Extraction Of Palladium Research Articles

Effective Pd(II) carriers for classical extraction and pseudo-emulsion system

This work aims to study the performance of three new extracting agents: N-decyloxy-1-(pyridin-3-yl)methaneimine (D-3MI), N-decyloxy-1-(pyridin-3-yl)ethaneimine (D-3EI) and N- decyloxy-1-(pyridin-4-yl)ethaneimine (D-4EI), in the solvent extraction of palladium. For this purpose, the effect of several parameters on the extraction of Pd(II) from hydrochloric acid medium was examined. The stripping of Pd(II), the stability of the extractant in multiple extraction/stripping cycles and the separation of Pd(II)/Pt(IV) were also investigated. After the classical solvent extraction studies, the Pseudo-Emulsion based Hollow Fibre Strip Dispersion (PEHFSD) technique was used for the recovery of Pd(II). The kinetics of permeation was found to be strongly dependent on the extractant concentration, the stripping of Pd(II) with thiourea being quite slower than its removal from the feed phase. The recovery of Pd(II) with the PEHFSD technique was also checked, using a commercial extractant, the amine Alamine 308, for comparison. The results obtained show that the ethaneimine D-3EI has the highest potential for extracting and stripping Pd(II) among the reagents tested. The use of 0.03 M D-3EI in toluene, as the membrane phase, allowed to remove practically all the metal content from the aqueous phase (100 ppm Pd, 1.5 M HCl) with relatively fast kinetics and led to a Pd(II) recovery above 90% for moderate permeation times.

Selective Palladium(II) Recovery Using a Polymer Inclusion Membrane with Tris(2-ethylhexyl) Phosphate (TEHP). Experimental and Theoretical Study

Extraction and recovery of palladium continues to be a technologically and economically challenging task, particularly in the recycling process of palladium from scrap automotive catalytic converte...

Structural Effect of Sulfide-Containing Diamides on the Extraction of Palladium(II) from HCl

ABSTRACT To understand the relationship between the structure and function of compounds for the extraction of Pd(II) from HCl solution, we investigated the Pd(II) extraction properties using three sulfide-containing diamides with the same N-substituents, N,Nʹ-dimethyl-N,Nʹ-diphenyl: thiodiglycolamide (mptdga), 3,3ʹ-thiodipropionamide (mptdpa), and 1,2-ethylene-bis(thioglycolamide) (mpebtga) diluted in chloroform. All of the diamides extract Pd(II) from 3.0 M HCl solution much faster than the conventional sulfide extractant, di-n-hexyl sulfide, and the extraction efficiency decreases in the order mpebtga > mptdpa > mptdga. The apparent stoichiometry of the Pd(II)−extractant complex extracted in the organic phase is 1:1 for mpebtga and 1:2 for mptdga and mptdpa. The FT-IR measurements show that the amide oxygen atoms in the diamides do not directly coordinate to Pd(II). These results indicate that the dominant complexes for the three diamides are [PdCl2(mptdga)2], [PdCl2(mptdpa)2], and [PdCl2(mpebtga)] with the sulfide coordinating to Pd(II).

Supercritical CO2 Extraction of Palladium Oxide from an Aluminosilicate-Supported Catalyst Enhanced by a Combination of Complexing Polymers and Piperidine.

Precious metals, in particular Pd, have a wide range of applications in industry. Due to their scarcity, precious metals have to be recycled, preferably with green and energy-saving recycling processes. In this article, palladium extraction from an aluminosilicate-supported catalyst, containing about 2 wt% (weight%) of Pd (100% PdO), with supercritical CO2 (scCO2) assisted by complexing polymers is described. Two polymers, p(FDA)SH homopolymer and p(FDA-co-DPPS) copolymer (FDA: 1,1,2,2-tetrahydroperfluorodecyl acrylate; DPPS: 4-(diphenylphosphino)styrene), were tested with regards to their ability to extract palladium. Both polymers showed relatively low extraction conversions of approximately 18% and 30%, respectively. However, the addition of piperidine as activator for p(FDA-co-DPPS) allowed for an increase in the extraction conversion of up to 60%.

Extraction of rhenium(VII) and palladium(II) from nitric acid solution using N-cyclohexyl-2-pyrrolidone as an extractant

ABSTRACT Extraction behavior of Pd(II) and Re(VII) from HNO3 aqueous solutions (0.1–5.0 M, M = mol∙dm−3) to CH2Cl2 containing N-cycrohexyl-2-pyrrolidone (NCP, 0.1–2.0 M) as an extractant has been examined. As a result, it was found that distribution ratios (D) of Pd(II) and Re(VII) under [HNO3] = 3.0 M increase with increasing [NCP] from 0.1 to 2.0 M and that plots of log D vs. log[NCP] show linear relationships with slopes of approximately 2. It was also found that the D values for Pd(II) increase with increasing [HNO3] up to 3.0 M and decrease in the higher [HNO3] region (<5.0 M) and those of Re(VII) increase with an increase in [HNO3] up to 1.0 M and decrease with a further increase in [HNO3] (<5 M). From these results, it was suggested that the extraction reactions of Pd(II) and Re(VII) take place with two NCP molecules and compete with the extraction of HNO3. Moreover, it was clarified that IR spectra (1550–1700 cm−1) of CH2Cl2 solutions containing extracted Pd(II) and Re(VII) species are consistent with that of trans-Pd(NO3)2(NCP)2 and similar to that of HReO4(NCP)2, respectively. From these results, it is proposed that Pd(II) and Re(VII) species in HNO3 aqueous solutions are extracted to CH2Cl2 phase containing NCP as Pd(NO3)2(NCP)2 and HReO4(NCP)2.

Miniaturized application of 3D‐printed large‐flow microreactor in extraction and separation of platinum, palladium and rhodium

AbstractProblems of long extraction time, large footprint, low single‐stage extraction efficiency, and complicated production processes in solvent extraction equipment in recycling of modern industrial precious metal waste liquids are addressed and application of miniaturized equipment to hydrometallurgy is proposed in this study. A 3D‐printed multichannel microfluidic reactor will likely replace traditional extraction equipment. The reactor was applied to experiments concerning tributyl phosphate extraction and separation of platinum, palladium and rhodium precious metal ions in a hydrochloric acid system. Results showed that, under the conditions of a ratio of 1:1 and a flow rate of 192.5 mL min‐1 (processing capacity of 1.5L h‐1), the extraction rates of platinum and palladium are 84.26% and 96%, and the separation coefficient is βPt/Rh and βPd /Rh is 132.35 and 753.5,moreover, the optimized extraction rate of platinum and palladium in the reactor increases by 2% and 1%, respectively. Hence, the extraction effect of this reactor is better than conventional industrial single‐stage extraction (extraction time 12min, platinum extraction rate 87.43%, palladium extraction rate 90.86%, separation coefficients βPd/Rh and βPt/Rh are only 65.3 and 45.7). In summary, compared with conventional extraction, microreactor extraction can increase the separation coefficient, shorten the extraction time, and the total processing capacity can reach the industrial production level. In addition, this study also discussed the influence of microreactor structure optimization on the extraction effect. © 2020 Society of Chemical Industry

Palladium extraction from chloride solutions with the disulfide of bis(2,4,4-trimethylpentyl)dithiophosphinic acid

ABSTRACT Palladium extraction from chloride solutions with the disulfide of bis(2,4,4-trimethylpentyl)dithiophosphinic acid (L) is reported in this work. The rate of palladium extraction with the disulfide in toluene is slow but it increases in the presence of trioctylamine (TOA). Within 5 min, the degree of palladium recovery (ε) is 99.6%, whereas in the absence of TOA, it is only 19.0% in 10 min. The extraction systems based on the disulfide and TOA mixtures exhibit fast kinetics, high selectivity and can be used for the extraction of palladium from various industrial solutions.

Palladium Extraction from Nitrate Solutions with the Disulfide of Bis(2,4,4‐trimethylpentyl)dithiophosphinic Acid

AbstractThis work presents data on palladium recovery from nitrate solutions with the disulfide of bis(2,4,4‐trimethylpentyl)dithiophosphinic acid (L) in toluene. Extraction of palladium with the disulfide is slow but it increases as the concentration of L in the organic phase increases. At a concentration of L equal to 0.01 mol/L, almost complete extraction of palladium (99.7 %) is achieved within 20 minutes. The extraction efficiency also increases with increasing temperature. Maximum palladium recovery occurs at an HNO3 concentration of 1.0 mol/L in the aqueous phase. Analysis of the interphase palladium distribution showed that the extraction of palladium with the disulfide in toluene is due to the formation of the complexes of variable composition [(Pd(NO3)2)n⋅L] in the organic phase where n=1–4. The disulfide can be used to recover palladium from nitric acid solutions containing metal impurities. The degree of palladium extraction in one‐stage is 98.2 %, therefore the extractant is highly selective toward Pd(II) in the presence of Ni(II), Cu(II), Co(II), Zn(II), and Fe(III). Almost complete palladium stripping from the organic phase is achieved with a mixture of thiourea and hydrochloric acid solutions.

New Mechanism for Depositing Platinum, Palladium, and Rhodium on Iron Metal Collector

The effect of using an iron metal collector (MC) instead of copper on the degree of extraction of platinum, palladium, and rhodium is investigated in processing ceramic-based automotive catalysts in an electric arc furnace. The dependence of the effect of melt holding time on platinum group metal (PGM) deposition rate on a furnace hearth is analyzed. It is determined that during creation of a homogeneous mixture and introducing a metal collector (MС) into the catalyst composition effective Pt, Pd, Rh extraction occurs in the first 20 minutes of melt exposure. In spite of the twice as high density of platinum, the degree of its extraction is at the level for Pd and Rh, which points to the possibility of depositing platinum group metals (PGM) on the furnace hearth using the surface of coarser added MС powder. Testing of various methods for adding MС demonstrate the effectiveness of introduction to the melt surface. When a melt is heated above the melting temperature of platinum and palladium, the maximum degree of extraction is reached in 6 min. This shows that solid rhodium may passivate the surface of added MС. In order to create conditions when there is always an MС free surface to which solid rhodium may adhere, the rate coefficient is determined for effective dissolution of Rh in iron MС. Determination of this coefficient makes it possible to scale up results of laboratory studies and to predict the minimum time required for melting MС on the furnace hearth without loss of valuable component.

Electrochemical extraction of palladium from spent heterogeneous catalysts of a petrochemical unit using the leaching and flat plate graphite electrodes

In this study, electrometallurgy recovery of Pd from the spent petrochemical unit Pd/Al2O3 catalyst has been reported. The electrochemical deposition of Pd from the acid solution (HCl/H2O2) was developed using flat plate graphite electrodes. The effect of the operating variables was assessed and optimized by employing the central composite design of the response surface methodology. The recovery efficiency of Pd was obtained 99.07% at the optimum condition of, reaction temperature of 67.0 °C, electrolysis time of 3.4 h, liquid/solid ratio of 24.7 ml/g, a current density of 196 A/m2 and stirring speed of 572 rpm. The results of the statistical analysis indicated that the anticipated data were in good suitable with the observed ones (R2 = 0.9762), in which the average deviation from experimental data was 0.32% for optimum condition. It indicates that the deposited Pd has spherical nanoparticles shape with a purity of 94.02%. The present study can provide a reliable process for extraction of Pd from the solid waste by the high efficiency and purity.

Promising polymer-assisted extraction of palladium from supported catalysts in supercritical carbon dioxide

Precious metals, in particular palladium (Pd), have a wide range of daily applications, from automotive catalysts to fine chemistry production. Nevertheless, these metals are relatively rare and highly expensive, considering their massive industrial utilization. In the last decades, different recycling methods have been explored. Nowadays, the most applied methods, namely pyro- and/or hydrometallurgy, involve energy-intensive processes and/or the generation of large amounts of effluents to be treated. Thus, the development of a more sustainable recycling process of precious metals is highly desirable. In the present work, we introduce a sustainable process based on the use of a green solvent, supercritical CO2, operated under mild conditions (P = 25 MPa and T = 40 °C). The extraction process is possible thanks to the addition of CO2-soluble complexing polymers bearing pyridine units. The proposed method leads to the extraction of more than 70 % of Pd from an aluminosilica-supported catalyst.

Highly selective extraction of palladium from spent automotive catalyst acid leachate using novel alkylated dioxa-dithiacrown ether derivatives

Novel macrocyclic extractants were synthesized and employed in liquid–liquid extraction (LLE) for palladium/platinum (Pd/Pt) separation in aqueous feed source. Dioxadithia-benzo-crown ether diols (BCES2O2) 2g–2i were prepared through bis-epoxide cyclization with aqueous 1,2-benzenedithiol under mild basic conditions. For improved miscibility and stability in the organic diluent (i.e. toluene), 2g–2i were alkylated to afford dimethoxy-BCES2O23g–3i. LLE experiments reveal their high stability, extraction efficiency, and separation performance (βPd2+/Pt2+=104−105) in highly acidic feed solutions (∼6M HCl). The most suitable extractant 3i followed a 1:1 3i-Pd2+ complex with stability constant Kex∼105. Density functional theory calculations reveal that the rigid cavity size (1.58–1.65Å) of 3i is ideal for Pd2+ (1.56Å) in forming S4 coordination geometry. The Pd2+ can be repeatedly extracted by 3i [in toluene] and stripped by 1M HCl+0.15M thiourea solution without performance deterioration. Each cycle can be accomplished <1h based on the derived extraction (kex=0.038min−1) and stripping (kstrip=0.063min−1) rate constants. The high extraction efficiency (99.5%) and purity (98.5%) of recovered Pd2+ from simulated acidic spent automobile catalyst liquor demonstrate the potential of 3i [in toluene] LLE system for selective Pd2+ recovery from automotive wastes.

Ionic liquid as adjuvant in an aqueous biphasic system composed of polyethylene glycol for green separation of Pd(II) from hydrochloric solution

An aqueous biphasic system (ABS) is considered to be an environmentally friendly technology for the extraction of diverse substances because the main component of the two phases is water. In this study, extraction behaviors of palladium(II) from hydrochloric solution using a typical polymer/salt ABS with ionic liquid (IL) as an adjuvant were studied. Three imidazolium-based ionic liquids ([Cnmim]Br, n = 4, 6 and 8) were used to tune the properties of the ABS to enhance the extraction performance of Pd(II). The parameters that influence palladium extraction including IL species, IL concentration, salinity, original Pd(II) concentration, equilibrium pH, temperature, and contact time, were systematically studied and discussed. These results demonstrate that incorporating ILs into the PEG2000/salt ABS markedly improved the extraction efficiency, and 96–99% of Pd(II) was distributed into the PEG-rich phase. Among the three imidazolium-based ILs, the maximum extraction efficiency was achieved by the IL that had the shortest alkyl chain attached to the imidazole ring, and it can be interpreted that the electrostatic attraction was the main driving force during Pd(II) extraction. The results of FT-IR and TEM characterization show that the anionic PdCl42− transferred into the PEG-rich phase via anion exchange with the anionic Br− in [C4mim]Br, and the mechanism was confirmed by the stoichiometry of the extracted species of [2C4mim+·PdCl42−]. Hydrazine hydrate (80 wt%) completely reduced Pd(II) in the PEG-rich phase, and EDX and SEM were used to analyze the sediments. The results established that the developed polymer/salt ABS with IL as an adjuvant is a potential environmentally friendly extraction system for palladium recovery from an acidic media.

Investigation of increasing the recovery rate of refi palladium powder from waste solutions

The research methods for extraction of palladium from waste electrolyte solutions with the use of chloronitric extraction are described. The methods of investigation of the purification from harmful impurities by selective precipitation to obtain a refined palladium powder are given, the parameters on the technological processes are defined, use of the new technologies and equipment used are justified

Efficiency and Mechanism of Palladium(II) Extraction from Chloride Media with N-Hexadecylpiperidinium Chloride

N-hexadecylpiperidinium chloride ([PIP16]Cl) has been synthesized and examined as a reagent for extractive recovery of palladium(II) from hydrochloric acid solutions. The effect of the contact time between the two phases, temperature and the concentration of palladium(II) ions, the extractant and HCl, were also evaluated. The anion-exchange mechanism of palladium(II) extraction with [PIP16]Cl was confirmed by Job’s method, UV–VIS, IR and 1H NMR analysis. The extraction of palladium(II) from 0.1 mol·L−1 HCl solution with [PIP16]Cl in toluene was very effective and amounted to almost 100%. Increases in both HCl and NaCl concentrations and increasing temperature had negative effects on the effectiveness of palladium(II) extraction. [PIP16]Cl also exhibited selectivity to extraction of palladium(II) over some other metals: rhodium(III), iron(III), aluminium(III), copper(II) and lead(II). From among the examined stripping solutions the most effective were 0.5 mol·L−1 aqueous solution of ammonia and 0.1 mol·L−1 thiourea in 0.1 or 1 mol·L−1 HCl. The percentage of palladium(II) stripped from loaded organic phase reached nearly 100%. The feasibility of regeneration of [PIP16]Cl and its reuse in subsequent extractions was also investigated.

Synthesis and evaluation of Fe3O4–Al2O3/SDS–DMG adsorbent for extraction and preconcentration of Pd(II) from real samples

In this study, a simple and reliable solid-phase extraction method for the extraction and preconcentration of palladium by using dimethylglyoxime and sodium dodecyl sulfateon on self-assembled magnetic alumina nanoparticles is presented. The optimization of the adsorption process is performed under various levels of variables including pH, temperature, sample volume, concentration and adsorbent dosage. Then, the related charts and tables are presented. To study responses, adsorption, desorption conditions, surface area and the size of adsorbent pores are analyzed. Moreover, magnetic properties of the adsorbent are investigated in different manufacturing stages. To justify results and confirm the accuracy, XRD, VSM, FT-IR, FESEM, EDX and BET analyses are carried out, and corresponding equations and graphs are presented. It is found that under the optimized conditions, the detection limit and relative standard deviation are 0.06 µg l−1 and 1.9%, respectively. Additionally, the maximum adsorption capacity of the synthesized Fe3O4–Al2O3/SDS–DMG for adsorbing palladium ions is 365 mg g−1. Based on results obtained in this research, it is proved that the proposed method is potentially applicable to determine Pd+2 at the trace values in real samples such as tap water and catalysts.

Palladium(II) Extraction by 4-[(Hexylsulfanyl)methyl]-3,5-dimethyl-1-phenyl-1Н-pyrazole from Hydrochloric Acid Solutions

Palladium(II) extraction from hydrochloric acid solutions by 4-[(hexylsulfanyl)methyl]-3,5-dimethyl-1-phenyl-1Н-pyrazole, a new complexing reagent dissolved in toluene or chloroform, was studied. The reagent showed high efficiency in palladium(II) recovery from 0.1–(5–6) М HCl. Palladium(II) is recovered from 1 М HCl by the nonprotonated reagent species according to the coordination mechanism to form the extracted compound [PdCl2μ-L]n (n > 2). The reagent is coordinated to metal ions via the nitrogen atom and the thioether sulfur atom as shown by 1H and 13С NMR spectroscopy. In the temperature range 10–40°С, palladium(II) extraction from 1 M HCl is an endothermic process. The palladium(II) can be quantitatively stripped by a hydrochloric acid solution of thiourea. The reagent (with toluene as diluent) may be recommended for use in palladium(II) concentration from hydrochloric acid solutions and for palladium(II) selective separation from platinum(IV), copper(II), nickel(II), iron(III), and aluminum(III).

Investigation of the Interaction of Palladium with Potassium Tetrafluorobromate

In this investigation, the interaction of metallic palladium with potassium tetrafluorobromate was examined in open system, the reaction products were identified using X-ray phase analysis. A thermogram of the interaction of Pd with KBrF4 was obtained, the temperature range of the reaction (187.9-328°C) and the thermal effect (431.31 J/g) were determined. It was found that the fluorination process is a multi-stage process. The solubility of the obtained K2PdF6 compound in nitric and hydrochloric acids was investigated. The process of extraction of palladium from nitric acid solutions with tributyl phosphate was carried out and the influence of the concentration of palladium and the acidity of the initial solution on the distribution coefficient was investigated.

Reactivity of metallic palladium in a K2CO3-K2O-B2O3-Al2O3 melt

The reactivity of metallic palladium in a K2CO3-K2O-B2O3 melt is investigated as a function of heating temperature and time. The aqueous solubility of heat-treated palladium is enhanced by controlling the heating conditions leading to an optimum palladium extraction of 53% from the heat-treated product. The alumina crucible used as a reactor partially dissolves during the heating of metallic Pd, which requires the analysis of palladium solubilization to be discussed in terms of K2CO3-K2O-B2O3-Al2O3 system. Oxidized palladium combines with boron and aluminum oxyanions as ligands in the molten medium to form water-soluble palladium compounds. Information regarding water-soluble palladium compounds was obtained by analyzing the precipitate collected from the palladium-containing solution produced by water-leaching of the heat-treated product. The precipitate contained Pd (0.19 wt%), Al (0.74 wt%), B (2.6 wt%), and K (45 wt%). Raman spectroscopy confirmed the presence of oxidized palladium in the precipitate. Aluminum oxyanions with AlO4 and AlO6 structures and boron oxyanions as diborate groups also were detected in the precipitate.

A novel deep eutectic solvent microextraction procedure for enrichment, separation and atomic absorption spectrometric determination of palladium at ultra-trace levels in environmental samples

A dispersive deep eutectic solvent microextraction procedure for the separation and preconcentration of palladium from environmental samples has been established prior to its flame atomic absorption spectrometric determination. The deep eutectic solvent (DES) was prepared by mixing disodium 4,5-dihydroxy-1,3-benzenedisulfonate, hydroxyl ammonium chloride, FeCl3 and phenol resulting in homogenous solution which used directly for the extraction of palladium. The analytical parameter including pH, amount of deep eutectic solvent and sample volume were optimized. The developed microextraction procedure was found to have tolerance for the common matrix ions in real samples. The optimization studies resulted in pH was suitable at 6.0 with sample volume up to 35 mL. The preconcentration factor was 116. The detection limit was found as 1.18 µg·L−1. The presented microextraction method was applied to determination of palladium in marble mine and catalytic converter samples.