Uptake Of Thorium Research Articles

Theoretical and experimental study on efficient thorium removal from aquatic environment using phosphate-modified graphene oxide polymeric beads

AbstractThorium is an element of immense importance in nuclear industry due to lower environmental impact compared to fossil fuels and conventional nuclear power. In the present study, highly selective adsorption of Th4+ on phosphate modified graphene oxide polymeric beads was investigated. The interaction of –PO4, –OH and –O– functional groups of graphene oxide with thorium ion was thoroughly investigated using Density Functional Theory. The adsorption induced density difference was utilized to investigate the bonding characteristics. The affinity of the Th4+ ions was obtained as –PO4 > –OH > –O– group of the phosphate modified graphene oxide. Phosphate modified Graphene oxide embedded in Calcium alginate matrix was characterized using ATR-FTIR, XRD, SEM and Raman spectroscopy. Highly efficient (> 93%) uptake of thorium at pH 5 with fast rate of sorption (< 5 min) was observed in the batch sorption studies.

Efficient removal of radioactive Th(IV) from nuclear wastewater using phosphate-functionalized Ti3C2Tx

In this study, Ti3C2Tx was synthesized from Ti3AlC2 by HF 40% and 12 M LiF + 9 M HCL in 24 hr at temperatures of 313.15 and 333.15 K. Morphology, structure, and functional groups were investigated by the XRD, SEM, EDS, and BET analyses. Under the conditions of thorium (IV) concentration of 150 mg.l−1, pH ∼ 3, temperature of 298.15 K, and contact time of 540 min, the adsorption uptake of thorium (IV) with Ti3C2Tx-HF and Ti3C2Tx-HF in situ was 148 and 346 mg.g−1, respectively. The 3-fold adsorption of Ti3C2Tx-HF in situ was because of the larger interlayer spacing, the larger number of hydroxyl functional groups, and the larger surface area due to the synthesis with 12 M LiF + 9 M HCL. Modification of Ti3C2Tx with phosphate groups was done to increase the adsorption capacity of thorium (IV). The results showed that the adsorption process of thorium (IV) with pristine and modified Ti3C2Tx followed pseudo-second-order kinetics and Freundlich model heterogeneous isotherm. Thermodynamic data revealed that the adsorption process was endothermic. Examining the adsorption mechanism indicated that electrostatic reactions and inner-sphere complexation were the dominant mechanisms of the process.

Selective uptake of thorium(IV) from nitric acid medium using two extraction chromatographic resins based on diglycolamide-calix[4]arenes: Application to thorium-uranyl separation in an actual sample

Two novel extraction chromatography resins (ECRs) containing two diglycolamide (DGA) -functionalized calix[4]arenes with n-propyl and isopentyl substituents at the amide nitrogen atom, termed as ECR-1 and ECR-2, respectively, were evaluated for the uptake of Th(IV) from nitric acid feed solutions. While both the resins were having a quite high Th(IV) uptake ability (Kd >3000 at 3 M HNO3), the uptake was relatively lower with the resin containing the isopentyl DGA, which appeared magnified at lower nitric acid concentrations. Kinetic modeling of the sorption data suggested fitting to the pseudo-second order model pointing to a chemical reaction during the uptake of the metal ion. Sorption isotherm studies were carried out showing a good fitting to the Langmuir and D-R isotherm models, suggesting the uptake conforming to monolayer sorption and a chemisorption model. Glass columns with a bed volume of ca. 2.5 mL containing ca. 0.5 g lots of the ECRs were used for studies to assess the possibility of actual applications of the ECRs. Breakthrough profiles obtained with feed containing 0.7 g/L Th(NO3)3 solution resulted in breakthrough volumes of 8 and 5 mL, respectively, for the ECR-1 and ECR-2 resins. Near quantitative elution of the loaded metal ion was possible using a solution of oxalic acid and nitric acid. A method for the separation of Th-234 from natural uranium was demonstrated for the possible application of ECR-1.

Batch and column studies of radium, actinium, thorium and protactinium on CL resin in nitric acid, hydrochloric acid and hydrofluoric acid

CL resin (TrisKem International) was characterized for separations of radium, actinium, thorium and protactinium. Batch studies are presented for radium, actinium and thorium in HCl and HNO3 as well as for radium, thorium and protactinium in HF. The uptake of thorium from dilute HNO3 (≤ 10−4 M) and dilute HCl (≤ 10−4 M) was found to be very high (Dw > 100 in HNO3 and > 1000 in HCl). Kinetics studies on thorium were performed in HCl and HNO3 to determine suitably for column separations. Six column separation studies are presented including the separation of trace thorium from radium and actinium in dilute HCl and HNO3, the separation of radium from 1 mg 232Th in dilute HCl, the separation of thorium and radium in the presence of HCl and excess Cl−, the separation of radium, protactinium and thorium by retention of protactinium and the separation of protactinium and thorium by retention of thorium.

Performance evaluation of sodium alginate/polyvinyl alcohol/polyethylene oxide/ZSM5 zeolite hybrid adsorbent for ion uptake from aqueous solutions: a case study of thorium (IV)

In this paper, the thorium uptake from aqueous solution using SA/PVA/PEO/ZSM5 nanohybrid adsorbent has been investigated. The effect of zeolite content, pH, adsorbent dose, contact time, initial concentration, and temperature parameters was scrutinized. Using adsorbent containing 10 wt% zeolite and at pH 5 and 45 °C, the highest uptake of thorium (139.2 mg g−1) occurred. Kinetic studies have shown that the process of thorium uptake follows the double-exponential kinetic model. Using different isothermal models, uptake isotherm was studied. The results showed that the thorium uptake onto the adsorbent is physical, spontaneous and endothermic reaction.

Uptake of radionuclide thorium by twelve native plants grown in uranium mill tailings soils from south part of China

The concentrations of thorium (232Th) in soil from a uranium mill tailings repository in South China were analyzed. The results showed that all the soil samples were acidic and the concentrations of 232Th in all the soil samples were more than the natural radionuclide content in soil of China. Through the field investigation, twelve kinds of dominant plants were discovered. The total quantity of 232Th in the whole plant is highest in rice flat sedge. We also found that Miscanthus floridulus has the greatest transfer factor (TF) for 232Th, rice flat sedge has the greatest bioconcentration factor (BF) for 232Th. At the mean time, M. floridulus has the greatest phytoremediation factor (PF) for 232Th. On the basis of the above conclusions and the definition for hyperaccumulator, rice flat sedge and M. floridulus could be the candidates of phytoremediation for radionuclide 232Th in the soil.

The Removal of Uranium and Thorium from Aqueous Solutions Onto by-pass Cement Dust (BCD)

<p>The adsorption behavior of uranium and thorium from aqueous solutions by By-pass cement dust (BCD) has been investigated by a batch technique. The uranium and thorium adsorption on BCD was studied as a function of initial concentration, weight of BCD, pH, shaking time and temperature. The uptake of uranium and thorium at the determined optimum conditions follows Freundlich isotherm. The adsorption control of both thorium and uranium are first order and uptake energy of activation E<sub>a</sub> =10 and 15 kJ/mol for thorium and uranium respectively. Thermodynamic parameters such as ΔH<sup>o</sup>, ΔS<sup>o</sup> and ΔG<sup>o</sup> were also investigated.</p>

Uptake of uranium, thorium, radium and potassium by four kinds of dominant plants grown in uranium mill tailing soils from the southern part of China

The concentrations of radionuclides in soil from uranium mill tailings in South China were analyzed. The results showed that all radionuclides in soil samples exceeded the soil background value. Through the field investigation, four kinds of dominant plants were identified. It was found that the total quantity of radionuclides in the whole plant from high to low were pokeberry, Cibotium barometz, reed and garden sorrel. We also found that Cibotium barometz had the highest transfer factor (TF) for 238U, garden sorrel had the highest TF for 232Th and reed had the highest TF for 226Ra and 40K. Cibotium barometz had the highest bioconcentration factor (BF) for 238U, 232Th and 226Ra, and pokeberry had the highest BF for 40K. Pokeberry had the highest phytoremediation factor (PF) for 238U, 232Th, 226Ra and 40K. On the basis of the above conclusions, pokeberry could be a candidate for phytoremediation of radionuclide-contaminated soils.

Uptake of uranium, thorium and radium isotopes by plants growing in dam impoundment Tasotkel and the Lower Shu region (Kazakhstan)

Abstract The activity concentrations of isotopes of uranium, thorium and radium-226 in dominant species of plants (Xantium strumarium, Phragmites communis, Artemisia nitrosa and Artemisia serotina) growing on the territories contaminated by uranium industry of Kazakhstan (close to dam impoundment Tasotkel and the Lower Shu region) are presented. The obtained data showed the significant variations of activity concentrations of isotopes of uranium, thorium and radium-226 in above ground parts. The concentrations of most of the investigated radionuclides in the root system are higher than in the aboveground parts; it can be explained by root barrier. It was found that the highest root barrier has Xantium strumarium, especially for uranium isotopes. The concentration ratios of radionuclides were calculated, and as the result it was found that the highest accumulation ability in the investigated region has Artemisia serotina.

Introduction of Bifunctional Groups into Mesoporous Silica for Enhancing Uptake of Thorium(IV) from Aqueous Solution

The potential industrial application of thorium (Th), as well as the environmental and human healthy problems caused by thorium, promotes the development of reliable methods for the separation and removal of Th(IV) from environmental and geological samples. Herein, the phosphonate-amino bifunctionalized mesoporous silica (PAMS) was fabricated by a one-step self-assembly approach for enhancing Th(IV) uptake from aqueous solution. The synthesized sorbent was found to possess ordered mesoporous structures with uniform pore diameter and large surface area, characterized by SEM, XRD, and N2 sorption/desorption measurements. The enhancement of Th(IV) uptake by PAMS was achieved by coupling of an access mechanism to a complexation mechanism, and the sorption can be optimized by adjusting the coverage of the functional groups in the PAMS sorbent. The systemic study on Th(IV) sorption/desorption by using one coverage of PAMS (PAMS12) shows that the Th(IV) sorption by PAMS is fast with equilibrium time of less than 1 h, and the sorption capacity is more than 160 mg/g at a relatively low pH. The sorption isotherm has been successfully modeled by the Langmuir isotherm and D-R isotherm, which reveals a monolayer homogeneous chemisorption of Th(IV) in PAMS. The Th(IV) sorption by PAMS is pH dependent but ionic strength independent. In addition, the sorbed Th(IV) can be completely desorbed using 0.2 mol/L or more concentrated nitric acid solution. The sorption test performed in the solution containing a range of competing metal ions suggests that the PAMS sorbent has a desirable selectivity for Th(IV) ions.

Preparation of Ca-alginate biopolymer beads and investigation of their decorporation characteristics for 85Sr, 238U and 234Th by in vitro experiments

The aim of this work was to investigate whether Ca-alginate biopolymer beads (CaABBs) can be used to reduce the bioavailability of radionuclides in the gastrointestinal tract of humans. The uptake of strontium, uranium and thorium from a simulated gastrointestinal system was studied by in vitro techniques using CaABBs. This agent was prepared from Na-alginate through cross-linking with divalent calcium ions according to the egg-box model. The effects of process variables such as pH of the gastrointestinal juice, incubation time and solid-to-solution ratio for the removal of radionuclides from the gastrointestinal juice were investigated. The results suggest that CaABBs are a potent material for reducing the bioavailability of radionuclides with a high uptake efficiency in the gastrointestinal tract.

Boroaluminosilicate glasses: Novel sorbents for separation of Th and U

Boroaluminosilicate glass having a specific composition could be successfully used for the selective uptake of thorium from a mixture containing uranium by controlling the solution pH only. Single ion uptake studies showed that the uptake of uranium and thorium was maximum at pH of 4.5 and 7.5, respectively. But uptake studies using mixtures with uranium and thorium showed that irrespective of the pH, the uptake of thorium was higher than that of uranium.

Native trees for environmental quality assessment in an ecological corridor of Atlantic Forest

Brazil has a mega biodiversity concentrated primarily in forest areas such as the Atlantic Forest, one of the most endangered ecosystems in the world. The Serra do Mar State Park (SMSP) in Sao Paulo state is the largest conservation unit of the Atlantic Forest, with both well-preserved and impacted areas such as Picinguaba and Itutinga-Piloes nuclei, respectively. Bioaccumulation patterns of chemical elements are important tools to evaluate the environmental quality of ecosystems. Here, chemical elements were determined in tree leaves and soils by Instrumental Neutron Activation Analysis (INAA). Arsenic and antimony hotspots were found in the soil of Itutinga-Piloes near Anchieta-Imigrantes highway system. Trees from Itutinga-Piloes showed higher uptake of rare earth elements, iron and thorium compared with Picinguaba, with a strong effect of seasonality. This study has demonstrated the potential of using the chemical composition of native trees and soils for the assessment of environmental quality in the Atlantic Forest.

Thorium biosorption by Aspergillus fumigatus, a filamentous fungal biomass

Thorium biosorption by Aspergillus fumigatus was carried out in a batch reactor to study the effect of initial pH and metal ion concentration, contact time, biomass dose and kinetics and equilibrium Th uptake. Thorium(IV) uptake by A. fumigatus was pH dependent (pH range, 2.0–6.0) and maximum sorption was observed at pH 4.0. The uptake was rapid and the biosorption process reached equilibrium within 2 h of contact times at pH 2–4 and initial Th concentration of 50 and 100 mg/L. The kinetics data fitted well to Lagergren's pseudo-second-order rate equation ( r 2 > 0.99). A maximum initial sorption rate of 71.94 (mg/g min) and second-order rate constant of 7.82 × 10 −2 (g/mg min) were observed at pH 4.0, 50 mg Th/L. The observed maximum uptake of thorium was 370 mg Th/g at equilibrium. Biosorption process could be well described by Langmuir isotherm in comparison to Freundlich and Temkin isotherms. Sodium bicarbonate was the most efficient desorbing reagent with desorption efficiency of more than 99%. Environmental scanning electron micrograph (ESEM) showed that the surface of the biomass after desorption was intact.

Uptake of uranium and thorium by native and cultivated plants

Large part of available literature on biogeochemistry of uranium and thorium refers to the studies performed either in highly contaminated areas or in nutrient solutions that have been artificially ‘spiked’ with radionuclides. Effects of background levels of natural radioactivity on soil-grown plants have not been studied to the same extent. In this paper, we summarised results of greenhouse and field experiments performed by the author from 2000 to 2006. We examined some of the factors affecting transfer of U and Th from soil to plants, differences in uptake of these radionuclides by different plants, relationships between U and Th in soil and in plants, and temporal variations of U and Th in different plant species. Concentrations of radionuclides (critical point for experimental studies on biogeochemistry of U and Th – rare trace elements in non-contaminated regions) and essential plant nutrients and trace elements were determined by instrumental neutron activation analysis.

Observation of changes in urinary excretion of thorium in humans following ingestion of a therapeutic soil

The study investigated the changes in urinary thorium excretion by humans following ingestion of a therapeutic soil, which contains about 10 ppm of thorium. This well-known healing earth in Germany has been considered as an alternative medicine for diarrhoea and gastric hyper-acidity. Six adult volunteers ingested this therapeutic soil in varying quantities for 1–15 days at levels approximating those described in the package insert of the medicine (10–60 g of soil per day). The subjects ingested about 0.1–0.6 mg of thorium daily, which is 100–600 times higher than the normal daily intake of about 1 μg thorium in Germany. All 24-h urine samples collected from the subjects during pre-ingestion, ingestion and post-ingestion periods of the soil were analyzed for 232Th using inductively coupled plasma mass spectrometry (ICP-MS). The measured excretion values varied in a wide range. Apparently, the high thorium amounts administered did not increase the 232Th excretion in urine as expected, suggesting that this soil ingestion will not result in a considerably higher and harmful uptake of thorium into the human body.

The distribution of uranium and thorium in samples taken from different polluted marine environment

Concentrations of uranium and thorium in seawater, sediment and some marine species taken from along the coastal areas of Malaysia were determined spectrophotometrically. The uranium and thorium concentrations in seawater were found to vary ranging from 1.80 to 4.1 and 0.14 to 0.88 μg/L, respectively. The concentration of uranium in sediment samples was reported to range from 3.00 to 6.60 μg/g while those of thorium were slightly lower ranging from 0.01 to 0.68 μg/g. The uptake of uranium and thorium in marine species was found to be rather low. Similar variations in total alpha activities in samples were also observed with the total alpha activities relatively lower than the beta activities in most samples.

Sorption of uranium and thorium from sulphuric acid using TVEX-PHOR resin

Solid-liquid extraction has been used to study the uptake of uranium(VI) and thorium(IV) from sulphuric acid using a TVEX-PHOR resin. The experimental results were found to fit the BET isotherm and show a higher affinity of the TVEX-PHOR resin towards the extraction of uranium than thorium under similar experimental conditions. The best separation of uranium from thorium is obtained from 3M sulphuric acid at V/m ratio of 20 ml/g. Elution of loaded uranium and thorium was carried out with 1M sodium carbonate and 0.075M sulphuric acid, respectively. After the elution of both elements, the regenerated resin could be reused with high efficiency.

Thorium uptake by wheat at different stages of plant growth

Data on biogeochemistry of thorium are rather limited. So far little is known about toxic effects of small amounts of the radionuclide on higher plants. In this study the uptake of thorium by wheat seedlings was measured by greenhouse experiments. Germination of wheat seeds for 6 days in the presence of thorium resulted in accumulation of the metal in all parts of the seedlings. When the Th-rich seedlings were transferred to normal soil and were grown there further for 7 days, Th concentrations in roots and leaves decreased significantly (in leaves the Th content decreased up to the level of Th in the control plants). In seeds, however, Th content remained unchanged. An increase of Th content in roots and seeds was also observed as a result of addition of thorium to soil but in this case the concentration of Th in leaves did not change. The accumulation of Th in plants affected the uptake of other elements including essential macro-nutrients. The most strongly affected part of the plants was leaf.

About the assumption of linearity in soil-to-plant transfer factors for uranium and thorium isotopes and 226Ra.

The linearity assumption for soil and plant concentrations of radionuclides is usually a good approximation for use in food-chain models. To verify this assumption, different samples of plant and substrate were collected from a granitic zone located near a disused uranium mine in order to cover a large range of concentrations. In all of the samples, the activity concentration of 226Ra and of different isotopes of uranium (238U and 234U) and thorium (232Th, 230Th and 228Th) were determined. The results indicate that the linearity assumption can be considered valid when the range of concentrations taken into account is large (approx. two orders of magnitude). Otherwise, there is a clear deviation from linearity. Also, the influence of different stable elements on the soil-plant transfer factors was studied by using multivariate regression methods. The uptake of uranium, thorium and radium was found to be mainly associated with the concentration of iron in the plant and the phosphorus and alkaline earths in the substrate.