Uptake Of Palladium Research Articles

Styrene divinyl benzene beads (SM-2) functionalized with triisobutylphosphine sulfide for selective uptake of palladium(II) from nitric acid medium

Resins impregnated with organic extractants regarded as effective adsorbent materials due to their ability for selective sorption. These resins consist of a polymeric material that is infused with accessible organic extractants. Furthermore, these resins merge the unique properties and the distinctive characteristics of both liquid-liquid extraction and solid-liquid sorption processes. In this work, the impregnation of Styrene divinyl benzene beads (SM-2 beads) with triisobutylphosphine sulfide (TIBPS = CYANEX 471X) was prepared. A SM-2 bead functionalized with CYANEX 471X (SM-2-TIBPS beads) was characterized using scanning electron microscope (SEM) and Fourier-transform infrared spectroscopy (FT-IR) techniques and investigated for recovery and separation of palladium ions from a 3 M nitric acid solution. Various parameters were studied, as shaking time effect, nitric acid concentration, SM-2-TIBPS beads weight, Pd(II) concentration and temperature. The Pd(II)/SM-2-TIBPS sorption system has an endothermic nature and was fitted with a Langmuir isotherm model with a 0.9860 regression factor. The kinetics modeling was fitted with PSO and IPD models with regression factors of 0.9889 and 0.9959, respectively. The maximum monolayer sorption capacity of SM-2-TIBPS was found to be 17.47 ± 0.9 mg/g. The sorption of Pd(II) from different media at 3 M takes the following sequence: HNO3 > HCl > H2SO4. Desorption of about 76.38 ± 2.4% was achieved with (1 M + 1 M) of thiourea + HCl after one desorption stage. Effect of other interfering ions, as Pt(II), Pb(II), Eu(III), Cu(II), Mo(VI), Co(III), Zr(IV), Fe(III), Cd(II), and Ce(III), indicates high separation factors between Pd(II) and other investigated metal ions, which ranged from 9.4 to 35.

Silicone Alleviates Palladium Toxicity by Modifying Palladium Uptake, Ascorbate–Glutathione Cycle, and Glyoxalase System in Maize Seedlings

Silicone Alleviates Palladium Toxicity by Modifying Palladium Uptake, Ascorbate–Glutathione Cycle, and Glyoxalase System in Maize Seedlings

Selective extraction of Pd(II) using 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra[(2-ethylthio)ethoxy]thiocalix[4]arene as extractant

In this study, a novel method for selective recovery of palladium from chloride systems has been proposed based on supramolecular chemistry. 5,11,17,23-Tetra-tert-butyl-25,26,27,28-tetra[(2-ethylthio)ethoxy]thiocalix[4]arene (TTCA), which is expected to have excellent complexation ability to Pd(Ⅱ) was synthesized and further used as the extractant for palladium uptake from the aqueous phase. The effects of various conditions on the complexation process between TTCA and Pd(II) were systematically investigated through liquid-liquid extraction experiments. The Pd(II) extraction efficiency of up to over 99 % was reached at Cl- concentration of 0.1 mol/L, TTCA/Pd(II) mole ratio of 3:1, and reaction time of 2.0 h. The remaining palladium in the aqueous phase after extraction was below 0.1 ppm. The results of Job’s method and 1H NMR titration showed that TTCA and Pd(II) were mainly complexed in 2:3 during the extraction process. TTCA showed good selectivity toward Pd(II) in the presence of completing ions. Particularly for the most competing element of platinum, the Pd-Pt separation coefficient reached 4 × 104 level. Moreover, palladium can be effectively stripped from the loaded organic phase by ammonia. The extraction efficiency of Pd(II) maintained at a high level of around 96 % after five extraction-stripping cycles, indicating the excellent reusability of TTCA in Pd(II) extraction from chloride systems.

Palladium-scavenging self-assembled hybrid hydrogels - reusable highly-active green catalysts for Suzuki-Miyaura cross-coupling reactions.

A hybrid hydrogel based on 1,3:2,4-dibenzylidene sorbitol (DBS) modified with acyl hydrazides combined with agarose was used for in situ reduction and binding of palladium from aqueous mixtures without the need for an external reducing agent. Palladium uptake was monitored and the formation of Pd nanoparticles (PdNPs) trapped within the gel and located close to the nanofibres was confirmed. This gel effectively scavenges palladium from solution to concentrations < 0.04 ppm - well below the recommended limits for pharmaceutical products. The resulting hybrid hydrogel with embedded PdNPs was used as a catalyst for Suzuki-Miyaura cross-coupling reactions. The gel network stabilises PdNPs, preventing aggregation/leaching and giving excellent catalytic lifetimes. The gel acts as a simple reaction dosing form, being simply added to reactions performed in green solvents in air. Once reactions are complete, the gel can be simply removed, recycled and reused (>10 times). Reactions were purified by simple washing protocols, and leaching of Pd from the gels is limited (<1 ppm). The gels were also used in flow-through mode, giving efficient, rapid reactions, with easy work-up. These catalytic gels combine advantages of homogeneous and heterogeneous catalysts - they are solvent compatible with the reaction taking place in a solution-like environment, while the solid-like gel network enables catalyst recycling. In summary, these hydrogels scavenge 'waste' palladium and convert it into gel 'wealth' capable of efficient, environmentally-friendly Suzuki-Miyaura catalysis.

Mechanism of palladium(ii) biosorption by Providencia vermicola

Palladium uptake process, multi-scale visualization and functional groups ofProvidencia vermicolabiomass in palladium biosorption were analyzed for the first time.

Minor Actinides Partitioning: Uptake of Palladium with Triazine-Containing Adsorbent under the Framework of SPMP Process

To remove Pd(II), a new triazine-containing silica adsorbent, BisDiOTP@SiO2–P, was prepared. The synthesis was achieved by impregnation in situ and immobilization of a multinitrogen ligand, BisDiOTP, into the pores of the SiO2–P support. The uptake of typical metals Sr(II), Pd(II), Li(I), Na(I), Cs(I), K(I), Rb(I), and Ba(II) onto BisDiOTP@SiO2–P was investigated. The effects of contact time and HNO3 concentration from 0.4 to 5.0 M were studied. The strong uptake ability and selectivity of BisDiOTP@SiO2–P for Pd(II) was indicated by six cycles of the batch uptake and desorption. The removal efficiency was always more than 99.2% for Pd(II) and less than 0.15% for others. In light of the results of batch experiments, the removal of Pd(II) from a simulated 1.0 M HNO3 was performed using BisDiOTP@SiO2–P as a stationary phase by extraction chromatography. Pd(II) adsorbed by BisDiOTP@SiO2–P was effectively desorbed with 0.2 M thiourea. An efficient removal of Pd(II) by BisDiOTP@SiO2–P was achieved. Some valuabl...

Dithiodiglycolamide impregnated XAD-16 beads for separation and recovery of palladium from acidic waste

N,N,N’,N’-Tetra-(2-ethylhexyl)-dithiodiglycolamide were impregnated onto XAD-16 resin and evaluated for the sorption of palladium from acidic medium. The sorption kinetics for Pd on the resin was fast, equilibrium was attained within 60–90min. The pseudo-first order kinetics model closely matches with the experimental data of sorption kinetics. The sorbed palladium can be eluted using 0.01M thiourea in 0.1M HNO3 solutions. Freundlich sorption isotherm model fit well with the isothermal sorption data with maximum sorption capacity of ≈29mg/g. Sorption studies with simulated HLW solution have shown high uptake of palladium and very small co-extraction of lanthanides.

A Study on the Utilization of Magnetite for the Recovery of Platinum Group Metals from Chloride Solution

ABSTRACTThe recovery of platinum group metals (PGMs) from chloride solution using magnetite was investigated. The adsorption of platinum, palladium, and rhodium in chloride medium onto synthetic magnetite powders were studied at different pH conditions, contact time, sodium chloride concentrations, and initial Pt, Rh, and Pd concentrations. Platinum and palladium uptake by magnetite was at a maximum at pH 6–7, and pH 3–4 for rhodium after 24 h with 0.1 mol/dm3 sodium chloride at an initial PGM concentration of 0.05 mol/m3. A sorption mechanism for PGMs was discussed based on the results.

Palladium uptake by Pisum sativum: partitioning and effects on growth and reproduction.

Environmental palladium levels are increasing because of anthropogenic activities. The considerable mobility of the metal, due to solubilisation phenomena, and its known bioavailability may indicate interactions with higher organisms. The aim of the study was to determine the Pd uptake and distribution in the various organs of the higher plant Pisum sativum and the metal-induced effects on its growth and reproduction. P. sativum was grown in vermiculite with a modified Hoagland's solution of nutrients in the presence of Pd at concentrations ranging 0.10-25 mg/L. After 8-10 weeks in a controlled environment room, plants were harvested and dissected to isolate the roots, stems, leaves, pods and peas. The samples were analysed for Pd content using AAS and SEM-EDX. P. sativum absorbed Pd, supplied as K₂PdCl₄, beginning at seed germination and continuing throughout its life. Minimal doses (0.10-1.0 mg Pd/L) severely inhibited pea reproductive processes while showing a peculiar hormetic effect on root development. Pd concentrations ≥1 mg/L induced developmental delay, with late growth resumption, increased leaf biomass (up to 25%) and a 15-20% reduction of root mass. Unsuccessful repeated blossoming efforts led to misshapen pods and no seed production. Photosynthesis was also disrupted. The absorbed Pd (ca. 0.5 % of the supplied metal) was primarily fixed in the root, specifically in the cortex, reaching concentrations up to 200 μg/g. The metal moved through the stem (up to 1 μg/g) to the leaves (2 μg/g) and pods (0.3 μg/g). The presence of Pd in the pea fruits, together with established evidence of environmental Pd accumulation and bioavailability, suggests possible contamination of food plants and propagation in the food chain and must be the cause for concern.

Uptake of Palladium Using Liquid Emulsion Membrane Technique

The waste stream generated at the reprocessing facility (first cycle raffinate-Hi level waste) contains Palladium as one of the fission products. The recovery of Palladium from the waste stream reduces the activity burden and lends its use for catalytic applications. This paper deals with its recovery from the waste stream generated at various stages of nuclear fuel cycle using liquid emulsion membrane technique. Complexants chosen were based on the chelating ability with metal ions with high stability constant in the waste stream. Complexants 8-hydroxy quinoline, Thio salicylic acid, dithiazone, cupferron, 1-Niroso-2-naphthol, Quinalizarin were chosen as complexants. The effect of surfactant concentration, complexant concentration, agitating speed, and emulsifcation time on the emulsion stability have been studied. Treat ratio, the ratio of the emulsion phase to the external phase and the impeller speed on the removal of Palladium have been studied. Results show that stable emulsion could be prepared by using 1.5 ml of surfactant span 80 in 50 ml emulsion, with impeller speed 3000 RPM, for duration of 20 minutes using complexants of strength of 70-200 moles/m3. Effective recovery of Pd could be achieved by using strippant of pH 1-3.7 in the emulsion phase at 250-300 RPM of impeller speed.

Applicability of diclofenac–montmorillonite as a selective sorbent for adsorption of palladium(ii); kinetic and thermodynamic studies

A novel organo–nanoclay, i.e., diclofenac modified montmorillonite was used as a green and selective support for the adsorption of Pd(II) ions from aqueous solution. The diclofenac–montmorillonite composite was prepared and characterized by Fourier transform infrared (FT-IR) spectroscopy, elemental analysis, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. Batch experiments were carried out with an equilibrium time of 30 min and the kinetics models of the interaction were studied. The selectivity of the sorbent towards Pd(II) was extremely good at a pH of 6.0–7.0, while the adsorption of other cations was low. The adsorption data were measured at room temperature and the yielded Langmuir monolayer capacity was 20.0 mg g−1. The adsorption reaction was exothermic and the thermodynamic parameters, ΔH, ΔS and ΔG, at room temperature were −34.37 kJ mol−1, −116.56 J K−1 mol−1, and +0.96 kJ mol−1, respectively. The specific surface area increased from 35.8 m2 g−1 to 80.6 m2 g−1 for the modified clay, suggesting that intercalation creates a porous framework thereby increasing the surface area and increasing the selectivity of this sorbent for the adsorption of Pd(II) ions. In order to evaluate the applicability of this support for the uptake of palladium from complex matrices, different real samples such as: road dust, rice, urine and water samples were analyzed.

Amberlite XAD-16 Functionalized with 2-Acetyl Amide Group for the Solid Phase Extraction and Recovery of Palladium from High Level Waste

Acetyl amide grafted XAD-16 (ACAM-XAD16) resin has been synthesized by acetylating Amberlite XAD-16 resin followed by coupling it with N,N′-diisobutyl-2-chloroacetamide. Various instrumental techniques such as FT-IR, TGA, and elemental analysis were used to characterize ACAM-XAD16 resin. The resin has been evaluated for the solid phase extraction of palladium and other metal ions present in high level waste (HLW). The sorption kinetics of Pd onto the resin was found to be fast, with equilibrium being attained within 45–60 min. The experimental data fit well with the pseudo-second-order kinetics model of sorption kinetics. With the increase in aqueous phase acidity, Pd sorption increases initially, reaches a maximum around 3.0 M and then decreases. The sorption process involves the complex formation between Pd(II) and the resin which contains the carbonyl groups from the acetyl and the amidic moieties. The loaded palladium can be effectively eluted using acidic thiourea solutions and HEDTA solutions. The isothermal adsorption data fit well with both the Langmuir and the Freundlich models with maximum sorption capacity equal to 9 mg/g, which corroborates well with the equilibrium sorption capacity. Sorption studies carried out with simulated high level waste solution have shown very high uptake of palladium and small coextraction of lanthanides compared to the other elements.

Amberlite XAD-16 functionalized with 2-acetyl pyridine group for the solid phase extraction and recovery of palladium from high level waste solution

Amberlite XAD-16 has been functionalized with 2-acteyl pyridine by coupling it with 2-chloro pyridine after acetylation. The resulting resin (AP-XAD 16) has been characterized by various techniques like FT-IR, TGA, elemental analysis, etc. and has been evaluated for the solid phase extraction of palladium and other metal ions present in high level waste (HLW) solution. Sorption equilibrium was attained within 30–45min. The pseudo-second order kinetics model yielded the best fit for the experimental data of sorption kinetics. Pd sorption was found to decrease gradually with increase in aqueous phase acidity. The sorption process involves the complex formation between Pd(II) and the resin which contains the carbonyl group and soft ‘N’ atom of pyridine moiety with lone pair of electrons. The loaded palladium can be effectively eluted using acidic thiourea solutions. The adsorption isotherm data fitted well with Langmuir as well as Freundlich models. The maximum sorption capacity of the resin was found to be 8mg/g which is in agreement with the equilibrium adsorption capacity. Sorption studies carried out with simulated high level waste solution have shown very high uptake of palladium as compared to the other elements, thus showing the potential for possible use of the resin for efficient separation and recovery of palladium from HLW solution.

Irreversible uptake of palladium from aqueous systems using l-cysteine methyl ester physisorbed on carbon black

The uptake of palladium from aqueous systems by L-cysteine methyl ester-modified carbon black (CysOMe-CB) has been investigated. A solution containing 20 ppm PdCl2 could be reduced to below the limit of detection within 15 min by using 2 mg carbon black per mL water. The Pd(II) was spontaneously reduced to Pd(0) on the carbon black (CB) surface, likely due to the known reducing nature of oxygen-containing carbonaceous materials, although the possible concurrent oxidation of cysteine to cystine is discussed. The presence of Pd(0) was demonstrated by X-ray Photoelectron Spectroscopy (XPS), with ca. 6 sulfur atoms detected for every Pd atom. CysOMe was predominately present on the CB as physisorbed material, and leaching of CysOMe back into solution was determined to be minor (ca. 0.4 mol% per mL water per mg CB over 24 hours). Attempted removal of Pd from the CB surface by extraction with hydrochloric acid or sodium acetate solutions was found to labilise other metal ions already present in the CB subsurface, and accumulate them at the CB surface.

ハイブリッドマイクロカプセルによるPd（_II_）の 選択的吸着

ハイブリッドマイクロカプセルによるPd（_II_）の 選択的吸着

Study of Pd(II) adsorption over titanate nanotubes of different diameters

Hydrogenotitanates (HNTs) nanotubes with different diameters were prepared by hydrothermal treatment of TiO 2 (P25) followed by washing with HCl aqueous solution. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermal analysis and N 2 adsorption/desorption. In order to determine the palladium uptake ability of different HNT samples, the interaction between HNTs and Pd(II) was subsequently studied in aqueous solution at pH 9 (NH + 4/NH 3 buffer). Transmission electron microscopy showed that the diameter of the nanotubes depends on the preparation conditions. Chemical analysis of residual sodium and thermal studies showed that the chemical formula of the two prepared HNT was H x Na 2 − x Ti 2O 5⋅H 2O with x = 1.61 or 1.65. The HNTs are mesoporous materials with a multi-walled nanotubular structure and high specific surface area. In order to determine the capacity of palladium retention of different HNTs samples, the interaction between HNTs and Pd(II) was subsequently studied in aqueous solution at pH 9 (NH + 4/NH 3 buffer). The adsorption kinetics of Pd(II) on the HNTs was very fast. The isotherms of Pd(II) on the HNTs showed that the adsorption occurred (1) initially through cationic exchange and (2) when the concentration of Pd(II) is high by precipitation of different Pd salts. The adsorption capacity of Pd(II) is strongly altered by the morphology of the HNTs samples.

Studies on the Sorption of Palladium using Cross‐Linked Poly (4‐Vinylpyridine‐Divinylbenzene) Resins in Nitric Acid Medium

Various cross‐linked (4, 8, and 12%) gel‐type weak‐base poly(4‐vinylpyridine) (PVP) resins were studied for palladium recovery from nitric acid medium. The sorption of palladium was found to decrease with an increase in cross‐linkage of the resin. 8 and 12% PVP resins exhibited maximum D Pd(II) values at 2–6 M HNO3, whereas 4% PVP resin showed maximum D Pd(II) values at lower acidities (0.1 M HNO3). FT‐IR, SEM, and XPS techniques were used for the characterization of palladium‐loaded resins. Detailed studies were carried out with the resin of modest cross‐linkage i.e., 8% PVP resin. The sorption isotherm studies revealed that the maximum palladium loading approaches the theoretical capacity of the resin, presuming the sorption of palladium as divalent anion at 4 M HNO3. The pseudo‐second order kinetics model yielded the best fit for the experimental data of sorption kinetics. An increase in temperature accelerates the rate of palladium extraction and also the addition of chloride ions increases the palladium uptake. Column studies were performed using 4 and 8% PVP resins in 2 and 4 M nitric acid concentrations. The loaded palladium could be eluted efficiently with acidic thiourea solution.

Palladium Recovery by Reactive Precipitation using a Cyanex 301‐Based Stable Emulsion

Cyanex 301®, di(2,4,4‐trimethylpentyl) dithiophosphinic acid, has been combined with gelatin and alginate to prepare a stable emulsion that can be used for the reactive precipitation of palladium (metal reaction with the sulfur functional group of Cyanex 301). The ionotropic gelation of alginate leads to material precipitation. The process has been successfully tested for Pd binding from 0.1–5 M HCl solutions. The maximum binding capacity was found to be close to 350 mg Pd g−1 Cyanex 301. A 1∶1 stoichiometric relation between Cyanex 301 and Pd has been identified. Extractant dependency plots showed that the ligand in the Pd‐Cyanex 301 complex can also have a solvation number higher than one. Palladium uptake is not significantly affected by the presence of competing metals such as Cu, Ni, Zn, or Pt. Quantitative stripping of Pd from the precipitated bio‐polymer could not be achieved.

Spectrophotometric Determination of Palladium by the Colouration with 2-(2-Quinolylazo)-5-diethylaminobenzoic Acid

Palladium has been used in various ways as a hydrogenation catalyst, microcontactors in the electronics, hard alloy in dentistry and in the last few years as a component in the three-way catalysts in automobile exhaust catalytic beads. Due to the introduction of palladium, platinum and rhodium for use in catalytic converters in motor vehicles, the emission of these metals into the environment has increased. In addition, an increased uptake of palladium by plants has led to soil pollution. Palladium is thought to be one of the strongest allergens from a health hazard viewpoint. For these reasons, establishing rapid and accurate methods for the determination of palladium for industrial process, quality and pollution control is important. Many sensitive methods, such as spectrofluorimetry, X-ray fluorescence spectrometry, neutron activation analysis, atomic absorption spectrometry have widely been used for the determination of palladium. However, spectrophotometric methods have gained popularity for palladium determination as advantageous in respect of simplicity and low operating costs. A wide variety of spectrophotometric reagents, such as azo dyes, rhodanine derivatives, porphyrin ligands, thiourea derivatives, 8aminoquinoline derivatives and nitroso dye have been developed for the determination of palladium. In our previous work, some 2-quinolylazo reagents were reported for the determination of metal ions. These reagents have a higher sensitivity than that of pyridylazo reagents because of its larger conjugated system. However, the use of these reagents for the determination of palladium has not been reported yet. We had synthesized 2-(2quinolylazo)-5-diethylaminobenzoic acid (QADEAB) and used it to the determination of cobalt. This reagent has high sensitivity. In this paper, we thoroughly studied the color reaction of QADEAB with palladium. The results show that QADEAB is a highly sensitive, selective and convenience reagent for palladium. Based on this, a highly sensitive, selective and convenient method for the determination of palladium in water and catalyst was developed.

New development of inorganic ion exchanger: Selective Uptake of Palladium by Insoluble Ferrocyanides

The selective uptake properties of Pd2+ions on different insoluble ferrocyanides (KNiFC, KCuFC, KCoFC, KFeFC and KZnFC) have been studied by the batch method. The particle size was estimated to be about 50 nm and the fine particles formed larger aggregates. The uptake rate of Pd2+ on KNiFC was fairly fast and the uptake equilibrium was attained within 1 h. A relatively large Kd value above 105 cm3 g-1 was obtained in the presence of HNO3 up to 7 M and the maximum Kd values above 105 cm3 g-1 were obtained in the temperature range of 30 to 50°C. The uptake of Pd2+ follows a Langmuir-type adsorption equation and the maximum uptake amount on KCuFC was estimated to be 2.07 mmol g-1. The Pd2+ions were incorporated into the products mainly by the ion exchange of 2K+ _??_Pd2+. The insoluble ferrocyanides were thus favourable adsorbents for the selective separation of Pd2+ ions from high-level liquid wastes.