Authors:H. El-Didamony, M. Ali, N. Awwad, M. Fawzy, and M. Attallah
Phosphogypsum (PG) is a residue of the phosphate fertilizer industry that has relatively high concentrations of harmful radioactive
materials. The reduction in concentration of the radionuclides from PG was investigated. The removal process is based on leaching
of radionuclides using suitable organic extractants. The studied radionuclides were 226Ra, 210Pb, 238U and 40K. The factors affect the leaching process such as type of leaching materials, contact time, concentration of the desired
solvent, liquid to solid ratio, and temperature were studied. Based on the experimental results, about 71.1, 76.4, 62.4, and
75.7% of 226Ra, 210Pb, 238U and 40K respectively were successfully removed from the PG. The reduction in the concentration of radionuclides was accompanied
by reduction in the concentration of rare earth elements (∑REE) equals to 69.8%. Using the desired organic extractant under
optimum conditions for treatment of the PG waste leads to obtain a decontaminated product that can be safely used in many
Separation of thorium, uranium and plutonium by basic tertiary amine, Alamine-336 and neutral organophosphoric extractant tri-n-octylphosphinoxide in xylene and cyclohexane solutions has been investigated. According to results obtained, Alamine-336 was chosen for the extraction of atmospheric precipitation samples. Separation process with tri-n-octylphosphinoxide based extraction can lead to higher chemical yields, but according to our results reproducibility is worse due to incomplete back-extraction of elements from organic phase. Analysis of simulated 1001 sample concentrate has shown significant effect of Ca2+, Fe3+ and Mn2+ ions concentration.
methyl methacrylate polymeric resin (XAD-7) was investigated incorporating both
acidic organophosphorous extractant (cyanex-301) and one neutral extractant
from the followings: dibenzo 18 crown 6 (DB18C6), 18 crown 6 (18C6) and 15
crown 5 (15C5). The sorption behavior of the solvent impregnated resin (SIR)
towards thorium ion, including batch equilibrium, and kinetic operation are
described. Different factors affecting the uptake of metal ions and hence, the
separation efficiency of the impregnated resins were investigated. The maximum
uptakes of Th4+ were found to be 62.9, 66.7 and 92.6% for DB18C6,
18C6 and 15C5, respectively. Synergistic extraction of various CE towards
thorium ion was tested with cyanex-301 to enhance the sorption capacity as well
as the selective separation efficiency. A relatively high capacity of the
chelating resin towards tetravalent thorium was found. The capacities of the
co-impregnated resins were found to be 2.11, 2.42 and 3.85 mmol/g for DB18C6,
18C6 and 15C5, respectively. The impregnated resin containing cyanex-301 and
15C5 can be utilized for selective separation and pre-concentration of thorium
ion from nitrate medium in the presence of several interfering metal ions.
The distribution of terbium in a three-phase system of an organic extractant, a fused salt and metallic gallium, as well as
in the corresponding two-phase subsystems has been studied. Changing the concentrations in the organic and ionic phases the
distribution ratios can favourably be varied and so the selectivity of extraction improved.
A method is described for the determination of gallium and other trace elements such as Ce, Cr, Hf, Lu and Th in bauxite by
the technique of neutron activation analysis using gold as internal standard. Isopropyl ether was used as organic extractant
to extract radioactive gallium from the sample. This method yields very good accuracy with a relative error of ±3%.
The determination of carbon, hydrogen, nitrogen, fluorine, chlorine and sulphur contents for characterization of plutonium complexes with organic ligands have been standardized and glove box adopted. Various plutonium(IV) mono- and di-carboxylates, plutonium(IV) chelates with pyrazolones, UO
complexes having pyrazolones as chelating agent and sulfoxides, amides and phosphine oxide ligands as oxodonors; uranium carbides and uranium nitrides and several potential organic extractants for actinides were analyzed satisfactorily. All these methods set up in double module glove box train are extremely useful for a low budget radioactive laboratory engaged in research in solid actinide complexes.
A separation method using some extraction zones consisting of different organic extractants adsorbed on a sheet of supporting
material, has been devised for separation of metal involving radionuclides. Glass paper is the best support to retain liquid
extractants zonally, so as not to mix, and TBP, TOPO and TOA retained on it, are employed as example. After feeding of metal
ions and washing with developing solution by the descending technique, each element is retained by an appropriate extraction
zone, and detection and determination are carried out radiometrically. Separations of Sn−Cd−Bi−As, Sn−Cd−Ag, Fe−Co−Zn and
Sn−Sb−Bi in 2M HCl system are demonstrated.
The extraction of strontium and cesium ions from high ionic strength acid, base, and salt solutions into an organic extractant
consisting of alkyl cobalt dicarbollide and polyethylene glycol (PEG) in diethylbenzene was investigated. Adding hexaethylene
glycol or PEG-400 improved the strontium extraction ≥100-fold, while cesium extraction was decreased at high PEG concentrations.
The extractions are rapid and selective, even in the presence of molar concentrations of sodium ion, suggesting that alkyl
cobalt dicarbollide extractants are useful for the treatment of alkaline nuclear wastes. A method for the synthesis of tetra-n-hexyl(cobalt dicarbollide) is described.
A method is described for the estimation by infrared spectrometry of some organic extractants such as tributyl phosphate (TBP), dioctyl sulfoxide (DOSO) and dibutyl decanamide (DBDA), which have importance as solvent extractants for fuel reprocessing. Measurements have been carried out using their characteristic donor peaks. Results indicate that Beer's law is obeyed in the concentration range of 0.01 to 0.2M with an optimum around 0.1M. The estimations have also been carried out by measuring the intensities of the OH stretches of the donor hydrates, which are very useful in estimating these donors in solvent extracted species. The method has been successfully applied to the determination of amide contents of irradiated dialkylamides.
The stability constants of the complex of Pu/III/ with a humic acid at pH 2.9 and 5.0 were measured using solvent-extraction technique. The organic extractant was dinonyl naphthalene sulphonic acid in sodium form /NaD/ in benzene while the humate aqueous phase had a constant ionic strength of 0.5M /NaClO4/. The total carboxylate capacity of the humic acid was determined by direct potentiometric titration to be 6.201 Meq g–1. The apparent pKa increased as the degree of ionization // increased. The 1g
1 values of the complex of Pu/III/ with humic acid have been determined to be 2.8 and 3.11 at pH 2.9 and 5.0, respectively.