Distribution Coefficient Of Uranium Research Articles

A novel cloud point back-extraction of uranium(VI) from organic radioactive solution to slightly acidic aqueous medium

ABSTRACT Stripping back uranium(VI) from an organic radioactive solution to an aqueous medium was rendered simple and quantitative by an unprecedented cloud point back-extraction (CPEback) method. The concentration difference of nitrate ions in and out of the micelle was employed to change the uranium distribution coefficient in favor of the bulk aqueous phase. In addition, the monophasic nature of cloud point extraction and the complexing ability of oxalic acid with uranyl ion in the bulk aqueous phase resulted in the quantitative recovery of uranium in a single step. The CPEback parameters were optimized through a cross-optimization process and the recovered uranium was quantified by the biamperometric titration method. The proposed analytical procedure resulted in high back-extraction efficiency and recovery of (99.6 ± 0.2)% and 99.2%, respectively. The process turned large volumes of organic radioactive solution into small volumes of a less hazardous organic medium having high viscosity and negligible vapor pressure. Analysis of two real samples of ~17 and 165 mL organic radioactive solutions resulted in 99% and 98.2% uranium recoveries, respectively. The leftover organic phase containing the extractant and nonionic surfactant can now be easily stored or reused.

Adsorption performance and mechanism of waste paper-derived phosphorus-rich carbon for separation of uranium from radioactive wastewater

The use of household waste-derived materials for wastewater treatment has double environmental benefit due to the availability of simultaneous disposal of household waste and wastewater. In this work, we report the facile production of phosphorus-rich carbon from waste paper as a potential adsorbent for the disposal of uranium (VI)-containing nuclear wastewater. A simple phosphoric acid activation-carbonization strategy is developed to effectively transform waste paper into carbon. The phosphorus content of the obtained carbon reaches 8.55 at% and large pores with sizes ranging from 2 to 100 nm are observed. Batch and column adsorption experiments verify that waste paper-derived carbon can efficiently adsorb uranium (VI) from aqueous solution under weakly acidic conditions. The maximum amount of uranium adsorption on the carbon attains 492 mg g−1 at pH 4.6, and adsorption of uranium (VI) on the carbon quickly reaches the equilibrium within 20 minutes. The distribution coefficient of uranium (VI) on waste paper-derived carbon is as high as 128 L g−1. The carbon can be reused for five times with uranium (VI) adsorption efficiencies above 89% and can be used for dynamic adsorption of uranium (VI) in a fix-bed column. Kinetics, thermodynamics and DFT calculations reveal a surface complexation mechanism between uranium (VI) ion and ionized phosphoric acid group. Moreover, to avoid the generation of secondary polluted water during the treatment of uranium-containing nuclear wastewater, a water-saving method is developed for the adsorption preparation and a water-free combustion method is employed for the disposal of uranium-containing spent adsorbent instead of recycling. This study demonstrates the good application potential of household waste-derived materials in wastewater treatment and provides more clues for the amalgamation of multifold subjects.

Achieving ultrahigh uranium/vanadium selectivity of poly(amidoxime) via coupling MXene-enabled strong intermolecular interaction and separated photothermal interface.

Poly(amidoxime) (PAO) has been recognized as the most potential candidate for extracting uranium from seawater, owing to its merits of outstanding uranium affinity, low cost, and large-scale production. Despite remarkable achievements, existing PAO sorbents suffer from unsatisfactory uranium extraction efficiency and selectivity, as imposed by the inherently sluggish uranium adsorption kinetics and inevitable spatial configuration transition of amidoxime, which diminishes uranium affinity. Herein, we discover a facile and integrated design to elaborate a PAO/MXene nanocomposite that delivers ultrahigh and durable uranium/vanadium (U/V) selectivity. The key to our design lies in harnessing MXene-enabled strong intermolecular interactions to PAO to minimize the spatial configuration transition of amidoxime and stabilizing its superior uranium affinity, as well as creating a separated photothermal interface to maximize temperature-strengthened affinity for uranium over vanadium. Such a synergetic effect allows the nanocomposite to acquire over a 4-fold improvement in U/V selectivity compared to that of pure PAO as well as an unprecedented distribution coefficient of uranium compared to most state-of-the-art sorbents. We further demonstrate that our nanocomposite exhibits durable U/V selectivity with negligible attenuation and good antibacterial ability even in long-term operation. The design concept and extraordinary performance in this study bring PAO-based sorbents a step closer to practical uranium extraction from seawater.

Pomelo peel derived phosphorus-doped biochar for efficient disposal of uranium-containing nuclear wastewater: Experimental and theoretical perspectives

The phosphoric acid activated biochar adsorbent is recognized as a good candidate for application in efficient disposal of uranium-containing nuclear wastewaters. However, the production of high-efficiency biochars with typical characteristics of large specific surface area, hierarchically porous structure and abundant adsorption group remains a challenge. In this work, we report a new hydrogelation-carbonization technique to facilely produce phosphorus-doped biochar from pomelo peel and meantime provide new sights into the interaction mechanism of phosphoric acid groups with uranium ion. An interesting hydrogelation phenomenon is found when simply mixing the phosphoric acid solution and pomelo peel powder. The resulted hydrogel readily undergo carbonization to produce desired biochar. The biochar exhibits good uranium removal efficiency (up to 99 %) with a maximum adsorption capacity of 603 mg/g at 313 K. The distribution coefficient of uranium (VI) attains 10.8 L/g. The biochar undergoes five desorption-adsorption cycles with desorption and adsorption efficiencies above 95 %. It can be applied in fix-bed column for dynamic adsorption of uranium from uranium-containing solutions and real nuclear wastewater with an adsorption capacity over 422 mg/g. Rather than direct interaction with uranium ion, our experimental and computational results reveal that the surface phosphoric acid groups initially undergo in-situ ionization to produce phosphonates and the complexation of phosphonate with uranium ion results in effective uranium adsorption. This work demonstrates the high efficiency of pomelo peel biochar for disposal of uranium-containing nuclear wastewater, and offers new insights into the mechanism of uranium adsorption on the adsorbents containing phosphoric acid and phosphonate groups.

Enhanced performance in uranium extraction by the synergistic effect of functional groups on chitosan-based adsorbent

In this study, a novel sponge phosphoric acid functionalized porous composite adsorbent (named SPCCHC) was prepared from chitosan and chlorella hydrothermal charcoal. Kinetics and thermodynamics experiments showed that the theoretical maximum adsorption capacity of SPCCHC to U(VI) is 579.27 mg/g (288 K, pH = 6.5), indicating a spontaneous exothermic reaction. SPCCHC showed good adsorption selectivity for uranium in the adsorption studies of simulated seawater and a mixed solution of uranium–vanadium. The characterization of SPCCHC before and after U(VI) adsorption proves that the introduction of the phosphate group can greatly improve the adsorption effect of the adsorbent on uranium, particularly the distribution coefficients of uranium and vanadium differ by up to 89.5 times. At the same time, SPCCHC has good recycling performance, which is expected to be used in natural seawater uranium extraction.

Determination of distribution coefficient of uranium from physical and chemical properties of soil.

Uranium is a long lived radioactive element which is naturally present in minute concentrations in igneous, sedimentary and metamorphic rocks. These rocks when subjected to weathering results in the formation of soil which also has traces of uranium. Distribution coefficient (Kd) is a crucial parameter in environmental assessment which is used to predict the interaction and transport of uranium in groundwater. The objective of the study is to estimate the Kd of uranium in soils and to develop a relation between this and the soil parameters. Seven rock samples and twenty three soil samples were collected during this study. The Kd of rock samples of different grain sizes where determined and the soil samples were analysed for electrical conductivity, pH, grain size, bulk density, particle density, porosity, calcium carbonate, cation exchange capacity and Kd. The Kd of the soil increases with increase in soil pH up to 6, after which it gradually decreases. Multiple regression analysis was performed to quantify the effect of various soil parameters on soil Kd and equations were statistically significant. Thus, soil Kd in a region could be predicted using limited soil properties with such statistically significant equations.

Measurement of uranium distribution coefficient and 235U/238U ratio in soils affected by Fukushima dai-ichi nuclear power plant accident

Fukushima Daiichi Nuclear Power Plant (FDNPP) accident resulted radioactive contamination in soil due to deposition of mainly radiocesium as well as many long-lived radionuclides surrounding a large area around FDNPP. Depending upon environmental conditions, radionuclides in soil can be mobilized in aquatic systems. Therefore, the fate and transfer of these radionuclides in the soil water system is very important for radiation protection and dose assessment. In the present study, soil and water samples were collected from contaminated areas around FDNPP. Inductively coupled plasma mass spectrometry (ICP-MS) is used for total uranium concentration. Emphasis has been given on isotope ratio measurement of 235U/238U ratio using thermal ionization mass spectrometry (TIMS) that gives us the idea about its contamination during accident. For the migration behavior, its distribution coefficient (Kd) has been determined using laboratory batch method. Chemical characterization of soil with respect to different parameters has been carried out. The effect of these soil parameters on distribution coefficient of uranium has been studied in order to explain the radionuclide mobility in this particular area. The distribution coefficient values for uranium are found to vary from 30 to 36000 L/kg. A large variation in the distribution coefficient values shows the retention or mobility of uranium is highly dependent on soil characteristics in the particular area. This variation is explained with respect to soil pH, Fe, Mn, CaCO3 and organic content. There is a very good correlation of uranium Kd obtained with Fe content. There is no enrichment of 235U has been noticed in the studied area.

Estimation of distribution coefficient of uranium in soil by batch tests

Sorption studies were performed to estimate the soil distribution coefficient (Kd). Since soil and groundwater are major controlling factors for the Kd value, it is important to determine the site specific Kd value. In this study, special emphasis has been given to soil and groundwater parameters which control the Kd value of uranium around the mineralized zone. Based on the analysis of soil sample, the distribution coefficient of uranium around the mineralized zone varies from 7 to 369 l/kg. It is also observed that distribution coefficient of uranium in this region not only depends on the individual parameter and it varies significantly with space. Increase and decrease in Kd value was observed when the pH ranges from 4 – 7 and 7 – 8.5 respectively which indicates that the increase in pH greater than 7 will reduce the Kd value. No significant correlation was observed between the Kd value and other parameters such as soil texture, CaCO3, CEC and major ion concentration in groundwater. Determination of Kd value in a uranium mineralized zone will be used to predict and model the contaminant transport.

Intra- and inter-annual uranium concentration variability in a Belizean stalagmite controlled by prior aragonite precipitation: A new tool for reconstructing hydro-climate using aragonitic speleothems

Aragonitic speleothems are increasingly utilised as palaeoclimate archives due to their amenability to high precision U–Th dating. Proxy records from fast-growing aragonitic stalagmites, precisely dated to annual timescales, can allow investigation of climatic events occurring on annual or even sub-annual timescales with minimal chronological uncertainty. However, the behaviour of many trace elements, such as uranium, in aragonitic speleothems has not thus far been as well constrained as in calcitic speleothems. Here, we use uranium concentration shifts measured across primary calcite-to-aragonite mineralogical transitions in speleothems to calculate the distribution coefficient of uranium in aragonitic speleothems (derived DU=3.74±1.13). Because our calculated DU is considerably above 1 increased prior aragonite precipitation due to increased karst water residence time should strongly control stalagmite aragonite U/Ca values. Consequently, uranium concentrations in aragonitic speleothems should act as excellent proxies for effective rainfall.We test this using a high-resolution ICP-MS derived trace element dataset from a Belizean stalagmite. YOK-G is an aragonitic stalagmite from Yok Balum cave in Belize with an extremely robust monthly-resolved chronology built using annual δ13C cycles. We interpret seasonal U/Ca variations in YOK-G as reflecting changes in the amount and seasonality of prior aragonite precipitation driven by variable rainfall amounts. The U/Ca record strongly suggests that modern drying has occurred in Belize, and that this drying was primarily caused by a reduction in wet season rainfall. This is consistent with published stable isotope data from YOK-G also very strongly suggesting modern rainfall reductions, previously interpreted as the result of southward ITCZ displacement. Our results strongly suggest that U/Ca values in aragonitic speleothems are excellent proxies for rainfall variability. This new tool, combined with the exceptional chronological control characteristic of aragonitic stalagmites and the high spatial resolution afforded by modern microanalytical techniques, should facilitate the construction of new exquisitely resolved rainfall records, providing rare insights into seasonality changes as well as long-term changes in local recharge conditions.

Radiological impact of surface water and sediment near uranium mining sites

The aim of this study is to assess the radiological impact of surface water and sediment around uranium mining sites 20 years after their closing. The areas under observations are 31 former classical underground uranium mining and exploratory sites in Bulgaria, named as objects. The extraction and processing of uranium ores in the Republic of Bulgaria were ended in 1992. To assess the radiological impact of radionuclides field expeditions were performed to sample water and bottom sediment. The migration of uranium through surface water was examined as one of the major pathways for contamination spread. The range of uranium concentration in water flowing from the mining sites was from 0.012 to 6.8 mgU l−1 with a geometric mean of 0.192 mgU l−1. The uranium concentrations in water downstream the mining sites were approximately 3 times higher than the background value (upstream). The concentrations of Unat, 226Ra, 210Pb, and 232Th in the sediment of downstream river were higher than those upstream by 3.4, 2.6, 2, and 1.7 times, respectively. The distribution coefficient of uranium reflects its high mobility in most of the sites. In order to evaluate the impact on people as well as site prioritization for more detailed assessment and water management, screening dose assessments were done.

Solvent extraction studies of uranium(VI) from phosphoric acid: Role of synergistic reagents in mixture with bis(2-ethylhexyl) phosphoric acid

The extraction of uranium(VI) from 5.3mol·L−1 H3PO4 (a typical concentration of wet phosphoric acid) with a series of neutral organosphosphorus synergistic reagents (0.125–0.250mol·L−1) used in mixture with 0.5mol·L−1 bis(2-ethylhexyl) phosphoric acid (D2EHPA) in Isane IP 185 (a 100% isoparaffinic aliphatic diluent) has been investigated. The series of synergistic reagents includes tri-n-butyl phosphate (TBP), di-n-butyl n-butyl phosphonate (DBBP), n-butyl di-n-butyl phosphinate (BDBP), tri-n-butyl phosphine oxide (TBPO), tri-n-hexyl phosphine oxide (THPO), tri-n-octyl phosphine oxide (TOPO), tri-n-decyl phosphine oxide (TDPO), di-n-hexyl n-decyl phosphine oxide (DHDPO), n-decyl di-n-hexyl phosphinate (DDHP) and di-n-hexyl octyl methoxy phosphine oxide (di-n-HMOPO). It appears that the presence of oxygen atoms at the vicinity of the phosphorus atom in the hydrophobic chains of the synergistic reagents, as in BDBP, DBBP and TBP, lowers significantly the extraction properties of uranium(VI) from phosphoric acid compared for instance to TBPO. Conversely, the increase of the hydrophobicity of the synergistic reagents by increasing the number of carbon atoms in their hydrophobic chains is responsible for an improvement of the extraction efficiency of uranium(VI). Among all the studied systems, the mixture of D2EHPA and di-n-HMOPO in Isane IP 185 leads to the best recovery of uranium(VI) from 5.3mol·L−1 H3PO4. A physicochemical model has been developed to simulate the extraction data and identify the equilibria involved in the recovery of uranium(VI) from 5.3mol·L−1 phosphoric acid by D2EHPA/di-n-HMOPO. A good agreement between experimental and calculated distribution coefficients of uranium(VI) is obtained by taking into account the following species in organic phase: H3PO4-S, (HL)2-S, (HL)5-S, (HL)2-(S)2 and UO2(HL2)2, UO2(HL2)2S, UO2L2S, where L denotes the monomeric deprotonated form of D2EHPA (HL) and S refers to di-n-HMOPO.

Batch Simulation of Multistage Countercurrent Extraction of Uranium in Yellow Cake from Monazite Processing with 5% TBP/Kerosene

In the processing of monazite ore to separate uranium, thorium and rare earth elements composed in the ore, uranium is first extracted and precipitated in the form of sodium diuranate (Na2U2O7) or yellow cake. This yellow cake requires further purification to remove thorium and traces of rare earth impurities from the cake. The extraction of uranium in 4N HNO3 with 5% TBP/kerosene extractant has been studied with a series batchwise extraction to simulate multistage countercurrent solvent extraction. Feed solutions were prepared from yellow cake obtained from the processing of monazite ore which has about 60% purity of uranium. Simulated continuous countercurrent extraction with 4, 5 and 6 extraction stages were carried out. Equilibrium distribution coefficients (D) of both uranium and thorium were found to decrease with increasing feed concentration and distribution coefficient of uranium is about 8.8 to 10.8 times higher than that of thorium. The highest distribution coefficient of uranium is 3.107 at uranium concentration of 3,182mg/L. Uranium recovery was found to increase from 83.76 to 90.91% with the increasing number of extraction stage from 4 to 5. Increasing of solvent to feed ratio from 1:1 to 2:1 also increases uranium recovery from 83.76 to 93.30%. However, purity of uranium obtained from most extraction seems to be limited at 93-94%. This suggests that a scrubbing process will be required to improve the purity of uranium in this extraction system.

Pysicochemical Phenomena Involved in the Recovery of Uranium from Phosphate by BiDiBOPP/di-n-HMOPO and Development of New Cationic Extractants

This paper studied the recovery of uranium (VI) from 5.3M phosphoric acid by bis(1,3-dibutoxypropan-2-yl) phosphoric acid (BiDiBOPP)/di-n-hexyl octyl metoxy phosphine oxide (di-n-HMOPO) and 5 analogs of BiDiBOPP mixed with tri-n-octylphosphine oxide (TOPO) diluted in Isane IP 185. First, this paper shows that the experimental and calculated distribution coefficients of uranium (VI) as a function of the concentration of BiDiBOPP and di-n-HMOPO match by using a thermodynamic model previously developed and validated on the bis(2-ethylhexyl) phosphoric acid (D2EHPA)-TOPO system. In this model the formation of complexes between the cationic extractant (HL) and the solvatant extractant (S) such as (HL)2, (HL)2S, (HL)2S2 and (HL)5S and the recovery of uranium (VI) as UO2(HL)2L2S, UO2L2S and UO2(HL)2L2 were taken into account where L refers to the deprotonated form of the cationic extractant HL. Secondly, the investigation of the extraction of uranium (VI) by the BiDiBOPP analogs mixed with TOPO in Isane IP 185 showed that the presence of oxygen atoms in the two aliphatic chains of BiDiBOPP and the increase of the hydrophobicity of these chains influence strongly the extraction properties.

Extraction of uranium from nuclear industrial effluent using polyacrylhydroxamic acid sorbent

Solid-phase extraction process using chelating sorbent is a novel technique due to its high separation efficiency and simplicity. A designed three-dimensional cross-linked hydrophilic chelating polymeric sorbent, polyacrylhydroxamic acid, was developed for enhanced uptake of uranium from waste solution (pH 6–9) by complexation between the sorbent’s active functional group and uranium. The sorbent was synthesized by polymerization of acrylamide with cross-linking agent, followed by conversion and functionalization with hydroxylamine hydrochloride. In this paper, removal and recovery of uranium from effluent of uranium material processing plant in the presence of competitive ions such as sodium, calcium and magnesium were studied using the sorbent. Uranium uptake property of the developed sorbent was also investigated with respect to sorbent’s physical characteristics such as bead size distribution and bead swelling, in batch experiments. Distribution coefficient of uranium in the sorbent was substantially high (1,250 mL of effluent/g of sorbent), and immobilization factor was 0.028. The results showed that more than 90 % recovery of uranium is viable from nuclear effluent without preconditioning. Breakthrough profiles of column operation were successfully described for effective removal of uranium in continuous mode. The novel sorbent has been used for polishing the nuclear wastewater and hence to mitigate the environmental issues.

Impact of Soil Surface Charge Properties on Migration Behavior of Radioactive Uranium, Strontium and Cesium

Static adsorption experiments were conducted to understand the impact of soil surface charge characteristics, such as pH, AEC and CECp values, on migration behavior of radioactive Uranium, Strontium and Cesium. The results demonstrate that distribution coefficient of Uranium (U-Kd value) increases with decreasing initial pH of solution, and increases with increasing AEC values for acidic clay and silty clay that were studied; distribution coefficients of Strontium and Cesium appear to be positively correlated with CECp values of and total contents of montomorillonite and illite in the soil.

Recovery of uranium (VI) from concentrated phosphoric acid by mixtures of new bis(1,3- dialkyloxypropan-2-yl) phosphoric acids and tri-n-octylphosphine oxide

Three new extractants, namely bis(1,3-dihexyloxypropan-2-yl) phosphoric acid, bis(1,3-dioctyloxypropan-2-yl) phosphoric acid and bis(1,3-di-2-ethylhexyloxypropan-2-yl) phosphoric acid, were synthesized and tested in mixture with tri-n-octyl phosphine oxide (TOPO) in Isane IP 185 for the recovery of uranium (VI) from 5.3molL−1 synthetic phosphoric acid and 30% wt P2O5 industrial wet phosphoric acid. The results were compared with those previously obtained with bis(1,3-dibutoxypropan-2-yl) phosphoric acid (BiDiBOPP), under similar experimental conditions. The increase of the length of the alkyloxy chains of bis(1,3-dialkyloxypropan-2-yl) phosphoric acid is responsible for an increase of the distribution coefficients of both uranium (VI) and iron (III) whereas steric hindrance effect arising from the increase of branching improves the selectivity for uranium (VI) against iron (III). A quantitative relationship between the distribution coefficients of uranium (VI) measured for the series of 7 extractants and two molecular descriptors has been developed. This opens a way for computer-guided design of new phosphoryl-containing extractants.

Development of New Cationic Exchangers for the Recovery of Uranium (VI) from Concentrated Phosphoric Acid

The extraction of uranium (VI) from 5.3 mol.L−1 phosphoric acid with a series of phosphoric, phosphinic, dithiophosphoric, or dithiophosphinic acid derivatives (0.5 mol.L−1) in mixture with 0.125 mol.L−1 TOPO in Isane IP 185 has been investigated. In the frame of the present work, eight acidic phosphorus and thiophosphorus compounds have been synthesized: bis(1,3-diisobutoxypropan-2-yl) phosphoric acid, bis(1,3-bis-(butylthio)propan-2-yl) phosphoric acid, bis(5,8,12,15-tetraoxanonadecan-10-yl) phosphoric acid, bis(1-butoxyheptan-2-yl) phosphoric acid, bis(undecan-6-yl) phosphoric acid, bis(2-(1,3-dibutoxypropan-2-yloxy)ethyl) phosphoric acid, bis(3-butoxy-2-(butoxymethyl)-2-methylpropyl) phosphinic acid, bis(1,3-dibutoxypropan-2-yl) dithiophosphoric acid. The properties of these molecules in mixtures with TOPO have been compared with those of other extractants such as bis(2-ethylhexyl) phosphoric acid, bis(2-ethylhexyl) dithiophosphoric acid, bis(2-ethylhexyl) phosphinic acid, Cyanex® 272, and Cyanex® 301. The replacement of phosphoric acid-type extractant by their phosphinic homologues dramatically decreases the affinity for uranium (VI) whereas the replacement of the phosphoric and phosphinic acid-type extractants by their dithio homologues affects positively the distribution coefficient of uranium (VI). It also appears that the steric hindrance effect is responsible for a significant decrease of the distribution coefficient of uranium (VI). Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science and Technology to view the free supplemental file.

Modeling of the extraction of uranium (VI) from concentrated phosphoric acid by synergistic mixtures of bis-(2-ethylhexyl)-phosphoric acid and tri-n-octylphosphine oxide

A thermodynamic model has been developed to describe the extraction of uranium (VI) from 5.3molL−1 phosphoric acid (a typical concentration encountered in wet phosphoric acid) by mixtures of bis-(2-ethylhexyl)-phosphoric acid (D2EHPA, also denoted hereafter HL) and tri-n-octylphosphine oxide (TOPO). A good agreement between experimental and calculated distribution coefficients of uranium (VI) was obtained by taking into account the following species in the organic phase: (HL)2TOPO, (HL)5TOPO, (HL)2(TOPO)2, UO2(HL2)2, UO2(HL2)2TOPO, and UO2L2TOPO where L is the deprotonated form of D2EHPA (HL). The speciation of uranyl, TOPO and D2EHPA in the organic phase was derived from this model as a function of the concentrations of the latter species.

Estimation of distribution coefficient of uranium around a uranium mining site

Distribution coefficient (Kd) of uranium and its daughter products are very important for migration study around uranium mining sites. Since the distribution coefficient depends very much on the soil and groundwater chemistry, generation of site specific Kd is very important. In the literature there is a large variation of Kd values of uranium. For realistic prediction of contaminant migration, literature Kd value is not very effective. So site specific experimental Kd values are required. The present study emphasizes on the estimation of site specific distribution coefficient for uranium around a uranium mining site. The soil and groundwater parameters which affect the Kd value of uranium have also been estimated. Soil and groundwater samples from nine locations around Turamdih uranium mining site were collected and chemically characterized for various parameters. The distribution coefficient of uranium in top and one meter depth soil samples from above locations were estimated using laboratory batch method. The distribution coefficient of uranium varies from 69 ± 4 to 5524 ± 285 l/kg. No significant difference in uranium Kd values was observed for top and one meter depth soil samples. In the top and one meter depth soil samples uranium Kd values vary from 129 ± 8 to 5524 ± 285 and 69 ± 4 to 3862 ± 195 l/kg respectively. For the estimation of distribution coefficient of uranium different parameters like equilibration time, solid to solution ratio, method of tracer addition to solution, solid-solution separation method etc. have been optimized. The distribution coefficient of uranium determined in the present study will be used for the migration study of uranium around uranium mining sites.

Extraction of uranium from hydrochloric acid solutions by alkylated crown ethers

The extraction recovery of uranium from 1–10 mol/L hydrochloric acid solutions into solutions of alkylated crown ethers di-tert-butyldibenzo-18-crown-6 (DTBDB18C6) and di-tert-butyldicyclohexyl-18-crown-6 (DTBDCH18C6) in organic solvents (nitrobenzene, 1,2-dichloroethane, chloroform, 1-octanol) was studied. It was found that with increasing HCl concentration, the value of the distribution coefficients of uranium (D) between the organic and aqueous phases increased to a maximum value at 9 mol/L HCl for DTBDB18C6 and 6–7 mol/L HCl for DTBDCH18C6. The properties of the solvent also greatly affect the values of D, reaching a maximum in the application of nitrobenzene, dichloroethane, or their mixture. Under these conditions, D for a 0.01 mol/L solution of DTBDCH18C6 in nitrobenzene is 830, which is the highest of known values. It was determined by the slope method and the complete saturation method that the extracted complexes of the studied alkylated crown ethers with uranyl ions have the 2 : 1 composition. Thus, new supramolecular extractants of uranium from hydrochloric acid solutions have been studied, having an extremely high extraction capacity, which can be used in the analytical and preparative chemistry of uranium.