Palladium Content Research Articles

The hydrogenation of furfural, 5-hydroxymethylfurfural and 5-methylfurfural over platinum and palladium catalysts based on porous aromatic frameworks.

Platinum and palladium catalysts supported on two types of porous aromatic frameworks, PAF-30 and PAF-30-NH2 (modified with amino groups), were examined in furfural hydrogenation. The influence of temperature, reaction time and solvent on selectivity and activity of the catalysts was investigated. Using isopropanol as solvent and conducting experiments at 40 ℃ led to sufficient decrease of side products yields. According to TEM Pt-PAF-30 and Pd-PAF-30-NH2 catalysts are characterized with uniform particles distribution on support. Elemental analysis shows a difference in palladium content between Pd-PAF-30 and Pd-PAF-30-NH2: 4.6% and 6.8% respectively. Whereas platinum catalysts have both 5.4% of metal. Catalyst Pt-PAF-30 was highly selective to tetrahydrofurfuryl alcohol (83% yield), whereas the catalyst Pd-PAF-30-NH2 exhibited unusually high selectivity towards tetrahydrofurfural (77% yield). All studied catalysts were also tested in the hydrogenation of 5-hydroxymethylfurfural and 5-methylfurfural, in these experiments up to 20% yield of 1-hydroxy-4-hexen-2-one was observed.

Plasmonic antenna enhancement on Pd cluster towards high selective FDCA production

2,5-Furandicarboxylic acid (FDCA), an excellent precursor for producing value-added green polymers, has recently garnered much attention. Traditional methods for oxidizing 5-Hydroxymethylfurfural (HMF) to FDCA typically require harsh conditions, such as high pressure, high temperature, and non-eco-friendly reactants, making them neither green nor economical. In this study, we present a novel photocatalytic system utilizing a plasmonic antenna effect to enhance Pd clusters supported on ceria (CeO2). This system drives the transformation from HMF to FDCA under ambient conditions, achieving an impressive yield of over 90% within 4 h under green light irradiation. Notably, the palladium content in this system is minimal. This discovery could pave the way for the development of new photocatalytic systems with varied nanostructures or elemental compositions for efficient chemical reactions.

Synthesis of Pd-decorated ZnO nanocomposites with improved gas-sensitive properties for acetone detection

ZnO/Pd nanocomposites containing 0.5–3.0 mol.% palladium and possessing improved gas-sensitive properties for VOC’s detection were prepared using solvothermal synthesis. The synthesised powders have been characterised using various methods of physicochemical analysis (DSC/TGA, XRD, SET/TEM, XPS). It is shown that Pd@PdO nanoparticles (4–7 nm in diameter) are localised on the surface of ZnO nanoparticles (40–50 nm in size). According to the combined XRD and XPS data, it was found that palladium is in partially oxidised state, and the nanocomposite has a structure close to "core@shell": Pd@PdO. The influence of palladium concentration in the ZnO/Pd composite on the complex of chemoresistive gas-sensitive properties was studied. It is shown that at 250 °C the obtained nanocomposites demonstrate a high (up to 57.8 a.u.) response to 100 ppb–20 ppm acetone, which can be used as a part of supersensitive devices for noninvasive diagnostics of diseases.

Mixed bio-based surfactant-templated mesoporous silica for supporting palladium catalyst

The study aimed on the synthesis of bio-based surfactant-templated mesoporous silica for supporting palladium catalyst using mixed bio-based templating agents namely cashew nut shell liquid (CNSL) and castor oil for pore direction purposes. The materials prepared through co-condensation of 3-aminopropyltriethoxysilane (APTS) and tetraethyl orthosilicate (TEOS) in a 1:4 M ratio using 1:1, 4:1 and 9:1 ratio of CNSL and castor oil. The resulting porous materials were utilized to support the palladium(II) chloride catalyst, resulting in a heterogeneous catalyst-a better and more environmentally friendly catalyst than a homogeneous one. Different instruments were used to characterize the prepared materials such as nitrogen porosimeter, Powder X-ray Diffraction, Diffuse Reflectance Infrared Fourier Transform Spectroscopy and Inductively coupled plasma optical emission spectroscopy. Physisorption studies of the prepared materials indicated that the largest pore diameter of 43.84 nm could be obtained by using a 1:1 M ratio of CNSL and castor oil. On the other hand, the largest surface area of 209 m2/g was obtained from a 9:1 whereas the largest pore volume was 1.55 cm3/g from a 4:1. Diffuse Reflectance Infrared Fourier Transform Spectroscopy analysis confirmed the presence of N-H group, the bending vibration bands at around 1640 and 1543 cm−1 indicating that the reaction of organoaminesilanes and tetraethyl orthosilicate had occurred. The palladium content of the supported catalyst was determined by ICP-OES which confirmed the attachment of palladium to the synthesized materials. The highest palladium loading was obtained from the adsorbent prepared by using 1:1 ratio of surfactants mixture which gave the adsorption value of 2.16 mmol/g. Powder X-ray Diffraction indicated that the synthesized organosilica materials are amorphous with improved crystallinity upon attachment of palladium catalyst. The incorporation of palladium in the synthesized materials using the mixed bio-based surfactant was successful.

Unusual holopelagic Sargassum mass beaching in Northwest Africa: Morphotypes, chemical composition, and potential valorisation

The rapid proliferation of holopelagic Sargassum spp. in the tropical Atlantic Ocean presents environmental challenges and economic opportunities. In 2022, Senegal witnessed its first significant holopelagic Sargassum beaching event, triggering widespread concern and interest from civil society, industrial sectors, and government. This study represents the first analysis of stranded holopelagic Sargassum's morphotypes and chemical composition in Northwest Africa. We highlight the nature of Sargassum stranding, dominated by S. fluitans III, and describe a putative new morphotype. Compared to most of the studies in the tropical Atlantic, Senegalese Sargassum displayed lower arsenic concentrations (9–29 ppm), higher cadmium levels (9–15 ppm), and increased mercury content (0.47–0.57 ppm). In addition, Senegalese Sargassum showed higher levels of iron (237–1017 ppm) and phosphorus (1300–1772 ppm). The biochemical analysis revealed high total protein levels (15–40 % DW) in Senegalese samples, though further analysis is required to confirm this. Furthermore, variations in biochemical composition within various parts of the Sargassum thallus were observed. The low arsenic content makes the beached Senegalese Sargassum attractive for valorisation and sets it apart from holopelagic Sargassum from all other regions where it occurs. However, caution should be taken regarding the high concentrations of cadmium. Our study highlights promising applications in Senegal and neighbouring countries, particularly in animal feed and agriculture. Noteworthy is the notable palladium content (2 ppm), valuable phenolic compounds, and mannitol, which present additional opportunities for the chemical industry. Our interdisciplinary approach enhances the global scientific understanding of the Sargassum issue. With the anticipation of more frequent Sargassum beaching events and, more generally, for seaweed exploitation, we advocate for inter-governmental African organisations to establish standardised norms for their exploitation. We recommend that the Food and Agriculture Organization/World Health Organization consider incorporating more seaweed in the Codex Alimentarius to facilitate their uses particularly when states deal with algal blooms.

Influence of iron content in palladium catalysts supported on alumina and their reduction conditions on the hydrodechlorination of diclofenac in aqueous solutions

Using the method of wet impregnation of alumina with iron and palladium nitrates, 1Pd0.5Fe and 1Pd10Fe catalysts modified with iron oxides were prepared with a target content of 1 wt % Pd, 0.5 or 10 wt % iron. The catalysts were compared with each other and with the monometallic catalyst 1Pd in the hydrodechlorination (HDC) of diclofenac (DCF) in dilute aqueous solutions at 30°C in batch and flow reactors after high-temperature (320°C) and mild (30°C) reduction; the latter was carried out in a batch or flow reactor. Using X-ray photoelectron spectroscopy (XPS), it was shown that after reduction at 320°C the surface of catalysts contains mainly Pd0, Fe2+ and Fe3+. The surface Fe2+/Fe3+ ratio increases as the iron content decreases. The reduction of Pd2+ to Pd0 is possible already at 30°C, but it proceeds much worse on the surface of 1Pd0.5Fe compared to 1Pd10Fe. According to XPS data, temperature-programmed reduction and infrared spectroscopy of diffuse reflection of adsorbed CO, modification with iron oxides increases the palladium content on the surface compared to 1Pd, promotes the emergence of new Pd–O–Fe centers, and affects the ability of palladium to be reduced. These effects increase with increasing iron content. Iron-modified catalysts reduced at 320°C showed similar activity and stability in the conversion of DCP in flow-through and batch systems. Unlike 1Pd0.5Fe, the 1Pd10Fe catalyst is highly efficient and stable even after mild reduction at 30°C. Under flow conditions with comparable DCF conversion, it provides increased selectivity in the HDC reaction of diclofenac compared to 1Pd, which is also active in hydrogenation.

Design and Production of Functionalized Electrospun Fibers for Palladium Recovery.

Adsorption stands out as a leading wastewater treatment method for ion removal or recovery. Polymeric fibers, notably electrospun ones, are gaining prominence due to their high capacity and easy recovery. Electrospinning offers a cost-effective means to produce fibers with a large surface area and high adsorption capacity. These fibers can be further functionalized with chemical substances acting as specific ligands for metal ions, bolstering their adsorption capabilities. In this study, dithioester-functionalized electrospun fibers were synthesized as an alternative to conventional sorbents for palladium recovery from acidic chloride solutions, similar to those used in hydrometallurgical processes for platinum group metal recovery (Pd, Pt, Rh···) from spent catalysts. Fibers with identical chemical composition but varying morphology were examined to assess their impact on palladium adsorption efficiency (i.e., beads-free and beads-on-string morphologies). Experimental investigations involved model solutions with varying palladium concentration, temperature, acidity (adjusted with HCl content), and salinity (adjusted with NaCl), utilizing both pure and dithioester-functionalized fibers. Experimental results demonstrate enhanced adsorption efficiency at lower temperatures and in 0.1 M HCl, with a negligible influence from solution salinity. Moreover, both pure polymeric and dithioester-functionalized electrospun fibers exhibit highly efficient palladium recovery. Furthermore, under optimal conditions, starting from an 80 mg/L palladium solution, a 95% recovery of palladium can be achieved with a sorbent dosage below 4 g/L of functionalized electrospun fibers. The adsorption data are well described by the Langmuir isotherm model for the pure polymeric fibers. At the same time, the contribution of dithioesters has been separately accounted for to describe the behavior of functionalized electrospun fibers. Thermal recovery of palladium from the spent sorbents has also been investigated.

High turnover and selective Bin-Pd-NCs catalyst for nitro group non-hydrogen reductions in H2O under air conditions: A sustainable and recyclable route to aromatic amines

A green synthesis of anilines by the non-hydrogen reduction of nitro compounds is described. The reaction and post-treatment purification processes can produce high-purity target products without the use of organic solvents. The key to success lies in the synergistic action of two reaction mechanisms. The hydrogen transfer system is significantly accelerated by the presence of binaphthyl-palladium nanoclusters, which permits the catalyzed selective transfer hydrogenation under air conditions, providing a general preparation of aromatic amines in good-to-high yields with excellent chemoselectivities. Benefitting from the heterogeneous manner in water, successful recycling of the catalysts was further achieved with high reaction efficiency maintained. Meanwhile, the ICP analysis results show that the residual palladium content in the target product was below 5 ppm.

Calculation of Surface Binding Energy in NixPdy Alloys Using Density Functional Theory

In the study, surface binding energies for pure Ni and Pd metals were calculated using density functional theory. The values obtained were 5.32 eV and 4.65 eV, respectively, which represents good accuracy for ab initio calculations. The work also included calculations of surface binding energy for different configurations of NiPd alloys with nickel and palladium concentrations of 66%, 50%, and 33%. Calculations were performed for each type of lattice for both Ni and Pd surface binding energies. Several types of lattices were simulated, and it was found that the average surface binding energies for Ni and Pd are: 5.02 eV and 4.36 eV respectively in the alloy with a Ni concentration of 50%; 4.89 eV and 4.22 eV respectively in the alloy with a Ni concentration of 66%; 5.12 eV and 4.40 eV respectively in the alloy with a Ni concentration of 33%.

Low palladium content CeO2/ZnO composite for acetone sensor with sub-second response prepared by ultrasonic method

Low palladium content CeO2/ZnO composite for acetone sensor with sub-second response prepared by ultrasonic method

Effects of membrane content, feed phase, and stripping phase for palladium solution extraction by using a polymer inclusion membrane.

Palladium is now frequently utilized in fuel cells, electroplating, electronics, and catalysis. Due to their rarity and high cost, precious metal recovery has taken on a significant role. The extraction method frequently utilized in polymer inclusion membranes (PIMs) is both efficient and simple since it has been demonstrated that precious metal adsorption on the membrane significantly controls the mechanism of chemical adsorption. In this study, polyvinyl chloride (PVC) as a polymer, A336 as a plasticizer, and trioctylamine (TOA) as a carrier were used to produce a PIM by evaporation. After the production of PIMs, palladium extract was studied. The stripping phase, palladium concentration in the feed phase, and components of the membrane were changed to determine the optimum condition with better extraction ability. When 0.5 M of HCl was used, higher kinetic parameter results and higher than 85% extraction efficiency were achieved compared to other concen- trations. When the EDX results were examined, 3.3% palladium was retained on the membrane surface. When the palladium concentration was selected at 2.5 ppm, higher kinetic parameters were observed, and the extraction efficiency was over 90%. The best membrane was the PIM containing 40% PVC-40% A336-20% TOA.

Oxime Palladacycle Supported on Magnetic Meoporous Silica: An Efficient Catalyst for Copper‐Free Acyl Sonogashira Reaction

AbstractThe catalytic activity of the supported bis(oxime palladacycle) catalyst was evaluated in the acyl Sonogashira reaction. The reaction conditions, such as solvent, base, and palladium content, were screened to achieve the best catalytic performance. Tetrahydrofuran (THF) solvent, triethylamine (Et3N) base, and the reaction temperature of 110 °C were found to be ideal for achieving high yields of the desired products. Furthermore, a catalyst loading of only 0.22 mol% palladium was sufficient to achieve good conversion. Broad ranges of aryl acetylenes and benzoyl chlorides were successfully coupled to give the desired acetylenic ketones. The reaction appeared to proceed efficiently using a small amount of catalyst. The magnetic property of the catalyst allowed for easy separation using an external magnet. The catalyst was stable and reused for multiple reaction runs without a significant deactivation. After seven cycles, the catalyst maintained over 90 % of its initial catalytic activity.

Redox control of the partitioning of platinum and palladium into magmatic sulfide liquids

The partitioning behavior of platinum group elements in magmas is critical for their use as tracers of planetary accretion and in understanding magmatic sulfide deposits. Here we use laboratory experiments to determine sulfide liquid–silicate melt partition coefficients for platinum and palladium at 1.5 GPa, 1400 °C, and oxygen fugacity 1.5–2 log units above the fayalite–magnetite–quartz buffer. We find that the partitioning coefficients of these elements are 2.3 × 105 to 1.1 × 106 and are independent of the platinum and palladium concentration in the system. Combined with previous data obtained at oxygen fugacity below the fayalite–magnetite–quartz buffer, this indicates redox-controlled partitioning behavior whereby at oxidizing conditions platinum- and palladium-enrichments are achieved through their dissolution in sulfide liquids, while at reducing conditions the entrapment of platinum- and palladium-rich clusters in sulfide liquids is more critical. This redox-controlled partitioning behavior should be considered when studying crust–mantle differentiation and the formation of magmatic sulfide deposits.

Testing of Electromigration Resistance of Copper and Silver Thick Films

This paper is focused on the electromigration resistance of copper and silver thick films. Electromigration was tested by water drop test. Four common conductive thick film pastes were used for testing – silver paste with low platinum content, and two silver pastes with different content of palladium and copper paste. Electromigration was tested under voltage of 6 and 12 V and time to shortcut was measured. Results of testing including the comparison of electromigration resistance depending on thick film paste type and different electrode spacing are described in this paper.

Platinum-Group Element Geochemistry of Igneous Rocks in the Chongjiang Cu–Mo–Au Deposit, Southern Tibet: Implications for the Formation of Post-Collisional Porphyry Cu Deposits

Abstract The timing and extent of sulfide saturation have been suggested as controlling factors in the formation of economically significant porphyry Cu deposits in subduction zone settings. However, details on the sulfide saturation history in post-collisional porphyry systems remain ambiguous. Accordingly, we have characterized the whole-rock geochemistry, including platinum-group elements (PGE), of igneous intrusions in the post-collisional Chongjiang porphyry Cu–Mo–Au deposit (southern Tibet) and utilize this data in conjunction with zircon U–Pb geochronological results and sulfide chemistry to assess the timing of sulfide saturation, the nature and amount of magmatic sulfide produced. The Chongjiang intrusions (monzogranite, biotite monzogranite porphyry, granodiorite, dacite porphyry, and quartz diorite porphyry) and mafic microgranular enclaves (MMEs) have zircon U–Pb ages of 14.2 to 12.8 Ma. Covariations in whole-rock major and trace elements among the Chongjiang intrusions and MMEs, together with similarities in their Sr–Nd and zircon Hf isotope compositions, indicate that they are co-magmatic and crystallized from a juvenile lower crustal melt that mixed with mafic melt derived from the lithospheric mantle; this hybrid melt subsequently evolved via fractional crystallization. Trace-element ratios in zircon and temperature − ∆FMQ estimates of the different intrusions suggest that they all crystallized from oxidized (average ∆FMQ = 1.9–2.6) and water-rich magmas. Palladium contents and Pd/Pt ratios in the Chongjiang igneous intrusions increase with decreasing MgO up to 3.9 wt % MgO, after which they abruptly decrease. The initial increase in Pd/Pt ratios likely results from the fractionation of a Pt-rich mineral (e.g. Pt–Fe alloy). The decrease in Pd contents and Pd/Pt ratios at 3.9 wt % MgO likely results from sulfide saturation during magma evolution, but prior to volatile exsolution, which occurred at approximately 1.4 to 2.4 wt % MgO. The presence of magmatic sulfide inclusions in amphibole and magnetite in samples with 3.9 wt % MgO, and the geochemical compositions of sulfide inclusions suggest that they represented trapped sulfide liquid and intermediate solid solution. Results of Monte Carlo simulations demonstrate that 0.003 to 0.009 wt % magmatic sulfide is required to have fractionated from the magma to explain the decrease in Pd contents at 3.9 wt % MgO. Highly chalcophile elements, such as Pd, will be sequestered by the magmatic sulfide that saturates at depth, decreasing their concentrations in the residual silicate melt, whereas concentrations of the less chalcophile elements, such as Cu, Mo, and even Au, will not be as significantly affected. Consequently, sufficient concentrations of Cu–Mo–Au will remain in the residual melt and, upon reaching volatile saturation, can be transported by the vapor phase to form porphyry Cu–Mo–Au deposits. In the case of the Chongjiang deposit, sulfide saturation was likely triggered by the high pressures and/or depletion of FeO caused by the thick (~70 km) crust beneath the Gangdese belt. This contribution presents evidence of sulfide saturation in post-collisional magmatic systems, and demonstrates that the amount of magmatic sulfide produced is a critical factor in controlling the formation of post-collisional porphyry Cu deposits.

Determination of palladium content in catalysts based on different carbon supports by inductively coupled plasma — atomic emission spectrometry (ICP-AES)

Catalytic processes and technologies are the structure-forming elements of modern chemical, petrochemical and pharmaceutical industries. Prospects of their development are strongly determined by continuous improvement of the existing catalysts and developing the advanced and more efficient ones. Among the available catalysts, an important place belongs to palladium catalysts with carbon supports. Palladium as an active component exhibits unique catalytic properties in various transformations of organic substances: hydrogenation, dehydrogenation, isomerization, dehydrocyclization, carbonylation, oxidation, etc. To control the content of the active component of a catalyst, precise and rapid physicochemical methods are used. ICP-AES shows a good performance in the analytical practice due to the rapidity, sensitivity, high accuracy and selectivity in determining various elements. The aim of the study was to develop a scientifically grounded methodological approach to estimate the palladium content in the catalysts synthesized on different carbon supports made of carbon black and Sibunit, which combines only the acidic decomposition of a sample and analysis by ICP-AES. A series of palladium catalysts synthesized on the carbon supports with different structural and textural characteristics was studied. An urgent goal is to control the content of the active component in the composition of catalysts. This characteristic affects the phase and electronic state of the metal, the structural and textural characteristics and thus determines the activity and selectivity of catalysts during operation. Therefore, quantitative chemical analysis is one of the main methods used to control the quality of catalysts. A method for quantitative determination of palladium concentration, which combines acidic decomposition of a sample and ICP-AES has been developed. The carbon support type was shown to exert no effect on the accuracy and reproducibility of data obtained by the analysis of supported palladium catalysts. The content of palladium in such catalysts can be measured using analytical lines 340.458 and 360.955 nm without lowering the measurement accuracy. The selected conditions of sample preparation make it possible to carry out a quantitative analysis of metal systems based on the carbon support with high accuracy. The relative error in determining the elements did not exceed 4%, the relative standard deviation was no more than 0.04. The results of this work can be used to analyze catalysts of similar chemical composition by ICP-AES.

Nanostructured Pd/Ag/Ni electrocatalysts for the Hydrogen Evolution Reaction

As palladium is the one of the most effective electrocatalyst for the hydrogen evolution reaction, it is crucial the development of new catalysts that require small amounts of palladium to perform, but that are highly active. In this work, the electrochemical characterization of a novel electrode with low palladium content is reported, where Pd nanoparticles are supported on macroporous nickel electrodes that contain silver nanoparticles previously electrodeposited on the surface, which after heat-treatment become rich in corners and edges. The values of η100 (overpotential needed to produce a fixed amount of hydrogen) and jm (indicative of catalytic activity per unit mass of metal nanoparticles) improved (for example, at 80 °C, a η100 of 109.9 mV and a jm of 12587 A·g−1) those of other authors who applied bimetallic AgPd nanoparticles for the HER, showing that the incorporation of nanostructures (Pd over Ag) significantly reduced the energy investment required to produce hydrogen due to synergistic effects between the deposited Pd particles and the electrodeposited silver, enhancing the catalytic activity.

Fast and simple method for simultaneous determination of palladium and rhodium in spent automotive catalysts by high-resolution continuum source electrothermal atomic absorption spectroscopy

This work established a novel and fast method for the simultaneous determination of palladium and rhodium in spent automotive catalysts by high-resolution continuum source electrothermal atomic absorption spectroscopy (HR-CS ETAAS). For this purpose, a simple approach for the extraction of Pd and Rh from auto catalysts with aqua regia (HCl + HNO3 (3:1)) leaching was developed. The optimum conditions for leaching of both elements in an open system are 4 h, at 108 °C and a solid-to-liquid ratio of 1:40. Palladium and rhodium concentrations in obtained leachate were determined simultaneously in one firing using the less sensitive adjacent secondary lines for Pd at 360.955 nm (7.7% relative sensitivity) and for Rh at 361.251 nm (2.2% relative sensitivity). The pyrolysis and atomization temperatures were 1200 °C and 2600 °C, respectively. Under these conditions, the limits of detection for Pd (0.19 mg kg−1) and Rh (0.48 mg kg−1) were relatively high but the sensitivity of the developed method corresponds to common concentrations of the elements in spent automotive catalysts. The repeatability of the method expressed as a relative standard deviation was typically 10% for Pd and 7% for Rh.The trueness of the method was confirmed by analysis of the certified reference material – spent automobile catalyst (ERM EB 504). The recoveries of Pd and Rh from the spent automobile catalyst were 96.9%, and 87.9%, respectively. The method was successfully applied to the simultaneous determination of Pd and Rh in spent automotive catalysts without preliminary chemical separation.

Data-driven stabilization of NimPdn-m nanoalloys: a study using density functional theory and data mining approaches.

Green hydrogen, generated through the electrolysis of water, is a viable alternative to fossil fuels, although its adoption is hindered by the high costs associated with the catalysts. Among a wide variety of potential materials, binary nickel-palladium (NiPd) systems have garnered significant attention, particularly at the nanoscale, for their efficacious roles in catalyzing hydrogen and oxygen evolution reactions. However, our atom-level understanding of the descriptors that drive their energetic stability at the nanoscale remains largely incomplete. Here, we investigate by density functional theory calculations the descriptors that drives the stability of the NimPdn-m clusters for different sizes (n = 13, 27, 41) and compositions. To achieve our goals, a large number of trial configurations were generated and selected using data mining algorithms (k-means, t-SNE) and genetic algorithms, while the most important physical-chemical descriptors were identified using Spearman correlation analysis. We have found that core-shell formation, with the smaller Ni atoms lying in the center of the particle, plays a major role in the stabilization of the nanoalloys, and this effect causes the alloys to assume a icosahedral-fragment configuration (as the unary nickel cluster) instead of a fcc fragment (as the unary palladium cluster). However, the core-shell formation in this alloy is unique in that Pd poor compositions exhibit scattered Pd atoms on the surface. As the palladium content increases, this gives rise to the complete Pd shell. This stabilization mechanism is quantitatively supported by the different correlations observed in the number of Ni-Ni and Pd-Pd bonds with energy, in which the latter tends to decrease alloy stability. Furthermore, a notable trend is the correlation between the coordination number of Ni atoms with alloy stabilization, while the coordination of Pd atoms shows an inverse correlation.

Study of sorption of platinum, palladium and rhodium ions on a carbon sorbent

The article is devoted to the sorption concentration of platinum (II,IV), palladium (II) and rhodium (III) ions from chloride media on a carbon synthetic sorbent. For the study of the sorption concentration of platinum group metals, the carbon synthetic sorbent Lewatit AF5 was chosen. This sorbent has high mechanical strength, high surface area, narrow pore size distribution, and low cost compared to silicate or polymer sorbents. Sorption concentration was carried out under static conditions from model chloride solutions. The concentration of analytes in the initial solutions ranged from 8 to 50 mmol/dm3. Equilibrium concentrations of metals in solutions were determined by inductively coupled plasma atomic emission spectrometry. The dependences of adsorption on contact time, free acidity and redox potential of the system were studied, and the limiting absorption values for each of the metals studied were determined. The study of the kinetic parameters of the sorption of Pt (IV), Pd (II) and Rh (III) ions was carried out from chloride solutions characterized by free acidity values of 0.01 mol/dm3. The time for establishing sorption equilibrium was determined, which was 4 hours for each of the ions. When studying the dependence of adsorption on free acidity and the oxidation-reduction potential of the system (ORP), it was revealed that with an increase in free acidity and redox potential, a decrease in sorption activity is observed, thus we can conclude that aquated complexes of platinum metals, in which metals present not in the highest oxidation state, involved in the sorption process. Processing of experimental data showed the applicability of the linear equation of the Langmuir isotherm for the description of the adsorption process, the limiting adsorption values were calculated, using which the sorption capacity of the sorbent was assessed. The sorption capacity for Pt (II, IV), Pd (II) and Rh (III) was 1.24 mmol/g; 1.16 mmol/g and 0.57 mmol/g, respectively. High values of sorption capacity, as well as a fairly short time to achieve sorption equilibrium without the use of means for the acceleration of the process, in combination with the mechanical characteristics of the sorbent, allow us to conclude that the Lewatit AF5 sorbent is promising for the concentration of platinum group metals from hydrochloric acid solutions.