LIX 84 as an extractant for throium(IV), uranium(VI) and molybdenum(VI)

The extraction order of Th(IV), U(VI) and Mo(VI) based on pH_0.5 values is Mo(VI)>U(VI)>Th(IV). Quantitative extraction has been observed for U(VI) by mixture of 10% (v/v) LIX 84 and 0.1M dibenzoylmethane at pH 4.2 and by mixture of 10% LIX 84 and 0.05M HTTA in the pH range 5.5–7.3 and for Mo(VI) by 10% LIX 84 from chloride media at pH 1.5. The order of extraction of Mo(VI) from 1N acid solutions is HCl>H₂SO₄>HNO₃>HClO₄ and extraction decreases very rapidly with increase in the concentration of HCl as compared to that from H₂SO₄, HNO₃ and HClO₄ acid solutions. The diluents C₆H₆, CCl₄ and CHCl₂ are found to be superior ton-butyl alcohol and isoamyl alcohol for extraction of Mo(VI). Influence of concentration of different anions on the extraction of U(VI) and Mo(VI) has been studied. Very little extraction has been observed in case of Th(IV) by LIX 84 or its mixtures with other chelating extractants or neutral donors.     

Extraction of U(VI) by cyanex-272

Extraction of U(VI) from HNO₃, HCl and HClO₄ media using cyanex-272 (bis[2,4,4 trimethyl pentyl] phosphinic acid)/n-dodecane has been carried out. In the case of HNO₃ and HClO₄ media, the distribution ratio (D) value first decreases and then increases, whereas from HCl medium it first decreases and then remains constant with increase in H⁺ ion concentration. At lower acidities, U(VI) was extracted as UO₂(HA₂)₂ by an ion exchange mechanism, whereas at higher acidities as UO₂(NO₃)₂ ^.2(H₂A₂) following a solvation mechanism. The D for U(VI) by cyanex-272, PC-88A and DEHPA at low acidities follows the order cyanex-272 > PC-88A > DEHPA. Also, cyanex-272 was found to extract U(VI) more efficiently than TBP at 2M HNO₃. The effect of diluents on the extraction of U(VI) by cyanex-272 followed the order cyclohexane > n-dodecane > CCl₄ > benzene. The loading of U(VI) into cyanex-272/n-dodecane from 2M HNO₃ has shown that at saturation point, cyanex-272 was 78% loaded. No third phase was observed at the saturation level. The stripping of U(VI) from the loaded organic phase was not possible with water, it was poor with acetic acid and sodium acetate but quantitative with oxalic acid, ammonium carbonate and sodium carbonate.     

Extraction of some elements of the groups IV b and VI b with 1-phenyl-3-methyl-4-caproyl-pyrazolone-5 (PMCP) from aqueous mineral acid solutions

Solvent extraction of Cr(VI), Mo(VI), W(VI) and Hf(IV) with 1-phenyl-3-methyl-4-caproyl-pyrazolone-5 (PMCP) in methyl isobutylketone (MIBK), xylene and chloroform (CHCl₃) from mineral acid solutions was studied. Chromium(VI) is not extracted from any of the acids studied (HCl, H₂SO₄ and HClO₄). Molybdenum(VI) is quantitatively extracted by the reagent in xylene and CHCl₃ from HClO₄ and HNO₃ solutions. It is also extracted quantitatively by the reagent in MIBK from HCl, HNO₃ and H₂SO₄ solutions but the participation of the diluent as extractant is considerable. Tungsten(VI) is quantitatively extracted in xylene from 9M HClO₄ solution. MIBK used as diluent also affects its extraction with PMCP. Hafnium(IV) is not extracted from H₂SO₄ solutions while it extracts more than 99% at 3M HNO₃ and above. The extracted species likely are: MoO₂(PMCP)₂, WO₂(PMCP)₂ and Hf(PMCP)₄, respectively.     

Extraction of molybdenum(VI) by 4-(5-nonyl)pyridine in benzene from aqueous mineral acid solutions containing thiocyanate ions

Extraction of Mo(VI) by 4-(5-nonyl)pyridine (NPy) in benzene from mineral acid solutions containing thiocyanate ions has been investigated at room temperature (23±2°C). From mineral acid (HCl, HNO₃, and H₂SO₄) solutions alone Mo(VI) is not extracted quantitatively while the presence of small amounts of KSCN in the system augments the extraction by a large factor. Stoichiometric studies indicate that ion-pair type complexes (NPyH)₂·[MoO₂(SCN)₄] are responsible for the extraction. Separation factors determined at fixed extraction conditions (0.1M Npy/C₆H₆–0.1M acid +0.2M KSCN) reveal that Ag(I), Cu(II), Co(II), Zn(II), Hg(II) and U(VI) are co-extracted while a clean separation from alkali metals, alkaline earths and some transition metals like Ln(III), Zr(IV), Hf(IV), Cr(III), Cr(VI) and Ir(III) is possible. Some of the complexing anions like oxalate, citrate, acetate, thiosulfate or ascorbate do not affect the degree of extraction of Mo(VI) allowing it to be recovered from diverse matrices.     

Efficacious selective separation of U(VI) over Mo(VI) using novel 2,9-diamide-1,10-phenanthroline ligands: Liquid-liquid extraction and coordination chemistry

Uranium and molybdenum are important strategic elements. The production of ⁹⁹Mo and the hydrometallurgical process of uranium ore face difficult problems of separation of uranium and molybdenum. In this study, the four phenanthroline diamide ligands were synthesized, and extraction and stripping experiments were performed under different conditions to evaluate the potential application of these ligands for separation of U(VI) over Mo(VI). With the growth of alkyl chain, the solubility of ligands could be greatly improved, and the separation effect of U(VI) over Mo(VI) gradually increased. The SF_U/Mo were around 10,000 at 4 mol/L HNO₃. Three stripping agents were tested with the stripping efficiency of Na₂CO₃ (5%) > H₂O > HNO₃ (0.01 mol/L). The stripping percentages of the three stripping agents were all close to unity, indicating that the ligands had the potential to be recycled. The chemical stoichiometry of U(VI) complexes with ligands was evaluated as 1:1 using electrospray ionization mass spectrometry, ultraviolet visible spectroscopy and single-crystal X-ray diffraction. The consistency between theoretical calculation and experimental results further explains the coordination mechanism.     

Determination of stability constants of U(VI), Np(VI) and Pu(VI) with chloride ions by extraction chromatography

The complex formation of U(VI), Np(VI) and Pu(VI) with chloride ions was studied in HClO₄−HCl solutions at ionic strength of 2.0 and [H⁺]=2.0M by the method of extraction chromatography using dilute HDEHP as the stationary phase.     

New Ionic Liquid Based on the CMPO Pattern for the Sequential Extraction of U(VI), Am(III) and Eu(III)

Extraction of U(VI), Eu(III) and Am(III) has been performed from acidic aqueous solutions (HNO₃, HClO₄) into the ionic liquid [C₄mim][Tf₂N] in which a new extracting task-specific ionic liquid, based on the CMPO unit {namely 1-[3-[2-(octylphenylphosphoryl)acetamido]propyl]-3-methyl-1H-imidazol-3-ium bis(trifluoromethane)sulfonamide, hereafter noted OctPh-CMPO-IL}, was dissolved at low concentration (0.01 mol·L^?1). EXAFS and UV–Vis spectroscopy measurements were performed to characterize the extracted species. The extraction of U(VI) is more efficient than the extraction of trivalent Am and Eu using this TSIL, for both acids and their concentration range. We obtained evidence that the metal ions are extracted as a solvate (UO₂(OctPh-CMPO-IL)₃) by a cation exchange mechanism. Nitrate or perchlorate ions do not play a direct role in the extraction by being part of the extracted complexes, but the replacement of nitric acid for perchloric acid entails a drop in the selectivity between U and Eu. However, our TSIL allows a sequential separation of U(VI) and Eu/Am(III) using the same HNO₃ concentration and same nature of the organic phase, just by changing the ligand concentration.     

Separation and Extraction of Uranium from Leach Liquor Containing Uranium and Molybdenum by Solvent Extraction with LIX 622N

The leach liquor (0.5 g/L Mo, 0.05 g/L U) obtained from the leaching process of molybdenum-uranium ore material was treated using solvent extraction to recover U(VI) by LIX 622N, which is a salicylaldoxime derivative. The influence of various basic variables such as pH, concentration of LIX 622N, temperature, different stripping reagents, phase ratio, and diluents was examined. Using 10% LIX 622N with the aqueous solution of equilibrium pH 6.0 and a phase ratio organic phase:aqueous phase (O:A) = 1:1, a two-stage McCabe-Thiele plot was constructed, which showed 99.9% of U extraction with no co-extraction of molybdenum. This was confirmed by a 6-cycle counter current simulation (CCS) study. The obtained data of temperature on the extraction of uranium showed that the extraction process is exothermic with enthalpy change of ?20.949 kJ mol^?1. The stripping of U(VI) was quantitative using 4 M H₂SO₄. The stable complex UO₂(HSO₄)R_org formed during extraction, which supports the cation exchange mechanism, and was confirmed by FTIR spectral analysis.      

Solvent extraction of hafnium(IV)

^{175, 181}Hafnium(IV) was extracted by HDBP in 2-ethylhexanol from 1–10M solutions of HClO₄, HCl and HNO₃, and 1–8M H₂SO₄. As with low polar organic phase diluents, the acidity dependence of the distribution ratio of Hf, D, passes through a minimum for HClO₄, HCl, and H₂SO₄ whereas only an increase of D can be observed with increasing HNO₃ concentration. From the slope analysis the following complexes were found to be extracted (HDBP=HA): HfA₄ at <4M HClO₄ and <5M HCl, lg K_extr=9, HfX₄(HA)₄ (X=ClO ₄ ⁻ , Cl⁻ or NO ₃ ⁻ ) at >5M HClO₄, >7M HCl and 1–10M HNO₃, Hf(SO₄)A₂(HA)_3–4 at <3M H₂SO₄, and Hf(SO₄)₂ (HA)₄ at >6M H₂SO₄. Coextraction of sulphate with hafnium from H₂SO₄ solutions was evidenced in experiments with macro concentrations of Hf(IV) and³⁵SO ₄ ²⁻ . Part XX: Coll. Czech. Chem. Commun., 40 (1975) 3617.     

Solvent extraction of uranium(VI) and molybdenium(VI) by Alamine 310 and its mixtures from aqueous H3PO4 solution

Liquid-liquid extraction of uranium (VI) from aqueous phosphoric acid solution by triisodecylamine (Alamine 310), tri-n-butyl phosphate (TBP), di-n-pentyl sulfoxide (DPSO) and their mixtures in benzene in the range 1–10M aqueous H₃PO₄ shows that extraction is maximum (80%) in the higher acidity range 6–8 M. Extraction of this metal ion by bis(2,4,4-trimethylpentyl)phosphinicacid (Cyanex 301) and its mixtures studied in the range 0.2–1.0M aqueous H₃PO₄ is far from being quantitative. Antagonism in extraction by mixtures of extractants is observed in most of the cases. Extraction of molybdenum(VI) under identical conditions shows that it is quantitative in the lower acidity range upto 2M H₃PO₄. Separation of uranium(VI) from molybdenum(VI) is feasible by Alamine 310, TBP and DPSO, the order of efficiency being TBP>DPSO>Alamine 310.     

Studies on extraction behaviour of molybdenum (VI) from acidic radioactive waste using 2(ethylhexyl) phosphonic acids,mono 2(ethylhexyl) ester (PC-88A)/<Emphasis Type="Italic">n</Emphasis>-dodecane

This paper describes the studies on the extraction of molybdenum (VI) from aqueous nitric acid medium by (2-ethylhexyl) phosphonic acid, mono (2-ethylhexyl) ester (PC-88A). The extraction affecting parameters such as concentration of HNO₃ in aqueous feed, effect of concentration of extractants, effect of diluents, and molybdenum concentration in the aqueous phase are investigated to optimize the extraction conditions for the quantitative separation of molybdenum from nitric acid medium. With increase of HNO₃ concentration in aqueous phase, percentage extraction was found to be decreased in all the cases. Percentage extraction of molybdenum increases with increase in PC-88A concentration till the 0.15 M of PC88A, and after that it becomes constant. Kerosene and n-dodecane was found to be most suitable diluents. Among the various strippants used 0.2 M (w/v) solution of Na₂CO₃ and 0.2 M (w/v) solution (NH₄)₂CO₃ are found to be the equally suitable for stripping of molybdenum from the loaded organic phase. The stripping of molybdenum from loaded organic layer by various reagents followed the order: (NH₄)₂CO₃ >Na₂CO₃ >0.1 M sodium salt of EDTA >2 M NaOH >8 M HNO₃. The optimized process conditions are employed to extract molybdenum (VI) from actual Davies–Gray waste as well as from diluted high level waste generated in the purex stream. More than 94% Mo(VI) was extracted from radioanalytical as well as from high level waste of purex process and quantitative recovery was achieved in both the cases when 0.2 M sodium carbonate was used as stripping agent.     

Oxidation of Am(III) and stability of Am(IV) and Am(VI) in mineral acid solutions

The oxidation of americium in HNO₃, H₂SO₄ and HClO₄ solutions by a mixture of potassium persulfate with silver salt in the presence of potassium phosphotungstate has been investigated. The influence of acid and its concentration, of (NH₄)₂S₂O₃, K₁₀P₂W₁₇O₆₁ and silver salt on Am(III) oxidation rate, yield and stability of Am(IV) and Am(VI), has been studied. The complexation of Am(III), Am(IV) and Am(VI) with phosphotungstate ions has been investigated. It has been established that Am(III) and Am(IV) form ML₂ complexes and their apparent stability constants have been estimated. The oxidation mechanism is discussed. A method for preparing of Am(IV) in 0.1–6M HNO₃, O.1–3M H₂SO₄, 0.1–1M HClO₄ solutions is proposed. The oxidation of Am(III) to Am(IV) by KBrO₃ and K₂Cr₂O₇ in HNO₃, H₂SO₄, HClO₄ solutions in the presence of K₁₀P₂W₁₇O₆₁ has been investigated.     

A Study on the extraction of uranium(VI) from sulphate leach liquor using LIX63

The sulphate leach liquor obtained from the sulphuric acid leaching process of Egyptian monazite was treated using solvent extraction to recover U(VI) by LIX63. The influence of various basic variables such as pH, concentration of LIX63, temperature, different stripping agent, phase ratio and diluents was examined. Using 10% LIX63 with the aqueous solution at equilibrium pH 5.5 and a phase ratio A/O?=?1/1, a four-stage McCabe-Thiele plot was constructed, which showed 85.57% of U(VI) extraction. The thermodynamic data showed that the extraction process is exothermic with enthalpy change ΔH?=???43.866?kJ/mol, the stripping of U(VI) was quantitative using 4?M HNO₃. The stable complex UO₂(HSO₄)R_org formed during extraction which supports the cation exchange mechanism was confirmed by FTIR spectral analysis. Uranium cake was finally obtained from the strip solution by the addition of hydrogen peroxide and ammonium hydroxide as precipitating agents, and a workable flowsheet was then formulated.     

Solvent Extraction Separation of Th(IV) and U(VI) with PC-88A

Liquid-liquid extraction of Th(IV) and U(VI) has been investigated by commercial extractant PC-88A in toluene. The optimum conditions for extraction of these metals have been established by studying the various parameters like acid concentration/pH, reagent concentration, diluents and shaking time. The extraction of Th(IV) was found to be quantitative with 0.1–1.0M HNO₃ acid and in the pH range 1.0–4.0 while U(VI) was completely extracted in the pH range 1.0–3.5 with 2.5·10^–2M and 2.·10^–2M PC-88A in toluene, respectively. The probable extracted species have been ascertained by log D-log C plot as ThR₄·4HR and UO₂R₂·2HR, respectively. The method permits separation of Th(IV) and U(VI) from associated metals with a recovery of 99.0%.     

Extraction of uranium (VI) from sulfuric acid solution with TOPO

The extraction of uranium(VI) from sulfuric acid medium with tri-octylphosphine oxide (TOPO) in n-heptane was studied. Accompanied with the increase in the concentration of H₂SO₄, the distribution coefficient of uranium(VI) increased in the region of dilute sulfuric acid. When the concentration of H₂SO₄ surpassed 3.5 mol·dm⁻³, the distribution coefficient of uranium(VI) was at maximum. This result was due to the competition extraction between uranium(VI) and H₂SO₄. From the data, the composition of extracted species and the equilibrium constant of extraction reaction have been evaluated, which were (TOPOH)₂UO₂(SO₄)₂ (TOPO) and 10^7.6±0.15, respectively.     

Extraction and separation of Th(IV) and U(VI) from nitric acid media using PIA-8 and HDEHP

Extraction behavior of Th(IV) and U(VI) has been investigated with bis(2-ethylhexyl) phosphinic acid (PIA-8) and bis(2-ethylhexyl) phosphoric acid (HDEHP) from nitric acid media in toluene. The optimum conditions for extraction of these metals have been established by studying various parameters like acid concentration, pH, reagent concentration, diluents and shaking time. The extraction of Th(IV) was found to be quantitative with 0.3-2.5M HNO₃ by 2.5^.10^-2M HDEHP and in the pH range 0.1-2.5 with 2.3^.10^-2M PIA-8 in toluene. U(VI) was completely extracted in the acidic range of 0.1-2.0M HNO₃ with 2.2^.10^-2M HDEHP and in the pH range of 1.0-3.0 with 2.0^.10^-2M PIA-8 in toluene. The probable extracted species have been ascertained by log D-log c plot as UO₂ R₂ ^.2HR with both the reagents and Th (NO₃)₂R₂ ^.2HR with PIA-8 and Th (NO₃)₃R^.3HR with HDEHP, respectively. Temperature dependence of the extraction equilibrium is examined by the temperature variation method. Separation of U(VI) and Th(IV) was also carried out from commonly associated metals.     

Studies on the extraction of americium(III) from aqueous nitrate media by sulfoxides

Solvent extraction behaviour of Am(III) from dilute nitric acid media with sulfoxides (R₂SO) in Solvesso-100 has been investigated over a wide range of conditions. Very poor extractability of Am necessitated the use of salting-out agents, viz., nitrates of Al, Mg, Ca, Li and NH ₄ ⁺ . Effects of certain variables such as acidity, extractant concentration, saltingout agent, temperature etc., on metal extraction by sulfoxides have been examined systematically. For a fixed sulfoxide concentration, extraction attains a maximum value up to around 0.2–0.4M HNO₃ and decreasing above 1M HNO₃. In contrast, increasing the concentration of sulfoxide (0.8M DISO, 1.3M DBuSO) gives almost quantitative Am extraction up to 1M HNO₃. For satisfactory extraction, di-n-octyl as well as di-n-hexyl sulfoxide are the most suitable extracting agents. Extractability of Am increases with increasing amounts of all the salting-out agents studied and their effect follows the sequence: Al³⁺>Mg²⁺>Ca²⁺>Li⁺>NH ₄ ⁺ ; this is also the relative dehydrating effect of the cations. The species extracted would appear to be Am(NO₃)₃.3R₂SO. Americium is easily stripped with 1–3M HNO₃ solutions from the loaded organic phase. Extraction decreases with increasing temperature, indicating the extraction to be exothermic. Extraction from partially non-aqueous solutions was also investigated.     

Extraction of uranium(VI) and thorium(IV) from nitric acid solution by N-alkylcaprolactam

Extraction of uranium(VI), thorium(IV) from nitric acid has been studied with N-octylcaprolactam and N-(2-ethyl)hexylcaprolactam. Distribution coefficients of U(VI), Th(IV) and HNO₃ as a function of aqueous NHO₃ concentration, extractant concentration and temperature have been studied. The compositions of extracted species, thermodynamic parameters of extraction have been evaluated. Third phase formation in extraction of U(VI) has been studied. Back extraction behavior of U(VI) and Th(IV) from the organic phase has also been tested. The results obtained are compared with those obtained by using TBP under the same experimental conditions.     

Extraction of plutonium from acidic media using various phosphine oxides

Extraction, loading and stripping studies of Pu(IV) have been carried out using three phosphine oxides namely Cyanex^Ò-923 (cyn-923), Cyanex^Ò-925 (cyn-925) and TOPO in dodecane from nitric acid medium. All the three phosphine oxides have shown very high extraction of Pu. The order of extraction for Pu by these compounds is cyn-923 > TOPO - cyn-925. Loading of Pu (30.0 mg/l) in 3.0M HNO₃ was carried out using 5% solution of each of the phosphine oxides in dodecane. It was found that even at an organic to aqueous phase ratio of 1:10, the loading of Pu is >96%. From the loaded organic phase, Pu could be almost quantitatively stripped using 0.1 or 0.5M oxalic acid. The extraction of Pu(IV) with cyn-925 has also been carried out from HCl, HNO₃ or HClO₄ (0.5 to 9.1M). The species extracted into the cyn-925/dodecane phase from 3.0M HNO₃ or HCl media was found to be Pu(L)₄ ^.2 cyn-925 where L = NO₃ ^– or Cl^–. Similar species were observed to be formed when dodecane was replaced by xylene, chlorobenzene or o-dichlorobenzene.     

Selective extraction of U(VI) over Th(IV) from acidic streams using di-bis(2-ethylhexyl) malonamide anchored chloromethylated polymeric matrix

A new chelating polymeric sorbent has been developed using Merrifield chloromethylated resin anchored with di-bis (2-ethylhexyl) malonamide (DB2EHM). The modified resin was characterized by CPMAS NMR spectroscopy, FT-NIR-FIR spectroscopy, CHN elemental analysis and also by thermo gravimetric analysis. The fabricated sorbent showed superior binding affinity for U(VI) over Th(IV) and other diverse ions, even under high acidities. Various physio-chemical parameters, like solution acidity, phase exchange kinetics, metal sorption capacity, electrolyte tolerance studies, etc., influencing the resin’s metal extractive behavior were studied by both static and dynamic method. Batch extraction studies performed over a wide range of solution acidity (0.01-10 M) revealed that selective extraction of U(VI) could be achieved even up to 4 M acidity with distribution ratios (D) in the order of ∼10³. The phase exchange kinetics studies performed for U(VI) and Th(IV) revealed that time duration of <15 min was sufficient for >99.5% extraction. But similar studies when preformed for trivalent lanthanides gave very low D values (<50), with the extraction time extending up to 60 min. The metal sorption studies performed for U(VI) and Th(IV) at 5 M HNO₃ was found to be 62.5 and 38.2 mg g⁻¹,respectively. Extraction efficiency in the presence of inferring electrolyte species and inorganic cations were also examined. Metal ion desorption was effective using 10-15 mL of 1 M (NH₄)₂CO₃ or 0.5 M α-hydroxy isobutyric acid (HIBA). Extraction studies performed on a chromatographic column at 5 M acidity were found to give enrichment factor values of 310 and 250 for U(VI) and Th(IV), respectively. The practical utility of the fabricated chelating sorbent and its efficiency to extract actinides from acidic waste streams was tested using a synthetic nuclear spent fuel solution. The R.S.D. values obtained on triplicate measurements (n = 3) were within 5.2%.