Separation of U(VI) and Th(IV) from Nd(III) by Cross-Current Solvent Extraction Mode Using Tri-iso-amyl Phosphate as the Extractant

Separation of U(VI) and Th(IV) from Nd(III) in nitric acid media with solutions of tri-iso-amyl phosphate (TiAP) in n-dodecane has been studied by batch extraction in cross-current mode to evaluate the feasibility of employing TiAP as an alternate extractant to tri-n-butyl phosphate (TBP) for monazite ore processing. The interference of U(VI), Th(IV), and Nd(III) in the presence of each other during their analyses by titrations has also been validated in the present study. The extraction studies substantiate that the high solvent loading conditions can be achieved without organic phase splitting in the extraction from concentrated feed solutions with TiAP based solvents, whereas TBP forms third phase under such conditions. The separation factor for Th(IV) with respect to Nd(III) can be improved with TiAP as the extractant and by carrying out the extraction with feed solution in 8 M HNO₃. Solvent extraction studies conducted with solutions of U(VI), Th(IV), and Nd(III) in nitric acid media by TBP and TiAP revealed the identical extraction, scrubbing, and stripping behavior of both the extractants with respect to U(VI), Th(IV), and Nd(III). The results insinuate that TiAP can be used as an alternate extractant to TBP for the separation of U(VI) and Th(IV) from monazite ores. The data generated in the present study can be exploited for the development of flow sheets using TiAP based solvents to separate U(VI) and Th(IV) from rare earths for the processing of monazite leach solutions.     

Cyto-Genotoxic and Transcriptomic Alterations in Human Liver Cells by Tris (2-Ethylhexyl) Phosphate (TEHP): A Putative Hepatocarcinogen

Tris (2-ethylhexyl) phosphate (TEHP) is an organophosphate flame retardant (OPFRs) which is extensively used as a plasticizer and has been detected in human body fluids. Contemporarily, toxicological studies on TEHP in human cells are very limited and there are few studies on its genotoxicity and cell death mechanism in human liver cells (HepG2). Herein, we find that HepG2 cells exposed to TEHP (100, 200, 400 µM) for 72 h reduced cell survival to 19.68%, 49.83%, 58.91% and 29.08%, 47.7% and 57.90%, measured by MTT and NRU assays. TEHP did not induce cytotoxicity at lower concentrations (5, 10, 25, 50 µM) after 24 h and 48 h of exposure. Flow cytometric analysis of TEHP-treated cells elevated intracellular reactive oxygen species (ROS), nitric oxide (NO), Ca⁺⁺ influx and esterase levels, leading to mitochondrial dysfunction (ΔΨm). DNA damage analysis by comet assay showed 4.67, 9.35, 13.78-fold greater OTM values in TEHP (100, 200, 400 µM)-treated cells. Cell cycle analysis exhibited 23.1%, 29.6%, and 50.8% of cells in SubG1 apoptotic phase after TEHP (100, 200 and 400 μM) treatment. Immunofluorescence data affirmed the activation of P53, caspase 3 and 9 proteins in TEHP-treated cells. In qPCR array of 84 genes, HepG2 cells treated with TEHP (100 µM, 72 h) upregulated 10 genes and downregulated 4 genes belonging to a human cancer pathway. Our novel data categorically indicate that TEHP is an oxidative stressor and carcinogenic entity, which exaggerates mitochondrial functions to induce cyto- and genotoxicity and cell death, implying its hepatotoxic features.     

The Influence of Extractant Structure on the Solvent Extraction of Uranium(VI) and Thorium(IV) from Nitrate Media by Dialkyl Sulphoxides

The solvent extraction of uranium(VI) and thorium(IV) from sodium nitrate solutions (0·20–6·00 M ) by a series of dialkyl sulphoxides with different structures was studied. For sulphoxides with n-alkyl groups (R₂SO, where R = n-hexyl, n-octyl and n-decyl) using 0·20 M solutions in xylene, the extractions of both uranium and thorium are relatively high, and the values of the separation factor β_Th^U are correspondingly low (≈20). Replacement of an n-hexyl group by a cyclohexyl group has little effect on metal extraction, whilst the introduction of a second cyclohexyl group causes a slight decrease in extraction. Similarly, there is little variation in the extraction of uranium and thorium through the series of asymmetrical compounds RR′SO, where R = n-octyl and R′ = cyclopentyl, cyclohexyl or cyclooctyl. When two aromatic (phenyl) rings are introduced into the sulphoxide, however, the extraction of both metals falls to zero. For the series of isomeric compounds R₂SO with C₈ alkyl groups, the separation factors increase in the order: R = n-octyl, 2-ethylhexyl, 2-octyl, 3-octyl, which is also the order of increasing steric bulk of the alkyl group. For these compounds, slope analysis studies are consistent with the formulation of the extracted metal complexes as UO₂(NO₃)₂(R₂SO)₂ and Th(NO₃)₄(R₂SO)₃. © 1997 SCI.     

Effect of an electric field on the transport of Th(IV) in the presence of Eu(III) and U(VI) through supported liquid membrane containing di‐2‐ethylhexylphosphoric acid

This paper investigates the transport of Th(IV) ions in nitric acid media through a supported liquid membrane (SLM) impregnated with di‐2‐ethylhexylphosphoric acid (HDEHP) in kerosene using an electric field. The transport was carried out in a three compartment cell fitted with microporous cellulose nitrate (SLM) and cation exchange membrane (Nafion). The effect of different parameters including nitric acid concentration in the feed solution, HDEHP concentration in the membrane, and HCl concentration were studied. The optimal conditions for Th(IV) transport were 0.1 mol dm^?3 HDEHP, 10^?3 mol dm^?3 HNO₃ in the feed solution, 1 mol dm^?3 HCl in compartment 2 and 1 mol dm^?3 HCl in compartment 3 at 25 °C. Under the optimal conditions of Th(IV) transport the recovery factor after 90 min was 0.25 without applying an electrostatic field, compared with 0.9 when the electric field was applied. The effect of electric current on the flux of Th(IV) through the membrane was also studied. The flux increased as the current density increased from 10 to 30 mA cm^?2 to reach a maximum value at 30 mA cm^?2 (8 × 10^?9 g eq cm^?2 s^?1). The transport percentages of 0.3 g dm^?3 Th(IV) in the presence of 0.1 g dm^?3 Eu(III) and 1 g dm^?3 U(VI) were 66, 84 and 15%, respectively. The determined selectivities of U(VI)–Th(IV) and Th(IV)–Eu(III) were 0.12 and 0.3, respectively, after 90 min. Therefore, the order of selectivity of this system is Eu(III) > Th(IV) > U(VI). © 2001 Society of Chemical Industry     

Selective Extraction and Separation of Ce (IV) and Th (IV) from RE(III) in Sulfate Medium using Di(2-ethylhexyl)-N-heptylaminomethylphosphonate

The extraction and separation of Ce(IV) and Th(IV) from trivalent rare earths (RE, including scandium) in sulfate medium using di(2-ethylhexyl)-N-heptylaminomethylphosphonate (DEHAMP, L) were studied. The effects of H₂SO₄ concentration, extractant concentration, and temperature on the metal extraction were investigated systematically. It was found that the extraction of metal ions by DEHAMP decreases in the following order: Ce(IV) > Th(IV) > Sc(III) > other RE(III). A possible extraction mechanism was proposed and the extracted complexes as Ce(SO₄)₂·2L and Th(HSO₄)₂SO₄·L were determined by the slope analysis method. Thermodynamic parameters (ΔH, ΔG, and ΔS) were calculated. The extraction reactions of Ce(IV) and Th(IV) were each exothermic processes. The loaded Ce(IV) and Th(IV) can be stripped efficiently by 3% H₂O₂ and 4 mol/L HCl, respectively. The extraction capacity of 0.63 mol/L DEHAMP is 30.0 g/L CeO₂ and 24.4 g/L ThO₂, respectively. Furthermore, a solvent extraction process to selectively extract and recover cerium and thorium from bastnaesite leaching was proposed, by which the purities of cerium and thorium products reached 97.2% and 96.5% with a yield of 85.4% and 98.8%, respectively.     

Evaluation of two-phase separation in N,N-di(2-ethylhexyl)butanamide-nitric acid systems using turbidity measurements

Quantitative evaluation of the two-phase separation between N,N-di(2-ethylhexyl)butanamide (DEHBA) and tri-n-butyl phosphate (TBP) diluted with n-dodecane and uranyl nitrate solution in nitric acid medium was achieved using turbidity measurements. The turbidities of DEHBA were relatively high, particularly at high DEHBA concentrations, while that of TBP rapidly decreased irrespective of nitric acid concentration. A high concentration of DEHBA, nitric acid, and uranium increased the turbidities in the organic phase, which could be ascribed to the increase in viscosity. Distribution ratios of uranium were also measured, and it was indicated that turbidity did not have a critical effect on the distribution ratio when the turbidity was below a certain value.     

Co-Extraction of U(VI) and HNO3 Using TBP and its Higher Homologues TiAP and TEHP: Comparison of Equilibria,Kinetics, and Rate of Extraction

In this work, bulk-liquid membrane (BLM) system is used to compare tri-n-butyl phosphate (TBP), tri-isoamyl phosphate (TiAP), and tris(2-ethylhexyl) phosphate (TEHP) for their relative ability to co-extract U(VI) and nitric acid from aqueous nitric acid feed-phase into water strip-phase, through hydrocarbon membrane-phase. The kinetics of extraction is modelled and the model is validated through experiments. The quantity which determines the efficiency of liquid emulsion membrane (LEM) process is the relative rate of extraction of U(VI) to nitric acid. This is in the order TiAP>TEHP>TBP, indicating that TiAP is most suitable for extraction of U(VI) from nitric acid using LEM.     

磷酸三丁酯和异丁基十二烷基亚砜萃取铀(VI)的研究

研究了以甲苯作稀释剂时 ,磷酸三丁酯 (TBP)和异丁基十二烷基亚砜 (BDSO)萃取铀 (VI)的机理。考察了硝酸浓度、温度对分配比的影响 ,求得萃取反应的热力学函数。考察了萃取剂浓度对协萃系数的影响 ,发现TBP和BDSO具有协萃效应 ,最大协萃系数在TBP :BDSO =1:1处     

Study of Mono-(2-ethylhexyl) Phosphoric Acid and Neutral Organophosphorus Synergists for Extraction of Uranium from Phosphoric Acid Solution

Abstract

The distribution of uranium(IV) and uranium(VI) between phosphoric acid solution and mono-(2-ethylhexyl) phosphoric acid (H₂MEHP)-trioctyl phosphine oxide (TOPO), and mono-(2-ethylhexyl) phosphoric acid-dibutyl butyl phosphonate (DBBP) in kerosene diluent has been investigated. The effects of extractant composition, phosphoric acid concentration, temperature, uranium concentration, and shaking time on the uranium extraction have been examined. Reductive extraction and oxidative stripping processes for the separation and concentration of uranium from phosphoric acid solution with synergic systems of H₂MEHP-TOPO and H₂MEHP-DBBP are proposed and discussed.     

Liquid-Liquid Extraction of Uranium(VI) from Aqueous Solution using 1-Hydroxyalkylidene-1,1-diphosphonic Acids

The extraction of uranium(VI) from aqueous solutions has been investigated using 1-hydroxyhexadecylidene-1,1-diphosphonic acid (HHDPA) and 1-hydroxydodecylidene-1, 1-diphosphonic acid (HDDPA), which were synthesized and characterized by elemental analysis and by FT-IR, ¹H NMR, ³¹P NMR spectroscopy. In this article, we propose a tentative assignment for the shifts of those two ligands and their specific complexes with uranium(VI). We carried out the extraction of uranium(VI) by HHDPA and HDDPA from [carbon tetrachloride?+?2-octanol (v/v: 90%/10%)] solutions. Various factors such as contact time, pH, organic/aqueous phase ratio, and extractant concentration were considered. The optimum conditions obtained were: contact time?=?20 min, organic/aqueous phase ratio?=?1, pH value?=?3.0, and extractant concentration?=?0.3 M. The extraction yields are more significant in the case of the HHDPA which is equipped with a hydrocarbon chain, longer than that of the HDDPA. Logarithmic plots of the uranium(VI) distribution ratio vs. pH_eq and the extractant concentration showed that the ratio of extractant to extracted uranium(VI) (ligand/metal) is 2:1. The formula of the complex of uranium(VI) with the HHDPA and the DHDPA is UO₂(H₃L)₂ (HHDPA and DHDPA are denoted as H₄L). A spectroscopic analysis showed that coordination of uranium(VI) takes place via oxygen atoms.     

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.     

吸附分离水体中铀的吸附材料研究新进展

铀是最危险的放射性金属之一,广泛存在于核燃料的制备、乏燃料后处理和矿石开采等生产活动所产生的含铀废水中,严重威胁水生生态系统与人类健康。吸附法处理水中的U(Ⅵ)具有便捷高效、经济和选择性好的优势。综述了近3年对水中铀吸附材料的研究新进展,介绍了无机、有机、有机无机复合和生物衍生类吸附材料的制备,结构特点,吸附性能,并对铀吸附材料的研究方向进行了展望。     

Distribution Studies of Zinc and Copper Salicylates with Tris(2-ethylhexyl)phosphate

Abstract

Tris(2-ethylhexyl)phosphate is proposed as an extractant for the solvent extraction of zinc and copper salicylate. The optimum extraction conditions are established by studying the various experimental parameters such as pH, sodium salicylate concentration, tris(2-ethylhexyl)phosphate concentration, equilibration period, and various diluents. The probable extracted species as ascertained by log D-log C plots is Zn(HSal)₂2T2EHP and Cu(HSal)₂2T2EHP. The method permits mutual separation of zinc and copper and can be used for separation and determination of zinc and copper in environmental and pharmaceutical samples.     

Cysteine-Functionalized Chitosan Magnetic Nano-Based Particles for the Recovery of Uranium(VI): Uptake Kinetics and Sorption Isotherms

Magnetic-chitosan nanoparticles, functionalized with cysteine, were synthesized and characterized by element analysis, FT-IR, XRD, TEM, and vibrating sample magnetometry. The sorbent was tested for U(VI) recovery, considering:

• a. pH effect,

• b. sorption isotherms (fitted by Langmuir equation), and

• c. uptake kinetics (modeled using the PSORE).

Maximum sorption capacity approached 100 mg U g^?1. The nanometric size of sorbent reduces the impact of resistance to intraparticle diffusion; this may explain the fast kinetics (equilibrium within 50 min). The reaction is exothermic, spontaneous. The metal could be desorbed using acidified urea solution and the sorbent could be recycled for 5 cycles.     

Extraction of Uranium and Thorium from Nitric Acid Solution by TODGA in Ionic Liquids

Extraction of uranium (UO₂²⁺) and thorium (Th⁴⁺) from a nitric acid solution into an imidazolium-type ionic liquids (ILs) of 1-alkyl-3-methylimidazolium hexafluorophosphate ([C_nmim][PF₆], n = 6 or 8) was carried out using N,N,N′,N′-tetraoctyl-3-oxapentanediamide (TODGA) as an extractant. It was found that the extraction efficiencies of UO₂²⁺ and Th⁴⁺ ions are higher in comparison with that done in n-dodecane. The extraction mechanism was deduced by the slope analysis and extraction experiment. Transfer of both ions is assumed to proceed predominantly through the neutral solvation mechanism from nitric acid solution into ILs. The UO₂²⁺ ion forms a 1:2 complex with TODGA in ILs at lower acidity, and a 1:1 complex in ILs and in n-dodecane at higher acidity. The Th⁴⁺ ion forms a 1:2 complex with TODGA in C₆mimPF₆ IL or a 1:1 complex in C₈mimPF₆ IL at lower acidity and a 1:1 complex in both ILs, and n-dodecane at higher acidity. Stripping studies were conducted using sodium salt of EDTA as a stripping ligand. The thermodynamics of extracting UO₂²⁺ ions and Th⁴⁺ ions from a 3 M HNO₃ solution was also studied. The results indicated that the extraction reactions are spontaneous and go through an exothermic process.     

Effect of Bis-(2-ethylhexyl)Phosphoric Acid on Sodium Bis-(2-ethylhexyl)Phosphate Microemulsion for Selective Extraction of Non-Ferrous Metals

The effect of bis-(2-ethylhexyl)phosphoric acid (DEHPA) on the region of existence, conductivity and structure of sodium bis-(2-ethylhexyl)phosphate (NaDEHP) microemulsion has a dual nature and depends on DEHPA concentration. In the system NaDEHP–DEHPA–kerosene–water, the narrowing of the microemulsion region is observed with DEHPA concentration in the organic phase growth from 0.1 to 0.5 mol/L. The increase of DEHPA concentration in the organic phase from 0.1 to 0.4 mol/L leads to the reduction of electrical conductivity of the microemulsions. Based on the conductivity and viscosity measurements, we suppose the transition from reverse microemulsion with isolated droplets to percolate microemulsion at volume fraction of water 0.18 ( \(W = C_{{H_{2} O}} /C_{\text{NaDEHP}}\)  = 8). Droplet size of the microemulsions increases linearly with W growth. The rise of DEHPA concentration in the organic phase from 0.1 to 0.3 mol/L causes the growth of the coefficient at W in the equation d = kW + b from 0.038 to 0.249, i.e., it increases the slope of the lines. In contrast, DEHPA introduction at the concentration 0.1 mol/L (in the organic phase) leads to the expansion of the microemulsion region, does not affect the conductivity and decreases the coefficient at W. The rate of copper recovery into the microemulsion increases considerably with the rise of DEHPA concentration from 0.0 to 0.3 mol/L; no dual effect is observed. The following composition of the microemulsion for non-ferrous metals leaching is recommended: C _NaDEHP = 1.6 mol/L, C _DEHPA = 0.3 mol/L (in the organic phase); W = 8–32.     

Uranium membrane separation from binary aqueous solutions of UO22+-K+ and UO22+-Ca2+ by the nanofiltration process

The performance of the nanofiltration process was investigated for uranium separation from binary aqueous solutions of UO₂²⁺-K⁺ and UO₂²⁺-Ca²⁺ containing uranium in high concentration ranges. Rejection coefficient, permeate flux, and membrane selectivity of PES-2, NF-1, and NF-2 membranes under various operational conditions of pH, pressure, and concentration of interfering cation were evaluated. In most cases, the order of metal rejections with these membranes was UO₂²⁺ > Ca²⁺ > K⁺. According to the obtained results, the nanofiltration process could be effectively used for selective uranium separation from aqueous solutions containing uranium and other monovalent and divalent cations.     

The Use of Tri-n-octylamine for the Separation of Vanadium(V) from Acidic Sulfate Uranium Leach Liquors

Abstract

Extraction of vanadium(V) from acidic sulfate solutions by a mixture of tri-n-octylamine and tributylphosphate (used as modifier) dissolved in kerosene has been studied. The distribution coefficient of vanadium(V) increases with an increase in pH and vanadium(V) concentration. The presence of iron(III) in aqueous solution does not have any appreciable effect, while large amounts of sulfate ion depress the distribution coefficient. Uranium(VI) has a distribution different from vanadium(V). Based upon these results, a scheme for the separation of vanadium(V) from uranium leach liquors has been made and checked experimentally.     

Studies on the Recovery of Uranium from Phosphoric Acid Medium Using Synergistic Mixture of 2-Ethyl Hexyl Hydrogen 2-Ethyl Hexyl Phosphonate and Octyl(phenyl)-N,N-diisobutyl Carbamoyl Methyl Phosphine Oxide

Abstract

This paper describes the extraction of uranium from aqueous phosphoric acid medium using 2-ethyl hexyl hydrogen 2-ethyl hexyl phosphonate (PC88A) and octyl (phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) individually as well as their synergistic mixture in different diluents. The extraction parameters such as variation in concentration of either of the extractants, concentration of H₃PO₄ and uranium in the aqueous phase are investigated to optimize the extraction conditions. Results indicate that the synergistic mixture, 0.9 M PC88A + 0.1 M CMPO in xylene, can be used for the extraction of uranium from the phosphoric acid medium. The loaded uranium from the synergistic organic phase can be stripped using 0.5 M solution of (NH₄)₂CO₃. This synergistic mixture is used to recover uranium from a typical wet process phosphoric acid sample and the recovery is found to be better than 90%.