Selection of the sample composition for the selective preconcentration of some platinum group metal ions by Donnan dialysis

The possibility of selective preconcentration of platinum group metal ions by Donnan dialysis was investigated. The effect of sample matrix (glycine) on self diffusion of the following platinum group metal ions Pt(IV), Pd(II), Rh(III), Ir(III) and Ir(IV) was determined. To separate a sample from the receiver electrolyte (0.5M NH₄Cl), anion or cation-exchange membrane were used. Excellent selective preconcentration of Pd(II) in the sample and Ir(III) in the receiver solution was achieved. Experiments performed enable to draw some conclusion on the charge sign of glycinepalladium complexes.     

Ion chromatography of chloro complexes of the platinum group metals and gold using bonded phase silica substrates

The ion chromatography of chloro complexes of Au(III), Ir(IV), Ir(III), Os(IV), Pd(II), Pt(IV), Rh(III) and Ru(III) was investigated using anion-exchange and ion-interaction techniques involving silica-based phases. Chloride was either absent or at a very low level and the pH was high enough to enable steel-fabricated liquid chromatography equipment to be used. With anion exchange, Ir(IV), Ir(III), Os(IV) and Pt(IV) gave good stable chromatography and all produced linear calibration plots, except Ir(IV) owing to instability of the sample solution. The detection limits were Ir(III) 5, Os(IV) 10 and Pt(IV) 2 ng ml^?1. The ion-interaction technique was not so successful, only Au(III) and Pd(II) giving stable chromatography. The calibration plots were slightly curved, although acceptable, and the detection limits were 10 and 30 ng ml^?1 for Au (III) and Pd(II), respectively.     

Highly efficient adsorbing noble metal ions by 3,4-dihydroxycinnamic acid-modified activated carbon

A method was established for the preconcentration of trace Au(III), Pd(II) and Pt(IV) by activated carbon modified with 3,4-dihydroxycinnamic acid. The separation and preconcentration conditions of analytes were investigated, such as effects of pH, the contacting time, the sample ?ow rate and volume, the elution condition and the interfering ions. At a pH of 1.0, the maximum static sorption capacity of the sorbent was found to be 374.8, 96.6 and 137.5 mg g^?1 for Au(III), Pd(II) and Pt(IV), respectively. The adsorbed metal ions were effectively eluted with 2.0 mL of 4% thiourea in 0.5 M HCl solution and determined by inductively coupled plasma optical emission spectrometry. The detection limit (3σ) of this method defined by IUPAC was found to be 0.12, 0.18 and 0.32 ?g L^?1 for Au(III), Pd(II) and Pt(IV), respectively. The relative standard deviation (RSD) was lower than 3.0% (n = 8) towards standard solutions. The method has been validated by analysing certified reference materials and successfully applied to the determination of trace Au(III), Pd(II) and Pt(IV) in road sediments samples.     

Determination of methylmercury by electrothermal atomic absorption spectrometry using headspace single-drop microextraction with in situ hydride generation

A new method is proposed for preconcentration and matrix separation of methylmercury prior to its determination by electrothermal atomic absorption spectrometry (ETAAS). Generation of methylmercury hydride (MeHgH) from a 5-ml solution is carried out in a closed vial and trapped onto an aqueous single drop (3-μl volume) containing Pd(II) or Pt(IV) (50 and 10 mg/l, respectively). The hydrogen evolved in the headspace (HS) after decomposition of sodium tetrahydroborate (III) injected for hydride generation caused the formation of finely dispersed Pd(0) or Pt(0) in the drop, which in turn, were responsible for the sequestration of MeHgH. A preconcentration factor of ca. 40 is achieved with both noble metals used as trapping agents. The limit of detection of methylmercury was 5 and 4 ng/ml (as Hg) with Pd(II) or Pt(IV) as trapping agents, and the precision expressed as relative standard deviation was about 7%. The preconcentration system was fully characterised through optimisation of the following variables: Pd(II) or Pt(IV) concentration in the drop, extraction time, pH of the medium, temperatures of both sample solution and drop, concentration of salt in the sample solution, sodium tetrahydroborate (III) concentration in the drop and stirring rate. The method has been successfully validated against two fish certified reference materials (CRM 464 tuna fish and CRM DORM-2 dogfish muscle) following selective extraction of methylmercury in 2 mol/l HCl medium.     

Application of a macroporous resin containing imidazoline groups to preconcentration and separation of gold, platinum and palladium prior to ICP-AES determination

A new functional resin with a long functional side chain was synthesized by modification of aminated macroporous poly(vinyl chloride) resin with cyanoethylene and ethylenediamine. Traces of Au(III), Pt(IV) and Pd(II) in aqueous solution were quantitatively adsorbed in the acidity range of pH 4 and C(H(+)) 3 M. The rate of equilibration is high; Cu(2+), Fe(3+), Ni(2+), etc. exhibit little interference on the adsorption of the sought noble metals. The saturated adsorption capacities for Au(III), Pt(IV), Pd(II) and Ir(IV) in 2 M HCl were 4.0, 1.57, 2.26, 1.85 mmol g(-1). Adsorbed ions can be quantitatively desorbed by 4% thiourea +0.25 M H(2)SO(4). The resin has good reusability, and can be used for preconcentration and separation of Au(III), Pt(IV) and Pd(II) prior to their determination by ICP-AES with satisfactory results.     

Selective solid-phase extraction and separation of trace gold, palladium and platinum using activated carbon modified with ethyl-3-(2-aminoethylamino)-2-chlorobut-2-enoate

Activated carbon was chemically modified with ethyl-3-(2-aminoethylamino)-2-chlorobut-2-enoate to obtain a material for selective solid-phase extraction of trace Au(III), Pd(II) and Pt(IV) prior to their determination by inductively coupled plasma atomic emission spectrometry. Experimental conditions such as effects of pH, shaking time, sample flow rate and volume, elution and interfering ions were studied. The ions Au(III), Pd(II) and Pt(IV) can be quantitatively adsorbed on the new sorbent from solution of pH 1. The adsorbed ions were then eluted with 0.1 mol L^?1 hydrochloric acid and containing 4% thiourea. Many common ions do not interfere. The adsorption capacity of the material is 305, 92, and 126 mg g^?1 for Au(III), Pd(II) and Pt(IV), respectively, and the detection limits are 5, 11 and 9 ng mL^?1. The relative standard deviation is less than 3.0% (n?=?8) under optimum conditions. The method was validated by analyzing two certified reference materials and successfully applied to the preconcentration and determination of these ions in actual samples with satisfactory results.

Synthesis of N-Methyl-2-Thioimidazole Resin and Its Complex Behavior for Noble Metal Ions

The functional group capacity and the percentage of functional group conversion of crosslinked polystyrene resin bearing N-methyl-2-thioimidazole (MTIR) synthesized under optimum conditions are as high as 4.08 mmol/g resin and 96.0%, respectively. The apparent activation energies of sorption of MTIR for Au(III) and Pt(IV) are 13.1 and 13.4 kJ/mol, respectively. The sorption behavior of MTIR for Au(III), Pt(IV), and Pd(II) obeys the Freundlich and Langmuir isotherms. The sorption capacities of MTIR for Au(III), Pt(IV), and Pd(II) are as high as 4.33, 2.12, and 2.33 mmol/g resin, respectively. Au(III), Pt(IV), and Pd(II) adsorbed on MTIR can be eluted quantitatively by the eluant. The resin can be regenerated easily and reused without an obvious decrease in the sorption capacity for Au(III) and Pd(II). The resin has high sorption selectivity for noble metal ions. Au(III) can be separated quantitatively in the presence of high concentrations of Cu²⁺, Fe³⁺, Ni²⁺, and Mn²⁺. The recovery of platinum from the spent industrial catalysts is 98.6% by MTIR. The preconcentration and separation of palladium and platinum from the anode deposits of electrolysis of crude copper have been investigated. The resin may have potential industrial uses.     

Investigation of the usefulness of NTA, EDTA and DTPA in separation of some platinum metals on cellulose exchangers

The possibility of using NTA, EDTA and DTPA as complexing agents for separation of some platinum group ions on cellulose ion-exchangers has been investigated. The greatest differences in the affinities of Pd(II) and Pt(IV) toward the cellulose ion-exchangers are obtained in the presence of DPTA, Cellex D (as ion-exchanger) in hydroxide form. The column separation of Pd(II) from Pt(IV), Rh(III) from Pd(II) and of a Rh(III)Pd(II)Pt(IV) mixture can be achieved with DPTA and chloride solutions. The method can be for determination of the components of RhPdPt alloys.     

Sorption preconcentration and separation of Palladium(II) and Platinum(IV) for visual test and densitometric determination

We have demonstrated the advantages of the dynamic preconcentration and separation of Pd(II) and Pt(IV) on paper carriers modified with 3-methyl-2,6-dimercapto-1,4-thiopyrone. The optimal conditions of the solid-phase reaction have been determined in Pd(II) sorption; after its separation Pt(IV), has been preconcentrated by sorption as its dimercaptides. Test scales have been produced for the visual determination of 0.5–40 μg Pd(II) and 1–195 μg Pt(IV) in 10- and 100 mL-samples, respectively. In addition, a procedure of their sorption-chromaticity densitometry determination from a single aliquot portion has been developed with detection limits of 5 and 1 ng/mL, respectively, and a procedure of Pd(II) determination using a test strip (c _min = 0.40 mg/L) has been proposed. The procedures have been applied to the determination of palladium and platinum in electrolytes, sludges, and alloys.     

Application of an imidazoline group-containing chelating fiber for the determination of trace noble metals in superhigh-temperature alloys

An imidazoline group-containing chelating fiber was prepared by means of the reaction of nitrile groups with ethylenediamine in an hydrazine-modified polyacrylonitrile fiber. The adsorption properties of the chelating fiber for Au(III), Pd(II), Pt(IV), Ir(IV), Os(IV), Rh(III) and Ru(IV) ions, such as binding capacity, distribution coefficient, sorptive rate and quantitative elution of Au(III), Pd(II) and Pt(IV) ions were investigated. The imidazoline group-containing chelating fiber possessed high binding capacities and good adsorption kinetic properties, exhibited high affinity for noble metals in 0.1–1.0 mol/L HCl and could be efficiently re-used. After the separation of trace Au(III), Pd(II) and Pt(IV) ions from a matrix using the chelating fiber, these ions could be determined by ICP-AES with satisfactory results, and the relative standard deviation for Au(III), Pd(II) and Pt(IV) ions was less than 6%. Received: 5 July 1999 / Revised: 4 October 1999 / Accepted: 4 October 1999     

Organophosphorus Ligands in Studies of Metal Complexes. Investigations of Ligand Exchange and Multielement Trace Analysis using Dithiophosphinic Ligands

Abstract

On mixing organic solutions of [Et₂PS₂]M/n and [Prop₂PS₂]M/n [M=Pd(II), Pt(II), Rh(III), lr(III), Cr(III)] an equilibrium is obtained containing statistical amounts of the corresponding mixed ligand complexes as can be shown by 31P{¹H}-NMR, HPLC and FD-MS. With Pt(II)- and Pd(II)-chelates the kinetics of ligand exchange was determined by HPLC. Mixed complexes ML₂L′ and MLL′₂ were isolated from the equilibrium solutions in case of the more inert Cr(III)-, Rh(III)- and lr(III)-chelates by preparative HPLC. Pd(II), Pt(II) and Rh(III) can be determined quickly and simultaneously in aqueous solutions at nanogramm level by complexation with Et₂PS₂? in a modified sample loop followed by reversed phase HPLC.     

Application of an imidazoline group-containing chelating fiber for the determination of trace noble metals in superhigh-temperature alloys

An imidazoline group-containing chelating fiber was prepared by means of the reaction of nitrile groups with ethylenediamine in an hydrazine-modified polyacrylonitrile fiber. The adsorption properties of the chelating fiber for Au(III), Pd(II), Pt(IV), Ir(IV), Os(IV), Rh(III) and Ru(IV) ions, such as binding capacity, distribution coefficient, sorptive rate and quantitative elution of Au(III), Pd(II) and Pt(IV) ions were investigated. The imidazoline group-containing chelating fiber possessed high binding capacities and good adsorption kinetic properties, exhibited high affinity for noble metals in 0.1-1.0 mol/L HCl and could be efficiently re-used. After the separation of trace Au(III), Pd(II) and Pt(IV) ions from a matrix using the chelating fiber, these ions could be determined by ICP-AES with satisfactory results, and the relative standard deviation for Au(III), Pd(II) and Pt(IV) ions was less than 6%.     

Selective preconcentration of Au(III), Pt(IV) and Pd(II) on silica gel modified with γ-aminopropyltriethoxysilane

Silica gel functionalized by reaction with γ-aminopropyltriethoxysilane was prepared and its adsorption characteirstics for metal ions were studied. This material selectively removes the Au(III), Pt(IV) and Pd(II) chloro complex ions from sample solutions containing Fe(III) and Cu(II) ions by ion exchange.     

Xylenol Orange‐Functionalized Halloysite Nanotubes as a Novel Adsorbent for Selective Solid‐phase Extraction and Determination of Trace Noble Elements

A novel method using xylenol orange‐modified halloysite nanotubes as a solid‐phase sorbent has been developed for the simultaneous preconcentration and separation of trace Au(III ) and Pd(II ) prior to their determination by inductively coupled plasma‐atomic emission spectrometry (ICP‐AES ). The experimental effects of pH , the amount of adsorbent, sample flow rate, sample volume, interfering ions, and the elution condition were investigated in detail. Au(III ) and Pd(II ) were retained on the column at pH 3, and eluted with 2.0 mL of 1.0 mol/L HCl + 2% CS (NH₂ )₂ solution. Common interfering ions did not have any impact on the adsorption, separation, and determination. An enrichment factor of 150 was obtained. The maximum adsorption capacities of the adsorbent were 41.63 and 47.82 mg/g for Au(III ) and Pd(II ), respectively, under the optimum conditions. By the definition of IUPAC , the detection limits (3σ ) of this method for Au(III ) and Pd(II ) were 0.31 and 0.27 ng/mL , and the relative standard deviations (RSDs ) were 2.7 and 3.2%, respectively (n = 8). This newly developed method was verified by certified reference materials, and has been successfully applied to the determination of trace Au(III ) and Pd(II ) in mine samples with satisfactory results. It can be confidently predicted that the method can be used for the determination trace Au(III ) and Pd(II ) in other real samples because of its high selectivity, sensitivity, and reproducibility.     

Ion flotation of rhodium(III) and palladium(II) with anionic surfactants

The ion flotation of rhodium(III) and palladium(II) with some anionic surfactants has been investigated. Two flotation procedures are proposed for the separation of some platinum metals, based on differences in the kinetic properties of the chloro-complexes of rhodium(III), palladium(II) and platinum(IV). The first involves the selective flotation of Rh(H(2)O)(3+)(6) from PdCl(2-)(4) and PtCl(2-)(6) in dilute hydrochloric acid with sodium dodecylbenzenesulfonate (SDBS). After precipitation of the hydroxide and redissolution in dilute acid, the Rh(III) is converted into Rh(H(2)O)(3+)(6), Pd(II) and Pt(IV) remaining as PdCl(2-)(4) and PtCl(2-)(6) respectively, and separation is achieved by floating the Rh(H(2)O)(3+)(6) with SDBS. The second is for separation of Pd(II). Prior to flotation, the solution of PdCl(2-)(4) and PtCl(2-)(6) is heated with ammonium acetate to convert PdCl(2-)(4) into Pd(NH(3))(2+)(4). The chloro-complex of Pt(IV) is unaffected. The complex cation, Pd(NH(3))(2+)(4), is then selectively floated with SDBS. The procedures are fast, simple and do not require expensive reagents and apparatus.     

Synthesis and characterisation of morin-functionalised silica gel for the enrichment of some precious metal ions

Silica gel was firstly functionalised with aminopropyltrimethoxysilane obtaining the aminopropylsilica gel (APSG). The APSG was reacted subsequently with morin yielding morin-bonded silica gel (morin-APSG). The structure was investigated and confirmed by elemental and thermogravimetric analyses, IR and (13)C NMR spectral studies. Morin-APSG was found to be highly stable in common organic solvents, acidic medium (<2molL(-1) HCl, HNO(3)) or alkaline medium up to pH 8. The separation and preconcentration of Ag(I), Au(III), Pd(II), Pt(II) and Rh(III) from aqueous medium using morin-APSG was studied. The optimum pH values for the separation of Ag(I), Au(III), Pd(II), Pt(II) and Rh(III) on the sorbent are 5.7, 2.2, 3.7, 3.7 and 6.8, giving rise to separation efficiencies of 43.9, 85.9, 97.7, 60.9 and 91.0%, respectively, where the activity was found to be >90% in the presence of acetate ion. The ion sorption capacity of morin-APSG towards Cu(II) at pH 5.5 was found to be 0.249mmolg(-1) where the sorption capacities of Ag(I) and Pd(II) were 0.087 and 0.121mmolg(-1) and 0.222 and 0.241mmolg(-1) at pH 2.2 and 5.7, respectively. This indicates a 1:1 and 1:2 morin/metal ratios at pH 2.2 and 5.7, respectively. Complete elution of the sorbed metal ions was carried out using 10mL (0.5molL(-1) HCl+0.01molL(-1) thiourea) in case of Au(III), Pd(II), Pt(II) and Rh(III) and 10mL 0.5molL(-1) HNO(3) in case of Ag(I). Morin-APSG was successfully employed in the separation and preconcentration of the investigated precious metal ions from some spiking water samples yielding 100-folds concentration factor. The relative standard deviation (R.S.D.) and the T-test (|t|(1)) were calculated.     

Simultaneous determination of gold(III), palladium(II), and platinum(IV) with N-phenyl-N′-(sodium p-aminobenzenesulfonate)thiourea

The preparation and characteristics of a new water-soluble reagent, N-phenyl- N'-(sodium p-aminobenzenesulfonate)thiourea (PPT) are described. In the presence of cetyltrimethylammonium bromide (CTMAB) PPT reacts with Au(III), Pd(II), and Pt(IV) to form colored complexes with absorption maxima at 317 nm, 306.1 nm, 778.4 nm, respectively. Optimum conditions for color development were studied. The reagent was used for the simultaneous determination of Au(III), Pd(II), and Pt(IV); Amberlyst A-26 macropore anion-exchange resin was used as a means of rapid separation. The method was applied to the determination of Au(III), Pd(II), and Pt(IV) in catalyst materials and anode mud with satisfactory results.     

Determination of platinum and palladium in road dust after their separation on immobilized fungus by electrothermal atomic absorption spectrometry

A flow solid phase extraction procedure based on biosorption of Pt(IV) and Pd(II) on Aspergillus sp. immobilized on cellulose resin Cellex-T was proposed for the separation and preconcentration of Pt and Pd before their determination by electrothermal atomic absorption spectrometry (ETAAS). The analytical conditions including sample pH, eluent type, flow rates of sample and eluent solutions were examined. The analytes were selectively retained on the biosorbent in acidic medium (pH 1) and subsequently eluted from the column with 1 mL of thiourea solution (0.25 mol L^− 1 thiourea in 0.3 mol L^− 1 HCl). The reproducibility of the procedure was below 5%. The limit of detection of the method was 0.020 ng mL^− 1 for Pt and 0.012 ng mL^− 1 for Pd. The method validation was performed by analysis of certified reference materials BCR-723 (tunnel dust) and SARM-76 (platinum ore). The developed separation procedure was applied to the determination of Pt and Pd in road dust samples by ETAAS.The applied biosorbent is characterized by high sorption capacity: 0.47 mg g^− 1 for Pt and 1.24 mg g^− 1 for Pd.     

Ion-exchange separation and spectrophotometric determination of traces of gold

Summary A combined ion-exchange — spectrophotometric method has been developed for the separation and determination of traces of Au(III) in seven metal ions: Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Se(IV) and Cd(II). Au(III) is adsorbed selectively on a DEAE column from dilute chloride solution, while other metal ions pass through the column. Au(III) is recovered by elution with 1M hydrochloric acid. Traces of Au(III) in the effluent are determined by a new spectrophotometric method, which is based on the formation and extraction of Au(III) — azide — methylene blue complex. Separations of traces of Au(III) from 1000-fold of Pd(II) and Pt(IV) and 10000-fold of Hg(II) are also effected on a DEAE column in mixed methanol 1M hydrochloric acid medium (8 2). While Pd(II), Pt(IV) and Hg(II) are retained on the column, Au(III) adsorbs very weakly, so that the separations can be accomplished easily.

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Zusammenfassung Eine mit Ionenaustausch kombinierte spektrophotometrische Methode zur Trennung und Bestimmung von Goldspuren neben sieben verschiedenen Metallionen wurde ausgearbeitet, nämlich neben Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Se(IV) und Cd(II). Das Gold wird an einer Säule aus Diäthylaminoäthylzellulose (DEAE) aus verdünnter Chloridlösung adsorbiert, wobei die anderen Metalle die Säule passieren. Durch Elution mit 1-m Salzsäure wird das Gold wieder gewonnen. Goldspuren im Effluenten werden mit Azid und Methylenblau komplex gebunden und so spektrophotometriert. Von der 1000fachen Menge Pd(II) und Pt(IV) sowie der 100000fachen Menge Hg(II) können Goldspuren auch aus Methanol + 1-m Salzsäure (12) mit einer DEAE-Säule abgetrennt werden. Während Pd(II), Pt(IV) und Hg(II) an der Säule festgehalten werden, wird Au(III) nur sehr schwach adsorbiert, so daß die Trennung leicht gelingt.

     

Quantitative separation of gallium from zinc, copper, indium, iron(III) and other elements by cation-exchange chromatography in hydrobromic acid-acetone medium

Gallium can be separated from Zn, Cu(II), In, Cd, Pb(II), Bi(III), Au(III), Pt(IV), Pd(II), Tl(III), Sn(IV) and Fe(III) by elution of these elements with 0.50M hydrobromic acid in 80% acetone medium, from a column of AG50W-X4 cation-exchange resin. Gallium is retained and can be eluted with 3M hydrochloric acid. Separations are sharp and quantitative except for iron(III) which shows extensive tailing. With 0.20M hydrobromic acid in 80% acetone as eluting agent, all the species above except iron(III) and copper(II) can be separated from gallium with very large separation factors. Only a 1-g resin column and small elution volumes are required to separate trace amounts and up to 0.5 mmole of gallium from more than 1 g of zinc or the other elements. Hg(II), Rh(III), Ir(IV), Se(IV), Ge(IV), As(III) and Sb(III) have not been investigated, but should be separated together with zinc according to their known distribution coefficients. Relevant elution curves, results for the analysis of synthetic mixtures and for amounts of some elements remaining in the gallium fraction are presented.