Authors:Robert Kandlbinder, Robert Schupfner, Otto Wolfbeis, and Bettina Zinka
The incorporation of naturally occurring thorium isotopes in human femur bones was studied by analyzing 28 bone samples. The
results show that the activity concentrations of 232Th and 230Th are in the range of the blank values resulting in an upper limit of theirs activity concentrations in human bones. The
presence of 228Th can be attributed, on the basis of model calculations, to the radioactive decay of deposited 228Ra. We conclude that thorium is not detectably incorporated into human bones.
Authors:Yones Khazaei, Hossein Faghihian, and Mahdi Kamali
Adsorptive behavior of natural clinoptilolite was assessed for removal of thorium from aqueous solutions. Natural zeolite
was characterized by X-ray diffraction and X-ray fluorescence. The zeolite sample composed mainly of clinoptilolite. Na-exchanged
form of zeolite was prepared and its sorption capacity for removal of thorium from aqueous solutions was examined. The effects
of relevant parameters, including initial concentration, contact time, solid to liquid ratio, temperature and initial pH on
the removal efficiency were investigated in batch studies. The pH strongly influenced thorium adsorption capacity and maximal
capacity was obtained at pH 4.0. Kinetics and isotherm of adsorption were also studied. The pseudo-first-order, pseudo-second-order,
Elovich and intra-particle diffusion models were used to describe the kinetic data. The pseudo-second-order kinetic model
provided excellent kinetic data fitting (R2 > 0.999) with rate constant of 1.25, 1.37 and 1.44 g mmol−1 min−1 respectively for 25, 40 and 55 °C. The Langmuir and Freundlich models were applied to describe the equilibrium isotherms
for thorium uptake and the Langmuir model agrees very well with experimental data. Thermodynamic parameters were determined
and are discussed.
Authors:You-Qun Wang, Zhi-bin Zhang, Qin Li, and Yun-Hai Liu
The ability of hexadecyltrimethylammonium cation pillared bentonite (HDTMA+-bentonite) has been explored for the removal and recovery of thorium from aqueous solutions. The adsorbent was characterized
using small-angle X-ray diffraction, high resolution transmission electron microscopy and Fourier transform infrared spectroscopy.
The influences of different experimental parameters such as solution pH, initial thorium concentration, contact time and temperature
on adsorption were investigated. The HDTMA+-bentonite showed the highest thorium sorption capacity at initial pH of 3.5 and contact time of 60 min. Adsorption kinetics
was better described by the pseudo-second-order model and adsorption process could be well defined by the Langmuir isotherm.
The thermodynamic parameters, ∆G° (298 K), ∆H° and ∆S° were determined to be −31.78, −23.71 kJ/mol and 27.10 J/mol K, respectively, which demonstrated the sorption process of
HDTMA+-bentonite towards Th(VI) was feasible, spontaneous and exothermic in nature. The adsorption on HDTMA+-bentonite was more favor than Na-bentonite, in addition the saturated monolayer sorption capacity increased from 17.88 to
31.20 mg/g at 298 K after HDTMA+ pillaring. The adsorbed HDTMA+-bentonite could be effectively regenerated by 0.1 mol/L HCl solution for the removal and recovery of Th(VI). Complete removal
(99.9 %) of Th(VI) from 1.0 L industry wastewater containing 16.8 mg Th(VI) ions was possible with 7.0 g HDTMA+-bentonite.
Authors:Jorge Guzmán-Mar, Aracely Hernández-Ramírez, Ulrico López-Chuken, Pedro López-de-Alba, and Víctor Cerdà
A fast and simple multisyringe flow injection analysis (MSFIA) method for routine determination of thorium in water samples
was developed. The methodology was based on the complexation reaction of thorium with arsenazo (III) at pH 2.0. Thorium concentrations
were spectrophotometrically detected at 665 nm. Under optimal conditions, Beer’s law was obeyed over the range from 0.2 to
4.5 μg mL−1 thorium, a 3σ detection limit of 0.05 μg mL−1, and a 10σ quantification limit of 0.2 μg mL−1 were obtained. The relative standard deviations (RSD, %) at 0.5, 2.5 and 4.5 μg mL−1 was 2.8, 1.5 and 0.8%, respectively (n = 10). It was found that most of the common metal ions and anions did not interfere with the thorium determination. The proposed
method was successfully applied to its analysis in various water samples.
The aim of this study is the separation and pre-concentration of thorium from aqueous solutions by cloud point extraction
(CPE) and its the radiometric determination by liquid scintillation counting (LSC). For CPE, tributyl phosphate (TBP) was
used as the complexing agent and (1,1,3,3-Tetramethylbutyl)phenyl-polyethylene glycol (Triton X-114) as the surfactant. The
radiometric measurements were performed after phase separation by mixing of the surfactant phase with the liquid scintillation
cocktail. The effect of experimental conditions such as pH, ionic strength (e.g. [NaCl]) and the presence of other chemical
species (e.g. Ca2+ and Fe3+ ions, and humic acid colloids) on the CPE separation recovery have been investigated at constant reactant ratio (m(TBP)/m(Triton) = 0.1). According to the experimental results the maximum chemical recovery is (60 ± 5)% at pH 3. Regarding the other
parameters, generally Ca2+ and Fe3+ ions as well as the presence of colloidal species in solution (even at low concentrations) results in significant decrease
of the chemical recovery of uranium. On the other hand increasing NaCl concentration leads to enhancement of chemical recovery.
Generally, the method could be applied successfully for the radiometric determination of thorium in water solutions with relatively
increased thorium content.
Authors:D. Baldová, R. Škoda, J. Kučera, L. Viererbl, and J. Uhlíř
With regard to the use of thorium fuel for future nuclear energy production, two methods of 233U assay were studied in neutron irradiated thorium and in a mixture of thorium and uranium. The former was based on gamma-spectrometry
determination of the 233Pa radionuclide, a precursor of 233U. The latter was direct determination of 233U by neutron activation analysis with counting of delayed neutrons. The mass of 233U determined by both methods is compared with that calculated using Maple9.5 software package.
Authors:Guo-long Guo, Ming-biao Luo, Jing-jing Xu, Teng-xiang Wang, Rong Hua, and Yu-zhen Sun
A method for continuous determination of the light rare earth elements (LREEs) and thorium in Baotou Iron Ore was established.
The light rare earths and thorium were adsorbed on a micro-column packed with HD-8 cation exchange resins. The light rare
earth elements were eluted with 4 mol L−1 HCl–2 mol L−1 NH4Cl solution and determined with tribromo-arsenzao by a 721-E spectrophotometry at 630 nm; thorium was eluted with 5% potassium
oxalate solution and determined with Arsenazo III by a 721-E spectrophotometry at 660 nm. The measured values by the proposed
method were in close agreement with the certified values (Baotou main ore standard sample, Baotou ore R-715 standard sample
and GSD-2 standard sample). The RSD of the light rare earths and thorium in Baotou Iron Ore were of <1.70% and <1.99%, respectively.
Authors:M. Eskandari Nasab, A. Sam, and S. Alamdar Milani
Solvent extraction of thorium was studied using Taguchi method. The effect of various parameters such as acid types (sulfuric,
nitric, hydrochloric, sulfuric + nitric) and their concentrations from 0.001 to 4 M, initial thorium concentration (0.0001,
0.001, 0.01, 0.1 M) and solvent type (TBP, D2EHPA, Cyanex921, Cyanex272) in the ranges of 0.001 to 1 M on thorium extraction efficiency were investigated. The maximum
extraction of thorium was obtained while 0.001 M hydrochloric acid, 0.001 or 0.01 M thorium and Cyanex272 were used. Under
these optimum conditions, the extraction percent and distribution coefficient of thorium were 98.7% and 73.8, respectively.
Compared with the hydrochloric aqueous solution, the nitric acid system showed less variation in the extraction of thorium.
The proposed process has been applied for the separation of Th(IV), U(VI), La(III), and Ce(III) from synthetic solution same
as thorium ores (monazite).
Authors:L. Oufni, S. Taj, B. Manaut, and M. Eddouks
The uptake of 238U and 232Th in different parts of some selected plants used in traditional treatment of hypertension and diabetes in south-eastern
Morocco (Errachidia area) has been studied using two different types of solid state nuclear track detectors (SSNTDs) LR-115
type II and CR-39. Plant uptake of radionuclides is one of many vectors for introduction of contaminants into the human food
chain. Thus, it is critical to understand soil–plant relationships that control nuclide bioavailability. Soil concentrations
of uranium ranged from 6.10 to 11.62 ppm, with a mean of 7.90 ppm. Soil concentrations of thorium ranged from 2.70 to 4.80
ppm, with a mean of 3.41 ppm. Mean uranium specific activities were 8.38 Bq kg−1 in root tissue, 5 Bq kg−1 in stem tissue and 6.02 Bq kg−1 in leaf tissue. Mean thorium specific activities were 2.53 Bq kg−1 in root tissue, 1.64 Bq kg−1 in stem tissue and 1.96 Bq kg−1 in leaf tissue. The transfer factors of 238U and 232Th from soil to different parts (root, stem, leaf, seed and fruit) of studied plant samples have been investigated. The transfer
factors obtained for root plants were markedly higher than those for leaf, stem, fruit and seed plants. Soil-to-plant transfer
factor (TF) is one of the most important parameters to be used in transfer models for predicting the concentration of radionuclides
in agricultural crops and for estimating dose impacts to man. This study of uranium and thorium uptake in plants used in traditional
medicine is also significant as far as the health hazard effects of uranium and thorium in human being are concerned.
Authors:Payam Motabar, Kenneth Inn, Jeff Davis, and Jerome LaRosa
A set of natural matrix Standard Reference Materials were developed by the National Bureau of Standards for analytical methods
evaluation. These materials were analyzed using a KF fusion procedure and an acid dissolution procedure. The latter method
yielded radioactive concentrations that were 15–20% lower then that of the former. This was thought to be due to a fraction
of the sample, “resistates,” that did not dissolve during the dissolution. In this study, HF dissolutions were conducted on
NIST natural matrix SRMs, in which ~0.08% of total sample mass remained after dissolution. The acid resistant residual materials
were concentrated, then dissolved using a LiBO2 fusion procedure and were found to contain a considerable fraction of the uranium and thorium.