Supercritical Fluid Extraction Of Uranium Research Articles

Supercritical Fluid Extraction of Uranium, Plutonium and Thorium

In recent decades, extraction of actinides (U,Pu,Th) employing supercritical CO2has drawn attention owing to its inherent potential to minimize liquid waste generation. Supercritical Fluid Extraction (SFE) offers faster extraction with fine control over extraction process by means of varying pressure , temperature conditions. Supercritical Fluids have hybridproperties of liquid and gas. Liquid like solvation and gas like diffusivity enable topenetrate deep inside solid matrix, extracting component of interest, thus capable of extraction from liquid as well as solid matrix. Metal ion is complexed withsuitable organic compound, which gets soluble in SC CO2 . SC CO2 acts as a solvent and after extractionescapes as gas leaving behind extractant. Various types of ligands such organophosphorus compounds, -diketones, macrocyclic compounds, amides, dithiocarbamates are employed.SFE offers attractive alternative to reprocessing of spent nuclear fuel and radioactive waste.In this paper, research work carried out on the SFE of actinides (U,Pu,Th) has been reviewed.

Supercritical Fluid Extraction of Uranium, Plutonium and Thorium: A Review

In recent decades, extraction of actinides (U,Pu,Th) employing supercritical CO2has drawn attention owing to its inherent potential to minimize liquid waste generation. Supercritical Fluid Extraction (SFE) offers faster extraction with fine control over extraction process by means of varying pressure , temperature conditions. Supercritical Fluids have hybridproperties of liquid and gas. Liquid like solvation and gas like diffusivity enable topenetrate deep inside solid matrix, extracting component of interest, thus capable of extraction from liquid as well as solid matrix. Metal ion is complexed withsuitable organic compound, which gets soluble in SC CO2 . SC CO2 acts as a solvent and after extractionescapes as gas leaving behind extractant. Various types of ligands such organophosphorus compounds, -diketones, macrocyclic compounds, amides, dithiocarbamates are employed.SFE offers attractive alternative to reprocessing of spent nuclear fuel and radioactive waste.In this paper, research work carried out on the SFE of actinides (U,Pu,Th) has been reviewed.

Supercritical fluid extraction of uranium and thorium from nitric acid medium using organophosphorous compounds

Abstract In recent years, Supercritical Fluid Extraction (SFE) technique has been widely used for the extraction of metal ions. In the present study, extraction of uranium from nitric acid medium was investigated using supercritical carbon dioxide (Sc-CO2) containing various organophosphorous compounds such as trialkyl phosphates e.g. tri-iso-amyl phosphate (TiAP), tri-sec-butyl phosphate (TsBP) and tri-n-butyl phosphate (TBP), dialkylalkyl phosphonates, e.g. diamylamyl phosphonate (DAAP) and dibutyl butyl phosphonate (DBBP), dialkyl hydrogen phosphonates, e.g. dioctyl hydrogen phosphonate (DOHP), dioctylphosphineoxide (DOPO), trioctyl phosphine oxide (TOPO), n-octylphenyl N,N-diisobutyl carbamoylmethylphosphine oxide (CMPO) and di-2-ethyl-hexyl phosphoric acid (HDEHP). Some of these ligands have been investigated for the first time in the supercritical phase for the extraction of uranium. The extraction efficiency of uranium was studied with TiAP, DAAP and DBBP as a function of nitric acid concentration; the kinetics of the equilibration period (static extraction) and transportation of the metal complex (dynamic extraction) was investigated. The influence of pressure and temperature on the extraction behaviour of uranium with DAAP was studied from 4 N HNO3. The extraction efficiency of uranium from 4 N nitric acid medium was found to increase in the order of phosphates < phosphonates < HDEHP < TOPO < CMPO. In the case of phosphates and phosphonates, the maximum extraction of uranium was found to be from 4 N HNO3 medium. The acidic extractants, HDEHP and DOHP showed relatively higher extraction at lower acidities. The relative extraction of uranium and thorium from their mixture was also examined using Sc-CO2 containing phosphates, phosphonates and TOPO. The ligand, TsBP provided better fractionation between uranium and thorium compared to trialkyl phosphates, dialkyl alkyl phosphonates and TOPO.

Supercritical fluid extraction of uranium and thorium employing dialkyl amides

N,N-dialkyl aliphatic amides with varying alkyl groups viz. N,N-dibutyl-2-ethyl hexanamide (DBEHA), N,N-dibutyl-3,3-dimethyl butanamide (DBDMBA), N,N-dihexyl octanamide (DHOA), N,N-di-sec-butyl pentanamide (DBPA), N,N-dibutyl octanamide (DBOA), have been evaluated for supercritical fluid extraction (SFE) of uranium and thorium from nitric acid medium as well as from tissue paper matrix. The trend in extraction efficiency could be correlated to the structure of the amides and the amide complex of uranium/thorium. Straight chain amide DBOA was found suitable for SFE of both uranium and thorium. Under optimised conditions (200atm. pressure, 323K temperature, 30min static time followed by 30min dynamic time, 0.5M amide in methanol), (94±3)% uranium and (85±4)% thorium could be extracted from 4M nitric acid medium. For tissue paper matrix, under optimised conditions (200atm pressure, 323K temperature, 45min static time followed by 30min dynamic time, 0.2M amide in methanol) (87±7)% uranium and (88±7)% thorium were extractable. For the amide having branching at Cα, DBEHA, extraction efficiency of thorium was as low as 7% for 2M HNO3 medium while extraction efficiency of uranium was still 95%. For tissue paper matrix, extraction efficiency for uranium with 0.2M DBEHA (in methanol) was 86% while only 11% thorium was extractable under same conditions. This fact could be exploited for separation of thorium and uranium.

Supercritical fluid extraction of uranium and fission products in reprocessing of simulated spent nuclear fuel in weakly acidic solutions of Fe(III) nitrate in the presence of tributyl phosphate

The kinetics of dissolution of ceramic UO2 in aqueous solutions of Fe(III) nitrate in the presence of TBP in supercritical CO2 was studied. Quantitative recovery of U into solutions of Fe nitrate in combination with its extraction from the solution into the fluid occurs under these conditions within ∼2 h, which is by more than an order of magnitude faster than in dissolution in a Fe(III) nitrate solution without TBP under common conditions. The behavior of uranium and simulated fission products (FPs) in reprocessing of simulated spent nuclear fuel (SSNF) in weakly acidic Fe(III) nitrate solutions using supercritical CO2 containing TBP was studied. Under these conditions, SSNF dissolves quantitatively with the simultaneous recovery of the U nitrate complex into the TBP-containing fluid phase. Uranium is recovered from the fluid phase by back extraction with an H2O2 solution with simultaneous precipitation of U in the form of the peroxide UO4·2H2O. In the process, high degree of uranium decontamination from all the FPs is reached, which allows repeated use of U in the nuclear fuel cycle.

Characteristics of an oxa-diamide–HNO3 extractant in the supercritical fluid extraction of uranium

An extractant is required in the recovery process to drive the uranium to a stage that enables it to be extracted using the extraction solvent. This paper proposes the composition of a composite extractant, N,N,N′,N′-tetrabutyl-3-oxapentane-diamide–HNO3 (TBODA–HNO3) as an extractant, to successfully achieve the objective using supercritical carbon dioxide (sc-CO2). The composite TBODA–HNO3 extractant has a chemical composition of TBODA(HNO3)1.0(H2O)1.5. The U(IV) in the UO2 containing solid phase is directly oxidized to U(VI) in the form of $$ {\rm UO}_{2}^{2 + } $$ in sc-CO2, which contains a CO2-soluble TBODA–HNO3 extractant at 200 atm and 50 °C. The resulting $$ {\rm UO}_{2}^{2 + } $$ /TBODA complex can be consequently extracted using acetone-modified sc-CO2. The chemical composition of the $$ {\rm UO}_{2}^{2 + } $$ /TBODA complex, which can be extracted by nonpolar sc-CO2, is proposed in the form of an ion pair: [UO2(TBODA)2]2+–2( $$ {\rm NO}_{3}^{ - } $$ ).

Supercritical Carbon Dioxide Extraction of Uranium from Acidic Medium Employing Calixarenes

Various calixarenes were evaluated for the supercritical fluid extraction of uranium from nitric acid medium. The extraction efficiency was found to be affected by various parameters, namely pressure, temperature, CO2 flowrate, extraction time, and molarity of nitric acid. The addition of HPFOA (pentadecafluoro-n-octanoic acid) for the production of CO2-phillic fluorinated counter ion enhanced the extraction efficiency. Under optimized conditions (pressure of 200 atm, temperature of 323 K, 30 minutes of static time followed by 30 minutes of dynamic time, CO2 flowrate of 2 mL min−1, nitric acid molarity of 0.1 M) for uranium: calixarene: HPFOA mole ratio of 1:5:10, highest extraction efficiency could be obtained with p-tert.-butyl calix[6]arene (79.9%). Solvent extraction study with hexane as the organic phase indicated the formation of [UO2 (calixarene)]2+. In order to assess the suitability of the developed method to extract uranium in the presence of a host of other ions, extraction efficiency for other metal ions was estimated.

Supercritical fluid extraction of uranium from sintered oxides (UO2, (U,Th)O2), soil and ore samples using tri-n-butylphosphate andN,N-di-(2-ethylhexyl) isobutyramide as extractants

ABSTRACT Direct extraction of uranium from different samples viz. sintered UO2, (U,Th)O2, soil, and ores was carried out by modifier free supercritical fluid containing tri-n-butylphosphate (TBP) and/or N,N-di-(2-ethylhexyl)isobutyramide (D2EHIBA) as extractants. These extractants were pre-equilibrated with nitric acid prior to their use in supercritical fluid extraction experiments. Uranium extraction studies from sintered UO2 showed that pre-equilibration with more concentrated nitric acid helped in its better dissolution and extraction. The extraction of uranium from (U,Th)O2 samples was signifi cantly lower for both TBP–HNO3 (∼17%) and D2EHIBA–HNO3 (∼12%) adducts in 2 h, under the conditions of present study. Modifier free supercritical fluid extraction appears attractive with respect to minimization of secondary wastes. This method resulted 80–100% extraction of uranium from different soil/ore samples. The results were confirmed by performing neutron activation analysis of original (before extraction) and residue (after extraction) samples.

Supercritical fluid extraction of uranium from sintered oxides(UO2, (U,Th)O2), soil and ore samples using tri-n-butylphosphate and N,N-di (2-ethylhexyl) isobutyramide as extractants

Supercritical fluid extraction of uranium from sintered oxides(UO2, (U,Th)O2), soil and ore samples using tri-n-butylphosphate and N,N-di (2-ethylhexyl) isobutyramide as extractants

A novel technique for modifier free delivery of ligands for supercritical fluid extraction

A novel method has been developed for the controlled delivery of various ligands including solid extractants using supercritical carbon dioxide (Sc-CO2). A ligand delivery vessel with a restricted geometry where its inlet and outlet are located beside each other, accomplished the task of the controlled delivery of ligands. The proposed method eliminates the usage of modifier solvent such as methanol for the delivery of various ligands during the supercritical fluid extraction of metal ions. Using neat Sc-CO2, the delivery profiles for the various ligands such as octyl(phenyl)-N,N-diisobutylcarbamoylmethyl-phosphineoxide (CMPO), tri-n-butyl phosphate (TBP), tri-n-octyl phosphine oxide (TOPO), theonyltrifluroacetone (TTA) and di(2-ethylhexyl)isobutyramide (D2EHIBA) were established. The delivery profiles were optimised by investigating the influence of various extraction parameters such as ligand delivery vessel geometry, temperature, pressure, flow rate of Sc-CO2 and ligand content. Applications of these ligand delivery modes were demonstrated for the supercritical fluid extraction of uranium from tissue paper matrix and preferential extraction of uranium over thorium. These results are compared with the extraction studies involving methanol or hexane modifier under similar experimental conditions. The extraction of neodymium nitrate was also demonstrated using modifier free delivery mode.

Study of effects of different parameters on supercritical fluid extraction of uranium from acidic solutions employing TBP as co-solvent

Abstract In the supercritical fluid extraction of uranium from acidic medium employing TBP as co-solvent, effects of various parameters on extraction efficiency were studied. Variation in pressure (80–300 atm), temperature (308–353 K), CO2 flow rate (0.5–3 mL/min), co-solvent percentage (1–10%), molarity of nitric acid (0.5–10 M) were found to influence uranium extraction efficiency. The uranium extraction efficiency depends on distribution ratio and kinetics of transport of U-TBP complex into supercritical CO2. In the 150–300 atm pressure range, variation in extraction efficiency was similar to that of uranium distribution ratio under equilibrium conditions. Whereas below 150 atm, it closely followed supercritical CO2 density variation which could be attributed to non-equilibrium behavior that eventually attained equilibrium. In the non-equilibrium region, increased supercritical CO2 density with pressure favored enhancement in solubility as well as extraction kinetics of the U-TBP complex. Increase in temperature generally resulted in enhanced volatility of U-TBP complex and a decrease in supercritical CO2 density which in turn affected the extraction efficiency. Up to 333 K temperature, extraction efficiency gradually increased due to enhancement in volatility of U-TBP complex which more than compensates for decrease in the supercritical CO2 density. Beyond this temperature, the steep fall in the extraction efficiency is attributed to combined effect of saturation in volatility of the U-TBP complex and significant decrease in the density of supercritical CO2 approaching the critical value at which supercritical CO2 tends to form large clusters thereby resulting in steep decrease in its solvating power. Extraction efficiency was found to increase with nitric acid molarity up to 7 M and afterwards showed small decrease possibly due to competitive co-extraction of HNO3. Up to CO2 flow rate of 1 mL/min increase in extraction efficiency was observed which attained saturation afterwards. Linear increase in extraction efficiency was observed with the amount of TBP. Extraction efficiency was found to increase linearly with logarithm of extraction time. Under optimised conditions (150 atm, 333 K, 1 mL/min CO2 flowrate, 10% co-solvent, 7 M nitric acid and 30 min dynamic extraction time) extraction efficiency was found to be (98±2) was observed. 30 min dynamic extraction mode was found equivalent to 40 min static mode. Online complexation mode was more efficient than in situ mode.

Supercritical fluid extraction of uranium and thorium from solid matrices

Supercritical fluid extraction (SFE) of uranium and thorium from solid matrices was carried out employing CO 2. Direct dissolution and extraction of oxides of uranium viz. UO 2 and U 3O 8 was performed. UO 2 and U 3O 8 powders (0.02–0.05 g) along with 2 ml of TBP–HNO 3 complex were taken in extraction vessel and CO 2 was fed until 150 atm. pressure and 60°C temperature were achievable. After 20 min uranium extraction was performed by continuously flowing supercritical fluid mixture of CO 2 and 10% TBP for 45 min. Uranium extraction efficiency for U 3O 8 was 97.05 ± 3.73% and for UO 2 was 98.07 ± 4.76%. For SFE of thorium from tissue paper matrix, TBP and TOPO (0.2 M in CCl 4) were investigated as complexing agents. In online complexation mode, mixture of CO 2 and 10% complexing agent was fed to the extraction vessel. The vessel was maintained at pressure of 200 atm. and temperature of 60°C for 20 min followed by 20 min of extraction. TOPO was found to be more effective than TBP as extraction efficiencies with TBP and TOPO were 52.51 ± 7.54% and 65.65 ± 7.78% respectively. The efficiency was found to improve with a combination of 1: 1 volume ratio of TBP and TOPO (0.2 M in CCl 4). No further improvement was observed with TOPO plus 10% methanol. In in-situ mode higher efficiency i.e. 89.83 ± 7.04% was observed with employing TOPO as a complexing agent. Uranium and thorium were determined spectrophotometrically employing arsenazo III metal indicator for color development.

Selective Supercritical Fluid Extraction of Uranium(VI) using N‐Phenyl‐(1,2‐Methano‐Fullerene C60)61‐Formohydroxamic acid and Simultaneous On‐line Determination by Inductively‐Coupled Plasma‐Mass Spectrometry (ICP‐MS)

Uranium(VI) is extracted with N‐phenyl‐(1,2‐methano‐fullerene C60)61‐formohydroxamic acid, PMFFHA, in dichloromethane by supercritical carbon dioxide (SF‐CO2)‐dichloromethane (modifier) medium. A 2.0 µL aqueous uranium is extracted accurately and also preconcentrated in an especially designed extraction vessel of 80 µL capacity. The extracted microdrop orange‐red colored uranium(VI)‐PMFFHA complex in dichloromethane was online measured by fiber optics spectrometry and ICP‐MS. The distribution ratio (DUO2 2+ ) of U(VI) was determined. The slopes of log DUO2 2+ versus PMFFHA concentration plot, the extracted species both in SF‐CO2 extraction (SFE) and the solvent extraction (SE) were determined to be 2.0 as UO2(PMFFHA)2 complex. The uranium is determined as low as 0.10 ng mL−1 in presence of several cations and anions. The effect of diluents, modifier concentration, temperature and pressure on the extraction and separation of uranium was studied. The uranium is determined in human blood serum, natural water, seawater, standard samples and also in monazite sand. The PMFFHA has been successfully used as carrier for the selective and efficient transport of uranium(VI). The feed comprised of a solution of uranium(VI) and aqueous solution of diverse cations and anions in pH 4.5, while 1M HNO3 was used as a stripping agent in the receiving compartment of permeated cell. Maximum transportation was observed for 12 minutes with t1/2 equal to 6.3 min. The uranium(VI) was determined in presence of uranium(IV).

Studies on the supercritical fluid extraction of uranium from tissue matrix

Summary Extraction of uranium from tissue matrix was studied using supercritical carbon dioxide containing modifier solvent. The extraction efficiency was investigated with carbon dioxide containing methanol, tri-n-octyl phosphine oxide (TOPO) in methanol and tri-n-butyl phosphate (TBP) in methanol as modifiers. The extraction behaviour of the UO2(NO3)2 · 2TOPO complex loaded on tissue was also investigated. Supercritical carbon dioxide modified with methanol alone was found to extract a maximum of about 76% uranium from tissue matrix.

Supercritical fluid extraction of uranium and thorium from nitric acid solutions with organophosphorus reagents

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSupercritical fluid extraction of uranium and thorium from nitric acid solutions with organophosphorus reagentsYuehe. Lin, Neil G. Smart, and Chien M. WaiCite this: Environ. Sci. Technol. 1995, 29, 10, 2706–2708Publication Date (Print):October 1, 1995Publication History Published online1 May 2002Published inissue 1 October 1995https://doi.org/10.1021/es00010a036RIGHTS & PERMISSIONSArticle Views548Altmetric-Citations100LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (330 KB) Get e-Alerts Get e-Alerts