THE EQUILIBRIUM REACTION OF THE EXTRACTION OF URANIUM(VI) WITH DI-(2-ETHYLHEXYL) PHOSPHORIC ACID FROM NITRIC ACID SOLUTIONS

The equilibrium reactions for the extraction of uranium(VI) with di(2-ethylhexyl)phosphoric acid from nitric acid solutions is investigated. In this work, proton NMR technique was used to verify that the nitrate ligand in the resulting complexes originated from the complexing of nitric acid. Organic solutions of 0.05 M (dimeric HDEHP, the upper bar denotes the species in the organic phase) in kerosene were used to extract aqueous solutions containing various concentrations of uranyl nitrate and nitric acid. The concentrations of nitric acid and uranium(VI) in the organic phase were measured, and used to determine the composition of the resulting complex. Which were found to be varied with the uranium(VI) loading and the nitric acid loading of HDEHP. Parallel reactions of forming UO were proposed to describe this extraction system. The proposed reactions elucidate the equilibrium behavior consistently, for the loadings of uranium(VI) and nitric acid ranging from very low value to the vicinity of saturation.     

STUDY ON THE SEPAEATION OF A BINARY METAL MIXTURE BY SOLVENT EXTRACTION

A study on the extraction of copper and zinc from aqueous binary metal solutions with terdodecylthioglycolic acid in kerosene has been realized. Distribution of the metal ions in a wide range of pH and carboxylic acid concentrations has been studied.The results show that an interaction occurs which influences the amount of each metal extracted, so that a mixed metal complex is formed in the organic phase, in addition to pure metal complexes and . The separation factor for copper and zinc has been expressed as a function of the species concentrations and the extraction constants involved. From these results, the extractant is shown to be moderately adequate for separation of copper and zinc.     

LAMELLAR INORGANIC ION EXCHANGERS K+-Cs+-H+ ION EXCHANGE IN Y-TITANIUM PHOSPHATE

An equilibrium study of the K⁺ -Cs⁺-H⁺ ion exchange on γ-titanium phosphate has been carried out. Isotherms for the ion exchange have been determined and phases formed during the exchange have been identified. Over the entire composition range, the exchanger prefers cesium to potassium.

When 25% of exchange is reached, a solid solution of formula (with a composition varying with the equilibrium solution composition) is formed. The equilibrium constant for the substitution process K⁺ -Cs⁺ in the phase was determined. For 25-50% of exchange, two solid solutions co-exist: A phase diagram of the ternary system is given. The results are compared to those previously obtained in the study of K⁺ -H⁺ and Cs⁺ -H⁺ binary systems. An exchange mechanism is proposed.     

ENHANCEMENT OF THE SINERGIC EXTRACTION OF COBALT WITH MIXTURES OF l-PHENYL-3-METHIL-’4-BENZOTtLPIRAZOL-5-ONE AND DODECYLAMINE BY EMULSION FORMATION.

The synergic extraction of cobalt (II) from sulphate medium (O.33M) with l-phenyl-S-methyl-l-benzoylpyrazol-S-one (HL) and n-dodecylamine (Am) in toluene has been explained by: of constant logK_s=5.15. When the extraction is performed from perchlorate and nitrate media ([X]=[C10₄]=[N0₃ ]=1.0M), an emulsion, in contact with a clear organic phase, is formed owing to the amphiphilic properties of AmH.X. This Induces an enhancement of the synergic extraction at low AmH.X concentrations. The extraction equilibrium is : Where int. denotes interfacial species and logK +log{AmH.X} -log[X;}_int =logK_int = -6.10 and -6.25 (X?ClO₄ and NO₃). (AmH⁺ denotes single or aggregated ammonium cations).     

LEAD(II) EXTRACTION FROM NITRATE SOLUTIONS WITH DI(2-ETHYLHEXYL)PHOSPHORIC ACID

ABSTRACT

In this paper, equilibrium studies were carried out on the extraction of trace amounts of lead(II) from 0.2 mol/dm³ (Na,H)NO₃ aqueous solutions with di(2-ethylhexy1)phosphoric acid (HR) dissolved in n-dodecane at 298 K. The composition of the extracted species was numerically found to be and ₂. A chemical equilibrium model was developed to evaluate the thermodynamic constants for the formation of the two complexes, based on the law of mass action, which took into account the activity corrections of reactive species in the aqueous phase by employing the Bromley and the simplified Pitzer equations and those of the extractant in the organic phase.     

SOLVENT EXTRACTION OF ZINC FROM CHLORIDE MEDIA WITH SECONDARY LONG-CHAIN ALKYLAMINE

In the solvent extraction of zinc from chloride media with a secondary long-chain alkylamine, Amberlite LA-2, aggregations of ammonium chloride salt of alkylamine and zinc-complex with alkylamine and distribution equilibrium of zinc were investigated at 30 "C using n-hexane as a diluent. The ammonium chloride salt of alkylamine exists as monomeric, dimeric, trimeric and tetrameric species (BHCl, (BHCl)₂, (BHCl)₃ and (BHCl)₄, respectively). The zinc-complex exists as monomeric and dimeric species ((BH)₂ZnCl₄ and ((BH)₂ZnCl₄)₂, respectively). Zinc is extracted according to the extraction reaction in the lower loading region of zinc to alkylamine and according to the extraction reaction in the higher loading region.     

THE EXTRACTION BY N.N-DIALKYLAMIDES. II. EXTRACTION OF ACTINIDE CATIONS

ABSTRACT

N,N-dialkylamides are potential alternative extractants to tributyl-phosphate for the actinide separation in nuclear fuel reprocessing.

Extraction mechanisms of U(VI), Th(IV) and Pu(IV) from nitric acid media are investigated for the amide DOBA(((C₄H₉) (C₂H₅) CHCH₂)₂ NC(O) C₃H₇) and DO_iBA (((C₄H₉) (C₂H₅) CHCH₂)₂ NC(O) CH(CH₃)₂).

For low aqueous acidities, amides are neutral extractants. Extraction stoichiometrics of (Amide = DOBA or DO_iBA), have been established. Th(IV) is supposed to form a di- and a trisolvate in the inner-coordination sphere. For concentrated solvents, bilogarithmic dependences of distribution coefficients with ligand concentration point out non-integer slopes higher than those expected from stoichiometry. Such features, very often noted for amides, do not seem to be due to new chemical second-sphere species, which has never observed experimentally, but to polyoriented interactions between free ligands and complexes and may be considered as part of non-ideality.

Amides behave as anionic extractants with increasing acidity. New species are formed, involving UO₂(NO₃)₃ ^? and PU(NO₃)₆ ^2? anions, with the protonated amide ligands in the outer-coordination sphere of metals.     

NOTE: SOLVENT EXTRACTION OF PLATINUM(IV) BY TRIOCTYLPHOSPHINE OXIDE

The equilibrium distribution of platinum(IV) between hydrochloric acid and trioctylphosphine oxide (T0P0) in toluene at 303 K was examined. From the concentration dependencies of the distribution ratio, it was determined that platinum(IV) is extracted as follows:

The extraction.equilibrium constant was found to be Ke = 3.6×10³.     

TEMPERATURE EFFECT ON ION EXCHANGE SORPTION OF PHOSPHATE

Phosphate sorption on the strong basic anion exchanger Amberlite IRA-400 (Cl^? form) is studied as a function of temperature ( 25^°C–50^°C), at two initial pH values (5 and 9 ) in the concentration range 120–190 ppm. Chloride released/phosphate sorbed ratios increase with the increase both in temperature and pH and decrease with the increase in the concentration of solution. It is suggested that phosphate sorption takes place initially as HPO₄ ^2? followed by H₂PO₄ ^?. The data is explained with the help of a modified Langmuir and mass law action equations. Various thermodynamic parameters (ΔG^°,ΔH^° and ΔS^°) are presented. The differential isosteric heat of adsorption, is computed at different temperatures, showing the sorption of phosphate to be endothermic on the anion exchanger Amberlite IRA-400.     

COMPARISON OF BENZOIC ACID WITH DECANOIC ACID AS AN EXTRACTING AGENT

The extraction of copper(II) with benzoic acid was carried out at 25 °C and aqueous ionic strength of 0.1 mol/dm³(NaClO₄). Copper(II) benzoate cannot be extracted in benzene, while it is extracted in 1-octanol as a monomeric copper(II) benzoate. The extraction equilibrium is described as:

with logK_ex(1,0) = ? 7.70. The extraction of copper(II) with benzoic acid(aromatic carboxylic acid) was found to proceed through a stoichiometry different from that with decanoic acid (aliphatic carboxylic acid).