Pyrrhotite Fe1–xS is the main sulfide component of platinum-group element (PGE) ores and commonly contains from a few tenths to a few dozen ppm of disseminated Pt. Here we report an X-ray absorption spectroscopy investigation into the state of Pt in synthetic pyrrhotite in combination with theoretical spectra modelling. The pyrrhotite crystals were obtained by means of the salt flux technique, using a eutectic mixture of alkali metal halides as the transport media. Analysis of the chemical composition of synthesised crystals showed that an increase of the temperature and sulfur fugacity yields higher concentrations of Pt in pyrrhotite. The Pt content reached 0.6 wt.% at the maximum temperature and sulfur fugacity (t = 720°C, log $f_{{\rm S}_ 2}$ = –0.1) achieved in a Pt-saturated system. X-ray absorption near-edge structure (XANES) analysis of Pt L3-edge spectra revealed that Pt is present in pyrrhotite in the 4+ and 2+ ‘formal’ oxidation states. Theoretical modelling of XANES and interpretation of extended X-ray absorption fine structure (EXAFS) spectra showed that Pt4+ substitutes for Fe in the crystal lattice of pyrrhotite, whereas Pt2+ forms PtS-like clusters disseminated in the pyrrhotite matrix. Atoms of isomorphous Pt4+ are surrounded by 6 S atoms at a distance of 2.39 ± 0.02 Å. According to theoretical simulations using the FDMNES program, the second coordination sphere of the solid-solution Pt contains one vacancy in the Fe sublattice within the Fe-layer. The Pt2+S-like clusters can be considered as a quench product. High sulfur fugacity stabilises the solid-solution Pt and prevents the formation of the PtS-like clusters during cooling. The maximum content of the solid-solution Pt in pyrrhotite is ca. 50 times lower than in pyrite and can be approximated by a straight line in the log C(Pt) vs. 1/T plot, it increases from 1 ppm at 350°C to 3 wt.% at 900°C.

Kufahrite, PtPb, is a new mineral (IMA2020-045) from the Ledyanoy Creek placer, Koryak Highlands, Russia. The mineral was found in isoferroplatinum (Pt3Fe) grains extracted from a heavy-mineral concentrate, together with tetraferroplatinum (PtFe), tulameenite (Pt2FeCu), native iridium, hollingworthite (RhAsS) and Cr-rich spinel. Kufahrite occurs as part of alteration rims which are formed together with tetraferroplatinum after isoferroplatinum, or as grains up to 150 μm in size. According to powder X-ray diffraction analyses kufahrite is isotypic to its synthetic analogue, it is hexagonal and crystallises in space group P63/mmc adopting the nickeline structure type. Its unit-cell parameters are: a = 4.2492(6) Å; c = 5.486(6) Å; V = 85.78 Å3 and Z = 2. The calculated density is 14.80 g/cm–3. The strongest diffraction lines are [d, Å (I, %) (hkl)]: 3.052 (80) (101), 2.197 (100) (102), 2.125 (28) (110), 1.747 (18) (210), 1.528 (35) (202), 1.240 (18) (212) and 0.958 (22) (312). The Vickers hardness is 295 kg/mm2 (range 262–320, n = 5), corresponding to a Mohs hardness of 4. The empirical formula of kufahrite, calculated from a mean value of 23 electron-microprobe analyses is (Pt0.94Rh0.04)Σ0.98(Pb0.83Sb0.19)Σ1.02. The name (pronounced as [ku fa rait]) honours Fahrid Shakirovitch Kutyev (1943‒1993), a geologist from the Institute of Volcanology of USSR Academy of Sciences, who played a key role in the discovery of the Koryak–Kamchatka Platinum Belt, including the Ledyanoy Creek placer platinum deposit, where the new mineral has been discovered.

This paper is devoted to the study of formation mechanism of metal solid solutions during the thermolysis of single-source precursors in Co–Pt systems with a wide range of superstructural ordering. It is shown that the thermal decomposition of [Pt(NH3)4][Co(C2O4)2(H2O)2]·2H2O salt in helium is critically different from that under hydrogen atmospheres. Thermal degradation under the helium atmosphere is followed by a gradual reduction of platinum and cobalt, and at each thermolysis temperature only one phase is present. At 380 °C an equiatomic Co0.50Pt0.50 solid solution is formed (a = 3.749 (4) Å, Fm−3m space group, V/Z = 13.17 Å3, crystallite size: 5–7 nm). When the precursor is decomposed under a hydrogen atmosphere, the process proceeds mainly through the simultaneous reduction of the platinum and cobalt atoms, and at each temperature section two metal phases are present. The formation of the close to equiatomic Co0.50Pt0.50 solid solution (a = 3.782 (4) Å, Fm−3m space group, V/Z = 13.52 Å3, crystallite size: 7–9 nm) occurs at 450 °C. The calculations of crystallite sizes are confirmed by transmission electron microscopy data.

Studies of the weathering of platinum-group minerals in natural deposits have indicated that the platinum-group elements (PGE) can be mobilized under appropriate conditions and have sufficient solubility to move into solution. Although inorganic chemistry provides feasible mechanisms under the extreme conditions encountered in laterites it appears likely that PGE-organic complexes offer a more convincing explanation of the apparent solubility. Experimental work undertaken to illustrate the organic processes and the reaction timescale examined various reactions including those between Pt and Pd foils and humic and fulvic acid solutions. These reactions appear pertinent to those that may occur between the PGE particles ejected by vehicle exhaust catalysts and the natural environment.

The experimental work produced up to 195 μ/l Pt and 102 μ/l Pd in humic acid solutions exposed to the metal foils for about a year at room temperature. The experimental conditions can be compared to those encountered in roadside drainage supplied with PGE particles and decaying vegetation.

Consideration of the possible health effects of the PGE from the particles ejected by vehicle exhaust catalysts has centred on inhalation of the particles or absorption through the skin. Intake from drinking water or from food produced using PGE-bearing water should now also be investigated. Due to the variety of organic compounds produced by decaying vegetation the identity of the PGE-organic products is not yet known so their toxicity cannot be estimated.

Chemical and structural data are reported for platinum–palladium intermediates from two nuggets found at Córrego Bom Sucesso, Minas Gerais, Brazil. Three grains with simple stoichiometries (i.e. PtxPd1−x with x ∼0.67, ∼0.5 and ∼0.33, which correspond to Pt2Pd, PtPd and PtPd2, respectively) were characterized by single-crystal X-ray diffraction and electron-probe microanalysis. In the absence of single-crystal data it might be tempting to hypothesize that such simple stoichiometries represent distinct mineral species, however structural analyses show that all of the phases are cubic and crystallize in space group Fmm. They are, therefore, natural intermediates in the palladium–platinum solid solution. Reflectance and micro-hardness values are reported for the samples and a comparison with the pure metallic elements made. On the basis of information gained from the chemical and structural characterization it can be concluded that there is a complete solid solution between Pt and Pd in nature. These findings corroborate results from experiments on synthetic compounds.

A tomographic heating holder for transmission electron microscopy that can be used to study supported catalysts at temperatures of up to ~1,500°C is described. The specimen is placed in direct thermal contact with a tungsten filament that is oriented perpendicular to the axis of the holder without using a support film, allowing tomographic image acquisition at high specimen tilt angles with minimum optical shadowing. We use the holder to illustrate the evolution of the active phases of Pt nanoparticles on carbon black and PtPd nanoparticles on γ-alumina with temperature. Particle size distributions and changes in active surface area are quantified from tilt series of images acquired after subjecting the specimens to increasing temperatures. The porosity of the alumina support and the sintering mechanisms of the catalysts are shown to depend on distance from the heating filament.

Les plus grands gisements technogènes des métaux de platine du monde sont situés dans la région industrielle de Norils. Ils se sont formés pendant plusieurs décennies lors du traitement des minerais de sulfure de cuivre-nickel de l’usine Norilsk nickel (Mining and Metallurgical Company Norilsk nickel, MMC NN). Dans cette usine, se sont accumulés au fil du temps plus de 300 millions de tonnes de résidus technogènes secs, qui constituent une source prometteuse de métaux précieux. Il est à noter que tous les principaux producteurs mondiaux de MPG (les métaux du groupe du platine) possèdent des dépôts de résidus technogènes de diverses importances, mais les plus grands gisements technogènes de platine sont liés uniquement aux secteurs d’exploitation minière et métallurgique russe. La nécessité du développement du complexe de production des métaux de platine russe et du renforcement de sa position sur le marché mondial de MPG est conditionnée à la rationalité de l’élaboration d’une technologie de traitement de matières premières technogènes efficace et sûre pour l’environnement.

Four heterometallic carbonyl complexes: (1) Cp(CO)2MnPt(μ-C=CHPh)dppm) (2) [Cp(CO)2MnCu(μ-C=CHPh)(μ-Cl)]2, (3) CpMnFe2(μ3-C=CHPh)(CO)8, and (4) η4-[Cp(CO)2MnC(CO)CHPh]Fe(CO)3 have been studied by X-ray powder diffraction and their unit cell parameters are reported. Orthorhombic cell parameters for complex (1) are a=18.5719(14) Å, b=18.6092(14) Å, c=23.8117(18) Å, Z=8, space group Pbca. Monoclinic cell parameters found for complex (2) are a=11.5816(5) Å, b=7.9784(5) Å, c=16.7819(7) Å, β=105.460(2)°, Z=2, space group P21∕n. Orthorhombic cell parameters for complex (3) are a=13.5260(9) Å, b=15.1487(10) Å, c=10.3330(6) Å, Z=4, space group Pna21. Monoclinic cell parameters for complex (4) are a=10.3545(45) Å, b=8.0002(43) Å, c=21.8355(95) Å, β=102.89(2), Z=4, space group P21∕c. Parameters found for complexes (1–4) are in good agreement with those obtained from single crystal X-ray diffractometry.

Au cours du 19e siècle les gisements des métaux du groupe du platine en Russie ont été les gisements de type placers de platine de l’Oural. Ils furent entièrement exploités au milieu du XXe siècle À l’heure actuelle on doit considérer les dunites et les chromitites de l’Oural comme des matières premières prometteuses de platine [1]. Dans la classification moderne les gisements des métaux du groupe du platine de l’Oural sont classés «non conventionnels» et sont considérés comme des gisements potentiellement prometteurs selon d’éminents chercheurs de la ceinture de Platine de l’Oural, N.K. Vysotsky et A.N. Zavaritsky (G.V. Petrov, T.N. Greyver, V.G. Lazarenko, L’état actuel et les perspectives technologiques de production des métaux de platine à partir de minerai de chromite, Saint-Pétersbourg, 2001 [2]). Aujourd’hui les dunites sont entièrement utilisées comme matières premières pour la production des matériaux réfractaires Les métaux du groupe du platine (MGP) ne sont pas extraits. C’est pour cela qu’il a été entrepris d’examiner dans le cadre de notre étude, les particularités techniques de différents types de dunites (minerais autochtone, alluvial et éluvial), pour contribuer au mieux à l’amélioration des connaissances sur la technologie d’extraction des M.G.P. et du chrome des dunites [3].

Superalloys based on platinum-group metals are being developed for high-temperature applications. These alloys have two-phase structures comprising either ordered precipitates in a matrix analogous to the nickel-based superalloys or a fine dispersion of oxide particles in a matrix analogous to oxide-dispersion-strengthened nickel-based alloys. Currently, alloys based on iridium, rhodium, and platinum have been obtained. This article reviews the rationale of developments and the progress made in this area. Oxidation and compression tests as well as characterization with scanning electron microscopy and transmission electron microscopy were undertaken. These tests showed encouraging results, and further work is being done on new alloying additions and tensile testing.

Very high angle (~100 mrad) annular dark-field (HAADF) images in a dedicated scanning transmission electron microscope (STEM) can be used to quantitatively measure the number of atoms in a cluster on a support material. We have developed a computer program which will automatically find the location of the particles and then integrate the intensity to find the number of atoms per cluster. We have examined ultra-small Pt clusters on a C substrate by this novel mass-spectroscopic technique. We discovered that the Pt clusters maintain their three-dimensional shape, and are probably spherical.