Synergistic Extraction of U(VI), Th(IV), and Lanthanides(III) from Nitric Acid Solutions Using Mixtures of TODGA and Dinonylnaphthalene Sulfonic Acid

The extraction of U(VI), Th(IV), and lanthanides(III) from aqueous nitric acid solutions with mixtures of N,N,N′,N′-tetra(n-octyl)diglycolamide (TODGA) and dinonylnaphtalene sulfonic acid (HDNNS) in n-decane has been investigated. The extraction efficiency of U(VI), Th(IV), and Ln(III) ions is greatly enhanced by addition of HDNNS to an organic phase containing TODGA. The synergistic effect arises from the higher hydrophobicity of U(VI), Th(IV), and Ln(III) extracted species formed by TODGA and DNNS^? anions as compared to those formed by TODGA and NO₃^? ions as counter anions. The synergistic effect for U(VI), Th(IV), and Ln(III) extraction from aqueous nitric acid solutions with mixtures of TODGA and HDNNS becomes weaker when the acidity of the aqueous phase increases. A high synergistic enhancement is accompanied with a high selectivity of Ln(III) extraction from nitric acid solutions.     

Adsorption of Eu(III), Th(IV), and U(VI) by mesoporous solid materials bearing sulfonic acid and sulfamic acid functionalities

ABSTRACT

SBA-15 mesoporous materials modified by sulfonic acid and sulfamic acid functionalities, abbreviated as SBA-15/SO₃H and SBA-15/NHSO₃H, were synthesized and applied for the removal–separation of Eu(III), Th(IV), and U(VI). SBA-15/NHSO₃H showed an excellent selectivity toward U(VI), while SBA-15/SO₃H was more efficient adsorbent for Eu(III) and Th(IV). It was found that in the presence of KNO₃ (1 mol L^?1), the separation of Eu(III)/Th(IV) from their mixtures is possible. The results of the sorption behavior indicated a high adsorption capacity toward U(VI) and Th(IV) ions (140.5 and 106.7 mg g^?1, respectively) and ultrafast kinetics (15 min) in Eu(III) adsorption.     

Elution Behavior of Metal Ions with Mixed Glycine-Nitric Acid Eluents in Dowex 50W-X8 Column: Separation of Th(IV), Ce(IV), Bi(III), Fe(III), and Al(III)

Abstract

Distribution coefficients (K) determined by the batch technique in acidic glycine media using Dowex 50W-X8 cation exchanger (H⁺?form, 100–200 mesh size) revealed that this medium can effectively be employed to separate a number of tetravalent and trivalent metal ions from bivalent metal ions. In fixed glycine (0.40 M) and varying concentration of nitric acid (0.10 to 1.0 M), a number of mixtures containing two or three metal ions were resolved on columns using about 8 g of exchanger. In 0.40 M glycine-1.0 M HNO₃ medium, Th(IV)/Ce(IV) were separated from Al(III)/Fe(III)/Bi(III)/Co(II)/Ni(II)/Cu(II)/Zn(II)/Cd(II)/Hg(II)/Pb(II)/Ag(I) and also Al(III)/Bi(III) from a number of divalent metal ions. In 0.40 M glycine-0.50 M HNO₃ medium, the resolution of following ternary mixtures were also achieved: Th(IV)/Ce(IV)-Al(III)/Bi(III)-Fe(III)/Co(II)/Ni(II)/Cu(II)/Zn(II)/Cd(II)/Hg(II)/Pb(II)/Ag(I). Th(IV)/Al(III)/Fe(III)/Bi(III) were also separated from other divalent metal ions in 1.60 M glycine-0.50 M HNO₃ medium. The values of K, elution characteristics of metal ions, elution curves, and the results of the resolution of a number of mixtures of metal ions along with standard deviations are reported.     

Evaluation of radionuclides concentration in Brazilian coals

Raw material samples of coal used by the main power plants in Brazil (RS; SC; PR) were evaluated. Radiological relevant radionuclides of the natural series, such as ²³⁸U, ²²⁸Ra, ²²⁶Ra, ²¹⁰Pb and ⁴⁰K were analyzed by direct gamma spectrometry. The results showed that the uranium concentration in coal from (PR) was at least three times higher than concentration found in other coal samples in Brazil (RS and SC). In spite of the high uranium concentration in the PR coal, the small (10 MW_e) local power plant currently operating in (PR) produced low amount of ashes, however more detailed studies should be done for the new power plant (140 MW_e) in project.     

PURIFICATION OF THORIUM FROM URANIUM-233 PROCESS RESIDUE

ABSTRACT

Thorium-229 can be used to produce ²¹³Bi. Researchers in phase I human trials are investigating the use of antibodies labeled with ²¹³Bi for selectively destroying leukemia cells. Other types of cancer may potentially be treated using similar approaches. Crude ²²⁹Th was liberated from Rachig rings by sonication in 7.5 M HNO₃ followed by filtration. Contaminants, included significant levels of uranium, a number of other metals, and radiolytic by-products of di-(2-butyl) phosphoric acid extractant (which was used in the original separation of ²³³U from thorium). Thorium was selectively retained on Reillex HPQ anion-exchange resin from 7.5 M HNO₃ at 65°C, where U(VI), Ac(III), Fe(III), Al(III); Ra(II), and Pb(II) were eluted. Thorium and uranium isotherms on Reillex HPQ are reported. The thorium was then easily eluted from the bed with 0.1 M HNO₃. To overcome mass transfer limitations of the resin, the separation was conducted at 65°C. The resin stood up well to use over several campaigns. Other researchers have reported that HPQ has excellent radiological and chemical stability. The eluted thorium was further purified by hydroxide precipitation from the organic contaminants. This process yielded 65 mCi of ²²⁹Th.

     

Hyperfiltration studies. III. Effect of certain metal ions on the salt filtration properties of cellophanes

The salt rejection properties of cellophanes are substantially increased, and permeation rates decreased, by pretreatment with certain metal ions or presence of these ions at low concentration in feed solutions. In a typical case, a cellophane which initially rejected about 20% of salt from a 0.05M NaCl solution rejected over 70% in Presence of 10^?3M ThCl₄. Permeation rates were decreased, usually be a factior of 2 or 3. Additives found to have a marked effect were Fe(III), Th(IV), U(VI), Cu(II), and hydrolyzed pb(II). Mg(II), Ba(II), La(III), and unhdrolyzed Pb(II) had little effect. The mechanism by which the additives affect the cellophane is not clear.     

Extraction of rare earth elements from nitrate solution using novel unsymmetrical diglycolamide

A novel unsymmetrical diglycolamide (DGA), namely N,N-dihexyl-N’,N’-didecyldiglycolamide (DHD²DGA), was synthesized for the extraction of Nd(III), Sm(III), Gd(III), Dy(III), Ho(III) and Er(III) in nitric acid solutions. The effects of HNO₃, HCl or H₂SO₄ on the distribution ratio of the investigated metal ions were investigated. A systematic investigation was carried out using DHD²DGA in n-dodecane from nitric acid solutions. The main extracted species of Nd(III), Sm(III), Gd(III), Dy(III), Ho(III) and Er(III) were studied at different nitric acid concentrations by the slope analysis method and the enthalpy change of the extraction reactions was determined. The IR spectra of the extracted species were also investigated. The values of thermodynamic functions for the extraction of the lanthanides were calculated. The obtained results indicated that the effective separation of Ln(III) from Fe(III), Ni(II), Co(II) and Cs(I) can be obtained.     

UPTAKE OF METAL IONS BY A NEW CHELATING ION-EXCHANGE RESIN. PART 5 : THE EFFECT OF SOLUTION MATRIX ON ACTINIDES

ABSTRACT

The influence of commonly occurring matrix constituents on the uptake of representative actinides in the tri-, tetra-, and hexavalent oxidation states by a new chelating ion exchange resin, called Diphonix?, has been investigated. The effect of increasing concentrations of HF at three fixed HC1 concentrations on the retention of U(VI), Np(IV), and Am(III) was measured. All three actinides showed strong retention in HF even up to a concentration of 1 M The effect of sulfuric, oxalic and phosphoric acids at three fixed HNO₃ concentrations on the retention of Th(IV), U(VI), and Am(III) was also measured. Only when the concentration of the complexing acids was above 0.1 M was the retention of the actinides decreased significantly at 0.1 M HNO₃ The effect was much less pronounced at higher HNO₃ concentrations.

Sodium, calcium, aluminum and iron were selected to study the influence of cationic matrix constituents on the uptake of actinide ions by Diphonix. In the case of tetra- and hexavalent actinides (represented by Th and U, respectively) only the very highest concentrations of Fe(III) and Al(III) caused a significant decrease in the retention of the two higher valent actinides. On the other hand, Am(III) retention was significantly lowered by Al and Fe(III) concentrations above 10^?2 M The influence of Al and Fe(III) on the uptake of Am(III) may be minimized by use of fluoride ion to complex Al and by reducing Fe(III) to Fe(II). Macroconcentrations of sodium and calcium had only minimal influence on the uptake of actinides in all three oxidation states.     

Extraction and Separation of Germanium Using Cyanex 301/Cyanex 923. Its Recovery from Transistor Waste

Abstract

The extraction of Ge(IV) from HCl, HNO₃ and H₂SO₄ media in toluene solution of Cyanex 301 and Cyanex 923 is investigated. It is almost quantitatively extracted (～95%) in Cyanex 301 and Cyanex 923 at 8 molL^?1 HCl but the extractions from H₂SO₄ and HNO₃ are poor in the entire investigated range of acid molarity. Detailed investigations were carried out from HCl medium. Based on the slope analysis data the extracting species is identified as GeCl₄·2R (R=Cyanex 301/Cyanex 923). The extraction of Ge(IV) is higher and comparable in diluents like toluene, n‐hexane and kerosene (160–200°C) and there is no correlation between the dielectric constant and the percent extraction. The extractants are stable towards prolonged acid contact and there is negligible loss in their extraction efficiency even after recycling them for several cycles. The extraction behavior of commonly associated metal ions namely As(V)/(III), Sn(IV), Tl(III), In(III), Ga(III), Fe(III), Al(III), Hg(II), and Cu(II) has also been investigated. Based on the partition data conditions for attaining some binary and ternary separations involving Ge(IV) have been optimized. The separation data have been fused to develop a scheme for the recovery (93%) of pure germanium (～99%) from semi conductor waste.     

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.     

Removal of SO2 Using a Magnetically Fluidized Bed in the Semi‐Dry Flue Gas Desulfurization Process: Roles of Ferromagnetic Particles and Applied Magnetic Field in the Desulfurization Reaction

A new semidry flue gas desulfurization (FGD) process is proposed. The process uses a magnetically fluidized bed (MFB) as the reactor in which ferromagnetic particles are fluidized with simulated flue gas under the influence of an external magnetic field. A slurry of lime is continuously sprayed into the reactor by an atomizer fixed at the top of the bed. As a consequence, the desulfurization reaction and slurry drying take place simultaneously in a same reactor. Experiments with a laboratory‐scale apparatus were carried out to investigate the roles of the ferromagnetic particles and the magnetic field applied in the desulfurization reaction. The results show that when ferromagnetic particles are used as the fluidization material, both sulfite (SO₃^2–) salts and sulfate (SO₄^2–) salts are found in the desulfurization products. When quartz particles are used, only sulfite (SO₃^2–) salts are found. This suggests that the Fe(III) ions and Fe(II) ions result from the ferromagnetic particles dissolving in the liquid phase. In addition, the ions act as catalysts in the oxidation of S(IV) to S(VI) and react with SO₂ producing FeSO₃ and Fe₂(SO₄)₃ as the products. On the other hand, the level of the sulfate (SO₄^2–) salts in the products increases with increasing intensity of applied field intensity, which suggests that the oxidation of S(IV) can be enhanced by the applied magnetic field. The oxidation of S(IV) can increase the solubility of SO₂, and therefore, intensify the reaction between SO₂ and Ca(OH)₂, leading to an increased SO₂ removal efficiency.     

Effect of sulfite on reduction kinetics of Fe(III)NTA chelate

The reduction of Fe(III)NTA (ferric ion coordinated to nitrilotriacetic acid) by sulfite has been found to be first-order with respect to Fe(III)NTA and of order minus one with respect to Fe(II)NTA (one of the reaction products). The order of reaction with respect to HSO^?₃ has been determined to be unity when the molar ratio of Na₂SO₃ to total Fe(III) is less than five. In this paper, the role of sulfite in the reduction scheme is reconsidered, and the reduction rate expression in which the coordination of Fe³⁺ to HSO^?₃ is incorporated, is newly presented. The proposed rate equation covers all reaction data for molar ratios of Na₂SO₃ to total Fe(III) in the range of 1 to 25.     

Selective Separation of Thorium Using Ion Imprinted Chitosan‐Phthalate Particles via Solid Phase Extraction

Abstract

We have studied a new method for the preparation of Th(IV)‐imprinted chitosan‐phthalate particles, which can considerably enhance the adsorption capacity and selectivity of thorium ions. In this study, chitosan‐phthalate was used as the complexing monomer, Th(IV) as template, epichlorohydrin as crosslinking agent. Initially, chitosan was modified with phthalic anhydrides and complex formation occured between carboxylic acid functional groups and Th(IV) ions. Secondly, particles were crosslinked with epichlorohydrin. After the removal of Th(IV) ions, thorium solid phase extraction (SPE) on the Th(IV) ion‐imprinted particles from aqueous solutions containing their different amounts, selectivity study of thorium versus other interfering metal ions mixture which are Fe³⁺, La³⁺, and Mn²⁺ and distribution and selectivity coefficients were reported here. A comparison of the selectivity coefficient of Th(IV)‐imprinted chitosan‐phthalate particles with the selectivity coefficient of non‐imprinted polymers showed that the imprinted matrix for Th(IV)/Fe(III), Th(IV)/La(III) and Th(IV)/Mn(II) was 8.35, 8.75 and 10.81 times greater than non‐imprinted matrix, respectively.     

4-ACYLBIS(1-PHENYL-3-METHYL-5-PYRAZOLONES) AS EXTRACTANTS FOR f-ELEMENTS

ABSTRACT

The liquid-liquid extraction of early actinides such as thorium(IV) and uranium(VI) and trivalent lanthanoids such as neodymium(lll), europium(lll) and lutetium(lll) from nitrate solutions was studied using 4-sebacoylbis(1-phenyl-3-methyl-5-pyrazolone) (H₂SP) and 4-dodecandioyl-bis(1-phenyl-3-methyl-5-pyrazolone) (H₂DdP) in chloroform as extractants. The results demonstrate that these metal ions are extracted into chloroform as Th(SP)₂, Th(DdP)₂, UO₂(HSP)₂, UO₂(HDdP)₂, Ln(SP)(HSP) and Ln(DdP)(HDdP) with H₂SP or H₂DdP. The equilibrium constants of the above species were deduced by non-linear regression analysis. The results clearly highlight that thorium(IV) can be selectively separated from uranium(Vl) and trivalent lanthanoids when extracted from 0.2 mol/dm³ nitric acid solutions using 4-acylbis(1-phenyl-3-methyl- 5-pyrazolones). Thorium(IV), uranium(VI) and lutetium(lll) complexes of H₂SP were synthesised and characterised by IR and ¹H NMR spectral data to further clarify the nature of the complexes.     

Regeneration of [Fe(II)-NTA]− catalyzed by activated carbon in the simultaneous removal of sulphur dioxide and nitric oxide

The combined control of NO and SO₂ can be finished with the [Fe(II)-NTA]⁻ solution because [Fe(II)-NTA]⁻ is capable of binding NO. However, the ability of [Fe(II)-NTA]⁻ to bind NO may be lost quickly due to the fast oxidation of [Fe(II)-NTA]⁻ to [Fe(III)-NTA] by oxygen in the flue gases. To make it possible to put this technology into commercial application, efficient measures should be taken to regenerate [Fe(II)-NTA]⁻ to maintain the NO removal efficiency for a long time. The catalytic activity of activated carbon in the reproduction of [Fe(II)-NTA]⁻ has been investigated in a fixed-bed reactor. The experiments indicate that [Fe(II)-NTA]⁻ reproduction increases with [Fe(III)-NTA] and SO₃²⁻ concentrations as well as temperature. Fast flow and high pH are unfavourable for the reproduction of [Fe(II)-NTA]⁻. An NO removal efficiency of 80.11%–89.78% is sustained for a long period of time with the [Fe(II)-NTA]⁻ reproduction catalyzed by activated carbon. The reaction orders with respect to [Fe(III)-NTA] and SO₃²⁻ are 0.784 and 0.336, respectively. The apparent activation energy for this catalytic reaction is estimated to be 41.01 kJ mol⁻¹.     

Extraction of U(VI), Th(IV), and Lanthanides(III) from Nitric Acid Solutions with CMPO-Functionalized Ionic Liquid in Molecular Diluents

The extraction of microquantities of U(VI), Th(IV), and lanthanides(III) from nitric acid solutions with CMPO-functionalized ionic liquid 1-[3[[(diphenylphosphinyl)acetyl]amino]propyl]-3-tetradecyl-1H-imidazol-3-ium hexafluorophosphate, CMPO-FIL(I) in molecular organic diluents has been studied. The effect of HNO₃ concentration in the aqueous phase and that of extractant concentration in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes was determined. CMPO-FIL(I) demonstrates greater extraction ability towards Ln(III) than its neutral CMPO analog, diphenylphosphorylacetic acid N-nonylamide. This inner synergistic effect increases with a decreasing organic diluent polarity. The partition of CMPO-FIL(I) between the equilibrium organic and aqueous phases is the dominant factor governing the extractability of Ln(III) ions in the extraction system.     

STUDIES ON U-Th SEPARATION USING TRI-sec-BUTYL PHOSPHATE

In this work, the extraction of Am(III), U(VI), Th(IV) and Fe(III) by P,P′-di(2-ethylhexyl) methylene- (H₂DEH[MDP]), ethylene- (H₂DEH[EDP]), and butylene- (H₂DEH[BuDP]) diphosphonic acids dissolved in the monomerizing diluent 1-decanol has been investigated. A comparison of the acid dependencies with those observed in o-xylene has revealed a number of novel features which have been ascribed to extraction of metal nitrates through a solvation mechanism made possible by facile transfer of nitrate ions into the 1-decanol phase. The use of 1-decanol as the diluent gives rise to strong suppression of metal extraction, which increases along the series Fe(III)2DEH[MDP]2DEH[EDP]≤H₂DEH[BuDP]. The extractant dependencies of U(VI) and Th(IV) have slopes equal to 2 with all extractants. Those for Am(III) and Fe(III) exhibit variable slopes with limiting values of 1 at the lowest and 3 at the highest extractant concentrations. From the combined information provided by the acid and extractant dependencies, stoichiometries and probable structures for complexes formed in the organic phase have been proposed. The data obtained in this work suggest a simple route for actinide stripping from diphosphonic acid extractants loaded in nonpolar diluents.     

Influence of ionic speciation on electrocatalytic performance of polyaniline coated platinum electrode: Fe(III)/Fe(II) redox reaction

Porous-polyaniline coated Pt electrode (PANI/Pt) was electro-synthesized potentiodynamically in 0.1 M aniline + 0.5 M H₂SO₄ and morphologically characterized by scanning electron microscopy (SEM). Nature of predominant Fe-species in HCl and H₂SO₄ was checked by UV-vis spectrophotometry. Electrocatalysis of Fe(III)/Fe(II) reaction was studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) for three different solution compositions viz. (i) FeCl₃/FeCl₂ in 1 M HCl, (ii) FeCl₃/FeCl₂ in 0.5 M H₂SO₄ and (iii) Fe₂(SO₄)₃/FeSO₄ in 0.5 M H₂SO₄. For different thicknesses of PANI, the peak current increased irrespective of the nature of the Fe-species, but the polarity of the charge on the Fe-species showed great influence on reversibility of electrocatalysis by PANI/Pt. The Donnan interaction of the polyaniline modified electrode for the three compositions was investigated with respect to [Fe(CN)₆]³⁻/H₂[Fe(CN)₆]²⁻ which are believed to be the predominant species present in K₃[Fe(CN)₆]/K₄[Fe(CN)₆] solution in 0.5 M H₂SO₄. The electrocatalytic performance of PANI/Pt for Fe(III)/Fe(II) redox reaction was found superior in HCl compared to that in H₂SO₄.     

Distribution Studies of Actinides Using a Tetradentate Extractant, 4,4′-Nonanedioyl-Bis(2,4-Dihydro-5-Methyl-2-Phenyl-3H-Pyrazol-3-One)

Abstract

The extraction of Th(IV), UO₂(II), Am(III), and Eu(III) from aqueous acid by a tetradentate extractant, 4,4′-nonanedioyl-bis(2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one), H₂NDBP, has been studied and compared with two bidentate model compounds, 4-hexanoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one, HHMPP, and 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one, HBMPP. The distribution coefficients of UO₂(II), Am(III), and Eu(III) were somewhat larger using H₂NDBP relative to the model compounds under the conditions studied. However, the Th(IV) extraction using H₂NDBP was greatly enhanced when compared to HBMPP or HHMPP. The distribution coefficient for Th(IV) from 0.5 M HNO₃ was 11.6 using 3.0 × 10^?3 M H₂NDBP compared with values of D < 0.01 using 3.0 × 10^?3 M HBMPP or HHMPP.     

Extraction Properties of P(O)-Modified N-Aryl-Carbamoylmethylphosphine Oxides in Nitric Acid Media

Novel polyfunctional neutral organophosphorus compounds, P(O)-modified N-aryl- carbamoylmethylphosphine oxides, Ph₂P(O)CH₂C(O)NH-(o-C₆H₄)(CH₂)_n-P(O)Ph₂ and Ph₂P(O)CH₂C(O)NH-(m-C₆H₄)(CH₂)_n-P(O)Ph₂ (n = 1,2), were synthesized and studied as extractants for U(VI), Th(IV) and Ln(III) from HNO₃ solutions. The influence of aqueous and organic phases on the extraction efficiency was elucidated and stoichiometry of the complexes extracted was determined. Introduction of an additional phosphoryl group into the phenyl substitutent at the nitrogen atom of diphenyl(N-phenylcarbamoylmethyl)phosphine oxide resulted in an increase of the efficiency of U(VI), Th(IV), Ln(III), and Re(VII) extraction.