KINETICS OF URANIUM EXTRACTION BY MACROPOROUS BIFUNCTIONAL PHOSPHINIC ACID RESIN

ABSTRACT

The rate of extraction of uranium by macroporous bifunctional phosphinic acid (MPBPA) resin from nitric acid medium has been studied under particle diffusion controlled conditions. The internal diffusion coefficient was found to increase with increase in temperature and decrease with increase in particle size. The activation energies and entropies suggest that the extraction of uranium essentially follows ion exchange mechanism at low concentration of nitric acid while it is through linkage of >P=0 group of the resin at high concentrations.     

RECOVERY OF URANIUM FROM ACID MEDIA BY MACROPOROUS BIFUNCTIONAL PHOSPHINIC ACID RESIN

ABSTRACT

The extraction of uranium from various acid media such as nitric acid, sulphuric acid, hydrochloric acid, phosphoric acid and perchloric acid by a macroporous bifunctional phosphinic acid resin (MPBPA) has been studied. The distribution coefficients for the extraction of uranium by the MPBPA resin are compared with the corresponding values reported in literature for the conventional sulphonic acid resin. The results clearly indicate the suitability of the MPBPA resin to recover uranium from different types of acid solutions of widely ranging acidities.     

EXTRACTION CHEMISTRY OF COBALT AND NICKEL BY DI(1-METHYLHEPTYL)PHOSPHINIC ACID

The fundamental characteristics and mechanism of extraction of cobalt (II) and nickel(II) by di-(1-methylheptyl) phosphinic acid (DMHPA) were studied. The extraction ability of cobalt(II), nickel (II) and various metals by DMHPA decreases in the order Fe(III) > Zn ? Pb(II) > Mn(II) > Cu(II) > Co(II) > Mg > Ca > Ni(II). The difference of the pH_½ values for nickel and cobalt reaches 2.06 pH units, which is apparently greater than those from extraction by di(2-ethylhexyl)phosphoric acid (DEHPA)and 2-ethyl-hexyl ester 2-ethylhexylphosphonic acid(DHEHPA).The slope analysis and IR spectroscopy reveal that the stoichiometrics of cobalt and nickel extracted species are Co(HA₂)₂ and Ni(HA₂)₂(H₂O)₂ respectively. As demonstrated by the study of the electronic spectroscopy the structure of the extracted complexes were shown as tetrahedral and octahedral configuration respectively. Furthermore, the coordination field parameters of the complexes were calculated.     

COBALT-NICKEL SEPARATION BY SOLVENT EXTRACTION WITH BIS(2,4,4 TRIMETHYLPENTYL)PHOSPHINIC ACID

Abstract

The use of an organophosphinic acid to separate cobalt from nickel by solvent extraction is described. Comparative data indicate that the phosphinic acid is superior to analagous phosphoric and phosphonic acids in terms of cobalt-nickel selectivity and the ability to reject calcium. Important reagent properties, such as low aqueous solubility and hydrolytic stability, are discussed. The results of continuous, counter-current, mini-plant tests demonstrate the recovery of high purity cobalt from concentrated nickel sulphate solutions.     

EXTRACTION OF DIVALENT METALS WITH BIS(2,4,4 TRIMETHYLPENTY) PHOSPHINIC ACID

The extraction of Cd(II), Cu(II) and Zn(II) from 0.1 mol dm^minus3 aqueous nitrate solutions with bis(2,4,4-trimethylpentyl)phosphinic acid (HBTMPP) dissolved in Isopar-H has been studied with relation to the total extractant concentration, the equilibrium pH and the total metal concentration in the aqueous phase.

The stoichiometry of the extracted species and their equilibrium constants have been determined by graphical and numerical methods and appear to be CdA₂ (HA)₂ and CdA₂ (HA)₃ for Cd(II), CuA₂(HA)₂ for Cu(II) and ZnAzHA and ZnAz(HA)₂ for Zn(II). The extraction efficiency follows the order Zn(II)<Cu(II)<Cd(II)     

EXTRACTION AND SEPARATION OF HEAVY RARE EARTH(III) WITH EXTRACTION RESIN CONTAINING DI(2,4,4-TRIMETHYL PENTYL) PHOSPHINIC ACID (CYANEX 272)

ABSTRACT

Extraction resins, of the type of Levextrel, (which is a collective term for styrene/divinylbenzene based copolymers of predominantly macroporous structure that contain a selective extractant) are important for the recovery and separation of metal ions, as they combine features of solvent extraction and ion exchange resins. This paper presents the results of the adsorption of heavy rare earth ions (Ho(III), Er(III), Tm(III), Yb(III), Lu(III) and Y(II1)) from hydrochloric acid solutions at 0.2 mol/L ionic strength and 50°C by the extraction resin containing di (2,4,4-trimethyl pentyl) phosphinic acid (Cyanex 272) and the chromatographic separation of (Er(III), Tm(III) and Yb(III)). Technological separation products, with purity and yield of Tm₂O3 >99.97%, >80%; Er₂O₃ >99.9%, >94% and Yb₂O₃ >99.8%, >80% respectively, have been obtained from a feed having the composition Tm₂O₃ 60%, Er₂O₃ 10%, and Yb₂O₃ 3%, the others 27%.

The distribution coefficients, extraction equilibrium constants and separation factors have been determined as a function of acidity, loading of the resin and rare earths, flow rates and column ratios. The resolutions and efficiencies of separation of Er/Tm/Yb each other have been calculated. The stoichiometry of the extraction of rare earth ions has been suggested as well.     

EXTRACTION OF TRIVALENT LANTHANIDES AND ACTINIDES BY “CMPO-LIKE” CALIXARENES

ABSTRACT

Extractive properties of calix[4]arenes bearing carhamoylmethylphosphine oxide moieties on their upper rim toward trivalent lanthanide and actinide cations were investigated. The study revealed that these molecules selectively extract light lanthanides and actinides from heavy lanthanides. All parameters present in the extraction system were varied to determine the origin of the selectivity. It was found that this selectivity requires a calix[4]arene platform and acetamidophosphine oxide groups containing phenyl substituents on the four phosphorus atoms.     

溶剂萃取法分离提取衣康酸

研究了溶剂萃取法提取衣康酸的工艺 .首先进行了萃取剂的选择 .研究了萃取剂浓度、pH值、萃取温度在不同萃取体系中对萃取衣康酸的影响 .并在实验基础上建立了相应萃取分配的数学模型     

草酸与乙醛酸的萃取分离

以草酸和乙醛酸的稀溶液为分离对象 ,采用三辛胺 (TOA)为萃取反应剂、正辛醇为稀释剂 ,研究了单溶质、双溶质有机酸的萃取分离特性 ,测定了溶液pH值、萃取反应剂的浓度等因素对双溶质有机酸萃取的影响 ,提出了萃取的化学反应发生在有机相中的假定 ,建立了TOA萃取草酸的数学模型 .实验结果表明 ,草酸与TOA的萃合物有 1∶1和 1∶2两种形式 .在本实验的条件范围内 ,草酸的分配系数较乙醛酸大 ,且随溶液pH值的增大而下降 ,草酸对乙醛酸的分离系数随pH值的增大而减小 .随萃取反应剂浓度的增大 ,两酸的分配系数皆随之增大 ,分离系数也随之增大 ,而且对于高浓度的萃取反应剂在较高的溶液pH值下草酸仍具有较大的分离系数 .采用单溶质萃取反应平衡常数及纯稀释剂中双溶质的分配系数预测双溶质萃取的结果 ,预测值与实验值相当接近     

乙醇酸与乙醛酸的萃取分离

以乙醇酸和乙醛酸的稀溶液为分离对象,采用三烷基氧磷 (TRPO)为萃取剂、甲基异丁基酮 (MiBK)为稀释剂,研究了单、双溶质有机酸的萃取分离特性,测定了TRPO、有机酸的浓度等因素对单、双溶质有机酸萃取平衡的影响,在适当假定的基础上,建立了描述TRPO萃取乙醇酸、乙醛酸单、双溶质特性的数学模型.结果表明,随TRPO浓度的增大,分离系数β_{（glycolic /glyoxylic）}由小于1逐渐增大至大于1,乙醇酸与TRPO的萃合物有1∶1和1∶2两种形式,采用单溶质萃取反应平衡常数预测双溶质萃取的结果,预测值与实验值相当接近.同时,还对三烷基胺、磷酸三丁酯等萃取剂分离乙醇酸和乙醛酸的特性进行了讨论.     

EXTRACTION BEHAVIOUR OF TECHNETIUM AND ACTINIDES IN THE ALIQUAT-336/NITRIC ACID SYSTEM

ABSTRACT

The extraction behaviour of technetium, thorium, uranium, neptunium, plutonium, americium and curium in the Aliquat-336 (diluted with 1,3-diisopropyl benzene) - nitric acid system have been studied. Aliquat-336 (tricapryl-methyl ammonium nitrate) is a quaternary ammonium salt extracting different species with an anion exchange mechanism. Distribution data obtained are modeled by anion exchange (technetium) and ion-pair formation mechanisms (actinides) with the extraction of nitric acid included to account for the lowering of the free extractant concentration. Reasonably high distribution ratios were obtained for technetium and the tetravalent elements (Th, Np and Pu) and Aliquat-336 can therefore be useful for partitioning of these elements.     

PURIFICATION OF HYDROCHLORIC ACID BY ISOOCTANE EXTRACTION

ABSTRACT

Removal of organic compounds from hydrocloric acid can be performed by a solvent extraction process followed by a solvent regeneration step by adsorption with sepiolite. The extraction study includes the analysis of the influence of the operating conditions, the determination of the solute distribution coefficient for isooctane and the effect of temperature on the extraction. The adsorption isotherms were calculated to check the technical viability of the method. The obtained efficiency of extraction is close to 90 wt%, whereas that of the solvent regeneration recovery is over 67 wt%     

三辛胺萃取草酸的机理

选择草酸稀溶液为萃取对象 ,采用三辛胺 (TOA)为络合剂 ,正辛醇为稀释剂 ,开展了TOA萃取草酸的机理研究 .以红外谱图为分析手段 ,通过测定络合剂及被萃溶质的浓度对萃合物组成的影响 ,得到其萃合物以 1∶1和 1∶2 (酸 :碱 )两种形式存在于有机相中 ;并通过萃取平衡实验 ,获得了TOA萃取草酸的平衡特性 ,进一步验证了萃合物组成 .以此为基础建立了草酸与TOA两种萃合比情况下的数学模型 ,拟合求得了K₁₁及K₁₂ ,其中 1∶2萃合物的化学萃取平衡常数远远小于 1∶1的相应值     

A REVIEW OF THIRD PHASE FORMATION IN EXTRACTION OF ACTINIDES BY NEUTRAL ORGANOPHOSPHORUS EXTRACTANTS

ABSTRACT

Data are reviewed on the formation of third phase in the extraction of acti-nide(IV.VI) nitrates by neutral organophosphorus extractants, mainly tributyl phosphate. The data are critically evaluated and the effect of variables on the third phase formation is discussed. The variables are the concentrations of nitric acid and the extractant, temperature, the nature of diluent, addition of modifiers and the ionic strength of the aqueous phase. Also discussed are systems involving two extracted actinide ions.     

EXTRACTION OF ACTINIDES AND SELECTED FISSION PRODUCTS FROM NITRIC ACID MEDIUM USING LONG CHAIN MONOAMIDES

A series of long chain disubstituted aliphatic amides have been prepared with different substituting groups and the extracting ability for U(VI), Th(IV) and some fission products like Am(III), Zr(IV), Eu(III) and Cs from nitric acid solutions has been studied. All results were compared with those obtained by using TBP under the same conditions. All prepared amides exhibit higher U-Th separation factors than TBP. Distribution ratios of U(VI) as function of nitric acid concentration, extractants concentration and salting-out agent have been measured by using N,N-dihexyloctanamide (DHOA) and N,N-dihexyl(2-ethyl)hexylhexanamide (DHEHA), which were chosen for further studies. The extraction behviour of U(VI), Th(IV) and Zr(IV) with gamma irradiated DHOA, DHEHA and TBP in toluene from 3 M HNO₃ has been studied as a function of absorbed doses. Back extraction of U(VI), Th(IV) and Zr(IV) from organic phases was also studied.     

EXTRACTION OF SOME LANTHANIDES AND ACTINIDES BY 15-CROWN-5 THENOYLTRIFLUOROACETONE MIXTURE IN CHLOROFORM

The extraction of Eu³⁺, Tm³⁺, and Yb³⁺ by a mixture of thenoyltrifluoroacetone (HTTA) and 15-Crown-5 (15C5) in chloroform from a 0.1-ionic strength acetate buffer was investigated. Large enhancement in the extraction for these lanthanides was obtained when a mixture of the two extractants was used. Experimental data indicated that this enhancement is a result of the formation of a lanthanide adduct in the organic phase of the type Ln(TTA) ³° 2CE, where CE refers to a crown ether. The synergistic factors (S.F.), mixed extraction constants and formation constants of the different adducts in the organic phase were found to take the sequence Eu³⁺ > Tm³⁺ > Yb³⁺.

Using 12-Crown-4 (12C4), no enhancement in the extraction was observed. This was explained in terms of the small cavity size of 12C4 relative to 15C5.

The same system comprising HTTA-15C5 was also studied for the extraction of Pu⁴⁺, Am³⁺, Nd³⁺, and Er³⁺. Moderate enhancement was obtained for the extraction of Am³⁺ while no increase in the extraction was found for Pu⁴⁺.The metal concentration in the aqueous phase was found to largely affect the S.F. values for Nd³⁺ and Er³⁺.     

EXTRACTION OF TRIVALENT LANTHANIDES AND ACTINIDES BY A SYNERGISTIC MIXTURE OF THENOYLTRIFLUOROACETONE AND A LINEAR POLYETHER

Abstract

Mixtures of a linear polyether, l,13-bis[8-quinolyl]-l,4,7,10,13-pentaoxatridecane, K-5, and thenoyltrifluoroacetone, HTTA, have been shown to exhibit synergistic character in the extraction of trivalent lanthanides and actinides. The effect of the addition of K-5 to the organic phase on the extractions of Ce(III), Eu(III), Tm(III), Am(III), Cm(III), Bk(III), and Cf(III) by HTTA in chloroform from 0.5M NaNO₃ at 25°C has been measured. These results indicate the extraction is enhanced by the formation of M(TTA)₃K-5 adduct in the organic phase. The organic phase stability constants for the formation of these synergistic species have been calculated for all the metals studied. The magnitude of these organic phase stability constants for K-5 are similar to other common neutral donors. The order of stability does not follow the normal trend based on charge-to-radius ratio, but follows a pattern based on size, with Am(III) being the most stable.     

EXTRACTION EQUILIBRIUM OF PHENOL BY SULFURIC ACID SALTS OF TRIOCTYLAMINE

An investigation was undertaken involving the extraction equilibrium of phenol from an aqueous solution using trioctylamine sulfate salt (TOA salt)/trioctylamine (TOA) as the extractant. The purpose of using trioctylamine as the organic solvent is to increase the total capability of phenol extraction as well as to avoid the use of other organic solvents. In order to prevent the formation of a second phase from the reaction of trioctylamine and sulfuric acid, 1-octanol in an appropriate amount was added to make the organic solution homogeneous. Equilibrium distribution coefficients (K_d) in the extraction of phenol by TOA salt/TOA were measured for various operating conditions. The equilibrium distribution coefficient of phenol (K_d) between two phases decreased with increasing the initial concentration of phenol, thereby decreasing the initial concentration of sulfuric acid, and subsequently increasing the volume ratio of aqueous phase to organic phase. We recommended that the extraction is carried out at low temperature. A higher value of K_d up to 800 was obtained in using trioctylamine sulfate/trioctylamine as the extractant for equal volume ratio of aqueous phase to organic phase.     

EXTRACTION MECHANISM OF PHENOL BY SULFURIC ACID SALTS OF TRIOCTYLAMINE

In the present study, the extraction mechanism of phenol from an aqueous solution by sulfuric acid salts of trioctylamine (TOA salts) was investigated. Based on the experimental evidence that the affinity of sulfuric acid and amine is greater than that of phenol and amine, the procedure of the extraction mechanism is assumed to involve two independent steps, i.e., trioctylamine (TOA) is first reacted with sulfuric acid to form TOA salts and phenol is extracted from the aqueous phase by TOA salts. The Wilson model, which accounts for the reaction of trioctylamine and sulfuric acid to form different kinds of TOA-salts, is employed to predict the extraction of phenol in the present study. The number of water molecules in the neighborhood of the different TOA-salts, which directly reflects the extraction capability of phenol, was determined. This prediction from the Wilson model is fairly consistent with the experimental data.     

THE EXTRACTION OF RHODIUM FROM AQUEOUS NITRIC ACID BY DINONYLNAPHTHALENE SULPHONIC ACID

The extraction of rhodium from aqueous nitric acid using dinonylnapthalene sulphonic acid has been investigated. The extraction occurs readily from 0.1M to 1.0m nitric acid and, since the rhodium is extracted as [Rh(H₂O)₆] ³⁺into the inverted micelles of the organic solution,equilibration times are less than 5 minutes. Extraction is enhanced by the addition of nitrite ion to form [Rh(H₂O)₅NO₂] ²⁺as the extracted species.