Extraction of gold, palladium and platinum from chloride, bromide and iodide solution with di-n-octyl sulphide (DOS) in cyclohexane

The extraction of gold, palladium and platinum from hydrochloric acid, hydrobromic acid and iodide media by solutions of di-n-octyl sulphide in cyclohexane was examined. From distribution data it was concluded that the monosolvates AuX(3).DOS and disolvates PdX(2).2DOS are extracted. Extraction of platinum was efficient only from iodide solutions; a disolvate PtI(4).2DOS was formed. The possibility of separation of gold and palladium from platinum by extraction from bromide or chloride solutions and simultaneous extraction of palladium and platinum from an iodide medium was demonstrated.     

Extraction of palladium thiocyanate with polyurethane foam

Conditions for the extraction of the thiocyanate complex of palladium by polyether-type polyurethane foam are reported. Distribution ratios of more than 10(6) with a capacity of about 0.8 mole per kg of foam were obtained. The palladium could be rapidly recovered from the foam with high efficiency by use of ammonia solution. The efficiency of palladium extraction depends on how well the cation associated with the complex fits into the polyether segment of the polyurethane foam.     

Extraction of cobalt(II) from aqueous thiocyanate and chloride solutions with alamine, alamine oxide and tri-n-octylphosphine oxide

Summary The extraction of Co(II) from KNCS, HNCS, LiCl and HCl solutions with Alamine 336-S, Alamine oxide and tri-n-octylphosphine oxide has been studied. For acid-deficient systems, the extraction efficiency decreases in the order AlamO > TOPO > Alamine, while the sequence is Alamine > AlamO > TOPO for extraction from acid solutions. Under acid-deficient conditions, extraction invariably proceeds through solvation. On the other hand, in the systems Alamine-HCl and -HNCS as well as AlamO-HCl, extraction is governed by anion-exchange. A mixed extraction mechanism occurs with the AlamO-HNCS, TOPO-HCl and TOPO-HNCS systems. The conclusions reported for liquid-extraction also appear to apply to reversed-phase thin-layer chromatography.

---

Extraktion von Kobalt(II) aus wäßrigen Thiocyanat- und Chloridlösungen mit Alamin, Alaminoxid und Tri-n-octylphosphinoxid

Zusammenfassung Die Extraktion von Kobalt(II) aus KNCS-, HNCS-, LiCl- und HCl-Lösungen mit Alamin 336-S, Alaminoxid und Tri-n-octylphosphinoxid wurde untersucht. Im Falle von nichtsauren Systemen nimmt die Extrahierbarkeit in der Reihenfolge AlamO > TOPO > Alamin ab, während für saure Systeme die Reihenfolge Alamin > AlamO > TOPO gilt. Unter nichtsauren Bedingungen erfolgt die Extraktion stets durch Solvatation, wogegen in den Systemen Alamin-HCl, Alamin-HNCS sowie AlamO-HCl Anionenaustausch maßgebend ist. Gemischte Extraktionsmechanismen herrschen in den Systemen AlamO-HNCS, TOPO-HCl und TOPO-HNCS. Die für die flüssig-flüssig-Extraktion beschriebene Schlußfolgerungen scheinen auch für die Umkehrphasen-Dünnschicht-Chromatographie zu gelten.

     

Ion-exchange recovery of palladium(II) from multicomponent chloride solutions

Ion-exchange sorption of palladium(II) from both concentrated aqueous hydrochloric acid solution containing Fe(III), Sn(II), Zn(II), and Cu(II) and weakly acidic concentrated aqueous ammonium chloride solution containing Zn(II) and Cu(II) was studied. The Purolite S920, Purolite S924, and Purolite S984 macroporous resins with the thiourea, thiol, and polyethylenepolyamine functional groups, respectively, were used as sorbents. Strongly basic Purolite A500 anion exchanger was also tested. The desorption of palladium(II) with aqueous ammonia, hydrochloric acid, and acidified aqueous thiourea was examined.     

Extraction of palladium(II) from hydrochloric acid solutions with triacylated ethyleneamines

Extraction of palladium(II) from hydrochloric acid solutions with novel efficient extractants, triacylated ethyleneamines, was studied. The most effective extraction of palladium(II) was observed from 0.5–1 M HCl solutions. Extraction of palladium(II) from 1 M HCl solutions was found to occur through mixed (coordination and anion-exchange) mechanism. In the field of dominance of the anion-exchange mechanism of the extraction of palladium(II) with triacylated pentaethylenehexamine the concentration constant of palladium(II) extraction was calculated, and thermodynamic parameters of extraction were evaluated.     

Extraction of cobalt from thiocyanate solutions with polyurethane foam

The extraction of cobalt (II) from aqueous thiocyanate solutions with polyurethane foam has been extensively investigated. The extraction is enhanced by high thiocyanate concentration, high ionic strength and low temperature. A pH of 1.0-9.0 can be used for efficient extraction. Cobalt can be extracted at low concentration and the distribution coefficient is independent of foam weight. Several foam types and foam pretreatments have been examined. The effect of various substances added to the cobalt thiocyanate solutions has been investigated. Some of these substances caused either enhanced or decreased extractions by interacting with the polyurethane foam or by changing the solution chemistry.     

Study of the extraction of vanadium(V)-N-p-octyloxybenzoyl-N-phenylhydroxylamine complexes from sulphuric acid solutions containing chloride, fluoride or thiocyanate

The extraction of vanadium(V)-N-p-octyloxybenzoyl-N-phenylhydroxylamine (OBPHA) complexes from sulphuric acid containing chloride, fluoride or thiocyanate is described. The purple, red and reddish blue complexes extracted, containing chloride, fluoride or thiocyanate, have molar absorptivities of 6.1 x 10(3), 5.08 x 10(3) and 7.9 x 10(3) 1.mole(-1) .cm(-1) with maximum absorption at 540, 490 and 570 nm, respectively. A spectrophotometric determination of vanadium(V) has been based on these results. The composition of the extracted complexes is estimated as V(V): OBPHA:X(-) = 1:2:1 (X(-) = Cl(-), F and SCN(-)).     

Extraction of molybdenum(VI) by 4-(5-nonyl)pyridine in benzene from aqueous mineral acid solutions containing thiocyanate ions

Extraction of Mo(VI) by 4-(5-nonyl)pyridine (NPy) in benzene from mineral acid solutions containing thiocyanate ions has been investigated at room temperature (23±2°C). From mineral acid (HCl, HNO₃, and H₂SO₄) solutions alone Mo(VI) is not extracted quantitatively while the presence of small amounts of KSCN in the system augments the extraction by a large factor. Stoichiometric studies indicate that ion-pair type complexes (NPyH)₂·[MoO₂(SCN)₄] are responsible for the extraction. Separation factors determined at fixed extraction conditions (0.1M Npy/C₆H₆–0.1M acid +0.2M KSCN) reveal that Ag(I), Cu(II), Co(II), Zn(II), Hg(II) and U(VI) are co-extracted while a clean separation from alkali metals, alkaline earths and some transition metals like Ln(III), Zr(IV), Hf(IV), Cr(III), Cr(VI) and Ir(III) is possible. Some of the complexing anions like oxalate, citrate, acetate, thiosulfate or ascorbate do not affect the degree of extraction of Mo(VI) allowing it to be recovered from diverse matrices.     

Extraction of copper(II) from ammonium chloride solutions with capric acid

Extraction of copper(II) with capric acid from ammonium chloride solutions was examined. The composition of the complex extracted was determined and it was found that the extraction process can be adequately described by the equation: 2Cu_(a)²⁺ + 3(HR)_2,(0) ⇌ (CuR₂·HR)_2,(0) + 4H_(a)⁺     

Extraction of cobalt(II) from aqueous thiocyanate solutions by tri-n-octylamine

The distribution of cobalt(II) between acidic thiocyanate solutions and tri-n-octylainine dissolved in various diluents has been measured for several cobalt(II) loadings and amine concentrations. Diluents investigated included n-hexane, cyclohexane, benzene, xylene, carbon tetrachloride, chloroform, chlorobenzene, o-dichlorobenzene and nitrobenzene. In all cases, the species extracted is bis(tri-n-octylammonium) tetrathiocyanatocobaltate(II). The ability of each diluent to extract cobalt(II) from acidic thiocyanate solutions is approximately correlated with the dielectric constant of the pure diluent, i.e., the smaller the dielectric constant, the larger the distribution ratio, with the exceptions of nitrobenzene and chloroform.     

Extraction kinetics of iron(III) from aqueous nitrate solutions to toluene solutions of tri-n-butylacetohydroxamic acid

The forward and reverse extraction rate of Fe³⁺ at time zero between aqueous nitrate solutions and toluene solutions of tri-n-butylacetohydroxamic acid, HX, has been studied as function of the composition of the system and the stirring speed of the two phases. Experimental information has been also obtained on the degree of aggregation of HX, its surface active properties, its solubility in the aqueous phase as well as on the equilibrium distribution of Fe(III). Rate equations have been derived. The rate determining step of the extraction reaction has been shown to be the reaction of the free and hydrolyzed iron ions, Fe³⁺ (hydrated) and FeOH⁺ (hydrated), with the HX undissociated molecules. The reactions occur simultaneously in the aqueous phase (homogeneous path) and at the interface (heterogeneous path). A correlation between the rate constants and the equilibrium constant of the extraction reaction of Fe(III) has been established.     

Extraction of Th(IV) with tributyl phosphate from aqueous HCl solutions containing sodium, calcium, or aluminum chloride

Extraction of thorium(IV) from 0.1–3 M aqueous hydrochloric acid solutions containing NaCl, CaCl₂, or AlCl₃ was studied. The experimental results are discussed.     

Extraction of lead(II) with cyanex 302 and its spectrophotometric determination with PAR

A method is developed for the extraction of lead(II) from an aqueous solution of pH 2.1-8.3 with cyanex 302 [bis(2,4,4-trimethylpentyl monothiophosphinic acid)] in toluene as an extractant. Lead(II) was stripped with 0.1 mol dm(-3) nitric acid and determined spectrophotometrically with PAR. The method is most sensitive and permits the separation of lead(II) from binary mixtures containing commonly associated metal ions. The method is applicable for the separation and determination of lead in alloys and environmental samples.     

Low-temperature equilibriums in solutions of isocyanide-phosphine complexes of palladium(II) chloride

cis-[PdCl₂(CNR)(PPh₃)] [R = Cy, t-Bu, C(Me)₂CH₂C(Me)₃] have been synthesized via the interaction of [(PPh₃)ClPd(μ-Cl)₂PdCl(PPh₃)] with isocyanide in CH₂Cl₂ at room temperature with 90–98% yield and characterized by means of mass spectrometry as well as ¹H, ¹³C{¹H, ³¹P}, and ³¹P{¹H} NMR spectroscopy. The complexes structure in the solid phase has been elucidated by means of X-ray diffraction analysis. Dynamic processes in the solutions of the complexes in CDCl₃ and CD₂Cl₂ at temperature of–95 to 60°С have been studied by means of ¹H and ³¹P NMR spectroscopy. It has been found that the studied compounds existed exclusively in the cis-[PdCl₂(CNR)(PPh₃)] form in the solutions. In the case of cis-[PdCl₂(CNCy)(PPh₃)] in CH₂Cl₂, the conformational transitions of the equilibrium forms (the transition of the substituent in the cyclohexyl cycle between the equatorial and axial positions) are slowed down, the equatorial conformer prevailing in the solution (2: 1 at–95°С). Quantum-chemical simulation (DFT) has revealed that the standard Gibbs energy of the conformational transition from the axial form of cis-[PdCl₂(CNCy)(PPh₃)] into the equatorial one in the CH₂Cl₂ solution at 178 K equals–2.5 kJ/mol, being in agreement with the experimental data.     

Crystallographic and spectroscopic studies on palladium(II) complexes containing pyrazole and thiocyanate ligands

Mononuclear palladium(II) complexes containing both pyrazole-type ligands and thiocyanate, of general formula [Pd(SCN)₂(L)₂] {L = pyrazole (HPz) and 1-phenyl-3-methylpyrazole (phmPz)} have been prepared and characterized by elemental analysis, i.r. and n.m.r. spectroscopy and by single crystal X-ray diffraction methods. The Pd atom in these structures lies on the crystallographic inversion center; in a square-planar coordination geometry made by two sulfur and two nitrogen atoms of the ligands, both in trans positions.     

Extraction of iron(III) with diphenyl-2-pyridylmethane dissolved in benzene from aqueous chloride solutions

The mechanism of extraction has been investigated by partition, slope analysis and loading-ratio data. The results obtained give a picture of the mechanism of extraction of FeCl ₄ ⁻ ions in relation to the hydration and solvation of the compound extracted. The possible formula of the extracted species is (DPPM)₃H₃O⁺(H₂O)_n−FeCl ₄ ⁻ . In dilute aqueous hydrochloric acid systems the influence of the concentration of a number of salts with cations of different electrical potentials (Ze/r), on iron(III) extraction, has been studied. Splitting of the organic phases occurs at high acid and/or high salt concentrations. The phenomenon is explained on the basis of the variability of the hydration number. Investigations have been made to understand the parameters controlling the extraction of the metal and its is shown that the extraction offers a simple, fast and selective separation method of iron from solutions.     

Extraction chromatographic studies of Ti(IV) with cyanex 301 as impregnant—Recovery from red mud

Summary A silica gel column impregnated with bis-(2,4,4-trimethylpentyl)dithiophosphinic acid has been studied for the uptake of Ti(IV). Its chemical stability has been examined and its regeneration power checked. The stoichiometry of the extracted species is proposed and the loading capacity of the column material for Ti(IV) assessed. Some important binary separations of Ti(IV) from commonly associated metal ions have been achieved and the column has been used to recover high-purity titanium from red mud, a secondary sector material.     

Structure of palladium chloride complexes with organic sulfides in solutions

EXAFS spectroscopy was used to study the influence of various factors on the structure of PdCl₂ complexes with organic sulfides in organic solvents. Absolute interatomic distances in the first coordination sphere of Pd were determined for the complexes [PdCl₂·2(C₆H₁₃)₂S] (I), [PdCl₂·(C₆H₁₃)₂S]₂ (II), [PdCl₂·2(C₆H₅)₂S] (III), and [PdCl₂·(C₄H₉)S(C₄H₇)] (IV) and for their solutions in some organic solvents. Our hypothesis that aromatic solvent molecules are coordinated to palladium atoms through weak π-bonds, which was proposed for complex (I) in benzene, is supported fror benzene and pseudocumene solutions of complexes (I), (II), and (III). It is shown that the characteristic features of the specific solvation of the complexes under study are determined by the electron properties and spatial structures of the molecules as well as by the donating abilities of the solvents. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 6, pp. 1030–1037, November–December, 1995. Translated by I. Izvekova