DERIVATIVES OF IMEDOPYROPHOSPHORIC ACIDS AS EXTRACTANTS. PART 6. DETERMINATION OF METAL ION EXTRACTION MECHANISM OF N,N-N',N'-OCTABUTYLIMIDO-DIPHOSPHOTETRAMIDE BY POTENTIOMETRY.

ABSTRACT

Extraction of tri-, tetra- and hexavalent metal ions by N, N-N',N'— octabutylimidodiphosphotetramide has been investigated. Imidodiphosphoryl extractants show promise for treatment of nuclear waste but the optimum extractant structure must still be determined. Extraction of rare earths was investigated using two—phase potentiometnc titrations as the more conventional slope analysis techniques could not be applied. The data thus obtained were analysed by the ESTA library of programs which was designed for modelling solution equilibria in aqueous phases. Results obtained showed that ESTA may be used for modelling two—phase systems providing corrections are made. Models were obtained for the extraction of Nd(III), Eu(III), Y(III) and Yb(III). Extraction equilibrium constants could be calculated as well as distribution ratios showing that imidodiphosphoryl extractants are promising as rare earth extractants. Extraction mechanisms     

SOLVENT EXTRACTION OF ZINC(II) BY ORGANOPHOSPHORUS ACIDS COMPOUNDS FROM PERCHLORATE SOLUTIONS.

ABSTRACT

The extraction of zinc from perchlorate solutions at 0.1 mol.dm^?3 of ionic strength by di(2-ethylhexyl)phosphoric acid (HDEHP), 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) and di(n-octyl)phosphinic acid (H[DOP]) dissolved in toluene has been studied at 25 ° C.

The distribution coefficient was determined as a function of pH and HA concentrations and the data were analyzed both graphically and numerically using the computer program LETAGROP-DISTR.

The results showed that the data can be explained assuming the formation of ZnA₂(HA)₂ and ZnA₂HA in organic phase for all the extractants used. A correlation between extracted species and concentration of the various extractants has been found.

The predominance of the different species into the organic phase has been correlated with the difference between their extraction constants.

The anion of the ionic medium is not extracted into the organic phase.     

EVALUATION OF EXTRACTANT-COATED FERROMAGNETIC MICROPARTICLES FOR THE RECOVERY OF HAZARDOUS METALS FROM WASTE SOLUTION

ABSTRACT

A magnetically assisted chemical separation (MACS) process developed at Argonne National Laboratory is a compact method for the extraction of transuranic (TRU) metals from, and volume reduction of, liquid waste streams that exist at many DOE sites. The MACS process utilized the selectivity afforded by solvent extractant/ion-exchange materials in conjunction with magnetic separation to provide a more efficient chemical separation. Recently, the principle of the MACS process has been extended to the evaluation of acidic organophosphorus extractants for hazardous metal recovery from waste solutions. Moreover, process scale-up design issues were addressed in respect to particle filtration and recovery.

Two acidic organophosphorus compounds have been investigated for hazardous metal recovery, bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex® 272) and bis(2,4,4-trimethylpentyl) dithiophosphinic acid (Cyanex® 301). These extractants coated onto magnetic microparticles demonstrated superior recovery of hazardous metals from solution as compared with data from solvent extraction experiments. The results illustrate the possibility for diverse applications of this technology for dilute waste streams. Preliminary process scale-up experiments with a high-gradient magnetic separator at Oak Ridge National Laboratory revealed the potential for very low microparticle loss rates.     

Kinetic behavior of lanthanide extraction with acidic phosphorus extractants

The kinetic behavior of lanthanide extraction from HAc–NaAc–EDTA media with three acidic phosphorus extractants(HL), bis(2-ethylhexyl)phosphoric acid (HDEHP), 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH(EHP)) and bis(2,2,4-trimethylpentyl)phosphinic acid (H(DTMPP)) in n-octane solution is reported. The observed rate constants, k_o for the metals (M) lanthanum, neodymium, gadolinium, holmium and lutetium with these three extractants were determined under vigorous mixing. The rate equation for extraction was determined to be: A mechanism has been proposed for the extraction reaction under the experimental conditions. For a given metal the rate constant as a function of ligand followed the order HDEHP > HEH(EHP) > H(DTMPP), the decrease from HDEHP to H(DTMPP) being less than an order of magnitude. It was also found that the rate constants for these metals and yttrium bear an inverse relationship to the stability constants of their complexes with EDTA.     

Dependence of Extraction Properties of 2,6-Dicarboxypyridine Diamides on Extractant Structure

Abstract

New diamides of dipicolinic acid have been prepared and their affinity for lanthanides, americium, and uranium has been explored using the liquid-liquid extraction method. These extractants feature mixed alkyl/aryl substituents. The highest extraction is seen for phenyl/ethyl derivatives. The structure-reactivity relationship for extraction and solubility is discussed.     

SOLVENT EXTRACTION OF SILVER BY CYANEX 272, CYANEX 302 AND CYANEX 30

ABSTRACT

The solvent extraction of silver from nitrate media by the extractants Cyanex 272 (bis)2,4,4-trimethylpentyl)phosphinic acid), Cyanex 302 ( bis(2,4,4-trimethylpentyl)thiophosphinic acid) and Cyanex 301 ( bis( 2,4,4-trimethyl-pentyl)dithiophosphinic acid) is characterized. Extraction shifts to lower pH with increasing sulfur substitution in the phosphinic acid, in accordance with the increased extractant acidity imparted by the soft nature of the sulfur donor atoms. The effects of extractant concentration, aqueous-phase ionic strength and organic-phase diluent on the extraction behavior are examined. The stoichiometry of the extraction reactions and the geometry of the extracted complexes are postulated based on slope analysis and spectroscopic measurements. All three extractants behave as bidentate ligands and combine in a 1:1 stoichiometric ratio with silver. The sulfur-containing ligands form multi-nuclear oligomeric complexes in which the ligands bridge between metal centers.     

SOLVENT EXTRACTION OF NITRIC,HYDROCHLORIC AND SULFURIC ACID AND THEIR URANYL SALTS WITH TRI-n-OCTYLPHOSPHINE OXIDE

ABSTRACT

The equilibrium constants of the extraction of nitric, hydrochloric and sulfuric acid and of their uranyl salts with trl-n-octylphoophlne oxide (TOPO), dissolved In different diluents, have been determined. Obtained extraction constants have been correlated with the corresponding dissociation constants of mineral aclda used. The more mineral acid dissociated, the less undlssoclated molecules of acid available and, as a consequence, the extraction process is less expressed.     

LIQUID-LIQUID EQUILIBRIUM OF THE WATER-PHOSPHORIC ACID-3-PENTANONE SYSTEM AT 25°C. A COMPARATIVE STUDY OF THE EXTRACTION POWER OF DIFFERENT SOLVENTS

Abstract

Solubility and liquid-liquid phase equilibrium data have been determined for the Water-Phosphoric Acid-3-Pentanone ternary system at 25 °C. Tie lines have been obtained and the plait point composition calculated. The phosphoric acid extraction capability of 3-Pentanone has been compared to that of other solvents previously studied. A systematic approach to the effects of chain length, functional group, branching and cyclation on the extraction power of the different solvents reported in the literature shows that the compatibility between solvent and phosphoric acid is higher for alcohols followed by ketones, esters and ethers. Branching and cyclation lead to a higher solubility of the acid into the organic phase, while an increase in the chain length results in a wider heterogeneous zone (i.e. in a decreasing solubility).     

Synergistic Extraction and Separation of Heavy Lanthanide by Mixtures of Bis(2,4,4‐trimethylpentyl)phosphinic Acid and 2‐Ethylhexyl Phosphinic Acid Mono‐2‐Ethylhexyl Ester

Abstract

The extraction of Yb³⁺ from chloride solution has been studied using mixtures of bis(2,4,4‐trimethylpentyl)phosphinic acid (Cyanex272) and 2‐ethylhexyl phosphinic acid mono‐2‐ethylhexl ester (P507). The results show that Yb³⁺ is extracted into heptane as YbA₃(HA)₃ with Cyanex272, YbL₃(HL)₃ with P507, and YbA₂L₄H₃ with synergistic mixture. The equilibrium constants, formation constants, and thermodynamic functions have been determined. Extraction mechanism and extraction process are also proposed. The extraction of heavy lanthanide ions by mixtures of Cyanex272 and P507 is studied and the possibility of separating heavy rare earth ions is discussed.     

VARIATIONS IN THE SOLVENT EXTRACTION BEHAVIOR OF BIFONCTIONAL PHOSPHORUS-BASED COMPOUNDS MODIFIED WITH TBP

ABSTRACT

The solvent extraction of americium from nitric acid by several modified bifunctional extractants in CCl₄has been investigated. For all the compounds examined, addition of a modifier such as tributylphosphate (TBP) enhances distribution ratios at high aqueous acidities. The effect of the modifier at lower acidities varies depending on the basicity of the bifunctional extractant. While the most basic extractants show significantly reduced distribution ratios from lower acid solutions upon TBP addition, for the less basic compounds only slight reductions or, in some cases, even moderate increases in extraction are observed. Studies of the effect of modifier basicity on extraction behavior have also been carried out. The changes in distribution ratios with modifiers fall within the range of variations observed for diluent effects with extractants of this type. Increases in high acid distribution ratios upon TBP addition to an extractant as simple as trioctylphosphine oxide indicate that this modification of extraction behavior may be of general use for a wide range of neutral extractants     

LIQUID - LIQUID EXTRACTION OF GALLIUM(m) FROM ACIDIC NITRATE MEDIA WITH BIS(2-ETHYLHEXYL) PHOSPHINIC ACID IN TOLUENE

ABSTRACT

The distribution equilibria of gallium(III) between bis(2-ethylhexyl) phosphinic acid dissolved in toluene and acidic aqueous nitrate media has been investigated as a function of the concentration of extractant in organic phase and concentration of hydrogen ion and gallium(III) ion in aqueous phase. The extraction characteristics of bis(2-ethythexyl) phosphinic acid are compared with that of bis(2-ethylhexyl) phosphoric acid to get further information. The stoichometry of the extracted species is determined on the basis of slope analysis and IR spectra. Gallium is extracted by a cation exchange mechanism as GaRs₃ by bis(2-ethylhexyl) phosphinic acid and as GaRs₃-HR by bis(2-ethylhexyl) phosphoric acid. Temperature dependence of the extraction equilibrium is examined by temperature variation method. Both extraction processes are endothermic in nature and increase in temperature is favorable.     

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)     

GLYCINE ENHANCED SEPARATION OF Co(II) AND Ni(II) WITH BIS(2,4,4-TRIMETHYLPENTYL)PHOSPHINIC ACID [CYANEX 272] BY LIQUID-LIQUID EXTRACTION AND SUPPORTED LIQUID MEMBRANES

ABSTRACT

The extraction behavior of Co and Ni ions from aqueous nitrate solution containing glycine, and their separation by liquid-liquid extraction and supported liquid membranes (SLMs) has been studied. The separation factor between the two metals is greatly enhanced by the presence of glycine. The enhancement is due to the preferential complexation of the Ni ions by glycine. The conditional equilibrium constants of the extraction reactions and the SLM permeability coefficients have been measured. The results indicate that metal glycinate complexes are not extracted and that in presence of glycine very clean Co-Ni separation can be obtained in a single SLM pass.     

STUDIES OF THORIUM NITRATE COMPLEXATION IN AQUEOUS SOLUTIONS BY A LIQUID-LIQUID EXTRACTION METHOD - APPLICATION TO THE CALCULATION OF THORIUM DISTRIBUTION IN THE THOREX PROCESSES

ABSTRACT

Apparent stability constants of the nitrato thorium complexes, Th(NO₃₊)³⁺Th(NO₃)₄, in aqueous solutions having ionic strengths in the range 0.5 to 3.0 mol/L have been determined using a liquid-liquid extraction method. The data have been used to calculate free nitrate ion concentrations in aqueous solutions with compositions typical of those in the THOREX extraction process. A model based on extraction chemistry has been developed to predict thorium distribution coefficients under a variety of conditions.     

Extraction of Phenol Using Trialkylphosphine Oxides (Cyanex 923) in Kerosene

Abstract

A group of extractants based on phosphine oxides have been reported as an alternative to conventional polar solvents for phenol liquid-liquid extraction. Among phosphoryl extractants, Cyanex 923 (a mixture of four trialkylphosphine oxides, alkyl = normal, C₆, C₈) has proved to combine high extraction efficiency and low water solubility (1, 2), obviating the necessity of removing the solvent from the aqueous raffinate, a need asso- ciated with the use of methyl isobutyl ketone and isopropyl ether, the solvents most widely employed for this application (3, 4).     

EXTRACTION OF SODIUM IN BIS (2, 4,4 - TRIMETHYLPENTYL) PHOSPHINIC ACID “CYANEX 272”TM BASIC CONSTANTS AND EXTRACTION EQUILIBRIA

A study has been made of the extraction of sodium into bis (2,4,4 -trimelhylpentyl) phosphinic acid. The following basic constants were measured at 25^°C using two-phase titration techniques: the solubility in water, S, the ionization constant, pKa the dimerization constant, K₂, and the distribution coefficient, Kd. The results were found to be in agreement with values reported in the literature for other phosphorus based extractants. A comparison was made with the data reported for sodium extraction iD phosphorous, phosphonic and phosphinic acid based ex-tractants. The data indicated that similar behaviour can be expected for all these compounds.     

Kinetic and Thermodynamic Separation of Cu(II) and Fe(III) by Liquid-Liquid Extraction with a β-Hydroxy-oxime in Toluene

Abstract

A quantitative study of the thermodynamic and kinetic separation of Cu(II) and Fe(III) by liquid-liquid extraction with toluene solutions of the oxime 2-hydroxy-5-t-octyl (acetophenone oxime) has been conducted. On the basis of the stoichiometry, equilibrium constants, rate laws and rate constants of the extraction reactions of Cu(II) and Fe(III) an equation has been derived which describes how the separation of Cu from Fe varies with the chemical composition of the system, the hydrodynamics of the extracting apparatus and the contact time between the aqueous and the organic phases. Our results show that separations which are not feasible thermodynamically are possible when the contact time between the two phases is kept much shorter than that required to reach equilibrium.     

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.     

The Extraction of Am(III) and Fe(III) by Selected Dihexyl N,N-Dialkylcarbamoylmethyl-phosphonates, -Phosphinates and -Phosphine Oxides from Nitrate Media

Abstract

A series of neutral bifunctional extractants related to dihexyl N,N,-diethylcarbamoylmethylphosphonate (DHDECMP) have been prepared and studied for the liquid-liquid extraction of Am(III) and Fe(III) from nitrate solutions. Changes in the steric bulk of the substitutent alkyl chains and in the electro-negativity of the groups attached to the phosphoryl center in these compounds have brought about large changes in distribution ratios and selectivities for the extraction of these metals. Comparisons of these extractants to related monofunctional phosphorus-based compounds have revealed that these bifunctional species behave as monodentate, rather than chelating, extractants. The presence of the carbamoyl portion of the extractant molecules is important not for coordination to the metal, but for the ability to buffer the extractant against the effects of HNO₃.     

The Extraction and Separation of Ho,Y, and Er(III) with the Mixtures of Cyanex 302 and Another Organic Extractant

Abstract

The extraction and separation of Ho, Y, and Er(III) with the mixtures of bis(2,4,4‐trimetylpentyl)monothiophosphinic acid (Cyanex 302) and another organic extractant, such as acidic organic extractant (di‐2‐ethylhexyl phosphoric acid P204, 2‐ethylhexyl phosphoric acid mono‐2‐ethylhexyl ester P507, di‐2‐ethylhexyl phosphinic acid P229, and sec‐nonylphenoxy acetic acid CA‐100), neutral organic extractant (tri‐n‐butyl phosphate TBP, di‐(1‐metylheptyl)metyl phosphate P350, and branched trialkylphosphinic oxide Cyanex 925) or primary amine N1923, has been investigated in this paper. The extractability and separation ability for the Ho, Y, and Er with the mixtures of Cyanex 302 and organic extractants has been compared. The synergistic effect of the Ho, Y, and Er extraction with the mixtures of Cyanex 302 and P229, Cyanex 925, CA‐100, or N1923 has been explored and the synergistic enhancement coefficients have been calculated. At last, the Y³⁺ synergistic extraction with the mixtures of Cyanex 302 and CA‐100 has been determined and the extracted complex has been deduced.