Selective Separation Of Palladium Research Articles

Selective capture of palladium by protonation-armed pyridine nitrogen in extreme water environments

Due to the hostile environment in which it is recovered, selective separation of palladium from the leachate of spent catalysts containing palladium is of considerable utility but faces substantial obstacles. This work designed and synthesized a bipyridine-based porous organic polymer (POP-BPy) via free radical polymerization. Meanwhile, its adsorption characteristics and the mechanism of adsorption in extreme environments were examined. In hostile conditions, the resultant POP-BPy display exceptional mechanical stability and environmental resistance. Impressively, POP-BPy has an excellent adsorption capacity of Pd(II) (248 mg/g) in harsh environments (aqua regia: AR; half-diluted aqua regia: AR“1 + 1”), and also had superior selectivity and rapid kinetics. The selectivity of POP-BPy for Pd(II) was verified in combination with relevant experiments (βPd(II)/Pt(II) = 36.19, βPd(II)/Pt(II) = 23.90). Furthermore, combining density functional theory (DFT) and molecular dynamics (MD) simulations, the mechanism of selectivity of POP-BPy for Pd(II) was revealed from static adsorption sites to dynamic adsorption processes in a holistic manner, which attributed to the strong attraction of protonated pyridine nitrogen to PdCl42- and site suitability. Furthermore, the application of POP-BPy to spent catalyst recovery resulted in up to 100% removal of Pd(II) from the actual leaching solution, and fixed bed column experiments can effectively treat 2688 bed volumes (L) of feed streams (10 mg/L) before reaching the breakthrough point (<1 mg/L). Overall, this work has opened up new avenues for the selective recycling of valuable metals in harsh environments.

Mutual separation of platinum group metals via seed-mediated growth on a polymer with metal-coordination unit

• Mutual separation of platinum group metals (PGMs) • Seed-mediated growth of platinum or palladium atoms on a polymer with a metal-coordination unit. • Selective separation of platinum from PGM mixture. • Selective separation of palladium from PGM mixture. • Various target platinum group metals are able to be selectively separated by selection of nucleation site. Platinum group metals (PGMs) are extremely difficult to separate from each other because of the similarity in their chemical and physical properties. We report here the effective mutual separation of PGMs utilizing a seed-mediated growth approach on a polymer with a metal-coordination unit (PMCU). Nucleation of Pt 4+ ions by sodium borohydride produced Pt 0 seeds on the metal-coordination unit (thiocarbonyl group) of PMCU. The Pt seeds-attached polymer was added into a solution containing Pt 4+ and other PGM ions, and reduction with L-ascorbic acid selectively assembled Pt atoms around the Pt seeds. The resulting polymer was removed from the mixture and washed to remove Pt and other PGMs that were only physically adsorbed, achieving selective separation of Pt. By changing the nucleation site from Pt to Pd, the immersion of Pd seeds-attached polymer in the mixed solution containing Pd 2+ and other PGM ions and reduction with L-ascorbic acid selectively separated Pd. Therefore, this approach is applicable to selective separation of various target PGMs by the selection of nucleation sites on PMCU.

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 PdCl2. 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.

Selective separation of palladium from synthetic highly active liquid waste by cloud point extraction using benzil mono-(2-pyridyl)hydrazone and Triton X-114

A simple and rapid cloud point extraction methodology has been developed for the separation and determination of palladium, after complexation with benzil mono-(2-pyridyl) hydrazone in acidic medium, using Triton X-114 as nonionic surfactant. Under the optimum experimental conditions, the calibration curve was linear in the range of 0.05–25 µg L−1. The enrichment factor was 104 for a 50 mL sample volume. The limits of detection, based on three times the standard deviation of the blank signal by seven replicate measurements was 0.12 µg L−1. The relative standard deviation (RSD) for seven replicate determination at 5 µg L−1 of palladium was 1.85 %. Under the presence of foreign ions and EDTA as a strong complexing agent, no significant interference was observed. The accuracy of the results was verified by analyzing spiked water samples. The proposed method has been applied for the separation and determination of palladium from synthetic highly active radioactive waste with satisfactory results.

Separation Studies of Pd(II) from Acidic Chloride Solutions of Pt(IV), Ni(II) and Rh(III) by Using 4-Aroyl-3-Phenyl-5-Isoxazolones

This study examined the effect influence of various factors on the extraction of Pd(II) to develop a new liquid-liquid extraction mechanism for the selective separation of palladium(II) from its acidic chloride solutions using 4-aroyl-3-phenyl-5-isoxazolones (HA), such as 3-phenyl-4-(4-fluorobenzoyl)-5- isoxazolone (HFBPI), 3-phenyl-4-benzoyl-5-isoxazolone (HPBI) and 3-phenyl-4- (4-toluoyl)-5-isoxazolone (HTPI). The extraction strength of Pd(II) with HA were in the following order: HFBPI &gt; HPBI &gt; HTPI, which is opposite to that observed with their pKavalues. HPBI was used to separate Pd(II) from Pt(IV), Ni(II) and Rh(III) metal ions and calculated their separation factors (S.F.) were followed in the order: Pd/Ni (40±0.4) &gt; Pd/Pt (25±0.2) &gt; Pd/Rh (15±0.3 &gt; Rh/Ni (2.7±0.3) &gt; Pt/Ni ≈ Rh/Pt (1.7±0.2). The loading and striping of Pd(II) (1.12×10-4mol L-1) were also examined using 1.0×10-3mol L-1HPBI in CHCl3and 1.0 mol L-1HCl, respectively. The results demonstrated that the maximum (97.5%) extraction and desorption (89%) of metal required at least 3.0 cycles. The developed method was applied successfully to the separation of palladium from synthetic water samples.

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)4S3 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 separation of palladium (II) from precious metal ions using thiosemicarbazone derivatives from acidic media by solid phase and solvent extractions

A newly reported chelating ligand, 9,10-phenanthraquinone ethylthiosemicarbazone (PET), has been used for selective separation of Pd(II) by solid phase extraction (SPE) and solvent extraction (SE) in highly acidic media. PET was chemically immobilized on aminopropylsilica gel, yielding PET-SG, and complexes of PET and PET-SG with Pd(II) were synthesized and confirmed by IR, UV, thermal and elemental analyses. Free PET forms a 1:1 complexwith Pd(II) in solution with a stability constant of 3.5 x 108 and e of 2.5 x 105 dm-3 mol-1 cm-1 those were determined spectrophotometrically at 605 nm. PET-Pd(II) shows a superior stability in concentrated H2SO4, H3PO4, HNO3, HClO4 and glacial acetic acids for at least 24 h. It is easily and quantitatively extractable (%E = 99.6) in a one-stage process into MIBK from 10 mol/dm3 H2SO4. PET-SG has a Pd-uptake capacity of 0.31 mmol/g and found to be stable in saline liquors from pH 8 to 2 mol/dm3 H2SO4 or equivalent acidity of the studied acids. Leaching of >99.7% of Pd(II)...

Selective Separation of Palladium from Organic Solutions Containing Nickel or Platinum using Polythioamide as a Sorbent

The feasibility of the selective recovery of Pd from organic liquid waste using polythioamide (PTA) as a sorbent has been investigated. PTA effectively sorbed Pd(II) in some organic solutions under not only acidic conditions but also basic conditions. PTA was also able to sorb Pd from organic solutions containing PdCl2(PhCN)2 and Pd2(dba)3. The results for the molecular structure of a model compound ([Pd(C11H15NS)4]Cl2) suggest that the presence of a S donor plays an important role in the sorption of Pd(II) by PTA. The sorbed Pd was quantitatively eluted using 1,3-bis(diphenylphosphino)propane in MeOH, and the recovered PTA can be reused at least five times. The selective separation of Pd(II) was achieved even from organic solutions containing a 100 times larger amount of Ni(II) or Pt(IV) under acidic conditions or basic conditions, respectively.

Selective separation of palladium from simulated intermediate radioactive waste nitrate by IRA-410 and IRA-900 anion exchangers

Selective efficient method have been for separation of palladium by strong basic anion exchangers IRA-410 and IRA-900 from intermediate radioactive nitrate medium. The different conditions for exchange behaviour of palladium from [ILLW] solutions containing numbre of elements were investigated by batch technique. Selective recovery of palladium from the [ILLW] solution was achieved using column technique. The elution of palladium was carried out via reduction with formic acid where the rate of the reduction process was increased by decreasing the formic acid concentration till 50% followed by dissolving the separated palladium by nitric acid.

A rapid and selective separation of palladium

Palladium was separated from Al, Ru, Rh, U, Pu and also from a mixture of fission products using α-benzoin-oxime as the extractant and Solvesso-100 as the diluent. The extraction is quantitative over a wide range of acidity from 0.1M to 4M HNO3. The method has been found to be equally effective to separate Pd at trace level (carrier-free form). The stoichiometry of the complex, the interference of foreign elements in Pd separation, etc., are reported. The applicability of the method to separate palladium formed in fission rapidly from all other fission products, especially the most strongly interfering molybdenum isotopes, and the recovery of this element from high level radioactive waste are also mentioned.

Ion-exchange resins containing s-bonded dithizone and dehydrodithizone as functional groups : Part 2. Desoprtion properties and development of separation procedures for gold and platinum group metals

The desorption of precious metals from the PD and PTD ion-exchange resins, containing S-bonded dithizone and dehydrodithizone as functional groups, is described. Each sorbent was loaded batchwise with individual or combined metals and then treated with excess of various extracting agents (6 M hydrochloric acid, 2 M perchloric acid, ammonium nitrate, sodium thiocyanate, thiourea). Strong retention of some adsorbed metals and instability during the loading and elution stages were found with the PD resin, but a selective separation of palladium and gold from accompanying metals was possible. The PTD resin had superior properties. Unsual effects were detected when elution rates were compared for individual metals and mixtures. While Pd and Pt, loaded individually, were desorbed quantitatively by thiourea, co-extracted Ir(IV) completely inhibited their elution. The regeneration of PTD by special sequences of eluents was utilized for selective chromatographic separation of Pd, Pt, Os, Au and (with restrictions) Ir from each other and also from large amounts of base metals and salts.