Solution Of Pd Research Articles

Surfactant-Free Synthesis of Carbon-Supported Palladium Nanoparticles and Size-Dependent Hydrogen Production from Formic Acid-Formate Solution.

Steerable hydrogen generation from the hydrogen storage chemical formic acid via heterogeneous catalysis has attracted considerable interest given the safety and efficiency concerns in handling H2. Herein, a series of carbon-supported capping-agent-free Pd nanoparticles (NPs) with mean sizes tunable from 2.0 to 5.2 nm are developed due to the demand for more efficient dehydrogenation from a formic acid-formate solution of pH 3.5 at room temperature. The trick for the facile size-controlled synthesis of Pd/C catalysts is the selective addition of Na2CO3, NH3·H2O, or NaOH to a Pd(II) solution to attain initial pH values of 7-9.5. For comparison, cuboctahedron modeling and electrochemical COads stripping methods are applied to evaluate active surface Pd sites for turnover frequency (TOF) calculation. Both mass activity and specific activity (TOF) of hydrogen production are not only time-dependent but also Pd-size-dependent. An initial H2 production rate of 246 L·h-1·gPd-1 is achieved on 2.0 nm Pd/C at 303 K, together with a TOF of 1815 h-1 on the basis of cuboctahedron modeling of surface-active Pd sites. The initial TOF exhibits a significant rise from 3.5 down to 2.8 nm and then levels off below 2.8 nm and even shows a maxima at ca. 2.2 nm using the electrochemical surface area for calculation. The volcano-shaped dependence of TOF on Pd NP size may be better attributed to the changing ratios of terrace sites to defect sites on Pd NPs.

Palladium(II) sorption of a diethylphosphate-modified thiacalix[6]arene immobilized on amberlite resin

p-Diethylphosphonomethylthiacalix[6]arene (1) was impregnated on Amberlite XAD-7 resin (1-XAD), and the sorption kinetics of 1-XAD towards Pd(II) ions in HCl media were investigated. The maximum Pd(II) sorption capacity (SC) of 1-XAD was 18.7mgg−1 after a contact time of 24h in a 200mgL−1 Pd(II) solution. Batch sorption studies were then conducted to optimize a range of equilibration conditions, such as contact time, Pd(II) concentration, and temperature. The sorption process was then explained in the context of Freundlich and Langmuir isotherm models, thermodynamic parameters ∆G°, ∆H°, and ∆S°, and sorption kinetics were calculated to understand the nature of the sorption. Pd(II) sorption with 1-XAD was found to be spontaneous and endothermic nature. Pd(II) sorption kinetics follows a pseudo-second-order model. In addition, the SC of 1-XAD was investigated using the leach liquors of automotive catalysts containing Al, Ba, Ce, La, Pd, Pt, and Rh ions. The resin developed herein exhibited high selectivity towards Pd(II) ions, with a SC value of 4.12mgg−1 being obtained from leach liquors of automotive catalysts. Finally, Pd(II) desorption from Pd(II)-sorbed 1-XAD was achieved using a thiourea solution as the desorption reagent, and the resin was reused effectively over 5cycles. Pd(II) separation using the 1-XAD as a adsorbent is eco-friendly method as compared with conventional solvent extraction. The 1-XAD is highly useful for selective recovery of Pd(II) from leach liquors of automotive catalysts and secondary resources.

Metal-selective Deprotection-mediated Palladium(II) Extraction by Ionic Liquids with Tetrahydropyran-2H-yl-protected Thiol Moieties

Ionic liquids (ILs) bearing tetrahydropyran-2H-yl (THP)-protected thiol moieties were designed and synthesized as extractants for Pd(II)-selective extraction into an IL phase from a mixed aqueous HCl solution of Pd(II) and Pt(IV) salts. 1H NMR measurements revealed that metal-selective THP-deprotection by the Pd(II) salt played a critical role to introduce the Pd(II)-selective extraction ability.

Thermodynamics of hydrogen solution in Pd–Y alloys

Abstract Equilibrium hydrogen isotherms (343–523 K) have been determined for some low Y content fcc Pd –Y alloys. At a given p H 2 ≤ 1 bar, the hydrogen solubilities increase with atom fraction Y, X Y . Partial thermodynamic parameters, ΔH H and ΔS H , have been determined from these isotherms over a range of H contents. Extrapolation of ΔH H and ΔS H to infinite dilution of H, give ΔH H ∘ and ΔS H ∘ for 1 2 H 2 (g, 1 bar) absorption where the superscript zero indicates infinite dilution of H in the solid phase and 1 bar for H 2 in the gaseous phase. These parameters become increasingly negative with atom fraction Y. Thermodynamic factors, ( ∂ lnp H 2 1 / 2 / ∂ ln r ) T where r = H-to-metal, mol ratio, are needed for the interpretation of diffusion parameters. From equilibrium isotherms, lnp H 2 1 / 2 vs ln r , the slopes give the thermodynamic factors over a range of H contents and temperatures. Plots of the thermodynamic factors as a function of r exhibit minima which suggests that Fick's diffusion constants should also exhibit minima.

Review on the Determination of Frumkin, Langmuir, and Temkin Adsorption Isotherms at Electrode/Solution Interfaces Using the Phase-Shift Method and Correlation Constants

This review article described the electrochemical Frumkin, Langmuir, and Temkin adsorption isotherms of over-potentially deposited hydrogen (OPD H) and deuterium (OPD D) for the cathodic H2 and D2 evolution reactions (HER, DER) at Pt, Ir, Pt-Ir alloy, Pd, Au, and Re/normal (H2O) and heavy water (D2O) solution interfaces. The Frum-kin, Langmuir, and Temkin adsorption isotherms of intermediates (OPD H, OPD D, etc.) for sequential reactions (HER, DER, etc.) at electrode/solution interfaces are determined using the phase-shift method and correlation constants, which have been suggested and developed by Chun et al. The basic procedure of the phase-shift method, the Frumkin, Lang-muir, and Temkin adsorption isotherms of OPD H and OPD D and related electrode kinetic and thermodynamic param-eters, i.e., the fractional surface coverage (0 ≤ θ ≤ 1) vs. potential (E) behavior (θ vs. E), equilibrium constant (K), interaction parameter (g), standard Gibbs energy (ΔGθ˚) of adsorption, and rate (r) of change of ΔGθ˚ with θ (0 ≤ θ ≤ 1), at the interfaces are briefly interpreted and summarized. The phase-shift method and correlation constants are useful and effective techniques to determine the Frumkin, Langmuir, and Temkin adsorption isotherms and related electrode kinetic and thermodynamic parameters (θ vs. E, K, g, ΔGθ˚, r) at electrode/solution interfaces.

Suzuki-Miyaura cross-coupling of phenylboronic acid with aryl halides catalyzed by palladium and nickel species supported on alumina-based oxides

Two different kinds of Al2O3-ZrO2 have been prepared by the alkoxide sol-gel process: bulky-shaped and formed into spherical granules with the diameter of 2–3 mm. The catalysts have been obtained either by impregnating the support with the metal precursor (Pd or Ni salt solution) or by simultaneous addition of the precursor during synthesis of the support (the co-precipitation technique). The catalysts have been characterized structurally with scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption studies and successfully applied in the Suzuki-Miyaura cross-coupling of phenylboronic acid with different kinds of aryl halides (2-bromotoluene, 4-bromotoluene, 4-bromoanisole or 4-iodoanisole). Our experiments have shown that nickel species supported on Al2O3-ZrO2 can be successfully employed as the catalyst in the Suzuki-Miyaura process.

Stability and Unimolecular Reactivity of Palladate(II) Complexes [Ln PdR3 ]- (L=Phosphine, R=Organyl, n=0 and 1).

The reduction of PdII precatalysts to catalytically active Pd0 species is a key step in many palladium-mediated cross-coupling reactions. Besides phosphines, the stoichiometrically used organometallic reagents can afford this reduction, but do so in a poorly understood way. To elucidate the mechanism of this reaction, we have treated solutions of Pd(OAc)2 and a phosphine ligand L in tetrahydrofuran with RMgCl (R=Ph, Bn, Bu) as well as other organometallic reagents. Analysis of these model systems by electrospray- ionization mass spectrometry found palladate(II) complexes [Ln PdR3 ]- (n=0 and 1), thus pointing to the occurrence of transmetallation reactions. Upon gas-phase fragmentation, the [Ln PdR3 ]- anions preferentially underwent a reductive elimination to yield Pd0 species. The sequence of the transmetallation and reductive elimination, thus, constitutes a feasible mechanism for the reduction of the Pd(OAc)2 precatalyst. Other species of interest observed include the PdIV complex [PdBn5 ]- , which did not fragment via a reductive elimination but lost BnH instead.

Comparative Study on Palladium(II) Extraction Using Thioamide-Modified Acyclic and Cyclic Extractants

For extraction from a single Pd(II) solution, 1,1′-bis[(dimethylthiocarbamoyl)oxy]-2,2′-thiobis[4-t-butylbenzene] (1) in a CHCl3 diluent was found to exhibit a higher extractability for Pd(II) ions (E% = 99.9%) in Cl– media (0.1 M) over 30 min as well as a higher extraction efficiency compared to 2,2′-thiobis[4-t-butylphenol] (2) as a starting material of 1 and macrocyclic compounds such as tetrakis[(dimethylthiocarbamoyl)oxy]thiacalix[4]arene (3) and p-tert-butylthiacalix[4]arene (4). Also, various parameters, such as the shaking time, diluents used, concentrations of Pd(II) and 1, effects of HCl, and effects of H+ and Cl– ions, were studied. Extractant 1 could also be used for the selective extraction of Pd(II) ions (E% > 99%) from the leach liquors of automotive catalysts that also contained the ions of Rh, Pd, Pt, Zr, Ce, Ba, Al, La, and Y in Cl– media and was found to be a more efficient extractant than 2 for Pd(II) recovery. In addition, the Pd(II) ions could be stripped from 1 using 0.1 M thiourea ...

Reuseable Monolithic Nanoporous Graphite-Supported Nanocatalysts (Fe, Au, Pt, Pd, Ni, and Rh) from Pyrolysis and Galvanic Transmetalation of Ferrocene-Based Polyamide Aerogels

Polyamide aerogels with ferrocene as a monomer repeat unit were prepared in one step from ferrocene dicarboxylic acid and tris(4-isocyanatophenyl)methane. Pyrolysis at ≥800 °C yielded nanoporous carbons doped throughout with crystallites of α-Fe (about 50 nm in diameter), which in turn were shrouded in graphitic ribbons (<30 graphene layers thick). Transmetalation was carried out with aqueous solutions of Au, Pt, Pd, Rh, and Ni salts, via a path akin to galvanic corrosion, whereas graphitic ribbons separated anodes (α-Fe particles) from cathodes (defects along the ribbons). The new metallic phases formed clusters of smaller crystallites (10–20 nm in diameter) on the graphitic ribbons, leaving behind empty cage-like formations previously occupied by the Fe(0) nanoparticles. All metal-doped carbons were monolithic and over 85% porous. Catalytic activity was demonstrated with the oxidation of benzyl alcohol to benzaldehyde catalyzed with carbon-supported Au or Pt, the reduction of nitrobenzene by hydrazine t...

Sensitive Dopamine Biosensor Based on Polypyrrole-Coated Palladium Silver Nanospherical Composites

We report a facile synthesis of polypyrrole-coated palladium silver nanospherical (PdAg NSPs-PPy) composites via direct reduction of Pd2+ and Ag+ in the presence of pyrrole monomers from an aqueous solution of Pd(CH3COO)2, AgNO3, and NaOH. The nanocomposites were synthesized with different ratios of Pd and Ag (2:1, 1:1, and 1:2). X-ray diffraction shows that the Pd2+ and Ag+ were completely reduced to Pd and Ag, respectively, during the formation of PdAg NSPs-PPy. The modified glassy carbon electrode with the Pd2Ag1 NSPs-PPy demonstrated excellent electrochemical activity toward dopamine oxidation compared with the bare GCE, Pd1Ag1 NSPs-PPy, and Pd1Ag2 NSPs-PPy. From the differential pulse voltammetry results, the estimated limit of detection (S/N = 3) and limit of quantification (S/N = 10) for the linear segment (0.001–200 μM of dopamine) are 0.0258 and 0.0860 μM, respectively.

Effect of surfactant and sonication on Pd(II) adsorption from synthetic electroless plating solutions using commercial activated charcoal adsorbent

This work addresses the evaluation of Pd(II) adsorption characteristics on commercial activated charcoal using synthetic electroless plating solutions with and without cationic surfactant. The experimental investigations involved wider Pd (50–500 mg/L) and surfactant solution concentrations (1–4 CMC). Surface characterization was conducted using Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, laser particle size analysis, scanning electron microscopy and energy dispersive X-ray spectroscopy techniques. It was observed that the Pd(II) adsorption characteristics from synthetic electroless plating solutions were distinct and referred to lower metal uptake and removal efficiency. The presence of CTAB surfactant significantly altered the adsorption characteristics with higher surfactant concentrations providing higher metal uptake and removal efficiency. Both agitation- and sonication-assisted adsorption were deployed to identify the optimal process parameters. The optimal batch adsorption process parameters have been evaluated to be 300 min, 10, 6 g/L, 500 mg/L and 4 CMC for contact time, pH, adsorbent dosage, Pd solution concentration and surfactant solution concentration, respectively. For these conditions, the maximum metal uptake and removal efficiency have been evaluated to be 62.46 mg/g and 93.82%, respectively. Further, it was evaluated that the sorption data fit well with Freundlich isotherm model and pseudo-second-order kinetic model. Also, the evaluated thermodynamic model parameters confirm endothermic nature of adsorption.

Phase Behavior of Poly(vinylidene fluoride)-graft-poly(diethylene glycol methyl ether methacrylate) in Alcohol-Water System: Coexistence of LCST and UCST.

A thermoresponsive polymer poly(diethylene glycol methyl ether methacrylate) (PMeO2MA) is grafted from poly(vinylidene fluoride) (PVDF) backbone by using a combined ATRC and ATRP technique with a high conversion (69%) of the monomer to produce the graft copolymer (PD). It is highly soluble polymer and its solution property is studied by varying polarity in pure solvents (water, methanol, isopropanol) and also in mixed solvents (water-methanol and water-isopropanol) by measuring the hydrodynamic size (Z-average) of the particles by dynamic light scattering (DLS). The variation of Z-average size with temperature of the PD solution (0.2%, w/v) indicates a lower critical solution temperature (LCST)-type phase transition (T(PL)) in aqueous medium, an upper critical solution temperature (UCST)-type phase transition (T(PU)) in isopropanol medium, and no such phase transition for methanol solution. In the mixed solvent (water + isopropanol) at 0-20% (v/v) isopropanol the TPL increases, whereas the T(PU) decreases at 92-100% with isopropanol content. For the mixture 20-90% isopropanol, PD particles having larger sizes (400-750 nm) exhibit neither any break in Z-average size-temperature plot nor any cloudiness, indicating their dispersed swelled state in the medium. In the methanol + water mixture with methanol content of 0-30%, T(PL) increases, and at 40-60% both UCST- and LCST-type phase separations occur simultaneously, but at 70-90% methanol the swelled state of the particles (size 250-375 nm) is noticed. For 50 vol % methanol by varying polymer concentration (0.07-0.2% w/v) we have drawn a quasibinary phase diagram that indicates an approximate inverted hourglass phase diagram where a swelled state exists between two single phase boundary produced from LCST- and UCST-type phase transitions. An attempt is made to understand the phase separation process by temperature-dependent (1)H NMR spectroscopy along with transmission electron microscopy.

Higher Dialysate Matrix Metalloproteinase-2 Levels Are Associated with Peritoneal Membrane Dysfunction.

♦ Peritoneal dialysis (PD) patients develop progressive and cumulative peritoneal injury with longer time spent on PD. The present study aimed to a) describe the trend of peritoneal injury biomarkers, matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-1 (TIMP-1), in incident PD patients, b) to explore the capacity of dialysate MMP-2 to predict peritoneal solute transport rate (PSTR) and peritonitis, and c) to evaluate the influence of neutral pH, low glucose degradation product (GDP) PD solution on these outcomes. ♦ The study included 178 participants from the balANZ trial who had at least 1 stored dialysate sample. Changes in PSTR and peritonitis were primary outcome measures, and the utility of MMP-2 in predicting these outcomes was analyzed using multilevel linear regression and multilevel Poisson regression, respectively. ♦ Significant linear increases in dialysate MMP-2 and TIMP-1 concentrations were observed (p < 0.001), but neither was affected by the type of PD solutions received (MMP-2: p = 0.07; TIMP-1: p = 0.63). An increase in PSTR from baseline was associated with higher levels of MMP-2 (p = 0.02), and the use of standard solutions over longer PD duration (p = 0.001). The risk of peritonitis was independently predicted by higher dialysate MMP-2 levels (incidence rate ratio [IRR] per ng/mL 1.01, 95% confidence interval [CI] 1.005 - 1.02, p = 0.002) and use of standard solutions (Biocompatible solution: IRR 0.45, 95% CI 0.24 - 0.85, p = 0.01). ♦ Dialysate MMP-2 and TIMP-1 concentrations increased with longer PD duration. Higher MMP-2 levels were associated with faster PSTR and future peritonitis risk. Administration of biocompatible solutions exerted no significant effect on dialysate levels of MMP-2 or TIMP-1, but did counteract the increase in PSTR and the risk of peritonitis associated with the use of standard PD solutions. This is the first longitudinal study to examine the clinical utility of MMP-2 as a predictor of patient-level outcomes.

Highly active and durable Pd/Fe2O3 catalysts for wet CO oxidation under ambient conditions

Pd/Fe2O3(FeOOH) catalysts were prepared in different ways: T – traditional incipient wetness impregnation (IWI) from a solution of Pd(NO3)2, D – modification of the support surface by dimethylformamide prior to IWI, and DF – variant D followed by treatment with a HCOONa.

Effects of Pd Nanoparticle Size and Solution Reducer Strength on Pd/C Electrocatalyst Stability in Alkaline Electrolyte

The degradation of two commercial (E-TEK) electrocatalysts, made of palladium nanoparticles supported on Vulcan XC-72 (Pd/C) and differing by their average Pd nanoparticles diameter, was studied in alkaline and acidic solutions. The fate of the electrocatalysts upon accelerated stress test (AST) in 0.1 M NaOH was compared to that in 0.1 M H2SO4. Whereas Pd/C nanoparticles suffer dramatic degradation in 0.1 M H2SO4, electrochemical measurements combined with Identical-Location Transmission Electron Microscopy (ILTEM) demonstrate their higher stability in 0.1 M NaOH at 25°C than reported in the literature for Pt/C electrocatalysts (supported on the same support). As palladium is an efficient anodic material for direct alkaline fuel cells, the stability of Pd/C was investigated in the presence of reducing species in the alkaline electrolyte: alkaline electrolytes containing hydrogen or hydrazine borane yield slightly larger instability for the Pd/C nanoparticles, and the effect is less pronounced for large Pd/C nanoparticles than for small ones.

N-doped ordered mesoporous carbon supported PdCo nanoparticles for the catalytic oxidation of benzyl alcohol

A highly ordered nitrogen doped mesoporous carbon was prepared by passing acetonitrile as carbon and nitrogen source over a mesoporous SBA-15 silica template at 900 °C by using a CVD bubbling method. The silica template was removed by etching with HF, followed by filtration, washing and functionalization with HNO3 to give N-CMK-3 (N = 11.3 wt%). This material exhibited good mesostructural ordering (XRD analysis), a high surface area (885 m2/g) and a large pore volume (1.70 cm3/g). Addition of a monodispersed colloidal solution of PdCo (d = 3.3 nm), Pd (4.2 nm) or Co (10.5 nm) nanoparticles to N-CMK-3 as support gave highly uniform and well dispersed nano-sized Pd, PdCo and Co nanoparticle supported catalysts. The synthesized catalysts were activated with H2 (5%)/Ar at 400 °C to remove capping agents. These activated PdCo, Pd and Co/N-CMK-3 catalysts were tested for benzyl alcohol oxidation under solvent free conditions using oxygen as an oxidant at different temperatures (110–140 °C) and times (1–8 h) and compared with an equivalent carbon (Vulcan XC-72) supported catalyst. In the aerobic oxidation of alcohols, the PdCo/N-CMK-3 showed similar activity to the Pd/N-CMK-3 catalyst but only using 50% of the amount of Pd in a PdCo catalyst. An important role of Co is to reduce the bulk Pd content of the catalyst. This can be explained by a core-shell structure for the PdCo catalyst. The catalytic oxidation of a range of benzyl alcohols (no solvent, O2 as oxidant, 130 °C) in the presence of PdCo/N-CMK-3 typically gave aldehydes with conversions in the range 87–99% (selectivity 99%) after 5 h. The catalyst also retained its selectivity and activity after four recycles.

Understanding the Solution and Solid-State Structures of Pd and Pt PSiP Pincer-Supported Hydrides.

The PSiP pincer-supported complex ((Cy)PSiP)PdH [(Cy)PSiP = Si(Me)(2-PCy2-C6H4)2] has been implicated as a crucial intermediate in carboxylation of both allenes and boranes. At this stage, however, there is uncertainty regarding the exact structure of ((Cy)PSiP)PdH, especially in solution. Previously, both a Pd(II) structure with a terminal Pd hydride and a Pd(0) structure featuring an η(2)-silane have been proposed. In this contribution, a range of techniques were used to establish that ((Cy)PSiP)PdH and the related Pt species, ((Cy)PSiP)PtH, are true M(II) hydrides in both the solid state and solution. The single-crystal X-ray structures of ((Cy)PSiP)MH (M = Pd and Pt) and the related species ((iPr)PSiP)PdH [(iPr)PSiP = Si(Me)(2-P(i)Pr2-C6H4)2] are in agreement with the presence of a terminal metal hydride, and the exact geometry of ((Cy)PSiP)PtH was confirmed using neutron diffraction. The (1)H and (29)Si{(1)H}NMR chemical shifts of ((Cy)PSiP)MH (M = Pd and Pt) are consistent with a structure containing a terminal hydride, especially when compared to the chemical shifts of related pincer-supported complexes. In fact, in this work, two general trends relating to the (1)H NMR chemical shifts of group 10 pincer-supported terminal hydrides were elucidated: (i) the hydride shift moves downfield from Ni to Pd to Pt and (ii) the hydride shift moves downfield with more trans-influencing pincer central donors. DFT calculations indicate that structures containing a M(II) hydride are lower in energy than the corresponding η(2)-silane isomers. Furthermore, the calculated NMR chemical shifts of the M(II) hydrides using a relativistic four-component methodology incorporating all significant scalar and spin-orbit corrections are consistent with those observed experimentally. Finally, in situ X-ray absorption spectroscopy (XAS) was used to provide further support that ((Cy)PSiP)MH exist as M(II) hydrides in solution.

33 Years of Peritoneal Dialysis-Associated Peritonitis: A Single-Center Study in Japan.

Peritoneal dialysis-associated peritonitis (PD-associated peritonitis) could influence the outcome of PD patients, including technique survival. Although the use of the twin-bag system has decreased the incidence of peritonitis, the effects of biocompatible PD solutions are controversial. Additionally, since both infection-causing microorganisms and antimicrobial therapies have changed over time, the duration of treatment of peritonitis (the duration of peritonitis) seems to have changed. The study included 527 patients who received PD between January 1980 and December 2012 at a single center. We divided patients undergoing PD into three groups according to the type of PD system used, namely single-bag and conventional PD solutions (S+C group, N = 145), twin-bag and conventional PD solutions (T+C group, N = 171) and twin-bag and biocompatible PD solutions (T+B group, N = 211), and analyzed PD-associated peritonitis incidences. Incidences of PD-associated peritonitis (times per patient-months) and peritonitis-free time were 1/59.4, 1/70.6 and 1/103.1, and 52, 97, and 100 months for the S+C, T+C and T+B groups, respectively. The duration of peritonitis, has thus, become dramatically shorter in recent years. Streptococcus sp. were associated with shortest and fungi with longest durations of peritonitis. Staphylococcus sp. and Pseudomonas aeruginosa were predominant in the S+C group. The twin-bag system has made a greater contribution to reductions in PD-associated peritonitis than biocompatible PD solutions. Furthermore, changes in microorganisms, antimicrobial therapies, patient education and improved PD system devices have presumably affected the reduction in the duration of peritonitis.

Selective reduction of nitrate into nitrogen using Fe–Pd bimetallic nanoparticle supported on chelating resin at near-neutral pH

Nano zero valent iron (nZVI) has emerged as a promising water treatment technology for reduction of contaminants. Unfortunately, for nitrate reduction by nZVI, near 100% of nitrate was converted to undesired ammonia (NH3) and not to nontoxic nitrogen (N2). In this study, supported bimetallic Fe–Pd nanoparticles were prepared by loading Fe and Pd on chelating resin (DOW 3N) by two different methods. The effect of the preparation method, solution pH and Pd loading on the reactivity and selectivity of Fe–Pd composites for nitrate removal was investigated at near-neutral pH in unbuffered solution. The results suggest that DOW 3N-Fe/Pd, which was prepared by loading Pd firstly and then Fe on DOW 3N, showed a remarkable nitrate removal (>95%). The selectivity to N2 was increased with the increase of Pd content and solution pH; the N2 selectivity of 69.2% was obtained at pH 6.75 using DOW 3N-Fe/Pd with 8wt.% Pd–8wt.% Fe. The high selectivity to N2 benefited from the closer contact distance between Pd and Fe on the surface of DOW 3N-Fe/Pd and low intraparticle diffusion resistance.

Mineral Chemistry of (Pt,Pd)-Bismuthotelluride Minerals In the Platreef At Zwartfontein, Akanani Project, Northern Bushveld Complex, South Africa

The (Pt,Pd)-bismuthotelluride minerals at the Akanani prospect show substantial substitution of Te and Bi. Individual grains are often markedly heterogeneous with concentrations of Te and Bi which vary by up to 26 wt.%. They occur as single phase crystals or form composite grains with other platinum-group minerals, and are predominantly associated with ( i.e. , are in direct contact with) primary and secondary silicate minerals, base-metal sulfides, and magnetite. The Pt-bismuthotelluride minerals are markedly associated with ( i.e. , tends to occur as composite grains with) Pd-bismuthotelluride minerals, isoferroplatinum, and sperrylite. The Pd-bismuthotelluride minerals are markedly associated with Pt-bismuthotelluride minerals, altaite, hollingworthite, plumbopalladinite, PdSbSn alloy, and sperrylite. The Pt-bismuthotelluride minerals are characterized by high ratios of Te/Bi and form a trend of solid solution from moncheite (PtTe2) towards maslovite (PtTeBi). A few analyses plot close to, or on, the composition of maslovite. The Pd-bismuthotelluride minerals are characterized by a lower ratio of Te/Bi than the Pt-bismuthotelluride minerals. They form a trend of solid solution along the join kotulskite (PdTe)–sobolevskite (PdBi), without merenskyite (PdTe2). There is very limited solid solution of Pt and Pd between the Pt-bismuthotelluride minerals (<5.7 wt.% Pd) and the Pd-bismuthotelluride minerals (<3.3 wt.% Pt), with only four analyses of michenerite (three grains) characterized by elevated levels of Pd (10.3 to 17.1 wt.%). In view of the strong spatial association between the Pt- and Pd-bismuthotelluride minerals at Akanani it is considered likely that the latter were originally in solid solution in a precursor Pd-rich Pt-bismuthotelluride host at temperatures of up to 1150 °C, from which they then exsolved during cooling. Further exsolution of Te- or Bi-rich domains in individual Pt- and Pd-bismuthotelluride crystals occurred during late cooling at substantially lower temperatures, and resulted in the observed compositional ranges of moncheite–maslovite and kotulskite–sobolevskite.