The sorption of strontium on synthetic hydroxyapatite was investigated using batch method and radiotracer technique. The hydroxyapatite
samples were prepared by a wet precipitation process followed by calcination of calcium phosphate that precipitated from aqueous
solution. Also, commercial hydroxyapatites were used. The sorption of strontium on hydroxyapatite depended on the method of
preparation and it was pH independent ranging from 4 to 9 as a result of buffering properties of hydroxyapatite. The distribution
coefficient Kd was significantly decreased with increasing concentration of Sr2+ and Ca2+ ions in solution with concentration above 1 × 10−3 mol dm−3. The percentage strontium sorption for commercial and by wet method prepared hydroxyapatite was in the range of 83–96%, while
calcined hydroxyapatite was ranging from 10 to 30%. The experimental data for sorption of strontium have been interpreted
in the term of Langmuir isotherm. The sorption of Sr2+ ions was performed by ion-exchange with Ca2+ cations on the crystal surface of hydroxyapatite. Although calcined hydroxyapatite is successfully used as biomaterial for
hard tissues repair, it is not used for the treatment of liquid wastes.
The distribution of strontium between the milk components, i.e., serum, casein micelles, whey and hydroxyapatite was determined.
The sorption on hydroxyapatite was investigated using batch method and radiotracer technique. The aqueous phase comprised
of either milk or whey. The sorption of strontium on hydroxyapatite depended on the method of its preparation and on the composition
of the aqueous phase. The sorption of strontium was increased with an increase of pH. The presence of citrate species resulted
in decrease of the sorption of strontium on hydroxyapatite. The sorption of 85Sr on hydroxyapatite decreased with the increasing concentration of Ca2+ ions. Addition of Ca2+ ions to milk resulted in milk pH decrease. The decrease in pH value after calcium addition to milk is related to exchanges
between added calcium and micellar H+. The average value of strontium sorption on casein micelles in milk with presence of hydroxyapatite was (47.3 ± 5.6) %. The
average value of sorption of 85Sr on casein micelles in milk without the addition of hydroxyapatite was (68.9 ± 2.2) %.
Authors:R. Yavari, Y. Huang, S. Ahmadi, and G. Bagheri
This study investigates uptake of cesium and strontium from aqueous solution similar to nuclear waste on three samples of
titanium molybdophosphate (TMP) synthesized under various conditions. Effects of concentration of sodium nitrate, pH and contact
time on the uptake of cesium and strontium have been studied by bath method. The results showed that TMP has high affinity
toward cesium and strontium at pH > 2 and relatively low concentration of sodium nitrate. Kinetic data indicated that cesium
uptake process to achieve equilibrium was faster than strontium. Cesium and strontium breakthrough curves were examined at
25 °C using column packed with H3O+ form of TMP and breakthrough curves showed symmetrical S-shaped profiles. At the same time, the calculated breakthrough capacity
for cesium was higher than strontium. The results of desorption studies showed that over 99% of cesium and strontium was washed
out of column by using 4 M NH4Cl solution. This study suggests that TMP can have great potential applications for the removal of strontium and specially
cesium from nuclear waste solution.
Authors:Jing-Guo Cao, Ping Gu, Jun Zhao, Dong Zhang, and Yue Deng
This study characterized the removal of strontium from an aqueous solution via co-precipitation followed by microfiltration
(CPMF) on a lab-scale. Sodium carbonate was used as the precipitating agent. Ferric chloride was added to a settler at a dosage
of 20 mg/L to improve strontium removal, and it was added to a membrane separator at a dosage of 10 mg/L to reduce membrane
fouling. The concentration of strontium in the raw water used in this study was about 5 mg/L. In two intermittent tests, where
dosages of sodium carbonate were 2000 mg/L and 1000 mg/L, the mean decontamination factors (DFs) were 237 and 158 and the
mean concentration factors (CFs) were 288 and 462, respectively. Although the mean DF value was lower when the sodium carbonate
dosage was 1000 mg/L instead of 2000 mg/L, the rate at which the specific flux (SF) of the membrane declined decreased as
the amount of the effluent treated increased. The problem of strontium release at the beginning of the operation was controlled
by a continuous test in which the dosage of sodium carbonate still was 1000 mg/L and the other parameters were the same as
in the other tests. The results showed that the mean DF and CF were 157 and 480, respectively.
Multiwall carbon nanotubes (MWCNTs) oxidized by nitric acid solution were used to investigate the adsorption behavior of strontium
from aqueous solutions similar to the nuclear waste media. The physical properties of both as produced and oxidized MWCNTs
were studied by Boehm’s titration method and nitrogen adsorption/desorption. The results showed that the surface properties
of MWCNTs such as specific surface area, functional groups and the total number of acid sites were improved after oxidation.
Furthermore, the effect of solution conditions such as initial concentration of strontium(II), pH, ionic strength, MWCNT concentration
and contact time were studied at room temperature. The results of this study showed that the adsorption of strontium(II) was
significantly influenced by the pH value and the solution ionic strength. According to the Langmuir model, the maximum adsorption
capacities of strontium(II) onto the as produced and oxidized MWCNTs were obtained as 1.62 and 6.62 mg g−1, respectively. The contact time to reach equilibrium was 100 min. The good adsorption of strontium(II) on oxidized MWCNTs
at the lower ionic strength, the relatively high pH and the short equilibrium time indicate that the oxidized MWCNTs have
great potential applications in the field of the environmental protection.
Authors:Anna Vesterlund, Annika Tovedal, Ulrika Nygren, and Henrik Ramebäck
Chemical yield determination can be a limiting source to the combined standard uncertainty in measurements of radionuclides.
Therefore, the combined standard uncertainties in yield determination in the measurement of radioactive strontium using two
methods were evaluated. The two methods compared were the measurement of stable strontium by atomic absorption spectrometry
(AAS) and the gamma spectrometric measurement of 85Sr. The evaluation showed that using gamma spectrometry for yield determination can reduce the combined standard uncertainty
by a factor of three compared to AAS. The expanded uncertainties of AAS and gamma spectrometry were calculated to be 10% and
3.3% (k = 2), respectively.
Authors:Jinsheng Wang, Rui Zuo, Yanguo Teng, Qinhong Hu, and Zongjian Sun
Because of the deposit and accumulation from the debris flow, the heterogeneous geological characteristics is obvious for
a candidate very low level waste (VLLW) disposal site, with the grain size ranging from tens of microns to 75 cm. Therefore,
it is challenging to directly measure the sorption capacity of the media and the distribution coefficient of some radionuclides,
such as strontium. We have studies the correlation of the particle mass content with different grade size and the sorption
capacity, which is important in the modeling of radionuclide migration in the heterogeneous disposal site. A total of three
deep pits and five shallow trenches were excavated, and 21 solid samples were collected for laboratory experiments. The grade
and percentage of the different-sized particles were obtained, and the fractal dimension (D) of the media was calculated from the results of sieved experiments. Steady state sorption time and sorption isotherm of
strontium was determined in the heterogeneous media, and sorption and distribution of strontium in the heterogeneous media
were evaluated by the relationship between the mass percentage and distribution coefficient (Kd) of the fine-particle media, which was comprised of selected particles with a diameter less than 1 mm, and the correlation
on the Kd and D was regressed fit. The results indicated that fractal dimension bounded from 2.39 to 2.62 in the media, and Kd values of strontium ranged between 119 and 126 in the fine-particle media, and corresponding value was 11 and 43 in the original
media. The correlation between Kd and D was approximately linear.
Instead of radioactive 90Sr, common strontium chloride was used to simulate the migration of radioactive strontium chloride in surface hydroxylated,
silanized, and common quartz sand. The sorption and retardation characteristics of strontium (Sr2+) in these surface modified quartz sands were studied by batch tests and column experiments. The equilibrium sorption data
for Sr2+ on different wettability sands were described by the Langmuir and Freundlich isotherm models, and the Langmuir model has
been found to provide better correlation for hydrophilic sand. The breakthrough curves (BTCs) of Sr2+ in these media were analyzed with the equilibrium convection–dispersion equation (CDE) and a non-equilibrium two-region mobile–immobile
model (TRM) using a nonlinear least square curve-fitting program CXTFIT. The TRM model showed better fit to the measured BTCs
of Sr2+, and the parameters of the fraction of mobile water indicated that significant preferential flow effected the non-equilibrium
transport of Sr2+. Although TRM model could not fit the Sr2+ BTCs very well, the parameter estimated by TRM model may be more reliable than those obtained from batch experiments because
the transport of Sr2+ in these kind of sand is non-equilibrium processes.
Authors:M. Galamboš, M. Osacký, O. Rosskopfová, A. Krajňák, and P. Rajec
Slovak bentonites characterized by good rheological, mineralogical and chemical stability are considered as suitable sealing
barriers for construction of Slovak deep geological repository for high-level radioactive waste and spent nuclear fuel. There
is several Slovak bentonite deposits, bentonites of which have appropriate adsorption properties meeting the geotechnical
requirements for this type of barriers. Study of adsorption properties of bentonites (mainly smectites) is an essential step
for developing the migration model long-lived corrosion and activation products, and fission products of uranium. Nuclear
wastes contain the most important nuclear fission products, β-emitter 90Sr with long half-life, biological half-life and high mobility. The present paper investigates and compares the strontium
adsorption properties of bentonites of different mineral composition consisted mainly of dioctahedral and trioctahedral smectites.
Authors:Sibel Kasap, Huseyin Tel, and Sabriye Piskin
The objective of this study is to evaluate the use of titanium dioxide nanoparticles which were prepared by novel sonochemical
method as an ion exchange material for the removal of Sr from aqueous solution. The pH effect on the Sr2+ sorption was investigated. The data obtained have been correlated with Freundlich, Temkin and Dubinin–Radushkevich (D–R)
isotherm models. Thermodynamic parameters fort he sorption system have been determined at four temperatures. Simple kinetic
models have been applied to the rate and isotherm sorption data and the relevant kinetic parameters were determined from the
graphical presentation of these models at 298°K. Results explained that the pseudo second-order sorption mechanism is predominant
and the overall rate constant of sorption process appears to be controlled by chemical sorption process. The value of sorption
energy E = 13 kJ/mol at 298°K and the value of Gibbs free energy ∆G° = 3,222 kJ/mol at 298°K prove that the sorption of strontium on titanium dioxide nanoparticles is an endothermic and non-spontaneous