Ion Exchange Separation of Platinum and Palladium by Nucleophilic Displacement With Thiocyanate or Thiourea1,2

The separation of platinum and palladium, by adsorption onto weak base anion exchange resins, Amberlite XE 299, or ionex (derived from Amberlite XE-305) from 1M hydrochloric acid, followed by ligand substitution with sulfur nucleophiles is described.

In the thiourea system, cationic thiourea complexes are produced, which cannot be readsorbed into the resin. In the thiocyanate system the formation of Pd(SCN)₄ ^2- is favored in both solution and polymer phases. The Pd(SCN)₄ ^2-. readsorption into the anion exchange resin is the basis for the separation of platinum from palladium.     

Ion-Exchange Preconcentration and Separation of Trace mounts of Platinum and Palladium

ABSTRACT

The preconcentration and separation of platinum and palladium from weakly acidic solution (pH=4) were done on microcolumn packed with Cellex-T resin. Selective platinum elution from the column was performed with 0.01 mol/l glycine solution at pH=12, while for palladium elution 1.2 mol/l thiourea (pH=0.5) or 4.0 mol/l potassium thiocyanate (pH=1) may be used. As the detection technique was used either FAAS or GFAAS, depending on the concentration of studied metals in the eluate.     

The separation of platinum and palladium by selective extraction of H(2)Pt(SCN)(6) and H(2)Pd(SCN)(4) using a polyTHF-impregnated filter

Platinum and palladium are known to form complexes with the thiocyanate ion in solution. The isolation and separation of both platinum and palladium as thiocyanate complexes is demonstrated by passing them through an organic-impregnated filter (OIF) prepared with polyTHF. Simultaneous extraction is performed by converting both metals into the extractable form. Sequential extraction is achieved by exploiting the difference in the rates of formation for the extractable complexes of the two metals. The extraction of both metals is rapid with quantitative recoveries of platinum with flow rates as high as 600 ml min⁻¹ in small samples, while recoveries from larger volume samples were considerably lower. Once extracted, the metals can be removed from the OIF by conversion to a non-extractable form with a high pH eluting solution. The rapid separation, isolation and preconcentration of both platinum and palladium from aqueous samples is demonstrated.     

Application of fluoroxidants for the decomposition and analysis of platinum metals and gold in black shale ores

In order to develop a reliable method for the platinum group metals (PGMs) determination in ores of organic origin like carbonaceous black shale a decomposition method with fluoroxidants like BrF₃ and KBrF₄ was established which avoids the commom losses of PGM organometallic compounds by volatilazation or chemisorption. The recovery from different trapping solutions is discussed. Platinum metals are evidently found in the carbonaceous black shale ores from the “Natalka” deposit situated in the Magadan area. PGMs are very inhomogenously distributed in the ores and ore concentrates and their total contents in ore are 5–18 g/t. The carbonaceous concentrate of black shale ore contains up to 23 g/t of the sum of platinum metals. ≥ 8% of the sum of platinum and palladium contained in this carbonaceous concentrate are soluble in organic solvents. Received: 16 July 1998 / Revised: 16 April 1999 / Accepted: 5 May 1999     

Application of fluoroxidants for the decomposition and analysis of platinum metals and gold in black shale ores

In order to develop a reliable method for the platinum group metals (PGMs) determination in ores of organic origin like carbonaceous black shale a decomposition method with fluoroxidants like BrF₃ and KBrF₄ was established which avoids the commom losses of PGM organometallic compounds by volatilazation or chemisorption. The recovery from different trapping solutions is discussed. Platinum metals are evidently found in the carbonaceous black shale ores from the “Natalka” deposit situated in the Magadan area. PGMs are very inhomogenously distributed in the ores and ore concentrates and their total contents in ore are 5–18 g/t. The carbonaceous concentrate of black shale ore contains up to 23 g/t of the sum of platinum metals. ≥ 8% of the sum of platinum and palladium contained in this carbonaceous concentrate are soluble in organic solvents. Received: 16 July 1998 / Revised: 16 April 1999 / Accepted: 5 May 1999     

Liquid-liquid extraction of platinum(II) with cyclic tetrathioethers

The liquid-liquid extraction of platinum(II) with 12-, 14- and 16-membered cyclic tetrathioethers from chloride solution was studied. Bromocresol Green ion as a counter anion and 1,2-dichloroethane as an extraction solvent were used. The effect of thiourea on the extraction rate of platinum(II) was examined. Platinum(II) was hardly extracted with macrocyclic tetrathioethers in the absence of thiourea because of the slow extraction rate. The extraction rate of platinum(II) was considerably enhanced by the addition of thiourea. The extraction rate of platinum(II) with 16-membered cyclic tetrathioether was faster than that with 12- and 14-membered ones. Platinum(II) was quantitatively extracted with 16-membered cyclic tetrathioether into 1,2-dichloroethane within 5 h in the presence of thiourea.     

Verfahren zur selektiven Abtrennung von Palladium

Summary The platinum group metals (PGM) as well as silver, gold and mercury can be preconcentrated and separated from matrix elements by sorption on specific sorbents. After elution with thiourea in dilute hydrochloric acid, the thiourea matrix is destroyed by NaNO₂. We found that the Pd-thiourea-complex forms an insoluble compound under specific conditions. Thereby the separation of Pd from all other platinum group metals, except Os which was not measured, and from Ag, Au and Hg can easily be done with thiourea and NaNO₂ in a solution buffered with acetate. The metals are finally determined by GFAAS (Perkin Elmer 400, HGA-74). If the concentration of Pd in the buffered solution is not lower than 25 g/ml, the rate of recovery of Pd is over 90%, except in the presence of Ru. Otherwise the precipitate of the Pd-complex is delayed and not complete. The same effect of retardation occurs if Au is involved. Therefore, high concentrations of Au and Ru in the solution should be absent.

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Für die Durchführung der RFA-Meßung bedanken wir uns bei Herrn Dr. L. A. Psotta und Frau Linnemann, AEG Forschungs-labor, Frankfurt am Main.     

Spectral Studies of Palladium(II)-Allyl Thiourea System

Abstract

Palladium(II) forms 1:1 and 1:4 complexes with allyl thiourea. The molar composition of the complexes was determined by molar-ratio and continuous variation methods and confirmed by means of elemental analysis of the compounds isolated from solution.

Conformity to Beer's law was observed for up to 12 μg ml^?1 of 4 palladium in strongly acidic medium (molar absorptivity 2.28×10⁴ 1 mol^?1 cm^?1 at 292 nm);the Sandell's sensitivity of the reaction for palladium is 0.0047 μg cm^?2 per 0.001 absorbance unit.

The tolerance of the system to platinum metals and other common cations is satisfactory.

A statistical evaluation of the analytical procedure of palladium determination has been undertaken.

The infrared spectra of allyl thiourea and of its 1:1 and 1:4 palladium complexes have been measured in the 2.5–50μ region. The absorption bands have been assigned. The spectra reveal that allyl thiourea forms sulphur-to-metal bonds only, rather than nitrogen-to-metal bonds in the complexes studied.     

Simple Selective Spectrophotometric Method for the Determination of Ruthenium in Carbon Supported Pt-Ru-Ge Catalyst

ABSTRACT

A simple spectrophotometric method for the determination of ruthenium in the presence of platinum in Pt-Ru-Ge catalyst applied in fuel cells has been developed. Platinum catalyst (20% Pt) with carbon support containing 0.5% Ru and 5% Ge was digested in the mixture of HCl+HNO₃ (6+1). Carbon was separated from the examined sample by filtration after dissolution of the metals. Ruthenium was converted into a complex with thiourea (λ_max=640 nm, ε = 2.9·10³ 1 mol^?1 cm^?1) in the medium of 5 M in HCl and 1% in thiourea after 15 min heating at 70 °C. Platinum does not interfere with the determination of ruthenium. Germanium is converted into volatile GeCl₄ and escapes from the examined sample during the digestion step. The content of ruthenium determined in the examined samples of catalyst amounted to 0.49% (RSD = 0.14%).     

Simultaneous Determination of Microgram Amounts of Platinum and Palladium in Presence of Base Metals by Isolation on Anion Exchange Resin-Loaded Paper and X-Ray Spectrometry

Abstract

A procedure for simultaneous determination of microgram amounts of platinum and palladium in solutions of base metals is described. The two metals are isolated on an anion exchange resin-loaded paper disk and determined by X-ray spectrometry. The method is applied to the determination of platinum and palladium in nickel matte.     

Simultaneous determination of platinum(II) and palladium(II) by reversed phase high-performance liquid chromatography with spectrophotometric detection after collection on and elution from resin coated with dimethylglyoxal bis(4-phenyl-3-thisomicarbazone)

Amberlite XAD-7 resin coated with dimethylglyoxal bis(4-phenyl-3-thiosemicarbazone) (DMBS) was prepared and applied to the preconcentration of platinum(II) and palladium(II) from aqueous solution. Platinum(II) and palladium(II) were collected quantitatively on resin coated with the reagent (DMBS-XAD-7) from acidic solution in the presence of iodide ion by a bach method. The metal ions were then easily eluted from DMBS-XAD-7 as their DMBS chelates with a small volume of N,N-dimethylformamide. This collection and elution method was applied to the simultaneous determination of platinum(II) and palladium(II) by reversed-phase high-performance liquid chromatography with spectrophotometric detection using an ODS column and acetone-water as the mobile phase. The proposed method was applied to the determination of the metals in commercially available samples.     

Extraction-spectrophotometric determination of palladium with triphenylphosphine (TPP)

Palladium is extracted with triphenylphosphine (TPP) solution in benzene from hydrochloric acid medium as the PdCl₂ · 2TPP complex showing maximum absorption at 346 nm and a molar absorptivity of ? = 2.26 × 10⁴.The conditions of palladium extraction have been examined and the composition of the extracted species has been found to be PdCl₂ · 2TPP.A 20-fold excess of other platinum and transition metals has no effect on the palladium extraction. Palladium can be determined at platinum concentrations up to 5 mg/ml provided that the result is corrected for the blank. The elaborated method has been applied to the analysis of platinum samples containing not less than 10^?3% of palladium.     

The determination of platinum and palladium in copperbased standard reference materials by neutron activation analysis

The determination of palladium and platinum by n.a.a. in 100-1 μg g^?1 Pd-Cu and Pt-Cu alloys is described. To avoid systematic errors, standards with approximately the same shape and composition as the samples were prepared by quantitative deposition of the noble metals from dilute hydrochloric acid medium on copper powder; after ignition in hydrogen, the powder was pressed to standard pellets. Platinum was determined by i.n.a.a. via ¹⁹⁹Au. For palladium an instrumental analysis via ¹¹¹Ag was possible only for the 100 μg g^?1 samples. For the lower concentrations copper was removed by cation exchange and palladium was determined via the ¹⁰⁹Pd-^109mAg isotopes. The precision for each analysis was 2–3 % relative. The accuracy was checked by comparison with results from other laboratories.     

Liquid chromatography of platinum metals and prospects of development

Summary A survey of the authors' work on liquid chromatography of platinum metals in the form of chelates with 1-(2-pyridylazo)-2-naphthol (PAN) is given. Extraction chromatography with PAN in isopentanol as a stationary phase was used to achieve a group concentration of these metals (Pd, Pt and Rh, concentration coefficient 100) from large volumes of aqueous solutions and a selective extraction of palladium from solutions containing other platinum, nonferrous and heavy metals on a 85–98° C thermostatted chromatographic column. The prospects for the use of liquid chromatography in the analysis of platinum metals are discussed.

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Flüssig-Chromatographie von Platinmetallen und zukünftige Entwicklungen

     

Dünnschichtchromatographie von Platinmetallen auf Zellulose

Zusammenfassung Die Dünnschichtchromatographie der Platinmetalle auf Zellulose in Mischungen von Salzsäure oder Bromwasserstoffsäure mit Alkoholen bzw. Ketonen wurde untersucht. Als Alkohole wurden Methanol, Äthanol, Propanol-(1), Butanol-(1) und Pentanol-(1), als Ketone Aceton, Dioxan, Äthylmethylketon und Isobutylmethylketon verwendet. Zum Teil ergaben sich beträchtliche Unterschiede zwischen denR _f-Werten der Chloro- und der Bromokomplexe dieser Metalle. Osmium wird mittels zweidimensionaler Chromatographie von den übrigen Platinmetallen getrennt. Durch Laufmittelwechsel können Pt, Pd, Ru und Rh voneinander getrennt werden.

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Thin layer chromatography of platinum metals on cellulose

Summary A study was made of the thin layer chromatography of the platinum metals on cellulose in mixtures of hydrochloric or hydrobromic acids with alcohols or ketones. The alcohols included methanol, ethanol, propanol-(1), butanol-(1) and pentanol-(1); the ketones used were acetone, dioxane, ethylmethylketone and isobutylmethylketone. In part considerable differences were observed between theR _f-values of the chloro- and the bromocomplexes of these metals. Osmium was separated from the other platinum metals by means of twodimensional chromatography. Platinum, ruthenium, palladium and rhodium can be separated from each other by change of the mobile phases.

     

Concentration and Separation of Ni2+, Cu2+ and Co2+ by Back Extraction Chromatography Using Lix 64N and Cationic Resins

Abstract

This paper describes the method for the concentration of Cu²⁺ by liquid-liquid extraction using Lix 64N solutions in kerosene, followed by back extraction chromatography.

It consists of a pass of the organic phase through columns filled with cationic resins (H⁺) which contains only the water surrounding the grains.

The effect of the pH of the aqueous film surrounding the resin grains on the capacity of Vionit CS-3 (-SO₃H) and Vionit CM-14 (-SH) has been established.

The loading curves of these resins have been drawn, as the optimum pH of the aqueous film and the resin capacities shown to increase in the order -SH < -SO₃H.

The effect of the flow-rate on the loading and the optimum elution conditions have been also determined.

A mechanism for the ion-exchange process is proposed.     

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.     

Extraction of Palladium(II) and Platinum(IV) from Hydrogen Chloride Solutions with 3,7-Dimethyl-5-thianonane-2,8-dione and Complexation of This Reagent with the Platinum Metals

Extraction of palladium(II) and platinum(IV) from acidic chloride solutions with solutions of 3,7-dimethyl-5-thianonane-2,8-dione in toluene and chloroform and complexation of this reagent with platinum metals in aqueous acetone were studied by ^1Hand ^13C NMR and IR spectroscopy. The possibility of extractive separation of palladium(II) from platinum(IV) and their separation from Cu(II), Ni(II), Co(II), Mn(II) and Fe(III) with solutions of 3,7-dimethyl-5-thianonane-2,8-dione in organic solvents was studied. The apparent concentration constants of extraction of palladium(II) and platinum(VI) with 3,7-dimethyl-5-thianonane-2,8-dione and the corresponding thermodynamic parameters were determined.     

Surfactant gel adsorption of platinum(II), (IV) and palladium(II) as chloro-complexes and kinetic separation of palladium from platinum using EDTA.

A micellar solution of cetylpyridinium chloride (CPC) can separate into two phases due to a temperature change or to the addition of salts. Platinum(II), (IV) and palladium(II) reacted with chloride ions to form stable anionic complexes of PtCl4(2-), PtCl6(2-) and PdCl4(2-), respectively, and were adsorbed onto the CPC gel phase. The CPC phase plays the role of an ion-exchange adsorbent for the anionic complexes. By such a procedure, the precious metals of platinum and palladium could be separated from base metals such as copper, zinc and iron. The kinetic separation was performed by a ligand exchange reaction of the palladium(II) chloro-complex with EDTA at 60 degrees C. The anionic palladium(II)-EDTA complex could not bind the opposite charged CP+ and was desorbed from the CPC phase. In the aqueous phase, the recovery of palladium(II) by the double-desorption was 101.1 +/- 1.2%. The platinum(II) and (IV) chloro-complexes were stable for at least 30 min and remained in the CPC phase.     

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.