THE EXTRACTION OF CADMIUM FROM A MIXTURE OF PHOSPHORIC AND HYDROCHLORIC ACIDS

ABSTRACT

The feasibility of using trialkylphosphine oxides to remove cadmium from mixed, acidic chloride-phosphate systems was investigated. Interpolations from extraction isotherms indicated that raffinates containing very low levels of cadmium (approximately 0.5 mg/L) could be produced readily. Stripping was accomplished with water. The co-extraction of acids was minimal.     

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.     

SOLVENT EXTRACTION OF COBALT(II) WITH TRI-n-BUTYL PHOSPHATE FROM AQUEOUS-ORGANIC SOLUTIONS

Cobalt(II) has been extracted by 50% (v/v) TBP solution in benzene from HC1, HBr, and LiC1 solutions containing water miscible alcohols and nonbesic and basic aprotic solvents. All solvents used caused the distribution ratio of Co(II) to increase due to diminished water activity and shifts in equilibria of cobalt(II) complexes in solutions. Hexamethylphosphor-triamide (HMPTA) has been found to behave exceptionally in that it extracted Co(II) from LiC1 solutions into neat benzene and in the presence of TBP induced a weak synergism caused by extraction of at least two mixed solvates.     

SOLVENT EXTRACTION OF COPPER(II) FROM CHLORIDE SOLUTIONS BY SOME PYRIDINE CARBOXYLATE ESTERS

n-octyl-3-pyridine carboxylate (NOPC), an analogue of the commercial reagent DS5443, was synthesized, and the stoichiometry of its reaction with copper(II) in chloride media was determined. At low metal loadings, copper(II) was extracted by the solvation reaction:

The factors affecting the separation of iron and copper from solutions containing copper(II),iron(II), and zinc(II)chlorides were determined in countercurrent extraction tests using DS5443.     

SOLVENT EXTRACTION OF COPPER(II), NICKEL(II), AND COBALT(II) FROM SODIUM CHLORIDE SOLUTIONS BY OCTANAL OXIME

The extraction of divalent copper, nickel, and cobalt from sodium chloride solutions with octanal oxime (OCOX) was found to proceed by the following reaction:

The association of octanal oxime in toluene was taken into account in the modelling of the extraction reaction, and the formation constants for dimers and trimers were calculated using vapour-pressure osmometry. Stability constants for the formation of aqueous copper-chloro species were also calculated.     

SOLVENT EXTRACTION WITH SULPHONIC ACIDS.

Advances in solvent extraction of metal ions with sulphonic acids is reviewed for the period 1973 to the present. Physical aspects of micelle formation and water uptake by the extractant are dealt with as well as applications to specific systems. The synergism of mixtures, notably those containing crown ethers, is reviewed.     

SOLVENT EXTRACTION EQUILIBRIA OF LEAD(II) WITH ACIDIC ORGANOPHOSPHATE AND PHOSPHONATE

Distribution equilibria of lead(II) in the extraction with di(2-ethylhexyl)phosphoric acid and 2-ethylhexyl 2-ethylhexylphosphonic acid in toluene from aqueous ammonium nitrate solutions were measured at 303 K to elucidate the concentration dependencies of the reactant species on the distribution ratio. It was found that lead(II) is extracted as the mononuclear complex, PbR₂2HR, with the former extrac-tant while it is extracted not only as the complex, PbR₂2HR, but also as the complex, Pb(NO₃)R;HR, accompanied by simultaneous transfer of nitrate anion with the latter ex-tractant. The extraction equilibrium constants of these complexes were evaluated as well as the stability constants of lead(II) -nitrato complexes, Pb(NO₃)⁺, Pb(NO₃)₂and Pb(NO₃)^? ₃.     

SOLVENT EXTRACTION OF Pa(V) and Th(IV) BY TRIPHENYLPHOS-PHINE AND TRIPHENYLARSINE OXIDES FROM HYDROCHLORIC ACID MEDIUM

The extraction of Pa(V) by both ph₃PO and Ph₃AsO in chloroform from HCl medium is performed. The extraction stoichiometry for each system is proposed which is assumed to proceed through the formation of monosolvate. The extraction behaviour of Pa(V) by both extractants is quantitatively described by an empirical equation for each case. The obtained data show that the extraction power of Ph₃AsO is much higher than the corresponding value of PH₃PO. This difference is ascribed to the difference in their electronic structure. The effect of using different diluents is studied. In the same way, the extraction of Th (IV) by both extractants from HCl medium is described and the separation factors for both systems are calculated and compared.     

SOLVENT EXTRACTION OF PALLADIUM(II) WITH A SCHIFF BASE AND SEPARATION OF PALLADIUM FROM Pd(II)-Pt(VI) MIXTURE

ABSTRACT

A new Schiff base extractant, N,N'-bis[l-phenyl-3-methyl-5-hydroxy-pyrazole-4-benzylidenyl]-l,3-propylene diamine (H₂A) was synthesized and characterized. The extraction mechanism of palladium(II) from HNO₃ or HClO₄ medium with H₂A in chloroform or toluene was investigated. The influences of the Schiff base concentration in the organic phase, the concentration of palladium, the pH and anions (Cl^?, S0₄ ^?, NO₃ ^?, ClO₄ ^?) in the aqueous phase and the temperature on the distribution ratio for palladium (II) have been examined. The extracted complex has been confirmed by chemical analysis, thermoanalyses and IR spectroscopy. It was found that palladium is extracted according to the following extraction reaction:

The extraction equilibrium constants of palladium(II) were 8·4 and 21·3 in chloroform and toluene diluents, respectively. The values for the enthalpy and standard free energy of extraction were also obtained. The separation of Pd(II) from the mixed solution of Pd(II)-Pt(IV) was achieved by adjusting the pH.     

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.     

SOLVENT EXTRACTION OF PALLADIUM(II) WITH A SULFUR-CONTAINING CARBOXYLIC ACID

The mechanism of solvent extraction of palladium (II) from aqueous ammonium chloride solution with α-butylthiolauric acid( α-BTLA = S) in toluene was investigated in terms of extraction equilibrium and kinetics at 303 K. From the results of extraction equilibrium, it was found that α-BTLA behaves as a solvating extractant for palladium(II) and that the extracted species is a 1:2 metal:reagent complex, PdCl₂S₂ The extraction rate of palladium(II) was measured in a batch-type vigorously stirred cell. The effects of the concentrations of palladium(I I), hydrogen ion, chloride ion and extractant on the extraction rate were quantitatively interpreted by a reaction mechanism where the parallel reactions of α-BTLA with PdCl₃(H₂0)- and PdCl₄ ^2- are the rate-determining steps.     

KINETIC STUDIES OF THE SOLVENT EXTRACTION OF PLATINUM(II) WITH DIPHENYLTHIOUREA

The race of extraction of plaCinum(II) wich diphenylthiourea (DPTU) into chloroform has been evaluated as a function of [DPTU]₀, [Cl] and the solution pH at 25° C. The homogeneous chemical reaction:

PtCl^? ₃ + DPTU → PtC1₃(DPTU)^?

is considered to be the rate determining step with a rate constant of 17.2 M^-1s^-1 The role of tetraheptylammonium chloride (THA^?,C1), thiourea (TU), thiocyanate, and iodide in catalyzing the extraction is examined.     

PALLADIUM WITH TRIOCTYLMETHYLAMMONIUM CHLORIDE SOLVENT EXTRACTION OF PALLADIUM(II) WITH TRIOCTYLMETHYLAMMONIUM CHLORIDE

Equilibrium distribution of palladium(II) was investigated in the solvent extraction with tri-octylmethylammonium chloride (QC1) in toluene from hydrochloric acid solutions at 303 K. The title extracting reagent extracted hydrochloric acid as the species of the types, QC1(HC1) (_n(n= 1,2), according to the similar extraction reactions as observed in the extraction of organic acids such as acetic acid and phenol with high-molecular-weight amines in the previous works. From the concentration dependencies of the reactant species on the distribution ratio and from the result of loading test, it was elucidated that palladium(II) is extracted as a mononuclear ion pair complex of the type, Q⁺;[PdCl]₃ (HCl)] in the very high concentration region of hydrochloric acid. The equilibrium constant of the extraction reaction was evaluated.     

SOLVENT EXTRACTION OP COPPER (II), NICKEL (II) AND COBALT(II) PROM HALIDE AND THIOCYANATE SOLUTIONS BY ALDOXIMES

The extraction of divalent copper, nickel and cobalt from acidic chloride solutions with solutions of heptaloxime, nonaloxime and 2-methyldekaloxime in toluene has been studied at 18*C.

These metals were found to be extracted according to the following solvation reaction:

The influence of syn-anti isomerization of aldoximes on the extraction has been discussed. Taking into account association and syn - anti isomerization constants of aldoximes in organic phase,hydration of extracted oomplexes and activities of salts in aqueous phase, effective extraction oonstants have been calculated for chloride solutions.

Separation of nickel and cobalt from aoidic chloride, bromide and thiooyanate solutions by extraction with heptaloxime has been studied.     

RECENT ADVANCES IN THE SOLVENT EXTRACTION OF MERCURY(II) WITH CALIXARENES AND CROWN ETHERS

This work is focused on the recent advances, mainly achieved during the past ten years on the solvent extraction separation of mercury from aqueous solutions using macrocyclic ligands such as calix[n]arene derivatives and crown ethers.     

EXTRACTION OF COPPER(II) FROM ACID CHLORIDE SOLUTIONS BY N-DODECYL- AND N.N-DIHEXYLPYRIDINECARBOXAMIDES

ABSTRACT

N-dodecyl- and N,N-dihexylpyridinecarboxamides with amide group at 2, 3 or 4 position were synthesized. Model individual amides were used to recover copper(II) from chloride solutions at constant water activity and constant total concentration of dissolved species in aqueous solution. It was found, that pyridine-2-carboxamide forms with copper complexes (CuCl₂)_x (Ext)₂. Remaining amides form with copper complexes CuCl₂(Ext)₂. Monoalkylamides are not suitable for extraction because they and their complexes are slightly soluble in the hydrocarbon diluents. N,N-dialkylpyridinecarboxamides and their copper complexes are sufficiently soluble in the hydrocarbon phase to carry out extraction. However, they are strong extractants and extract efficiently copper already from dilute chloride solutions ([Cl] = 0.1 M). They extract also significant amounts of copper from concentrated (3-4M) nitrate solutions.     

SOLVENT EXTRACTION EQUILIBRIA OF TRIS(BENZOYL- TRIFLUOROACETONATO)COMPLEX OF COBALT(II) AND NICKEL(II) AS ION-PAIRS WITH TETRABUTYLAMMONIUM

Abstract

Solvent extraction of cobalt(Il) and nickel(II) in aqueous 1 mol dm^?3 NaCl solutions with benzoyltrifluoro-acetone(Hbfa) in carbon tetrachloride has been measured in the absence and presence of tetrabutylammonium(tba⁺). In the absence of tba⁺, M(bfa)₂ species is extracted and the extraction of cobalt(II) is better in the higher Hbfa concentration range but in the presence, M(bfa)₃ ^?tba⁺ type ion-pair is extracted and the extraction of nickel-(II) is always better. This is explained in terms that although the bis-nickel(II) complex is more stable, it is much more strongly hydrated than the bis-cobalt(II) complex and consequently its extraction is hindered but in the tris-complexes such a large difference of the hydration may not occur and the more stable nickel(II) complex is extracted better.     

COPPER EXTRACTION FROM CHLORIDE SOLUTIONS WITH MIXTURES OF SOLVATING AND CHELATING REAGENTS

ABSTRACT

Equimolar mixtures of N,N,N',N'-tetrahexylpyridine-3,5-dicarboxamide (L) with 2-hydroxy-5-t-octylbenzophenone oxime or l-phenyldecane-l,3-dione (HB), were used to extract copper from chloride solutions of various concentration of chloride ions. Chloride ions were then scrubbed out with water or ammoniacal solutions and copper was transferred from the solvate CUCl₂L₂ to chelate CuB₂- Both studied systems permit effective extraction of copper and removal of chloride ions from the organic phase. Some protonation of solvating reagent L occurs, however, when copper is stripped from the chelate with hydroxyoxime. This negative effect can be suppressed when 1-phenyl decane-1,3-dione is used as a chelating agent. The scrubbing of chloride ions must be then carried out with ammoniacal solutions to avoid simultaneous stripping of copper.     

GERMANIUM SOLVENT EXTRACTION FROM SULFURIC ACID SOLUTIONS (AND CO-EXTRACTION OF GERMANIUM AND GALLIUM)

The U.S. Bureau of Mines investigated solvent extraction methods for recovering germanium from sulfuric acid leach filtrates. A new organic extractant system was developed which synergistically and selectively recovered germanium from these solutions. A continuous solvent extraction circuit was operated for over 150 hr, extracting over 90% of the germanium from 0.30 g/L Ge filtrates containing 40 to 60 g/L free acid. Over 90% of the loaded germanium was stripped from the organic phase with water at 75 °C. A section on germanium and gallium co-extraction is also presented.     

SOLVENT EXTRACTION OF MOLYBDENUM (VI) WITH LIX 63

The equilibrium and kinetics of the extraction of molybde-num(VI) with LIX 63 was investigated. The extraction of Mo(VI) is both favored by high acidity and high LIX 63 concentration. From the equilibrium studies, the extraction constant for the reaction was found to be log K_ex - 16.43. The rate of extraction is first ex order in both metal and extractant but decreases non-linearly with pH. The rate-determining step of the reaction was deduced to be the formation of a 1:1 complex between Mo(VI) and LIX 63 in the aqueous phase. A mechanism in which different Mo(VI) species react concurrently with the neutral ligand is proposed. The logarithmic values of the second order reaction rate constants (in M^?1 s^?1 units) involving each Mo(VI) species are as follows: molybdate - 2.30, bimolybdate - 5.82, and molybdic acid - 8.16. These results agree well with the results reported for other ligands.