Evaluation of unsymmetrical dithiodiglycolamide as novel extractant for application in selective separation of palladium(II) from aqueous solutions

A novel unsymmetrical multidentate ligand namely; N,N'-dimetyl-N,N'-didecyldithiodiglycolamide (DMD³TDGA) was synthesized and used as agent for the selective extraction of palladium(II) from hydrochloric acid solutions. A systematic investigation was carried out on the extraction of Pd(II) using DMD³TDGA. The quantitative extraction of Pd(II) with DMD³TDGA in n-dodecane is observed at ~4 M HCl. The main extracted species of Pd(II) is PdC_l2. DMD³TDGA and IR spectra of the extracted species were investigated. The extraction of palladium(II) from various concentrations of hydrochloric acid solutions in the presence of metal ions, such as Pt(IV), Rh(III), Cr(II), Ni(II), Fe(III), Nd(III), Zr(II), and Mn(II) was carried. DMD³TDGA showed very high selectivity and extractability for Pd(II). Quantitative back extraction of Pd(II) was obtained in single contact using thiourea solution. The results obtained indicated that, excellent separation of Pd(II) from the investigated metal ions can be achieved. Five successive cycles of extraction/back-extraction, indicating excellent stability and re-utilization of this new extractant can be used for selective separation of Pd(II) from other elements in hydrochloric acid medium.     

Extraction of palladium(II) from hydrochloric acid solutions by (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)-pentan-3-ol

The extraction properties of (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)-pentan-3-ol (with chloroform as a diluent) with respect to palladium(II) were studied. Palladium(II) was found to be efficiently extracted by the reagent from 0.1–6 M HCl solutions by the coordination mechanism. The rate of palladium(II) recovery depends on the hydrochloric acid and chloride ion concentrations in the aqueous phase. Conditions for the selective separation of palladium(II) and copper(II) from nickel(II), cobalt(II), and iron(III) were determined.     

Palladium(II) recovery in extraction and sorption systems with 5-amino-1,2,4-thiadiazole derivatives

The distribution of palladium(II) between the solutions of hydrochloric and nitric acids and the solutions of 5-amino-1,2,4-thiadiazole derivatives in 1,2-dichloroethane depending on acid and extractant concentrations in the aqueous and organic phases, respectively, was studied. The stoichiometry of the extracted complexes was determined, and the concentration constants of extraction were calculated. The applicability of macroporous polymer sorbents noncovalently modified with the test reagents to the sorption recovery of palladium(II) from nitric acid solutions was demonstrated.     

Propiconazole and Penconazole as Effective Extractants for Selective recovery and concentration of platinum(IV) and palladium(II) from hydrochloric acid solutions formed in leaching of spent aluminoplatinum and aluminopalladium catalysts

Selective recovery and concentration of platinum(IV) and palladium(II) from hydrochloric acid solutions of varied composition was studied using commercial reagents propiconazole and penconazole as extractants. The ranges of hydrochloric acid concentrations for effective extraction and highly selective separation of platinum metals from Al(III) and Ni(II) with propiconazole (toluene with 15 vol % n-decanol as deluent) and penconazole (chloroform) were determined. The conditions for 10-fold selective concentration of platinum metals with recovery of more than 99.9% of metal ions into the organic phase were found. The conditions for quantitative (>99%) stripping of platinum(IV) with a hydrochloric acid solution of thiourea and palladium(II) with ammonia solution were determined. The results obtained can be used for optimizing the modes of selective recovery of platinum(IV) and palladium(II) from hydrochloric acid solutions formed in leaching of alumina-supported platinum-rhenium, platinum-nickel, and palladium catalysts.     

Functionalized di- and tetrathia-crowns and their use to quantitatively separate and recover gold(III), palladium(II), silver(I) and mercury(II) Ions

Two new dithia-crowns containing a hydroxy group and 1,4,7,10-tetrathia-18-crown-6 containing an allyl-oxymethyl substituent were prepared in good yields. Two of these crowns were covalently attached to silica gel. The silica gel-bound thia-crowns were used to separate gold( III ), palladium( II ), silver( I ) and mercury( II ) ions from an aqueous 0.1 M nitric acid solution which also contained 1.0 M ferric chloride.     

Liquid Extraction of Noble Metal Ions with an α-Amino Phosphonate

The extraction of Au(III), Pt(IV), and Pd(II) ions from aqueous hydrochloric acid solutions with solutions of bis(2-ethylhexyl) N-butyl-N-octylaminomethylphosphonate in chloroform and xylene was studied. The recovery of the noble metal ions is the most efficient at low acidities of the aqueous solution, with a high selectivity of separation from the concomitant Fe(III), Cu(II), Ni(II), and Co(II) ions.     

Extraction of palladium(II) with (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)pentan-3-ol from nitric acid solutions

Extraction of palladium(II) with (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)pentan-3-ol from nitric acid solutions (carbon tetrachloride as diluent, octanol as modifier) was studied. Optimal extraction conditions were found. The reagent was shown to extract efficiently metal ions in a wide range of aqueous phase acidity by coordination mechanism. Aqueous ammonia solution was proposed as stripping agent for palladium(II). Concentrational extraction constants were calculated and thermodynamic parameters of extraction were determined.     

Extraction of group VIII elements with 1-phenyl-3-methyl-4-trifluoroacetyl-pyrazolone-5

The extraction of group VIII elements with 1-phenyl-3-methyl-4-trifluoracetyl-pyrazolone-5 from aqueous solutions in chloroform has been studied as a function of pH. Fe(III), Ni(II), Pd(II) and Rh(III) show partial extraction whereas Co(II) is extracted quantitatively. The effect of citrate, cyanide, fluoride, iodide, thiosulphate and thiourea on the extraction of metal ions has been investigated. Back-extraction studies were carried out to strip metal ions from organic phase into appropriate aqueous solutions. Based on these findings some useful analytical separations have been proposed and a few of their possible applications have been discussed.     

The separation of palladium and platinum by ion flotation

Differences in the ion flotation properties of palladium(II) and platinum(IV) chloro complexes in aqueous solutions are used to achieve separations of these metals. The anionic chloro complex PtCl^2-₆ is floated selectively with cationic surfactants of the type, RNR'₃Br, from solutions of PdCl^2-₄ and various concentrations of hydrochloric acid. The palladium(II) does not float from solutions of ? 3.0 M HCl and the platinum(IV) floated from these solutions can be recovered free of palladium. However, the separation is incomplete as much of the platinum(IV) is also unfloated from these solutions. Quantitative separations are obtained by conversion of the palladium(II) to the cationic ammine, Pd(NH₃)₄²⁺ with aqueous ammonia prior to flotation. The anionic chloro complex of platinum(IV) is unaffected by the presence of ammonia and is floated quantitatively with the surfactant n-hexadecyltri-n-propylammonium bromide from 0.01 M ammonia solutions.     

Palladium(II) Extraction from Hydrochloric Acid Solutions with 4-[(Hexylsulfanyl)methyl]-3,5-Dimethyl-1H-Pyrazole

Palladium(II) extraction from hydrochloric acid solutions with a novel weakly basic complexing reagent, 4-[(hexylsulfanyl)methyl]-3,5-dimethyl-1H-pyrazole, dissolved in chloroform was studied. Palladium(II) was found to be highly efficiently extracted from 0.1–3 mol/L HCl solutions. A coordination mechanism of palladium(II) extraction with a protonated form of the reagent via fast interphase transfer of ion associates was proposed. The composition of the extracted compound, [PdCl₂μ-L]_n (n > 2), was found, and the way of coordination of the reagent to metal ions through N(2) nitrogen atom and thioether sulfur atom was determined. The reagent can be recommended for concentrating palladium(II) and selectively separating it from platinum(IV), copper(II), nickel(II), and iron(III).     

Palladium(II) Extraction by Pyridinecarboxylic Acid Esters

The commercial extractant Acorga CLX-50 and model individual di-2-ethylhexyl pyridine-3,5-dicarboxylate and 2-ethylhexyl pyridine-3-carboxylate in toluene were used for palladium(II) extraction from aqueous HCl solutions. The studies of extraction rate and equilibrium were carried out in systems containing palladium(II) ions in 3.0, 0.1, and 0.1M HCl in the presence of 0.5M sodium chloride and in 0.1M HCl in the presence of 0.1–6.0M lithium chloride and in 0.1M HCl in the presence 0.1–3.5M sodium nitrate. The examined extractants can efficiently extract palladium(II) from aqueous hydrochloric acid and nitrate solutions. The extraction is slow and equilibrium is obtained after 2 hours. The best extraction of palladium(II) is observed from 0.1M HCl solution in the presence of 3.5M sodium nitrate. A spontaneous transfer of palladium(II) to the toluene phase without any phase mixing is also observed.     

Palladium(II) extraction with 1-{[2-(2,4-Dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]-methyl}-1H-1,2,4-triazole from nitric acid solutions

Palladium(II) extraction from nitric acid solutions with 1-{[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]-methyl}-1H-1,2,4-triazole in toluene is studied. The reagent efficiently extracts palladium(II) from 0.2–6 M HNO₃ by a coordination mechanism yielding the complex Pd₂(NO₃)₄ S ₃ in the organic phase. The reagent can be used for selective separation of palladium(II) from nickel(II), copper(II), and iron(III) in the specified aqueous phase acidity range.     

Mutual binary separations of cadmium(II), indium(III) and thallium(III) as chlorides by their extraction in high molecular weight amines

The extraction of cadmium(II), indium(III) and thallium(III) with high molecular weight amines have been studied from aqueous hydrochloric acid solutions. Using the data mutual binary separations of these three elements with high separation coefficients are proposed. Various variables like type of amine, amine concentration and organic diluent were explored to propose the best conditions of separations.     

Chromatography of inorganic ions on cellulose phosphate layer in hydrochlorid acid and in acid ammonium thiocyanate media

Summary Thin-layers of an intermediately acidic cation exchanger, cellulose phosphate (P-cellulose), have systematically been used to study the chromatographic behavior of 58 inorganic ions in both hydrochloric acid and acid ammonium thiocyanate media (0.01–2.0 mol dm⁻³). In both solvent systems, the R _f values of many bivalent cations increase with increasing concentration of the acid and thiocyanate. Polyvalent metal ions including beryllium (II) and the others are strongly retained on the P-cellulose in the acid and thiocyanate systems tested. Palladium(II), mercury(II), ruthenium(III), rhenium(VII), arsenic(III), selenium(IV) and tellurium(IV) are not adsorbed on P-cellulose to any great extent. For silver(I), indium(III), gold(III), and platinum(IV), there are marked differences in the chromatographic behavior between hydrochloric acid and acid ammonium thiocyanate systems. Multicomponent separations conducted on P-cellulose plates with these eluents are presented.     

Extraction of actinides and fission products by octyl(phenyl)-N,N-diisobutylcarbamoylmethyl-phosphine oxide from nitric acid media

Extraction of promethium(III), uranium(VI), plutonium(IV), americium(III), zirconium(IV), ruthenium(III), iron(III) and palladium(II) has been carried out with a mixture of octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) and tributyl phosphate (TBP) in dodecane. The effects of nitric acid, TBP and CMPO concentrations on the extraction of these metal ions have been studied. The nature of the species of the above metal ions extracted into the organic phase has been suggested.     

Extractive separation of Th(IV), U(VI), Ti(IV), La(III) and Fe(III) from Zarigan ore

In this study, the effects of various extraction parameters such as extractant types (Cyanex302, Cyanex272, TBP), acid type (nitric, sulfuric, hydrochloric) and their concentrations were studied on the thorium separation efficiency from uranium(VI), titanium(IV), lanthanum(III), iron(III) using Taguchi^??s method. Results showed that, all these variables had significant effects on the selective thorium separation. The optimum separations of thorium from uranium, titanium and iron were achieved by Cyanex302. The aqueous solutions of 0.01 and 1 M nitric acid were found as the best aqueous conditions for separating of thorium from titanium (or iron) and uranium, respectively. The combination of 0.01 M nitric acid and Cyanex272 were found that to be the optimum conditions for the selective separation of thorium from lanthanum. The results also showed that TBP could selectively extract all studied elements into organic phase leaving thorium behind in the aqueous phase. Detailed experiments showed that 0.5 M HNO₃ is the optimum acid concentration for separating of thorium from other elements with acidic extractants such as Cyanex272 and Cyanex302. The two-stage process containing TBP-Cyanex302 was proposed for separation thorium and uranium from Zarigan ore leachate.     

Inorganic polarography in organic solvents-III Analytical applications of metal-acetylacetonate complexes in toluene

Indium and palladium are determined polarographically with a dropping mercury electrode in a toluene phase, following extraction as the acetylacetonates from aqueous solutions containing 2-10 ppm of the metals (or 0.1-0.5 ppm with a greater ratio of sample volume to solvent volume). Of 31 elements examined, only Co(III), Cr(III), Cu(II), Fe(III), In, Mo(VI), Pd and Ti(IV) gave extractable complexes with reduction waves in the available potential range. Specificity for palladium is obtained by extraction at pH 0.5, and for indium at pH 9 m the presence of cyanide and ascorbic acid as masking agents.     

Reversed-phase partition chromatographic separations with 2-ethylhexyl dihydrogen phosphate and di-2-ethylhexyl hydrogen phosphate

Di-2-ethylhexyl hydrogen phosphate (HDEHP) and 2-ethylhexyl dihydrogen phosphate (H(2)MEHP) are compared as stationary phases in reversed-phase chromatography of selected lanthanides, strontium, yttrium, barium, manganese(II), iron(III), cobalt(II), nickel, gold(III), platinum(IV), palladium(II) and silver. Chromatograms were mainly developed with hydrochloric acid at various concentrations. In general H(2)MEHP was found to be less satisfactory than HDEHP. Development of chromatograms by dilute aqueous electrolytes on paper is slower and separations of chemically similar metals such as lanthanides is not encouraging. However, movement of lanthanides by EDTA at pH 3 in an aqueous sodium perchlorate medium occurs only on H(2)MEHP-treated paper. Good separations of iron(III) and cobalt(II) are possible on paper treated with either ester, and gold(III) and platinum(IV) are separated on HDEHP-impregnated paper. Column methods for the separation of carrier-free gold-199 and iron-59 from macro-amounts of neutron-irradiated platinum and cobalt, respectively, have been developed.     

Methyl isobutyl ketone extraction of iodide complexes from sulphuric acid-potassium iodide media and back-extraction into an aqueous phase

The methyl isobutyl ketone extraction of 15 elements (Cu, Ag, Zn, Cd, In, Tl, Ge, Sn, As, Sb, Bi, Se, Te, Mo and Pd) as iodide complexes from 0.1-5 M sulphuric acid/0.01-0.5M potassium iodide media has been studied. At the optimum potassium iodide concentrations, and a 1:2 v v ratio of organic to aqueous phase, Cu(II), Ag, Cd, In(III), Tl(III), Sb(III), Bi, Te(IV) and palladium(II) are completely extracted in a single step from 1-5M sulphuric acid. All these elements except palladium are also quantitatively extracted from 0.05-0.5M iodide/2M sulphuric acid. Zn, Sn(IV) and As(III) are completely extracted at high acid and iodide concentrations, and at the highest concentrations of acid and iodide investigated, Ge is partly extracted and Mo(VI) is slightly extracted. The extraction of Se(IV) is incomplete because of its reduction to the elemental state by iodide. The back-extraction of the elements has also been investigated and the forms in which they are extracted and potential analytical separations and interferences are discussed.     

Extraction and concentration of palladium(II) from simulated refining process solutions using 1<Emphasis Type="Italic">Н</Emphasis>-1,2,4-triazole derivatives

A procedure was developed for recovery and concentration of residual palladium(II) from a “lean” refining solution by extraction with 1Н-1,2,4-triazole derivatives. Palladium(II) is extracted quantitatively from 1 M hydrochloric acid solutions and under optimum conditions is selectively separated from platinum(IV) and rhodium(III).