Untersuchungen zur Trennung der Pt-Metalle Durch Mehrstufige Extraktion mit Tributylphosphat aus Salzsaurer Lösung

The separation of compounds of Rh, Pd, Ir and Pt by multistage batch liquid-liquid extraction with tributyl phosphate (TBP) from hydrochloric acid solution has been studied. The existence of complexes of the same platinum group metal, which are capable of being extracted to different degrees, has been concluded from the variation of the distribution coefficient of the respective platinum group metals with the stage number. In addition to monomeric chlorocomplexes, metastable inert species (presumably polymeric chloroaquo or aquo/oxo complexes) were found, which were not formed during the extraction, but had been present already in the initial solutions. Because the solvent TBP does not enter the internal coordination sphere, the separation effect attainable is determined by the extraction behaviour and the content of these complex types in the initial solutions. This fact explains the strong influence of solution preparation on the separation effect.      

Specificity of noble metals dynamic sorption preconcentration on reversed-phase sorbents

The reversible sorption preconcentration of noble metals (NMs) using different schemes “sorbent–reagent–eluent” was investigated. The extraction of Au, Pd, Pt, Ir, Rh and Ru chlorocomplexes from hydrochloric acid solutions on hyper-crosslinked polysterene MN-200 in the form of ion associates with tributylamine (TBA) and 4-(n-octyl)diethylenetriamine (ODETA) was investigated. It was found that Pd, Pt and Au were quantitatively and reversibly extracted using TBA on hyper-crosslinked polysterene; the appropriate eluent for desorption was 1 M solution of HCl in ethanol. Ir, Rh and Ru under these conditions were not sorbed quantitatively. It was found that sorbent hydrophobicity is not the main characteristic that defines the efficiency of sorption of a particular NM ion associate. Different efficiencies of hyper-crosslinked polysterene MN-200 for sorption of square-planar chlorcomplexes of Pt, Pd and Au and octahedral complexes of Ir, Rh and Ru were found. For the first time, the sorbents with their own N-atoms – StrataX and StrataX-AW – were used for the sorption of Ir, Rh and Ru. Using these sorbents, the sorption of Ir was increased up to 95%, and the sorption of Ru and Rh was increased to about 40%. We can explain these results by nonspecific interaction of chlorcomplexes of Ir, Rh and Ru with ethylenediamine groups of the sorbent. Weak bases with large anions may be applied for desorption of Ir, Rh and Ru. Two schemes of dynamic sorption preconcentration of NMs from hydrochloric acid solutions were proposed – hyper-crosslinked polysterene MN-200 for the determination of Au, Pd, Pt, and StrataX-AW for Ir, Rh and Ru.     

Extractive concentration of platinum-group elements and their determination by atomic-absorption spectrophotometry

The extraction of Pt, Pd, Ir, Rh, Ru, Ag, Au, Co, Cu, Ni and Fe with n-octylaniline has been investigated. Noble metals are extracted 10(3)-10(4) times better than Cu, Ni, Co and Fe. A method of determination of Pt, Pd, Ir, Rh and Ru is proposed. They are first separated from Cu, Ni, Co and Fe by means of extraction (and then determined, in either the aqueous or organic phase, by atomic-absorption spectrophotometry. The atomic absorption of platinum metals (with the exception of Pd) is affected by other elements of the platinum group and by non-noble metals. La(NO(3))(3) and Nd(NO(3))(3) lower the limit of detection for Pt, Rh, Ir and Ru and inhibit the effect of Co, Cu, Ni, Fe, Bi, Zn, Na, etc. on their determination. Lanthanum and neodymium chlorides and sulphates produce a similar effect but only on the determination of Pt and Rh. The coefficient of variation of the determination, in both phases, is within 2-6.8%.     

Sorption of palladium(II), rhodium(III), and platinum(IV) on Fe(3)O(4) nanoparticles

The adsorption of palladium(II), rhodium(III), and platinum(IV) from diluted hydrochloric acid solutions onto Fe(3)O(4) nanoparticles has been investigated. The parameters studied include the contact time and the concentrations of metals and other solutes such as H(+) and chloride. The equilibrium time was reached in less than 20 min for all metals. The maximum loading capacity of Fe(3)O(4) nanoparticles for Pd(II), Rh(III), and Pt(IV) was determined to be 0.103, 0.149, and 0.068 mmol g(-1), respectively. A sorption mechanism for Pd(II), Rh(III), and Pt(IV) has been proposed and their conditional adsorption equilibrium constants have been determined to be logK=1.72, 1.69, and 1.84, respectively. Different compositions of eluting solution were tested for the recovery of Pt(IV), Pd(II), and Rh(III) from Fe(3)O(4) nanoparticles. It was found that 0.5 mol L(-1) HNO(3) can elute all of the metal ions simultaneously, while 1 mol L(-1) NaHSO(3) was an effective eluting solution for Rh(III), and 0.5 mol L(-1) NaClO(4) for Pt(IV). In competitive adsorption, the nanoparticles showed stronger affinity for Rh(III) than for Pd(II) and Pt(IV).     

Sorption recovery of platinum(II) and platinum(IV) chloro complexes with a heterochain sulfur-containing sorbent

The recovery of platinum(II) and platinum(IV) chloro complexes from hydrochloric acid and chloride solutions with a new heterochain S,N-containing sorbent, MITKhAT, was studied. The suggested mechanism of formation of platinum(II) mercapto-thio ether complexes in the course of sorption was confirmed by DFT calculations. The results of group and selective recovery of platinum metals with MITKhAT sorbent from simulated and real industrial solutions are reported.     

Retention and elution of precious metals on cyano-modified solid phase microparticle sorbent

We report on a study on the retention and elution of ions of the precious metals Au, Ir, Pd, Pt, Rh and Ru, sometimes in the presence of ions of the nonprecious elements Co, Cu, Fe, Ni, Pb and Te. A commercial cyano-modified microparticle-based solid phase was used as a sorbent and hydrochloric acid in various concentrations for sample solution and elution. Only Au and Pd (in the form of their chloro complexes) were retained, and Au is found to have a much higher affinity for the sorbent compared to Pd. In addition to the affinity of the metal towards the functional groups, the retention behavior of the precious metals seems to be mainly influenced by steric factors of their respective chloro complexes. Elution with 7.5 M HCl does not require the addition of organic eluent as required in other cases. The method can separate Au or both Au and Pd, from hydrochloric acid solutions containing ions of other precious metals or nonprecious elements. The sorbent was applied to recover gold from a mineral digest containing large amounts of metals such as Fe, Pb, Te, Cu, Ni and Zn.

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

     

Some features found in the extraction of platinum group metals and gold with calix[4]arenamines and calix[n]arene thioethers from hydrochloric acid solutions

Extraction of platinum group metals and gold from hydrochloric acid solutions with calix[4]arenamines (CAA) and calix[n]arene thioethers (n = 4, 6; CTE) was studied. The high macrocyclic effects (10²–10³) are due to chelation between metals and the donor centers of macrocycles in the systems CAA-Pd and CTE-Ag, Pt^II, and Pt^IV. New CAA-based extracting systems for collective extraction of Pd, Pt, Au, Ir, and Rh and new CTE-based systems for separation of Au and Pd from Ag and Pt were justified.     

Recovery of palladium(II) and rhodium(III) chloride complexes with a complexing S,N-containing sorbent

Specific features of sorption recovery of palladium(II) and rhodium(III) chloride complexes from hydrochloric acid and chloride solutions with MITKhAT S,N-containing sorbent were revealed. The kinetic and capacity characteristics of the sorbent were determined in relation to the solution composition and kind of the metal. The most probable mechanism of sorption recovery and the composition of the forming Pd(II) and Rh(III) complexes were suggested.     

Pyrimidinethiol as a reagent for extraction separation of platinum metals and gold Determination of Pd(II), Os(VIII) and Ru(III)

The solvent extraction separation of Pt(IV), Pd(II), Os(VIII), Ru(III) and Au(III) from one another and also from Rh(III) and Ir(III) with 1-(2'-nitro-4'-tolyl)-4,4,6-trimethyl-(1H, 4H)-2-pyrimidinethiol has been investigated. Photometric procedures have been developed for the determination of Pd(II), Os(VIII) and Ru(III) with the same reagent. The reagent allows the enrichment of Pd(II) and Au(III) at the trace level from a large volume of aqueous medium even in the presence of base metals. The method can be used for the determination of platinum metals and gold in alloys.     

Untersuchungen zur Extraktion der Pt-Metalle mit Tributylphosphat aus salzsauren Lösungen

Investigations on the Extraction of the Platinum-Group Metals from Hydrochloric-Acid Solutions by the Use of Tributyl Phosphate Comparative investigations on the extraction of Rh, Pd, Ir, and Pt from hydrochloric acid solutions by the use of tributyl phosphate (TBP) have been carried out in various organic phases (type of the ester and diluting agent) and in aqueous phases (concentration of the platinum group metals, acidity, salt additives). Pretreatment of aqueous initial solutions to avoid disturbances by metastable complexes was of special importance. Extraction proceeded rapidly and was reversible. Extractibility of the platinum group-metals and its dependence upon the extraction conditions decreased in the following order: The structure of the extracted compound (schematically represented by [H+(H₂O)_x(TBP)_y]_n[MeCl_m]) is assumed to be uniform and, based on this assumption, the extraction results are discussed.     

Investigation of the usefulness of NTA, EDTA and DTPA in separation of some platinum metals on cellulose exchangers

The possibility of using NTA, EDTA and DTPA as complexing agents for separation of some platinum group ions on cellulose ion-exchangers has been investigated. The greatest differences in the affinities of Pd(II) and Pt(IV) toward the cellulose ion-exchangers are obtained in the presence of DPTA, Cellex D (as ion-exchanger) in hydroxide form. The column separation of Pd(II) from Pt(IV), Rh(III) from Pd(II) and of a Rh(III)Pd(II)Pt(IV) mixture can be achieved with DPTA and chloride solutions. The method can be for determination of the components of RhPdPt alloys.     

Chromatographie von Metallchelaten

Zusammenfassung 1-Hydroxy-2-pyridinthion bildet mit den Platinmetallen stabile, wohl definierte Chelatkomplexe, die sich mit Chloroform aus wäßriger Lösung extraktiv anreichern lassen. Aus dem Extrakt können Rh, Pd, Ir, Pt adsorptions-chromatographisch getrennt und nebeneinander bestimmt werden. Beschrieben werden Trennbedingungen für die HPLC zur qualitativen und quantitativen Analyse der Platinmetalle. Die Standardabweichung des ausgearbeiteten Verfahrens liegt für eine 1 ppm Lösung um 10%. Die Nachweisgrenze der Metalle liegt zwischen 0,5 und 3,5 ng absolut.

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On the chromatography of metal chelatesIV. HPLC of the platinum metals with 1-Hydroxy-2-pyridinthione

Summary 1-Hydroxy-2-pyridinthione forms stable, well defined chelate complexes with the platinum metals which can be enriched by extraction with CHCl₃ from aqueous solutions. In the extract Rh, Pd, Ir, Pt can be separated and determined in one step by adsorption chromatography. The separation conditions for the qualitative and quantitative analyses of the platinum metals by HPLC are reported. The standard deviation of the described procedure is about 10% for a 1 ppm solution. The detection limits of the metals are between 0,5 and 3,5 ng absolute.

     

Sorption of noble-metal ions on silica with chemically bonded nitrogen-containing ligands

A study has been made of the sorption of Ir(IV), Rh(III), Pt(IV), Ru(IV), Os(VIII), Pd(II) and Au(III) from aqueous solutions by silica chemically modified with nitrogen-containing organic ligands, as a function of hydrochloric acid concentration, time of contact, concentration of the element and the ionic strength. Sorption of noble-metal ions at pH > 1 on a sorbent containing monoamine groups seems to be due to a complexation mechanism, and to an anion-exchange mechanism at pH < 1. With aminopropyl-silica 1000-fold concentration of Ir(IV) and Rh(III) from their 10(-8)-10(-7)M solutions was achieved and these metals were subsequently determined on the sorbent surface by X-ray fluorescence. Detection limits were 10-20 ng/ml. There was no interference from 1000-fold quantities of non-ferrous metal ions and Fe(III). With the sorbent containing bonded diethylenetriamine groups, 1000-fold concentration of Au(III) was achieved, and it was then determined on the sorbent surface by an atomic-emission method. Conditions for desorption of Au(III) with pyridine and potassium thiocyanate were developed.     

Correlations between hydrogen electrosorption properties and composition of Pd-noble metal alloys

Hydrogen adsorption on and absorption into Pd alloys with other noble metals was studied in acidic solutions (0.5 M H₂SO₄) using cyclic voltammetry. Correlations were found between the potentials of adsorbed/absorbed hydrogen oxidation peaks and surface/bulk compositions of Pd–Rh alloys. The potential of the α–β-phase transition depends linearly on Pd bulk content in Pd–Au, Pd–Rh, Pd–Pt and Pd–Pt–Rh alloys. The obtained relationships can be utilized for the determination of the composition of homogeneous Pd-noble alloys from hydrogen electrosorption experiments.     

A Combined Deep Eutectic Solvent–Ionic Liquid Process for the Extraction and Separation of Platinum Group Metals (Pt,Pd, Rh)

Recovery of platinum group metals from spent materials is becoming increasingly relevant due to the high value of these metals and their progressive depletion. In recent years, there is an increased interest in developing alternative and more environmentally benign processes for the recovery of platinum group metals, in line with the increased focus on a sustainable future. To this end, ionic liquids are increasingly investigated as promising candidates that can replace state-of-the-art approaches. Specifically, phosphonium-based ionic liquids have been extensively investigated for the extraction and separation of platinum group metals. In this paper, we present the extraction capacity of several phosphonium-based ionic liquids for platinum group metals from model deep eutectic solvent-based acidic solutions. The most promising candidates, P₆₆₆₁₄Cl and P₆₆₆₁₄B2EHP, which exhibited the ability to extract Pt, Pd, and Rh quantitively from a mixed model solution, were additionally evaluated for their capacity to recover these metals from a spent car catalyst previously leached into a choline-based deep eutectic solvent. Specifically, P₆₆₆₁₄Cl afforded extraction of the three target precious metals from the leachate, while their partial separation from the interfering Al was also achieved since a significant amount (approx. 80%) remained in the leachate.     

Determination of precious metals in ores and rocks by thermal neutron activation/γ-spectrometry after preconcentration by nickel sulphide fire assay and coprecipitation with tellurium

The six platinum group elements (Ru, Rh, Pd, Os, Ir and Pt) can be determined in geological samples down to the μg kg^?1 level, by using nickel sulphide fire assay and neutron activation of the residue ramaining after dissolution of the nickel sulphide button in concentrated hydrochloric acid. Losses for the platinum group elements during this dissolution step are usually insignificant, except when the elements are present at ultra-trace levels. The can be recovered from the filtrate by coprecipitation with tellerium. The latter approach also permits determination of silver, which is significantly lost in the hydrochloric acid treatment (recovery <98% instead of typically ≈ 10%). The coprecipitation with tellurium considerably improves the results for gold (recovery ≈ 95% instead of typically 75%).     

Countercurrent extraction separation of some platinum group metals: part III

The bromo complexes of platinum(IV), palladium(II), rhodium(III), and iridium(IV) were prepared and studies were made on their distribution between hydrobromic acid solutions and various common solvents. The solvents employed were n-tributyl phosphate (TBP), methyl isobutyl ketone, amyl acetate, and various TBP-benzene mixtures. Distribution coefficients as a function of HBr concentration are given for each metal for each solvent system. A careful study of the measured distribution coefficients clearly showed that a number of binary and ternary mixtures of the metals can be resolved with a Craig countercurrent distribution apparatus. Rh-Pt and Rh-Pd mixtures in 4.38M HBr solutions were quantitatively separated on a Io-stage Craig apparatus using a 90% TBP-10% benzene solvent. Rh-Ir mixtures in 4.38 M HBr were resolved by 3 consecutive batch extractions with 90% TBP-10% benzene. Mixtures of Pd, Rh, and Ir in 4.38 M HBr were resolved in 90 stages using methyl isobutyl ketone as the solvent. Pd, Rh and Ir were recovered in 97.0, 87.6 and 94.5% yields, respectively. Mixtures of Pd, Rh and Pt in 4.38 M HBr were resolved in 90 stages using amyl acetate and methyl isobutyl ketone as solvents. Pd, Rh and Pt were recovered in 90.0, 96.0 and 94.0% yields, respectively. Two computer programs for the IBM 1620 Computer are given ; these facilitate the comparison of theoretical and actual solute distributions.     

A solvent-extraction scheme for the determination of platinum,palladium, rhodium,iridium and gold in platiniferous materials

The integrated scheme described for the determination of five noble metals, combines solvent extraction procedures with atomic absorption spectrometric finishes. It comprises an initial extraction of gold, a simultaneous extraction of platinum and palladium as iodides, and a subsequent simultaneous extraction and preconcentration of rhodium and indium as their 2-mercaptobenzothiazol? complexes. The same solvent, methyl isobutyl ketone, and the same acidity, 6 M, are used throughout the extractions. As large amounts of platinum and palladium can be extracted quantitatively as readily as small amounts, the proposed scheme is applicable to a wide range of platiniferous materials, particularly to those with extremely high Pt + Pd to Rh + Ir ratios.     

Investigation of ICP-MS spectral interferences in the determination of Rh, Pd and Pt in road dust: Assessment of correction algorithms via uncertainty budget analysis and interference alleviation by preliminary acid leaching

A method for classification of the potential spectral interferences in inductively coupled plasma mass spectrometry (ICP-MS) was proposed based on statistical assessment of the interfering signals. The concept was applied to investigate the variety of spectral interferences over the isotopes of Rh, Pd and Pt concerning their analysis in road dust samples. For the significant interferences the applicability of mathematical corrections using two alternative algorithms were studied by uncertainty budget analysis and the approach resulting in lower combined uncertainty of the corrected signals was selected. Further the uncertainty evaluation was used for assessment of the most appropriate Pd isotope to be measured. The adequateness of the mathematical corrections for Rh and Pd was highly relevant to the number of elements causing spectral interferences and the relative analyte/interferent concentrations. This was overcome by preliminary road dust leaching with 0.35 mol l⁻¹ hydrochloric acid. Interferents present as easily soluble salts were substantially removed form the samples while the platinum group metals were not leached which allowed a relative analyte preconcentration to be obtained. For the leached samples the isotopes of Rh and Pd were still spectrally interfered from Sr, Y and Pb but at considerably lesser degree thus after mathematical correction the ICP-MS analysis of Rh, Pd and Pt was reliable and robust using the isotopes 103, 105 and 195, respectively. The method was validated via an alternative analysis based on selective separation of the platinum group metals by microwave-assisted cloud point extraction.