Specificity of noble metals dynamic sorption preconcentration on reversed-phase sorbents

The reversible sorption preconcentration of noble metals (NMs) using different schemes “sorbent–reagent–eluent” was investigated. The extraction of Au, Pd, Pt, Ir, Rh and Ru chlorocomplexes from hydrochloric acid solutions on hyper-crosslinked polysterene MN-200 in the form of ion associates with tributylamine (TBA) and 4-(n-octyl)diethylenetriamine (ODETA) was investigated. It was found that Pd, Pt and Au were quantitatively and reversibly extracted using TBA on hyper-crosslinked polysterene; the appropriate eluent for desorption was 1 M solution of HCl in ethanol. Ir, Rh and Ru under these conditions were not sorbed quantitatively. It was found that sorbent hydrophobicity is not the main characteristic that defines the efficiency of sorption of a particular NM ion associate. Different efficiencies of hyper-crosslinked polysterene MN-200 for sorption of square-planar chlorcomplexes of Pt, Pd and Au and octahedral complexes of Ir, Rh and Ru were found. For the first time, the sorbents with their own N-atoms – StrataX and StrataX-AW – were used for the sorption of Ir, Rh and Ru. Using these sorbents, the sorption of Ir was increased up to 95%, and the sorption of Ru and Rh was increased to about 40%. We can explain these results by nonspecific interaction of chlorcomplexes of Ir, Rh and Ru with ethylenediamine groups of the sorbent. Weak bases with large anions may be applied for desorption of Ir, Rh and Ru. Two schemes of dynamic sorption preconcentration of NMs from hydrochloric acid solutions were proposed – hyper-crosslinked polysterene MN-200 for the determination of Au, Pd, Pt, and StrataX-AW for Ir, Rh and Ru.     

New solid extractants for preconcentrating noble metals

New solid extractants are synthesized with the use of imidazolium and phosphonium ionic liquids for preconcentrating noble metals. Ionic liquids are selected and conditions for their immobilization on various solid matrices are found. The adsorption properties of the synthesized solid extractants for platinum(IV) in hydrochloric acid solutions are studied. The solid extractants obtained by binding 1-hexadecyl-3-methylimidazolium bromide and trihexyltetradecylphosphonium chloride to polymeric matrices and multiwall carbon nanotubes possess good kinetic properties and selectivity in 1 M HCl, and can be used to preconcentrate Pt(IV), Pd(II), and Au(III) in combined methods of their determination.     

New chelating sorbents of the pyrazolone type based on styrene-divinylbenzene copolymer

Summary The sorption of milligram amounts of gold, palladium and silver on a chelating sorbent of pyrazolone type is studied. A fourfold increase in sorbent capacity towards the precious metals is recorded at 65°C, compared to room temperature. The developed procedure permits to separate milligram amounts of gold, palladium or silver from both microgram or milligram amounts of non-precious metals.Part I: see [6]     

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     

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%.     

A selective sorbent for concentrating noble metals

New chelating sorbents have been synthesized by aminating chloromethylated styrenedivinylbenzene macroporous copolymers with 3(5)-methylpyrazole. The sorption of noble metals from acid solutions and the selectivity has been studied. The sorbents are of interest for selective concentration and extraction of the noble metals.     

Some new chelating polymers for toxic metals

Several novel polymers capable of binding mercury(II) have been prepared, all of which contain mercaptal linkages. Their selectivity for binding mercury(II) in preference to other metal ions varies considerably as the structures are varied. Those prepared from terephthaldicarboxaldehyde and polythiols tend to be fairly selective, while one prepared from glutaraldehyde and pentaerthritol tetrathioglycolate is less selective and tends to bind lead, cadium and copper, as well as mercury.     

Modified anthracites as selective sorbents for platinum metals

Methods of preliminary modification were used to obtain activated carbons with low ash content (0.2%), developed π-conjugated electronic system, large surface area, and wide pore size distribution, from exclusively microporous carbons to those of mesoporous type. The adsorption of compounds of platinum-group metals on activated anthracite from single-component (as regards the platinum metal: Pd, Pt, or Rh) and multicomponent (Pd, Pt) solutions containing compounds of concomitant metals was studied.     

Neutron activation analysis of some noble metals with preconcentration procedure using a new type of cation chelating resin

The characteristic properties of the chelating resin-3926(II) and the advantage of using it in the preconcentration procedure was described. The chemical recoveries determined by the trace technique were presented. The preconcentration procedure put forward in this paper may be used satisfactorily in neutron activation analysis.     

Analytical techniques for corrosion studies on noble metals

The suitability of various analytical methods for studying the corrosion of gold, silver and palladium in various electrolytes has been investigated. The methods included potentiometry with ion-selective electrodes, polarography and atomic-absorption spectrophotometry. All three methods are useful for monitoring low corrosion rates by solution analysis but each has its limitations. Concentrations in the ng/ml range can be measured routinely with errors of 10% or less.     

New sorbents and indicator powders for preconcentration and determination of trace metals in liquid samples

Two approaches to immobilize complex-forming analytical reagents (PAN, PAR, Xylenol orange, Brombenzothiazo, Crystal violet, Cadion, and Sulfochlorophenolazorhodanine) for the preparation of new sorbents and indicator powders are suggested: on-line coating of reversed-phase silica gel by reagents or doping of porous sol-gel silica with reagents. The retention of Ag, Cd, Cu(II), Co(II), Fe(III), Mn(II), Ni, Pb, and Zn on the sorbents developed was investigated. Quantitative sorption and desorption conditions were optimized. Procedures for the determination of Cd, Cu(II), Fe(III), Pb, and Zn with flame atomic absorption, spectrophotometric, and diffusion scattering spectrometric detection were elaborated. Detection limits for Cd, Cu(II), Fe(III), Pb, and Zn were 3 μg/L, 6 μg/L, 5 μg/L, 40 μg/L, and 1 μg/L, respectively. The procedures were used for the analysis of various real samples, e.g., natural and waste waters, and food. Received: 17 July 1997 / Revised: 20 January 1998 / Accepted: 5 February 1998     

New sorbents and indicator powders for preconcentration and determination of trace metals in liquid samples

Two approaches to immobilize complex-forming analytical reagents (PAN, PAR, Xylenol orange, Brombenzothiazo, Crystal violet, Cadion, and Sulfochlorophenolazorhodanine) for the preparation of new sorbents and indicator powders are suggested: on-line coating of reversed-phase silica gel by reagents or doping of porous sol-gel silica with reagents. The retention of Ag, Cd, Cu(II), Co(II), Fe(III), Mn(II), Ni, Pb, and Zn on the sorbents developed was investigated. Quantitative sorption and desorption conditions were optimized. Procedures for the determination of Cd, Cu(II), Fe(III), Pb, and Zn with flame atomic absorption, spectrophotometric, and diffusion scattering spectrometric detection were elaborated. Detection limits for Cd, Cu(II), Fe(III), Pb, and Zn were 3 μg/L, 6 μg/L, 5 μg/L, 40 μg/L, and 1 μg/L, respectively. The procedures were used for the analysis of various real samples, e.g., natural and waste waters, and food.     

POLYORGS as complexing sorbents for preconcentration of trace metals

Summary The main characteristics of the complexing sorbents POLYORGS are reviewed. These sorbents contain pyrazole, imidazole, amidoxime, 2-mercaptobenzothiazole, thioglycolanilide and arsenazo groups and exhibit high selectivity in respect to noble, rare-earth and heavy metals. The sorbents POLYORGS are applied for the preconcentration of these metals to be determined in ores, rocks, natural and waste waters, and industrial products. The metal determinations after preconcentration are carried out by means of different instrumental methods (e.g., AAS, XRFA, ICP-AES, NAA) either directly in the sorbent, after elution of the analytes or decomposition of the sorbent.     

New chelating sorbents based on pyrazolone containing amines immobilized on styrene-divinylbenzene copolymer-I Synthesis and analytical characterization

A series of new cheating sorbents has been prepared by modification of styrene-divinylbenzene copolymer with different pyrazolone-containing amines. The substances were characterized by elemental analysis and infared spectroscopy. The complexation ability of the sorbents towards alkali, alkaline-earth, transition and precious metals has been studied. The new sorbents may successfully be applied to the simultaneous preconcentration of alkaline-earth and transition elements in neutral medium and to the selective separation of precious metals in acidic medium.     

Atomic-absorption spectroscopic determination of noble metals

Zusammenfassung Die AAS-Bestimmung von Platin wird von zahlreichen Elementen zum Teil sehr stark gestört. Durch Zusatz von Uran kann der Einfluß von Palladium und Rhodium mit Hilfe quadratischer Korrekturgleichungen beseitigt werden. Lanthan ist als Puffer ungeeignet.Teil 3: diese Z.280, 359 (1976)     

Sorption methods of concentrating noble metals

Summary The possibility of concentrating microamounts of noble metals on inorganic collectors and chelating sorbents has been investigated. Optimum conditions have been found for simultaneous concentration of Pd, Pt, Rh, Ir, Au and Ag from solutions of complicated composition. For trace analysis a method is suggested based on co-precipitation of the noble metals on copper sulphide, with separation from large amounts of Ni, Co, Fe and associated components. For separation of the noble metals from copper, thin-layer chromatography or sorption on a chelating sorbent under static conditions can be used. The purity of the concentrations obtained allows use of various methods of determination: spectral, atomic-absorption, radioactivation etc.

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Zusammenfassung Die Möglichkeit, Edelmetalle in Mikromengen an anorganischen Kollektoren und Chelatbildnern anzureichern, wurde untersucht. Optimale Bedingungen für die gleichzeitige Anreicherung von Pd, Pt, Rh, Ir, Au und Ag aus Lösungen komplizierter Zusammensetzung wurden gefunden. Für spurenanalytische Zwecke eignet sich die Mitfällung von Edelmetallen mit Kupfersulfid, wobei sie von Ni, Co, Fe und sonstigen Begleitstoffen getrennt werden. Zur Trennung von Kupfer kann die Dünnschichtchromatographie oder die Adsorption an Chelatbildnern unter statischen Bedingungen dienen. Die Reinheit der Konzentrate ermöglicht dann die Bestimmung durch Spektralanalyse, Atomarabsorption, Aktivierungsanalyse usw.

     

Chemical vapor generation of noble metals for analytical spectrometry

As is apparent from the literature devoted to the analytical atomic spectrometry, chemical vapor generation (CVG) of noble metals by reaction with tetrahydroborate in acidic media may enhance the introduction of these elements into different atomic spectrometric sources. Recent developments in the CVG of noble metals species by reaction with tetrahydroborate in acidic medium are surveyed. Different aspects of this novel technique are discussed, including type of instrumentation used for the reaction, separation and transport of the species, effect of chemical and physical factors, identification of the species, and the efficiency of the process. Limitations and future prospects of the CVG technique are discussed.