Palladium Content Research Articles

Palladium(II) Extraction by 4-[(Hexylsulfanyl)methyl]-3,5-dimethyl-1-phenyl-1Н-pyrazole from Hydrochloric Acid Solutions

Palladium(II) extraction from hydrochloric acid solutions by 4-[(hexylsulfanyl)methyl]-3,5-dimethyl-1-phenyl-1Н-pyrazole, a new complexing reagent dissolved in toluene or chloroform, was studied. The reagent showed high efficiency in palladium(II) recovery from 0.1–(5–6) М HCl. Palladium(II) is recovered from 1 М HCl by the nonprotonated reagent species according to the coordination mechanism to form the extracted compound [PdCl2μ-L]n (n > 2). The reagent is coordinated to metal ions via the nitrogen atom and the thioether sulfur atom as shown by 1H and 13С NMR spectroscopy. In the temperature range 10–40°С, palladium(II) extraction from 1 M HCl is an endothermic process. The palladium(II) can be quantitatively stripped by a hydrochloric acid solution of thiourea. The reagent (with toluene as diluent) may be recommended for use in palladium(II) concentration from hydrochloric acid solutions and for palladium(II) selective separation from platinum(IV), copper(II), nickel(II), iron(III), and aluminum(III).

Improved H2 utilization by Pd doping in cobalt catalysts for reductive amination of polypropylene glycol.

Cobalt based catalysts having enhanced H2 dissociation and desorption were synthesized by inserting a trace amount of palladium. These catalysts were used for the reductive amination of polypropylene glycol (PPG) to polyetheramine (PEA). The catalytic activity toward PEA was significantly increased by incorporating an extremely low content of palladium (around 0.01 wt%) into cobalt based catalysts. The Pd inserted cobalt catalysts promoted reduction of cobalt oxide to cobalt metal and inhibited formation of cobalt nitride in the reductive amination. The Pd inserted cobalt catalysts not only enhanced hydrogen dissociation but also accelerated hydrogen desorption by increasing the electron density of cobalt through interaction between cobalt and palladium. These play a critical role in reducing cobalt oxide or cobalt nitride to cobalt metal as an active site for the reductive amination. Thus, the Pd inserted cobalt catalysts provide improved catalytic performance toward PEA production by maintaining the cobalt metal state.

Investigation of the Interaction of Palladium with Potassium Tetrafluorobromate

In this investigation, the interaction of metallic palladium with potassium tetrafluorobromate was examined in open system, the reaction products were identified using X-ray phase analysis. A thermogram of the interaction of Pd with KBrF4 was obtained, the temperature range of the reaction (187.9-328°C) and the thermal effect (431.31 J/g) were determined. It was found that the fluorination process is a multi-stage process. The solubility of the obtained K2PdF6 compound in nitric and hydrochloric acids was investigated. The process of extraction of palladium from nitric acid solutions with tributyl phosphate was carried out and the influence of the concentration of palladium and the acidity of the initial solution on the distribution coefficient was investigated.

Reflectometric and visual test determination of Pd(II) in objects of complex composition using the indicator paper

RIP-Pd-Test reagent indicator paper based on 1-phenyl-5-(3,4-dihydro-6-methyl-4-oxo-3H-pyrimidin-2-yl)-formazan-6-cellulose has been proposed for determining the palladium content using the sorption-reflectometry and visual-test methods in objects of complex composition. The RIP synthesis technique was described. The estimated composition of the metal complex formed as a result of the heterogeneous indicator reaction at pH 1.5–2.5 was indicated, and the forced coordination of palladium : reagent = 1:1 was ensured. When the RIP interacted with palladium (II) ions, the yellow indicator strip became green with different intensities. Under the selected conditions, the high selectivity for the detection and determination of Pd(II) was shown. With the help of the «Ecotest-2040» portable reflectometer, the reflectometry measurements were carried out using the red LED with the radiation wavelength of 660 nm. For the visual testing, the color scales were used. The indicator reaction was proposed to be carried out in three modes: without concentration and with concentration of the test solution in 100 and 1000 times on the reaction indicator zone of the paper strip (using the pocket pumping device). By the statistical method, the limit of Pd(II) determination for the visual test method (40, 0.47, 0.042 mg/l) was estimated. The palladium detection limit using the reflectometer (19, 0.22, 0.018 mg/l) for the three modes, respectively, was calculated by 3s criterion. The found values of the limiting concentrations were comparable with the metrological characteristics of the known analysis methods in which solid-phase reagents were used. The trueness of the palladium determinations in technological objects of complex composition and drugs has been proven by the independent methods - atomic emission, spectrophotometric and gravimetric methods of analysis. The value of the relative standard deviation of the determined Pd(II) concentration using the portable reflectometer did not exceed 7%. Keywords: palladium(II), formazan, reagent indicator paper, sorption, reflectometry, visual test analysis DOI: http://dx.doi.org/10.15826/analitika.2020.24.2.007 V.M. Ostrovskaya 1 , E.A. Reshetnyak 2 , O.S. Chernyshova 3 , E.Yu. Bryleva 3 1 25 State research institute of the Ministry of Defence of Russian , 10 Molodogvardeyskaya St r. , Moscow , 121467, Russia n Federation 2 V.N. Karazin National University, 4 Svoboda Sq., Kharkiv, 61022 , Ukraine 3 SSI Institute for Single Crystals NAS of Ukraine, 60 Nauky Ave, Kharkiv, 61072 , Ukraine

Состав, электронное и атомное строение наночастиц палладия при различных концентрациях металла в матрице полиэтилена

The composition, electronic and atomic structure of palladium nanoparticles stabilized in high pressure polyethylene (with palladium concentrations of 10 and 20 mass%) were studied by transmission electron microscopy, X-ray diffraction, and X-ray absorption spectroscopy. It was found that nanoparticles consist of metal (Pd) and oxide (Pd2O3) components, and their average size and coordination numbers for first Pd coordination sphere decrease(from 7 to 6 nm and from 7 to 5.7, respectively) with a decrease in metal concentration.

Platinum, palladium, and rhodium in airborne particulate matter.

Measurable quantities of platinum, palladium, and rhodium, even in remote areas of the planet, evidence the global nature of pollution with these metals, mostly from catalytic converters of modern vehicles (other sources are jewellery production, chemical industry, and anticancer drugs). The amount of the platinum group metals (PGMs) emitted from automobile catalysts varies with the type, age, and condition of the engine and the catalyst, as well as the style of driving. Current literature suggests that the concentrations of these metals have increased considerably over the last twenty years, palladium concentrations in particular, as it has been proved more effective catalyst than platinum. However, whether and to what extent the emitted PGMs are toxic for people is still a controversy. The potential health risk from exposure to these elements is most likely for those living in urban environments with busy roads or along major highways. Because of the importance of PGMs and their trace levels in particulate matter, sensitive methods are required for reliable determination. This review discusses particular steps of analytical procedures for PGM quantification in airborne particulate matter and addresses the common preparation, detection, and determination methods.

Electron irradiation of palladium-copper alloy

The process of high-energy electron irradiation of the Cu – 40 Pd alloy in air under 350 °C is considered. After irradiation, a layer of copper oxide CuO was formed on the alloy surface, which under normal thermal conditions forms at the temperature of 400 – 500 °C. Reflections of the ordered β-phase disappeared in the surface layer. The elemental composition of the alloy changed along the distance from irradiated surface of the metal. Phases with low degree of long-range order and an increased palladium content formed. The presence of these phases is caused by selective oxidation of copper.

Activity of a Sulfated Zirconia Catalyst in Isomerization of n-Butane Fractions

Palladium-containing catalyst based on binder-free granular sulfated zirconium oxide for n-butane isomerization has been investigated. It has been found that Pd content of 0.2–1.0 wt % slightly influences textural characteristics and other physicochemical properties of bifunctional catalysts; however, it determines their activity and selectivity in the reaction studied, with the optimal palladium content being 0.5 wt %. Parameters of the isomerization process have been studied depending on the composition of industrial n-butane fractions. It has been shown that impurities of isobutane, propane, neopentane, isopentane and pentane in an amount of no more than 2% do not exert a effect on isobutane production; nonetheless, the conversion of n-butane and selectivity for isobutane both increase when more pure n-butane fractions are used. It has been found that the process for isobutane production by isomerization of the n-butane fraction under the optimal conditions at H2 /n-C4 = 0.1 and 140–150°C makes it possible to obtain a high isobutane yield (up to 52 wt %) and avoid the undue formation of С1–С3 alkanes.

A New Method of Control Over the Content of Palladium in Intermetallic Alloys

We study the interaction of 4-methoxy-1-(5-benzylthiazol-2-yl)azo-naphthalene-2-ol with palladium (II) ions. The conditions required for the formation of a complex and for getting the optimal fractions of its components are established. We propose a new extraction-photometric method for the analytic control over complex palladium-containing compounds with the use of 4-methoxy-1-(5-benzylthiazol-2-yl)azonaphthalene-2-ol and verify it for Yb40Pd40Ga20 and Yb40Pd38Sn22 alloys.

The HR-CS-GF-AAS determination and preconcentration of palladium in contaminated urban areas, especially in lichens

The increasing content of platinum group metal particles emitted into the environment by car traffic is gradually attracting the attention of the scientific community. However, the methods for the determination of platinum group metals in environmental matrices are either costly or suffer from low sensitivity. To facilitate the use of less sensitive, but significantly cheaper, devices, the preconcentration of platinum group metals is employed. For platinum, a multitude of preconcentration approaches have been published. On the contrary, the preconcentration approaches for palladium are still rare. In this work, the development, optimization, and testing of a new approach is described; it is based on a preconcentration of palladium on octadecyl modified silica gel together with the complexing agent dimethylglyoxime, and it is then analyzed with the high-resolution continuum-source atomic absorption spectrometry. For comparison, a newly developed sorbent, QuadraSil™ TA, with a high affinity for platinum group metals was also tested. The preconcentraiton approach was tested on the lichen Hypogymnia physodes, which served as a bioindicator of palladium emissions. The case study site was a mid-sized city in central Europe: Brno, Czech Republic. The dry “bag” monitoring technique was used to collect the palladium near roads with a large span of traffic density. The developed analytical approach confirmed an increasing concentration of palladium with increasing exposure time and intensity of the traffic. Consequently, a simple relationship between the amount of bioaccumulated palladium and traffic density was established.

Development of Advanced Electrode Materials on Porous Silicon for Micropower Formic Acid-Oxygen Fuel Cells

In this work, in order to create electrode materials for electrochemical energy converters, composites on porous silicon modified by palladium have been obtained. The functional characteristics of the electrodes have been studied by scanning electron microscopy, X-ray phase analysis, ex-situ and in-situ cyclic voltammetry. The electrode materials based on porous silicon had demonstrated high catalytic activity and specific characteristics in fuel cells with direct oxidation of formic acid. The fuel cell prototype with low palladium content showed the maximum specific power of about 30 mW/cm 2 at a current density of 95-100 mA/cm 2 . Copyright © VBRI Press.

Mutual impact of crystal volume and heat of alloy formation on hydride stabilities in Zr(PdxCr1−x)2 and similar intermetallics

Hydrides of Zr(PdxCr1−x)2 pseudobinary compounds (x = 0.05, 0.1, 0.175) exhibit slight destabilization and more sloped hydrogen plateau pressures with the increase of the palladium content. The former feature conforms to the rule of reverse stability but violates the trend of increased hydride stability upon increasing the unit cell intermetallic volume. A combination of the two effects, the heat of alloy formation and the crystal volume, shows better correlation with the hydride stabilities than considering separately each property. Hydrogen absorption is found in ZrPd2 at ∼60 atm and associated with its moderate shear modulus.

Collagen-graphene oxide magnetic hybrids anchoring Pd(0) catalysts for efficient H2 generation from ammonia borane

Because of the rapid development in the utilization hydrogen energy, various hydrogen storage techniques have attracted much attention. Among them, the hydrolysis of ammonia borane (NH3BH3, AB) over high-efficient and low-cost catalysts is one of the most interesting pathways. In this work, the magnetic collagen powder-graphene oxide hybrids (CGP-GO-Fe3O4) are synthesized by a facile self-assembly method combined with co-precipitation synthesis routes. Then, the hybrids are employed to immobilize palladium nanoparticles with an in-situ reduction strategy. The as-prepared Pd/CGP-GO-Fe3O4 catalysts exhibit good catalytic activity and excellent recyclability for H2 generation from AB. Under the present reaction conditions, the activation energy and turnover frequency for the hydrolysis of AB are 36.5 kJ mol−1 and 27.4 molH2·molPd−1·min−1, respectively. In addition, the hydrolysis reaction is found to be of 0.93 and 0.40 orders with respect to the palladium and AB concentrations, respectively. The results demonstrate that Pd/CGP-GO-Fe3O4 could be efficiently applied in the utilization of hydrogen energy.

Pd-doped or Pd impregnated 30% La0.7Sr0.3CoO3/Al2O3 catalysts for NOx storage and reduction

Here we report the effects of the incorporation of palladium into 30% La0.7Sr0.3CoO3/Al2O3 catalyst by different methods on the NOx storage and reduction behaviour. Several catalysts were prepared incorporating four palladium nominal loadings (0.75, 1.5, 2.25 and 3.0%) by doping the perovskite formulation (30% La0.7Sr0.3Co1-yPdyO3/Al2O3) or by wetness impregnation over alumina-supported perovskite (y% Pd-30% La0.7Sr0.3CoO3/Al2O3). The results of X-Ray diffraction, N2 adsorption-desorption at −196 °C, electron microscopy, temperature programmed techniques, Raman and X-ray photoelectron spectroscopies demonstrated that the wetness impregnation method induces the formation of small PdO particles homogenously distributed over the surface in strong interaction with the perovskite. Meanwhile, doping method leads to the formation of a mix between intraframework palladium species and surface agglomerated PdOx particles with weaker interaction with the perovskite phase. Therefore, palladium accessibility and the synergetic effects with the perovskite are lower for Pd-doped samples. The NO-to-NO2 conversion is similar irrespective of the palladium content and the incorporation method. This confirms the perovskite phase as the main active site for NO oxidation. However, NOx adsorption during lean conditions and NOx reduction to N2 during rich periods are significantly promoted after the incorporation of palladium, especially by impregnation method. This enhancement is assigned to better NOx adsorption sites regeneration and to a promotion of NOx reduction rate, respectively. Thus, the best De-NOx performance of Pd-impregnated catalysts is derived from the higher efficient use of the palladium active sites. Among the developed formulations, the 1.5% Pd-30% LSCO/Al2O3 sample shows the best balance between NOx removal efficiency and minimum palladium content. This sample shows a NO removal efficiency and nitrogen yield as high as 86.2% and 69.5%, respectively. Based on these results, the developed formulation is revealed as a promising alternative to the NSR model catalyst (1.5% Pt-15% BaO/Al2O3) for NOx removal in the automotive application.

Molecular Dynamics Study of the Deposition of Palladium-Silver Films on a Silver Substrate

The formation of PdxAg1-x thin films from the gas phase on silver substrates is modeled by molecular dynamics. The effect of substrate temperature on the structure of coatings of various compositions (x = 0, 0.25, 0.5, 0.75, 1) is studied in the range from 300 K to 900 K. The films are shown to have an unevenly deformed fcc structure over the entire range of considered temperatures and compositions. The surface of the coating is not smooth; it contains holes and cavities with a characteristic height difference of several angstroms. No misfit dislocations are formed in the studied systems. Higher substrate temperatures during the deposition of the coating lead to the increased average adsorption energy in the formed layer (which is true for all elemental compositions of the films.) This is caused by the fact that diffusion rate is higher on hotter substrates, and the surface of the coating is therefore smoothed. It is notable that the change of adsorption energy as a function of the substrate temperature during film deposition is directly proportional to the palladium content in the film. A high accuracy (above 0.01 eV) procedure is proposed for the calculation of cohesive energy in the film. This characteristic is shown to be virtually independent on the substrate temperature during nanolayer deposition. This is a direct indication that the structure of the coating volume is not changed, regardless of its elemental composition, as the temperature of formation increases.

Removal of Platinum and Palladium from Wastewater by Means of Biosorption on Fungi Aspergillus sp. and Yeast Saccharomyces sp.

The emission of platinum group metals from different sources has caused elevated concentrations of platinum and palladium in samples of airborne particulate matter, soil, surface waters and sewage sludge. The ability of biomass of Aspergillus sp. and yeast Saccharomyces sp. for removal of Pt(IV) and Pd(II) from environmental samples was studied in this work. The pH of the solution, the mass of biosorbent, and contact time were optimized. The Langmuir and Freundlich adsorption isotherms and kinetic results were used for interpretation of the process equilibrium of Pt(IV) and Pd(II) on both microorganisms. The maximal efficiency of retention of Pt(IV) on yeast and fungi was obtained at acidic solutions (pH 2.0 for Pt(IV) and pH 2.5–3.5 for Pd(II)). The equilibrium of the biosorption process was attained within 45 min. The best interpretation for the experimental data was given by the Langmuir isotherm. Kinetics of the Pt and Pd adsorption process suit well the pseudo-second-order kinetics model. Fungi Aspergillus sp. shows higher adsorption capacity for both metals than yeast Saccharomyces sp. The maximum adsorption capacity of fungi was 5.49 mg g−1 for Pt(IV) and 4.28 mg g−1 for Pd(II). The fungi possess the ability for efficient removal of studied ions from different wastewater samples (sewage and road run-off water). It was also demonstrated, that quantitative recovery of Pd from industrial wastes could be obtained by biosorption using Aspergillus sp.

Kinetic model of ethylene oxidation by p-benzoquinone in solutions of cationic palladium(ii) complexes in a binary acetonitrile—water solvent

A kinetic model was developed for the reaction of ethylene oxidation to acetaldehyde by p-benzoquinone (Q) at 30 ℃ catalyzed by the cationic palladium(II) complexes in a binary acetonitrile—water solvent at a molar fraction of water of 0.67. The three-route mechanism was proposed that adequately describes all experimental dependences of the concentrations of consumed ethylene on time at various partial ethylene pressures and concentrations of palladium, perchloric acid, and Q. The time-dependent (a) palladium distribution between the intermediates and (b) ratio of the rates of steps of acetaldehyde oxidation via different routes were analyzed. The role of the PdII, PdI, and Pd0 complexes in the catalytic formation of olefins was discussed. The quantum chemical estimates of the composition of the coordination sphere for several intermediates and probabilities of some elementary steps in the reaction mechanism were obtained.

Highly Sensitive to Methane Sensor Materials Based on Nano-Pd/SnO2

Catalytic activities of nanomaterials based on tin dioxide with various palladium contents in the oxidation of CH4 and sensitivities of adsorption semiconductor sensors to methane based on them were studied. It was shown that responses of the sensors to methane are determined by the catalytic activites of the materials of their gas sensitive layers in the oxidation of CH4 by oxygen chemisorbed on active sites localized at the Pd–SnO2 interface.

Characterisation of the Carpinus betulus L. Phyllomicrobiome in Urban and Forest Areas.

Urban green areas are highly valued by citizens for their contribution to the quality of life in cities. Plants play an important role in mitigating airborne pollutants and are assisted in this role by the metabolic capacities of the millions of microbial cells that colonize leaf surfaces (phyllosphere). Many factors influence phyllosphere microbial community composition and function, but to what extent does airborne pollution in cities impact the composition of microbial communities and their functional degradation genes? Here we describe the characterization of the phyllospheric bacterial communities of Carpinus betulus L. trees (hornbeam) across three locations: the city center of Warsaw (Poland), a forest in a UNESCO World Heritage Site (Białowieża), and a forest in one of the world’s oldest operational oil fields (Bóbrka). C. betulus contained higher particulate matter (PM) concentrations, with higher concentrations of palladium and radon in the PM, on leaves in Warsaw than in the forests. Volatile organic compound (VOC) analyses of sampled air revealed higher concentrations of butanone methyl propanal, butylbenzene, and cyclohexane in Bóbrka than Warsaw and Białowieża, while in Warsaw, xylene and toluene were higher. Shotgun microbiome sequencing uncovered a dominance of Gammaproteobacteria (71%), mainly Pseudomonas spp., Actinobacteria, Alpha- and Betaproteobacteria, and Firmicutes. Community composition and function differed significantly between the forests and Warsaw city center. Statistically more hydrocarbon degradation genes were found in Białowieża compared to Warsaw and Bóbrka, and in vitro tests of diesel degradation and plant growth promotion traits of culturable representatives revealed that Białowieża held the highest number of bacteria with plant beneficial properties and degradation genes. This study provides the first detailed insights into the microbiome of C. betulus and sets the stage for developing to a more integrated understanding of phyllosphere microbiota in cities, and their relationships with human health.

Bimetallic Pt–Pd nano-catalyst: size, shape and composition matter

The goal of this work is to understand how the phase diagram (PHAD) of the platinum–palladium (Pt–Pd) alloy changes with size and shape and how it correlates with catalytic properties. By using nano-thermodynamics, the size and shape effects on the PHAD of Pt–Pd nanoparticles were determined theoretically. The PHAD of some nanoparticles (sphere, tetrahedron, octahedron, decahedron, cube, cuboctahedron and rhombic dodecahedron) exhibits a congruent melting point that becomes more and more pronounced when the size decreases. At the right of the congruent melting point i.e. close to the Pt-rich side, the coexistence region exhibits a contraction while an expansion is noticed at larger palladium concentrations. From the Gibbs free energy analysis, the stability of all the considered shapes has been determined versus temperature and composition. Furthermore, the surface segregation was also calculated and it is shown that the surface segregation is reversed at very small sizes. Indeed, below a critical size, Pd does not segregate anymore at the surface like it normally does for larger nanoparticles; but Pt does. The critical size range has been determined for each considered shape; and within this range Pt and Pd co-exist at the surface. Finally, the most catalytically active shapes are predicted to be the tetrahedron and the cube in agreement with the available experimental data and other theoretical results.