEDTA 2− and TcOHEDTA − complexes are 10 20.0 ± 0.4 and 10 25.3 ± 0.5 , respectively. The modeled Tc(IV) solubility was calculated to be 3.9 × 10 −7  M at near-neutral pH and in presence of 2.5 mM EDTA, a result found to be in good agreement with published solubility experimental data. Speciation calculations showed that TcOEDTA 2− is the predominant species between pH 4 and 7.5 in presence of 0.171 mM EDTA, while TcO(OH) 2 0 is predominant in basic solution. These studies show that EDTA has a very strong affinity for complexation with Tc(IV) and can increase the environmental mobility of Tc(IV).

No-carrier-added (nca) rhenium isotopes ( 182,182m,183 Re) were produced by irradiation with 30 MeV α particles on natural tantalum target. The short-lived 182,182m Re were allowed to decay and long-lived nca 183 Re was separated from bulk tantalum matrix by aqueous biphasic system (ABS) using 2 M solutions of nine different salts, namely, Na 2 SO 4 , Na 2 SO 3 , NaHSO 3 , Na 2 S 2 O 3 , Na 2 HPO 4 , Na 2 CO 3 , Na-citrate, Na-tartrate, and (NH 4 ) 2 SO 4 as salt rich phases against 50% (w/w) PEG-4000 as polymer rich phase at room temperature. The influence of temperature and thermodynamic parameters Δ H º and Δ S º were obtained for the partition of 183 Re and tantalum in these systems. Nca 183 Re was extracted in high amount in polymer rich phases irrespective of the salt rich phases. Bulk tantalum showed tendency to remain in salt rich phases. ABSs with PEG-4000 polymer rich phase in combination with Na 2 SO 4 , Na 2 SO 3 , NaHSO 3 , Na 2 HPO 4 , Na 2 CO 3 , Na-citrate and Na-tartrate as salt rich phases at basic pH and at ambient temperature (27 ºC) offered single-step separation between nca 183 Re and bulk Ta. When Na 2 S 2 O 3 and (NH 4 ) 2 SO 4 were used as salt rich phase, slight extraction of bulk tantalum was observed in PEG-4000 rich phase. The dynamic dissociation constant of 183 Re-PEG-4000 complex was measured by dialysis of the PEG-rich phase against de-ionised water. The k dissociation value was found as low as 0.0185 min −1 . Therefore, it is possible to have pure 183 Re in de-ionized water immediately after the dialysis.

Extraction of Eu(III) with a synergistic mixture of polydentate N -phosphorylated bis-ureas with the general formula ( i -PrO) 2 P(O)NHC(O)NHXNHC(O)NHP(O)( Oi -Pr) 2 (X = (CH 2 ) 7 , (CH 2 ) 2 O(CH 2 ) 2 and (CH 2 ) 2 O(CH 2 ) 2 O(CH 2 ) 2 ) and chlorinated cobalt bis(dicarbollide) ion (CCD − ) with formula closo -[(1,2-C 2 B 9 H 8 Cl 3 ) 2 -3-Co] − was studied using nitrobenzene as the solvent. Extraction of Eu(III) was very effective up to high concentrations of nitric acid. Eu(III) is most likely extracted into the organic phase as the [EuL 2 ] 3+ species whereas the positive charge of extracted complex is compensated by CCD and/or nitrate anions.

Hydrogen titanate nanotubes (H 2 Ti 3 O 7 ) were synthesized by hydrothermal process using 10 M NaOH and TiO 2 anatase powder. The material synthesized was characterized by powdered X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to ensure the structural and morphological details of the above said nanotubes. This nanosized material behaved as a cation exchanger and it was employed to separate carrier-free 137m Ba from 137 Cs in column chromatographic technique using 1.0 M HNO 3 as eluting agent.

Thulium-170 ( T 1/2 = 128.4 d, E β (max) = 968 keV, E γ = 84 keV (3.26%)) has radionuclidic properties suitable to be used in palliative therapy of bone metastases as an alternative to 89 SrCl 2 . 170 Tm can be produced by a relatively easy route involving thermal neutron bombardment on natural Tm 2 O 3 (100% 169 Tm) in medium flux research reactors. The requirement for an enriched target does not arise and radionuclidic impurities are not formed by radiative capture during neutron activation. In this study 170 Tm was produced using Tm(NO 3 ) 3 , prepared by neutron activation (3–4E13) of a natural sample. Ethylenediamine (tetramethylene phosphonic acid) (EDTMP) was synthesized and radiolabeled with 170 Tm. Complexation parameters were optimized to achieve maximum yields (>99%). The radiochemical purity of 170 Tm-EDTMP was checked by RTLC. It was found to retain its stability at room temperature even after 2 months of preparation (> 95%). Biodistribution studies of the complexes carried out in wild-type rats showed significant bone uptake with rapid clearance from blood. The properties of produced 170 Tm-EDTMP suggest applying a new efficient bone pain palliative therapeutic agent in the country instead of some other in-use radiopharmaceuticals, such as 89 SrCl 2 and 32 P, in order to overcome metastatic bone pains.

Instrumental neutron activation analysis (INAA) was used to determine concentrations of 42 elements in samples of surface soil collected at seven sites polluted from various anthropogenic activities and a control site in a relatively clean area. Elements studied were Ag, Al, As, Au, Ba, Br, Ca, Cd, Ce, Co, Cr, Cs, Eu, Fe, Gd, Hf, Hg, K, La, Lu, Mg, Mn, Mo, Na, Nd, Ni, Rb, Sb, Sc, Se, Sm, Sr, Ta, Tb, Th, Ti, U, V, W, Yb, Zn, and Zr. The results are compared with data for trace elements atmospheric deposition in lichen transplants from the same sites. The most severe soil contamination was observed at Copsa Mica from non-ferrous metallurgy. Appreciable soil contamination was also indicated at Baia Mare (non-ferrous mining and metallurgy), Deva (coal-fired power plant, cement and building materials industry), Galati (ferrous metallurgy), Magurele and Afumati (general urban pollution), and Oradea (chemical and light industries). In most cases excessive levels of toxic metals in soils matched correspondingly high values in lichen transplants. Compared to Romanian norms, legal upper limits were exceeded for Zn and Cd at Copsa Mica. Also, As and Sb occurred in excessive levels at given sites.

Intermediates of low temperature (77 K) X-rays radiolysis of 1-octanol and di-tert-butylcyclohexano-18-crown-6 solutions in 1-octanol were studied by ESR spectroscopy. Hydroxyalkyl CH 3 (CH 2 ) 6 C • HOH and interior-type alkyl R 1 C • HR 2 OH radicals were found to be main paramagnetic products stabilized in 1-octanol irradiated at 77 K. In addition to abovementioned radicals, macrocyclic –O–CH 2 –C • H– and acyclic –C • H–C(H)=O radicals produced from crown ether were identified in irradiated 1.0 M DtBuCH18C6 solution in octanol. No deviation in radiation-chemical yield of the stabilized acyclic radicals from the value expected in accord with “additive” rule was observed in the latter case. It was supposed that macrocycle cleavage in DtBuCH18C6 occurred at early stages of radiolysis rather than in secondary radical reactions between products of 1-octanol radiolysis and crown ether. Meanwhile, alkyl radicals formed from 1-octanol can react with crown ether, resulting in formation of macrocyclic products of radiolysis.

Natural radioactivity in the crude oil, produced water, sludge and scale wastes from the petroleum industry on the Suez gulf (Abu Redeis), Egypt were investigated. A low radioactivity was found in the produced water and crude oil samples. In the sludge waste samples, the levels of radioactivity were found to be 11.96 and 1.75 kBq kg −1 for Ra-226 (of U-series) and Ra-228 (of Th-series), respectively. In the scale waste samples, the levels of radioactivity were 11.7 and 4.2 kBq kg −1 for Ra-226 and Ra-228, respectively. Leaching of different radionuclides in the sludge and scale wastes was investigated using mineral acid alone or after treatment with certain carbonate solutions. The different parameters affecting the treatment were optimized. It is found that high removal of Ra-226 was achieved from sludge and scale wastes when pretreated with 10% sodium carbonate solution, followed by acid dissolution. Removal % of Ra-226 reached 77 and 87% from the sludge and scale wastes, respectively.