A facile and novel process for the preparation of <Superscript>147</Superscript>Pm source

Aiming the selective recovery of palladium from high level radioactive liquid waste (HLW), a chelating thiamide type sorbent, CWP–TU, was prepared by the modification of Japanese cedar wood powder (CWP). Convection oven and microwave heating were separately used for modification purpose and found that microwave heating is more effective over oven heating. CWP–TU was extensively studied for the adsorption of Pd(II) from nitric acid medium. The batch test showed that nitric acid concentration of 3 M or higher is favorable for Pd(II) loading. Consistent adsorption of Pd(II) under gamma irradiation condition demonstrated the feasibility of using CWP–TU in real HLW. Also, Pd(II) only adsorption from simulated HLW solution verified the palladium only selectivity of the sorbent as well as the lack of influence of coexisting metal ions on its affinity toward Pd(II). CWP–TU holds maximum Pd(II) loading capacities of 0.98 mol/kg at 30 °C and 1.04 mol/kg under gamma irradiation. A comparative study using some ion exchange resins revealed that the resins are either ineffective in nitrate medium or lack stability under irradiation.     

Preconcentration procedure trace amounts of palladium using modified multiwalled carbon nanotubes sorbent prior to flame atomic absorption spectrometry: 1st Nano Update

A method for preconcentration of palladium at trace level on modified multiwalled carbon nanotubes columns and determination by flame atomic absorption spectrometry (FAAS) has been developed. Multiwalled carbon nanotubes (MWCNTs) were oxidized with concentrated HNO₃ and the oxidized multiwalled carbon nanotubes were modified with 5-(4′-dimethylamino benzyliden)-rhodanine, and then were used as a solid sorbent for preconcentration of Pd(II) ions. Factors influencing sorption and desorption of Pd(II) ions were investigated. The sorption of Pd(II) ions was quantitative in the pH range of 1.0–4.5, whereas quantitative desorption occurs with 3.0 mL 0.4 mol L^?1 thiourea. The amount of eluted palladium was measured using flame atomic absorption spectrometry. The effects of experimental parameters, including sample flow rate, eluent flow rate, and eluent concentration were investigated. The effect of coexisting ions showed no interference from most ions tested. The proposed method permitted a large enrichment factor (about 200). The relative standard deviation of the method was ±2.73% (for eight replicate determination of 2.0 μg mL^?1 of Pd(II)) and the limit of detection was 0.3 ng mL^?1. The method was applied to the determination of Pd(II) in water, road dust, and standard samples.     

A new aspect of Heck catalyst formation

Abstract  

The mechanism of the formation of the active Pd(0) complex from trans-dichlorobis(diethanolamine-N)palladium(II) complex in the presence of strong base was investigated by using density functional theory (M06 method). Our investigation shows that in the basic environment trans-dichlorobis(diethanolamine-N)palladium(II) complex undergoes abstraction of the alcoholic proton, and coordination of alkoxide oxygen to palladium. The intermediate complex, in which hydrogen is coordinated to Pd, undergoes reductive elimination of HCl, yielding the catalytically active low ligated Pd(0) complex.     

Potassium iron(III)hexacyanoferrate(II) supported on polymethylmethacrylate ion-exchanger for removal of strontium(II)

Potassium iron(III)hexacyanoferrate(II) supported on poly metylmethacrylate has been synthesized and investigated for the strontium(II) removal from HNO₃ and HCl solutions. The ion exchange material characterized by different techniques and found to be stable in 1.0–4.0 M HNO₃ solutions, has been used to elaborate different parameters related to ion exchange and sorption processes involved. The data collected suggested its use to undertake removal of Sr(II) from more acidic active waste solutions. Thus the material synthesized had been adjudged to present better chances of application for Sr(II) removal as compared to other such materials.     

Sorption-spectrometric determination of palladium and gold using silica chemically modified with dipropyl disulfide groups

It has been found that silica chemically modified with dipropyl disulfide groups (DPDSS) quantitatively extracts palladium(II) from solutions in the acidity range from 4 M HCl to pH 4 and gold(III) in the range from 1 M HCl to pH 2 with a partition coefficient at the level of n × 10⁴ cm³/g. The adsorption of palladium(II) and gold(III) at room temperature is highly selective, whereas non-ferrous and other platinum metals are not adsorbed. Sorption-atomic absorption, sorption-ICP-atomic emission, and sorption-photometric methods for the determination of palladium and gold have been developed using DPDSS. The accuracy of the methods was tested by the analysis of certified reference samples.     

Influence of Pd precursors on the catalytic performance of Pd–H4SiW12O40/SiO2 in the direct oxidation of ethylene to acetic acid

The effects of palladium precursors (PdCl₂, (NH₄)₂PdCl₄, Pd(NH₃)₂Cl₂, Pd(NO₃)₂ and Pd(CH₃COO)₂) on the catalytic properties in the selective oxidation of ethylene to acetic acid have been investigated for 1.0 wt% Pd–30 wt% H₄SiW₁₂O₄₀/SiO₂. The structures of the catalysts were characterized using X-ray diffraction, N₂ adsorption, H₂-pulse chemical adsorption, infrared spectrometry of the adsorbed pyridine, H₂ temperature-programmed reduction and X-ray photoelectron spectroscopy. The present study demonstrates that the different palladium precursors can lead to the significant changes in the dispersion of palladium. It is found that Pd dispersion decreases as follows: PdCl₂ > (NH₄)₂PdCl₄ > Pd(NO₃)₂ > Pd(NH₃)₂Cl₂ > Pd(C₂H₃O₂)₂, which is nearly identical to the catalytic activity. This indicates that the dispersion of palladium plays an important role in the catalytic activity. Furthermore, density of Lewis (L) and Brönsted (B) acid sites are also strongly dependent on the palladium precursors. It is also demonstrated that an effective catalyst should possess a well combination of Brönsted acid sites with dispersion of palladium.     

Extraction of palladium from nitrate solution by triphenylphosphine or triphenylphospine oxide in chloroform

It is found that from aqueous nitric acid media, Pd is highly extracted by chloroform solutions containing triphenylphosphine (Ph₃P) and not extracted by triphenylphosphine oxide (Ph₃PO) diluted with chloroform. The effect of diluent, nitric acid molarities, Ph₃P concentration and temperature on palladium extraction by Ph₃P was investigated. Slope analysis of the experimental results indicated that the main extracted species is in the form of Pd(NO₃)₂·2Ph₃P.IR spectrum analysis of the extracted complex indicated the direct extraction of palladium as nitrate and bonding to phosphorus. Extraction of some fission product radionuclides from 2M HNO₃ showed the selective extraction of palladium by Ph₃P in chloroform.     

Comparative study of dye-sensitized solar cell utilizing selenium and palladium cathode

This work is concerned with the comparative study of dye-sensitized solar cell (DSSC) utilizing selenium (Se) and palladium (Pd) cathode. The influence of concentration of selenium dioxide (SeO₂) and palladium chloride (PdCl₂) on the performance of the device has been investigated. The Se and Pd cathode have been prepared via dip coating-based multilayer deposition technique. The device using Se cathode with seven layers possesses the highest performance in term of short-circuit current density (J_sc). The photovoltaic measurement results show that the device utilizing Pd cathode demonstrates higher power conversion efficiency (η) compared with that of the device using Se cathode. The highest η of the device with Se and Pd cathode are 0.071 and 0.169%, obtained at the 0.5 ?M SeO₂ and 0.60 ?M PdCl₂, respectively. The Pd cathode-based device prepared with 0.60 ?M PdCl₂ owns the highest η due to the lowest sheet resistance (R_s). These photovoltaic results imply single material has potential to be modified into binary or ternary cathode material in order to improve the performance of DSSC.     

Evaluation of unsymmetrical dithiodiglycolamide as novel extractant for application in selective separation of palladium(II) from aqueous solutions

A novel unsymmetrical multidentate ligand namely; N,N'-dimetyl-N,N'-didecyldithiodiglycolamide (DMD³TDGA) was synthesized and used as agent for the selective extraction of palladium(II) from hydrochloric acid solutions. A systematic investigation was carried out on the extraction of Pd(II) using DMD³TDGA. The quantitative extraction of Pd(II) with DMD³TDGA in n-dodecane is observed at ~4 M HCl. The main extracted species of Pd(II) is PdC_l2. DMD³TDGA and IR spectra of the extracted species were investigated. The extraction of palladium(II) from various concentrations of hydrochloric acid solutions in the presence of metal ions, such as Pt(IV), Rh(III), Cr(II), Ni(II), Fe(III), Nd(III), Zr(II), and Mn(II) was carried. DMD³TDGA showed very high selectivity and extractability for Pd(II). Quantitative back extraction of Pd(II) was obtained in single contact using thiourea solution. The results obtained indicated that, excellent separation of Pd(II) from the investigated metal ions can be achieved. Five successive cycles of extraction/back-extraction, indicating excellent stability and re-utilization of this new extractant can be used for selective separation of Pd(II) from other elements in hydrochloric acid medium.     

Effect the conditions of the acid–thermal modification of clinoptilolite have on the catalytic properties of palladium–copper complexes anchored on it in the reaction of carbon monoxide oxidation

The dependence of the physicochemical and structural–adsorption properties of natural and acid–thermal modified clinoptilolite, and of Pd(II)–Cu(II) catalysts based on them, on the duration of acid–thermal modification is investigated. The samples under study are described via XRD and thermal gravimetric (DTG and DTA) analysis, IR, DR UV–Vis, EPR spectroscopy, and water vapor adsorption. Values of both the specific surface area (S_sp) and pH of aqueous suspensions are determined. The resulting catalysts are tested in the reaction of low-temperature carbon monoxide oxidation with air oxygen. A conclusion is drawn about the nature of surface bimetallic Pd(II)–Cu(II) complexes. The greatest catalytic activity is shown by complexes based on clinoptilolite and modified with 3 M HNO₃ for 0.5 and 1 h.     

Preconcentration and voltammetric determination of palladium (II) at sodium humate modified carbon paste electrodes

A chemically modified carbon paste electrode was prepared by incorporating appropriate amounts of sodium humate(NaA). Palladium(II) was selectively accumulated in a solution of Britton-Robinson(B-R) buffer (pH 2.8) onto the electrode surface in open circuit mode. The subsequent electrochemical measurement was carried out by cyclic voltammetry (CV) and linear sweep anodic stripping voltammetry (LSASV) in a supporting electrolyte of 1.0 M HCl. The obtained oxidation currents (I_pa1 and L_pa2) were proportional to the Pd(II) concentration in the range of 4.7 × 10^–6 - 9.4 × 10^–8 M. The developed method was applied to the quantitative determination of palladium in real samples. Received: 6 March 1998 / Revised: 3 June 1998 / Accepted: 3 July 1998     

Structural studies on some antimonate exchangers

The possibility of simultaneous extraction of palladium and technetium from nitrate solutions was investigated using tri-n-octylamine (TOA) solutions in carbon tetrachloride as a heavy, non-flammable diluent. Conditions of technetium extraction being essentially known, the main attention was focussed on the extraction of palladium which was studied in dependence on the concentration of nitric acid, salts (nitrates, chlorides, nitrites), urea and palladium. A strong decrease of Pd extraction with 10% TOA in CCl₄ has been found above a palladium concentration of 10⁻⁴M but in the presence of chlorides and nitrites a satisfactory high distribution can be preserved. Both Tc and Pd extracted with TOA/CCl₄ can be stripped into dilute ammoniacal solutions. An extraction procedure for the simultaneous isolation of Pd (80% yield) and Tc (99%) from fission product waste solutions (0.20 g Tc and 0.17 g Pd/dm³ 0.5–1.0M HNO₃) is proposed.     

Modification of a novel macroporous silica-based crown ether impregnated polymeric composite with 1-dodecanol and its adsorption for some fission and non-fission products contained in high level liquid waste

A novel macroporous silica-based chelating polymeric composite, DtDo/SiO₂-P, was synthesized by molecular modification of 4,4′,(5′)-di-(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6) with a long carbon chain organic compound 1-dodecanol. It was performed through impregnation and immobilization of DtBuCH18C6 and 1-dodecanol molecules into the pores of the SiO₂-P particles. The adsorption of a few fission and non-fission product elements Sr(II), Ba(II), Cs(I), Ru(III), Mo(VI), Na(I), K(I), Pd(II), La(III), and Y(III) onto DtDo/SiO₂-P was investigated at 323 K. The effects of contact time and the HNO₃ concentration in a range of 0.1-4.0 M were investigated. It was found that at the optimum concentration of 2.0 M HNO₃, DtDo/SiO₂-P exhibited strong adsorption ability and excellent selectivity for Sr(II) over all of the tested elements, which showed very weak or almost no adsorption except Ba(II). The bleeding of total organic carbon (TOC) from DtDo/SiO₂-P was evaluated. The quantity of TOC in aqueous phase increased with an increase in HNO₃ concentration in terms of a linear equation [TOC] = 35.82[HNO₃] + 115.5 with a correlation coefficient of 0.9751. The TOC content leaked from DtDo/SiO₂-P modified by 1-dodecanol, 119.0-269.3 ppm, in the range of 1.0-4.0 M HNO₃ was significantly lower than that of 424.8-634.6 ppm in the case without modification. It resulted from the intermolecular interaction force of DtBuCH18C6 and 1-dodecanol through hydrogen bonding. The reduction of DtBuCH18C6 leakage by molecular modification was achieved. It is of great benefit to application of DtDo/SiO₂-P in partitioning of Sr(II), one of the main heat generators, from high level liquid waste (HLLW) in reprocessing process of nuclear spent fuel in MAREC (Minor Actinides Recovery from HLLW by Extraction Chromatography) process developed.     

Application of Metalfix Chelamine prior to the determination of noble metals by the inductively coupled plasma atomic emission spectrometry

Metalfix Chelamine chelating resins of two different bead sizes (150-300 and 40-80 μm) were examined and compared regarding their application for sorption of Au, Ir, Pd, Pt, Rh and Ru ions from medium of HCl, HNO₃ and mixtures of HCl and HNO₃. The quantitative enrichment of Au, Ir, Pd and Pt was established for the resin of 150-300 μm particle size and for solutions acidified with HCl and HNO₃ (3:1) up to the concentration of 0.50 mol l⁻¹. In the case of Rh and Ru, the uptake of these metals by the resin was lower than 50%. For the elution, solutions of different reagents, i.e. HCl, HNO₃, KCN, KI, KSCN and (NH₂)₂CS, were studied with respect to the complete release of the analytes retained by the resin. In addition, influence of various base metals, i.e. Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn, on the retention of the noble metals was investigated. Under the selected conditions for the retention and elution of Au, Ir, Pd and Pt, the analytical performance of the proposed pre-concentration procedure was evaluated and it was applied to the determination of these noble metals in anodic sludge sample.     

Properties of nitric acid palladium solutions with a high metal concentration

Nitric acid solutions (c _Pd up to 3.2 M) with variable HNO₃ concentration were studied by electronic spectroscopy, ¹⁴N and ¹⁷O NMR, acid-base titration, gravimetry, and other methods. Solid phases that precipitated on storing these solutions were studied by X-ray phase analysis, thermogravimetry, and IR spectroscopy. The conditions for stability of particular Pd(II) species were determined, and specific features of aging of such highly concentrated palladium solutions were revealed. A procedure for palladium isolation as [Pd(NH₃)₄](NO₃)₂ from nitric acid solutions in 98% yield was developed.     

Electronic absorption spectra of palladium(II) in concentrated nitric acid solutions

Palladium complexation in concentrated nitric acid solutions was studied by UV/Vis absorption spectrophotometry. The ionic strength of the solutions was fixed to I = 1, 3, or 5 mol dm⁻³ (M) by mixing of HNO₃ and HClO₄. The major palladium species were found to be Pd²⁺, PdNO₃ ⁺, and Pd(NO₃)₂. The formation constant of PdNO₃ ⁺ was determined to be β ₁ = 1.32 (I = 1 M), 1.49 (I = 3 M), or 1.47 (I = 5 M), while that of Pd(NO₃)₂ to be β ₂ = 0.45 (I = 3 M) or 0.14 (I = 5 M).     

Date pits waste as a solid phase extraction sorbent for the analysis of lead in wastewater and for use in manufacturing brick: An eco-friendly waste management approach

Lead (Pb(II)), an extremely hazardous heavy metal that has been shown to have detrimental effects on both the environment and humans, mostly gets into the ecosystem through industrial activities. In this work, a new solid-phase extraction (SPE) based on treated date pits bio-sorbent and iCAP Q inductively-coupled plasma mass spectrometry (iCAP Q ICP/MS) method has been optimized for the trace determination of Pb(II) in various industrial wastewater effluents. A cost-effective biomass material was prepared from date pits (DP), and chemically modified with H₂O₂ and successively used as SPE bio-sorbent for Pb(II) extraction. Extracting solutions for instance H₂SO₄, HNO₃ and HCl at various concentrations (1–5 mM) were optimized, and best extraction of Pb(II) was obtained by HCl (1 mM). The optimized SPE and iCAP Q ICP/MS method has offered excellent validation conditions in terms of coefficient of determination (CoD, R² > 0.999), detection limit (DL, 0.011 µg/L), quantification limit (QL, 0.034 µg/L), and run-to-run and day-to-day precision (RSD < 6 %). The optimized procedure was practically applied in the determination of Pb(II) in industrial wastewater comprising iron and steel, textile, printing and battery industries. Among the analyzed samples, the battery industry produced higher amounts of Pb(II) (18.55 µg/L) followed by iron and steel (14.65 µg/L), petroleum (12.38 µg/L) printing (5.78 µg/L) and textile (3.76 µg/L) industries. The recovery values were achieved between 95 % and 99 %. The obtained results have established the appropriateness of the offered technique as a new useful method for the routine examination of Pb(II) in industrial wastes. In addition, the current method could be expansively used in the proficient removal and identification of other heavy metals contaminants from similar matrices. Further, the metal ions saturated bio-sorbents were used in the preparations of bricks and it was found to be a successful approach for heavy metals and agricultural waste management.     

Palladium(II) extraction with 1-{[2-(2,4-Dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]-methyl}-1H-1,2,4-triazole from nitric acid solutions

Palladium(II) extraction from nitric acid solutions with 1-{[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]-methyl}-1H-1,2,4-triazole in toluene is studied. The reagent efficiently extracts palladium(II) from 0.2–6 M HNO₃ by a coordination mechanism yielding the complex Pd₂(NO₃)₄ S ₃ in the organic phase. The reagent can be used for selective separation of palladium(II) from nickel(II), copper(II), and iron(III) in the specified aqueous phase acidity range.     

Selective extraction of platinum,iridium, and palladium with macrocyclic endo-receptors from hydrochloric acid solutions

Extraction of Pt, Ir, Pd by the macrocyclic polyethers dibenzo-18-crown-6 (DB18C6) and cis-syncis-dicyclohexyl-18-crown-6 (DCH18C6, isomer A) in organic solvents (chloroform, dichloroethane) from 3–10 M aqueous HCl was studied. It was found that DCH18C6 in dichloroethane excellently extracted Pt, Ir, and Pd in the presence of KSCN. Re-extraction of Pt, Ir, and Pd from the organic phase can be fulfilled by 1 M HNO₃. Thus, the macrocyclic polyethers are effective reagents for isolation of Pt, Ir, and Pd from HCl solutions.     

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⁻.