Rhodium and palladium joint extraction by dihexyl sulfide and alkylanilinium nitrate mixtures from nitrate solutions

We studied nonequilibrium distribution of inert rhodium(III) in extraction by dihexyl sulfide (DHS)and alkylanilinium nitrate mixtures from joint nitrate solutions of triaquatrinitrorhodium (0.1–4 g/L Rh) and palladium (0–2 g/L Pd). We discovered the effect of increasing rhodium recovery in the presence of palladium. This effect has a kinetic nature and arises from the fact that bis(alkyl sulfide) palladium(II) species catalyze the reaction between dihexyl sulfide and a rhodium intermediate based on alkylanilinium nitrate micelles. Depending on initial rhodium and palladium concentrations, the extraction system provides effective distribution factors for rhodium in the range D _Rh* = 8−300 and rhodium recoveries of 43–97% with ∼100% palladium recovery; single 5-min phase contact at 35°C ensures the 10-fold concentration of both metals in the extract. Our results are useful for developing processes for recovering fission rhodium from spent nuclear fuel. Original Russian Text ? V.V. Tatarchuk, I.A. Druzhinina, T.M. Korda, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 8, pp. 1401–1407.     

Study on the Interactions of Ruthenium(III), Rhodium(III) and Palladium(II) Ions with DNA

Fluorescence, absorption and circular dichroism spectra have been used in the interactions of ruthenium(III), rhodium(III) and palladium(II) ions with DNA with berberine as a probe (berberine, Scheme 1). The results are as follows: ruthenium(III) and rhodium(III) ions show different effects from that of the palladium(II) ion on the fluorescence spectra characteristics of berberine-DNA system. Quenching fluorescence is seen with palladium(II) ion addition, whereas increasing fluorescence is observed for ruthenium(III) and rhodium(III) ions. The addition of ruthenium(III), rhodium(III) and palladium(II) ions causes the increasing absorption of the DNA solution. The addition of ruthenium(III), rhodium(III) and palladium(II) ions to the DNA solution also causes the circular dichroism spectra to change. The above results suggest that different metal ions exhibit different affinity when binding to DNA, which could correlate well with the ions’ charge, structure and the ability to coordinate. There is a comparison between Pt(IV) and Pd(II) ions on the fluorescence of the berberine-DNA system.     

Simultaneous Determination of Palladium, Platinum and Rhodium by On-Line Column Enrichment and HPLC with 4-Hydroxy-1-Naphthalthiorhodanine as Pre-Column Derivatization Reagents

In this paper, 4-hydroxy-1-naphthalthiorhodanine (HNTR) was synthesized, and a new method for the simultaneous determination of palladium, platinum and rhodium ions as metal-HNTR chelates was developed using rapid column high-performance liquid chromatography combined with on-line enrichment. The palladium, platinum and rhodium ions were pre-column derivatized with HNTR to form colored chelates. The Pb-HNTR, Pt-HNTR and Rh-HNTR chelates could be absorbed onto the front of the enrichment column when they were injected into the injector and sent to the enrichment column [ZORBAX Stable Bound, 4.6 × 10 mm, 1.8 μm] with a buffer solution of 0.05 mol L⁻¹ sodium acetate-acetic acid (pH 4.0) as mobile phase. After enrichment, and by switching the six-ports switching valve, the retained chelates were back-flushed by mobile phase and traveling towards the analytical column. Separation of these chelates on the analytical column [ZORBAX Stable Bound, 4.6 × 50 mm, 1.8 μm] was satisfactory with 68% acetonitrile (containing 0.05 mol L⁻¹ of pH 4.0 sodium acetate-acetic acid buffer salt and 0.1% of tritonX-100) as mobile phase. Palladium, platinum and rhodium were separated completely within 2 min. The detection limits (S/N = 3) of palladium, platinum and rhodium are 1.2 ng L⁻¹, 1.5 ng L⁻¹ and 1.8 ng L⁻¹, respectively. This method was applied to the determination of palladium, platinum and rhodium in water, urine and soil samples with good results.     

The interaction of hexamethylenetetramine with platinum group metals

Summary Complexes of the geabneral formula MX_n · hmta [where hmta=hexamethylenetetramine; MX_n=rhodium(III), ruthenium(III) iridium(III), palladium(II), or platinum(II) halides; n=2 or 3] and other related complexes, have been prepared in aqueous or methanolic solution.The compounds were characterized by elemental analyses, i.r. spectra and conductivity measurements.     

RuO2/Co3O4 thin films prepared by spray pyrolysis technique for supercapacitors

RuO₂/Co₃O₄ thin films with different RuO₂ content were successfully prepared on fluorine-doped tin oxide coated glass plate substrates by spray pyrolysis method, and their capacitive behavior was investigated. Electrochemical property was performed by cyclic voltammetry, constant current charge/discharge, and electrochemical impedance spectra. The capacitive performance of RuO₂/Co₃O₄ thin films with different RuO₂ content corresponded to a contribution from a main pseudocapacitance and an additional electric double-layer capacitance. The specific capacitance of pure Co₃O₄, 15.5%, 35.6%, and 62.3% RuO₂ composites at the current density of 0.2 A g⁻¹ were 394 ± 8, 453 ± 9, 520 ± 10, and 690 ± 14 F g⁻¹, respectively; 62.3% RuO₂ composite presented the highest specific capacitance value at various current densities, whereas 35.6% RuO₂ composite exhibited not only the largest specific capacitance contribution from RuO₂ (C _sp ^RuO2) at the current density of 0.5, 1.0, 1.5, and 2.0 A g⁻¹ but also the highest specific capacitance retention ratio (46.3 ± 2.8%) at the current density ranging from 0.2 to 2.0 A g⁻¹. Electrochemical impedance spectra showed that the contact resistance dropped gradually with the decrease of RuO₂ content, and the charge-transfer resistance (R _ct) increased gradually with the decrease of RuO₂ content.     

Determination of noble metals by resonance neutron activation technique

Rhodium, palladium, platinum and iridium have been determined in silver matrix by nondestructive activation analysis upon activation with cadmium- and silver-filtered resonance neutrons. Experiments with different types of filter combinations are reported. The sensitivity of the method is 5·10⁻³% for rhodium, 5·10⁻³% for palladium, 3·10⁻²% for platinum and 5·10⁻³% for iridium.     

NMR studies of some second and third row transition metal complexes of monothio-β-diketones

A ¹³C and ¹⁹F NMR study of twenty-four ruthenium, rhodium, palladium and platinum complexes containing a difluoromethyl or a trifluoromethyl substitutent(R′) on the monothio-β-diketone, RCSCH₂COR′, is reported. The R-substituents are 2′-thienyl, 2′-naphthyl, phenyl, p-fluorophenyl or p-methylphenyl. The ¹³C NMR data show the chemical shift of the diketonate ring carbons to be geometry dependent. Similarly, the ¹⁹F NMR spectra show chemical shift data which are also metal dependent. The thiocarbonyl and methine carbon's shieldings are also dependent on the nature of the R-group. The rhodium and platinum complexes show carbon-metal and carbon-fluorine spin coupling. The paramagnetic ruthenium(III) complexes give ¹⁹F NMR spectral resonances which are broad and shifted upfield from the corresponding diamagnetic rhodium, palladium and platinum complexes. ¹³C and ¹⁹F NMR data supports a facial octahedral geometry for the rhodium(III) complexes.     

Ru oxide/carbon fabric composites for supercapacitors

Ru oxide/carbon fabric composites (Ru oxide/CF) were prepared by impregnating carbon fabric (CF) with a hydrous RuO₂ suspension. Their properties were characterized by scanning electron microscopy, impedance spectroscopy, cyclic voltammetry, and constant current discharging. Specific capacitance increased with increasing loading of Ru oxide. The apparent average specific capacitance of the Ru oxide component reached 1,085 F g⁻¹ for a 9.15% loading, with a peak of 1,984 F g⁻¹ at approximately 0.3 V vs Ag/AgCl. The presence of Ru oxide decreases the ionic resistance of the CF and appears to increase its specific capacitance by generating additional electroactive surface functionality.     

Reduction of palladium(II) monoglycinate complexes at rotating disc palladium electrode in acid media

Reduction of palladium(II) glycinate complexes in strongly acid 0.5 M NaClO₄ solutions (pH 0.6 and 1.0) with variable palladium(II) complex and free glycine concentration was studied by the taking of cyclic voltammograms at palladium rotating disc electrode. It is shown that it was a chelate monoglycinate palladium(II) complex that was present in all studied solutions and underwent the reduction. The diffusion coefficient of the chelate monoglycinate palladium(II) complex D = (6.5 ± 0.5) × 10⁻⁶ cm²/s was determined from the limiting diffusion current of the complex reduction. The monoglycinate palladium(II) complex reduction occurred in the double-layer segment of the palladium charging curve; it was not complicated by hydrogen adsorption at electrodes. The palladium(II) complex reduction half-wave potential was determined (E _1/2 = ∼0.300 to 0.330 V (SCE)). It is shown that the decreasing of the number of ligands coordinated by palladium via nitrogen atom facilitates the complex reduction process. In particular, the reduction potentials of palladium(II) complexes with different ligand number at palladium electrode shifted markedly toward negative potentials in the series: Pdgly⁺ < Pd(gly)2 < Pd(gly)₄²⁻.     

Neutron activation analysis of noble metals in vegetation

Detection limits are presented for the platinum metals in vegetation for different neutron activation analysis conditions, namely, short irradiation, cyclic and long irradiations both thermally and epithermally. These detection limits for instrumental neutron activation analysis are compared with those using preconcentration technique—dry ashing and fire assay and post irradiation separation of the platinum metals using Srafion NMRR in exchange resin. The results are evaluated for plant material and it is concluded that dry ashing followed by cyclic, epithermal irradiation for rhodium and palladium and long, thermal irradiations for osmium, platinum, iridium and ruthenium enable these elements to be detected in plants at background levels.     

Cation-exchange behaviour of the platinum group and some other rare elements in hydrobromic acid-thiourea-acetone media

Ion-exchange distribution coefficients and elution curves are presented for copper(I), silver, gold(I), palladium, platinum(II), rhodium(III), iridium(III), ruthenium(III), osmium(III), mercury(II), thallium(I), tellurium(II), lead and bismuth in mixtures of thiourea, hydrobromic acid, acetone and water, with the cation-exchange resin AGW50W-X4. The system affords excellent separations of rhodium, mercury, silver (or copper), tellurium, gold, and palladium (or platinum) from each other.     

Defect-enriched heterointerfaces N–MoO2–Mo2C supported Pd nanocomposite as a novel multifunctional electrocatalyst for oxygen reduction reaction and overall water splitting

Developing highly efficient, cost-saving, and durable multifunctional electrocatalysts for oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) continues to be a significant challenge in the energy field. In this work, we decide to prepare an unusual multifunctional electrocatalyst, such as icosahedral palladium nanocrystals (PdNCs) encapsulating on N–MoO₂–Mo₂C half-hollow nanotube (HHNT) heterointerface, using an in-situ chemical reaction and following sonic probe irradiation method. All the experiments demonstrate that special defect-enriched heterointerfaces N–MoO₂–Mo₂C supported Pd nanocomposite can greatly improve the ORR activity (E_onset = 1.01 V and E_1/2 = 0.90 V) with good stability, outstanding HER (η₁₀ = 65 mV) and OER (η₁₀ = 180 mV) performances than those of commercial precious electrocatalysts (Platinum on carbon [Pt/C] and ruthenium oxide [RuO₂]). The overall water splitting electrolyzer fabricates by Pd/N–MoO₂–Mo₂C as both anode and cathode electrodes to achieve a current density of 10 Ma/cm² at a cell voltage of 1.56 V, which surpasses the most recent reported electrocatalysts.     

Separation and concentration of some platinum metal ions with a new chelating resin containing thiosemicarbazide as functional group

A new chelating ion-exchange resin containing thiosemicarbazide as functional group and based on macroreticular polystyrene-divinylbenzene (8%) has been prepared. Its sorption characteristics for palladium(II), platinum(IV), rhodium(III), ruthenium(III) and iridium(III) have been studied. These platinum metal ions can be quantitatively separated by sorption on this chelating resin and selective elution. The resin is highly stable in acid and alkaline solution.     

Chemical assembling of silica surface using a reaction of catalytic hydrosilylation

Chemical assembling of the silica surface modified by dimethylchlorosilane was performed by the catalytic hydrosilylation of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, α-methyl styrene, acetophenone, allyl butyl and allyl glycidyl ethers with dimethylchlorosilane. The effect of the nature of complexes of platinum, palladium, rhodium and ruthenium on the parameters of hydrosilylation was studied. It was shown that the maximum rate of hydrosilylation was observed in the reaction with allyl glycidyl ether, and minimum, with α-methylstyrene; the most effective catalyst of hydrosilylation was [Rh(CO)₂(acac)].     

Catalytic oxidation and C–C coupling reactions of new ruthenium(III) Schiff base complexes containing PPh<Subscript>3</Subscript> or AsPh<Subscript>3</Subscript> co-ligands

New mononuclear ruthenium(III) Schiff base complexes of the type [RuX₂(EPh₃)(L)] (X = Cl or Br; E = P or As; L = monobasic tridentate Schiff base derived from o-aminophenol or o-aminothiophenol with ethylacetoacetate or ethylbenzoylacetate) have been synthesized. The Schiff base ligands chelate to ruthenium through O, N, and O/S by dissociation of the phenolic proton/thiophenolic proton forming chelate rings. These complexes have been characterized by physico-chemical and spectroscopic methods. Cyclic voltammetric data of all the complexes showed Ru(III)/Ru(IV) oxidation and Ru(III)/Ru(II) reduction within the range of 0–1.5 V and 0 to −1.5 V with respect to Ag/AgCl, respectively. The complexes were tested as catalysts in the oxidation of alcohols using molecular oxygen at ambient temperature, and also in C–C coupling reactions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Rhodium(III), palladium(II), and platinum(II) complexes with 2-(2-hydroxybenzoyl)-N-methylhydrazinecarbothioamide: Syntheses,structures, and spectral characteristics

The syntheses and spectral (IR, UV-VIS, XPS, and ¹H and ¹³C NMR) characteristics of the rhodium(III), palladium(II), and platinum(II) complexes with 2-(2-hydroxybenzoyl)-N-methylhydrazinecarbothioamide (HBMHCTA) are described. The coordination of HBMHCTA to the central metal ion and its intraligand rearrangement in the complex formation of rhodium(III) ions are studied. The structure of the mixed-ligand complex [Pd(H₂L)PPh₃] is determined by X-ray diffraction analysis.     

A simple cathodic process for carboxylating noble metals and generating new versatile electrode interfaces

The electrochemical reactivity of polarized metals such as platinum, palladium, and rhodium toward carbon dioxide in aprotic dimethylformamide (DMF) solutions of tetramethylammonium tetrafluoroborate (TMABF₄) is presented. The capacity of metals such as Pd and Pt to cathodically insert the electrolytes under superdry conditions (via the generation of organometallic intermediates analogous to Zintl metals) is combined with the concomitant carboxylation of those metals within a potential range from − 1 V to − 2.5 V vs. Ag/AgCl/KCl(sat). Under these conditions, dense surface carboxylation of these precious metals occurs, totally suppressing their catalytic activity. Thick layers of the carboxylated metals (platinum-CO₂^– and palladium-CO₂⁻) are chemically stable and may then be further functionalized for specific applications.     

Kinetics and mechanism of uncatalysed and ruthenium(III)-catalysed oxidation of <Emphasis Type="SmallCaps">d</Emphasis>-panthenol by alkaline permanganate

The oxidation of d-panthenol by MnO₄ ⁻ was studied in the absence and in the presence of ruthenium(III) catalyst in alkaline medium at 298 K and at constant ionic strength of 0.50 mol dm⁻³ by spectrophotometry. The stoichiometry in both the cases was [panthenol]: [MnO₄ ⁻] = 1:4. The oxidation products were identified by IR and GC–MS. The reaction was first-order with respect to both MnO₄ ⁻ and ruthenium(III), while the orders with respect to both panthenol and alkali varied from first order to zero order as the concentrations increased. The effects of added products, ionic strength and dielectric constant were studied. The reaction constants, activation parameters and thermodynamic quantities were calculated for both the uncatalysed and catalysed reactions.     

Correction to: The effect of small silver inclusions on the palladium activity in formicacid oxidation reaction and corrosion stability

A PdAg deposit containing ~ 25 at.% Ag is obtained by the electrochemical codeposition from an aqueous solution of Pd and Ag sulfates (Au support, 0.5 M H₂SO₄). The deposit is characterized by means of various physical, physicochemical, and electrochemical methods. The PdAg deposit demonstrates the ~ 2 times higher specific activity (per the electrochemically active surface area (EASA) of Pd) in the formic acid oxidation reaction (FAOR) as compared with the individual Pd deposit prepared under the same conditions. The effect of silver additions on the palladium activity depends on many factors. The corrosion stability of PdAg is studied in 0.5 M H₂SO₄ solution based on the overall cyclic voltammograms (CVAs) and also on anodic and cathodic half-cycles in the region E = 0.3 − 1.25 V (vs. reversible hydrogen electrode (RHE)). The electrochemical estimates are compared with the results of direct analytical determination of dissolution products in solution after anodic polarization of deposits. The total amounts of Pd dissolved substantially increase with incorporation of Ag, which is associated, first of all, with the considerable increase in the EASA; at the same time, the specific dissolution of Pd also substantially increases. The possible factors determining the active dissolution of PdAg deposits are discussed; in particular, the specific mechanism of their dissolution via silver adatoms is proposed.

     

Microwave-assisted synthesis of organic–inorganic poly(3,4-ethylenedioxythiophene)/RuO2·xH2O nanocomposite for supercapacitor

An organic–inorganic poly(3,4-ethylenedioxythiophene) (PEDOT)/RuO₂·xH₂O nanocomposite (approximately 1 wt.% RuO₂) has been successfully prepared for the first time under microwave irradiation within 5 min with power 900 W via in situ chemical polymerization. The morphology and structure of the resultant material is characterized by transmission electron microscope and Fourier transform infrared. Moreover, the electrochemical properties of the synthesized nanocomposite can be controlled by adjusting the annealing temperature, which is definitely illustrated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectra. Electrochemical data have shown that the PEDOT/RuO₂·xH₂O nanocomposite annealed at 150 °C possesses the most favorable charge/discharge ability with a specific capacitance of 153.3 F g⁻¹ at a current density of 150 mA g⁻¹ and the high efficient utilization of PEDOT at various current densities. Furthermore, such composite has a less capacitance degradation of 23.8% after 1,000 continuous cycles. The improved electrochemical performance are mainly attributed to the large electroactive surface of nanocomposite and the existence of amorphous RuO₂·xH₂O particles as well as a synergistic effect of the polymer PEDOT and annealed RuO₂·xH₂O. Thus, the PEDOT/RuO₂·xH₂O nanocomposite annealed at 150 °C can act as a promising electroactive material for supercapacitor application.