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.     

Agricultural biomasses as sorbents of some trace metals

The studies of sorption of six metal ions (Cd²⁺, Cu²⁺, Pb²⁺, Zn²⁺, Ni²⁺, Cr³⁺ and Cr(VI)) from by-products of agriculture are taken into account. The Langmuir q_max values obtained with the use of different biomasses are evaluated and, in order to acquire comparable results, the necessity of using molar concentrations is stressed. The main effects of pH on sorption are estimated by considering both the behaviour of metal ions (hydrolysis and hydroxide precipitation) and the effect of pH on coordination, using a simulated example. Some considerations are made on the information that can be obtained using the most common isotherms and on the need to use chemical dimensions rather than weight in order to make comparison among various metal ions (since atomic weight differences deeply alter the significance of parameters in non-chemical units) and to predict the effects of competition between two (or more) of these for the same sorbent sites on the biomass surface.     

Potassium thiocarbonate as a precipitant for platinum metals

Potassium thiocarbonate reagent is proposed for the gravimetric determination of ruthenium(III), rhodium(III), palladium(II) and platinum(IV) in a highly acidic medium (pH 0.5-0.7) under suitable conditions. Ni, Zn, Mn(II), Al, Fe(III), Ti(IV), Zr, Th, Ca, Ba, Sr and Mg do not interfere. The largest relative error is 0.7% and the average error 0.2%.     

New chelating sorbents for noble metals

The properties of the new ehelate-forming “POLYORGS” sorbents for concentration of noble metals are discussed. POLYORGS are made from different polymeric matrices (polystyrene, copolymers of styréne with divinylbenzene, fibrous materials). They contain heterocyclic amine and amidoxime groups, and are selective for noble metals. Some methods of noble metal determination after preliminary concentration of POLYORGS sorbents are given.     

Estimation of metals as sulphides : Estimation of platinum metals

1. It has been shown that all the platinum metals with the exception of osmium can be estimated as sulphide if the solution containing the metal is treated with a large excess of alkali sulphide followed by excess of acetic acid and ammonium acetate. The precipitate of the sulphide can be washed with water, alcohol and ether successively, dried in a vacuum desiccator, and weighed. 2. By the above procedure it is possible to complete the analysis for all the platinum metals within 3 hours, whereas the procedures described in the literature require much longer time —in many cases more than 24 hours. 3. The precipitates obtained by the older procedures were very sticky and difficult to filter. By carrying out the precipitation in the presence of acetic acid and ammonium acetate it has been possible to obtain the precipitate in an easily filterable form. 4. The above method not only provides a very convenient general method of estimating the platinum metals, but also throws interesting light on the formation of thiosalts and the precipitation of sulphides by their decomposition.     

Carborane-based metal-organic frameworks as highly selective sorbents for CO(2) over methane

Separation of CO(2)/CH(4) mixtures was studied in carborane-based metal-organic framework materials with and without coordinatively unsaturated metal sites; high selectivities for CO(2) over CH(4) ( approximately 17) are obtained, especially in the material with open metal sites.     

Hexamethylenetetramine as a reagent for microscopic tests for gold and the platinum metals

Summary A study of the compounds formed in acid solutions by the chlorocomplexes of gold and the platinum metals with hexamethylenetetramine (urotropine), or its salts, shows that characteristic crystals are formed which can be observed under the microscope and used for confirmatory tests.Several new tests are described including those with hexamethylenetetramine anhydromethylene citrate (helmitol). The limit of identification, limiting concentration and in the case of interferences, the limiting proportions, are given for each compound.

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Zusammenfassung Eine Untersuchung der Verbindungen, die von den Chlorokomplexen von Gold und den Platinmetallen oder deren Salzen mit Hexamethylentetramin (Urotropin) erhalten werden, zeigte, daß sie Kristalle geben, die unter dem Mikroskop charakteristische Formen erkennen lassen und für den Nachweis der genannten Metalle geeignet sind.Einige neue Nachweise werden beschrieben, darunter jene, bei denen Hexamethylentetramin-anhydromethylenzitrat (Helmitol) als Reagens zur Verwendung gelangt. Die Erfassungsgrenze, die Grenzkonzentration und die Grenzverhältnisse bei allenfalls auftretenden Störungen werden für jeden Nachweis angegeben.

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With 8 figures.     

Steroids as chiral model compounds for selective reactions with metals

Our own work on steroid compounds with defined conformation as chiral model compounds for investigations of chemo-, regio- and stereoselectivity of metal-mediated new reactions is reviewed. Reactions with nickelacycles, (π-allyl)zirconoxycarbene complexes, iron tricarbonyl complexes of dienes and 1-azadienes, the Ru-catalyzed synthesis of 1,3-dihydropyrrol-2-ones from 1-azadienes, the Pd-catalyzed cyclopropanation of 1-azadienes, syntheses with cuprio steroids, copper complexes of amino alcohol derivatives and the copper-mediated hydroxylation of nonactivated C-H bonds with molecular oxygen are discussed.     

Polyurethane foams as selective sorbents for noble metals : Quantitative extraction and separation of rhodium from iridium in hydrochloric acid containing tin(II) chloride

The distribution of rhodium(III) between polyether-type polyurethane foam and 0.5–5.0 mol dm^?3 hydrochloric acid in the presence of small amounts of tin(II) chloride is described. The distribution of rhodium is affected by the extraction temperature, acid concentration and the Sn(II):Rh ratio. The capacity of the polyurethane foam for rhodium is in excess of 0.5 mmol g^?1. Rhodium is presumably sorbed in the form of a chloro(trichlorostannato)rhodium(III/I) complex anion. Iridium is not extracted by the foam under corresponding conditions and can be separated quantitatively from rhodium.     

Amorphous and ordered organosilicas functionalized with amine groups as sorbents of platinum (II) ions

Two groups of amine-functionalized organosilicas have been synthesized: amorphous polysiloxane xerogels (APX) and ordered mesoporous organosilicas (OMO) by co-condensation of tetraethoxysilane and appropriate alkoxysilanes: aminopropyltriethoxysilane and N-[3-(trimethoxysilyl)propyl]ethylenediamine. The obtained materials were characterized by sorption measurements, X-ray diffractometry, elemental analysis, transmission electron microscopy, and scanning electron microscopy. The OMO samples have well developed porous structure—the values of specific surface area are in the range 740–840 m²/g. While the APX samples are less porous having the corresponding values in the range 280–520 m²/g. The sizes of the ordered mesopores of OMO are in the range 5.9–6.5 nm while for the APX they are 2.9–12.1 nm indicating structural differences between both groups of the samples. All samples were tested as the sorbents of Pt(II) ions. The influence of various parameters such as pH, contact time, equilibrium concentration on Pt(II) adsorption ability onto prepared adsorbents was studied in detail. Additionally, the effect of chloride concentration on Pt(II) adsorption was investigated. The values of static sorption capacities were in the range of 32–102 mg_Pt(II)/g and 20–139 mg_Pt(II)/g for OMO and APX series, respectively.     

Evaluation of titanium and titanium oxides as chemo-affinity sorbents for the selective enrichment of organic phosphates.

Titanium (Ti) and TiO, Ti2O3, Ti3O5 and TiO(1.98) as well as TiO2 have been evaluated as chemo-affinity sorbents for the selective enrichment of organic phosphates. A column-switching high-performance liquid chromatography (HPLC) system, constructed with a precolumn (4.6 mm i.d. x 10 mm) packed with the titanium sorbents, an anion-exchange analytical column and a UV detector (215 nm) was used. When an aqueous 0.015% trifluoroacetic acid (TFA) was used as a sample-loading solution, O-phospho-L-tyrosine (P-Tyr), phenyl phosphate and phenylphosphonic acid were adsorbed onto all of the titanium sorbents with recoveries of 60.9 - 102.9%. Some acidic compounds other than phosphates, such as benzenedicarboxylic acid (BDA) isomers, were also adsorbed onto all of the titanium sorbents. To improve the selectivity to organic phosphates, various sample-loading solutions were examined using a Ti precolumn, two phosphorylated peptides [Ile-Ser(p)-Val-Arg (PP1) and Gln-Ile-Ser(p)-Val-Arg (PP2)], P-Tyr, BDA isomers and diglutamic acid (Glu-Glu) as test compounds. Among the sample-loading solutions tested, such as TFA, HClO4, organic acids, boric acid and NaCl, the use of 100 mM NaCl in 10 mM boric acid was found to be effective. The recoveries of PP1, PP2 and P-Tyr were 73.0, 88.3 and 71.5%, respectively, whereas those of Glu-Glu and BDAs were suppressed to only below 10%.     

Cellulose fibrous sorbents with conformationally flexible aminocarboxylic groups for preconcentration of metals

New cellulose fibrous sorbents, containing a diethylenetriamine tetraacetate groups, are proposed for the preconcentration of heavy metals. Quantitative extraction of heavy metals from river and sea water is achieved in a wide pH range (3–8) at a high solution flow rate (up to 100–150 volumes of sorbent per minute). Quantitative desorption of metals is achieved with a very small volume of the acid.     

Catalytic kinetic methods for the determination of platinum metals

A review is given of developments over the last two decades in the determination of platinum metals by catalytic kinetic methods.     

The Microchemistry of the platinum metals

Summary A method is outlined for the separation and determination of small amounts of osmium, iridium and platinum. Osmium and platinum are determined colorimetrically, and iridium is determined by titration. The procedure gives reproducible results, and provides a convenient method for the determination of each of the elements.

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Zusammenfassung Eine Methode zur Trennung und Bestimmung kleiner Mengen Osmium, Iridium und Platin wurde beschrieben. Osmium und Platin werden kolorimetrisch bestimmt, Iridium maßanalytisch. Das Verfahren gibt reproduzierbare Ergebnisse und eignet sich zur Bestimmung jedes der genannten Elemente.

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Résumé On recommande une méthode pour la séparation et le dosage de petites quantités d'osmium, d'iridium et de platine. On dose par colorimétrie l'osmium et le platine et par titrage l'iridium. Le procédé donne des résultats reproductibles et fournit une méthode appropriée pour le dosage de chacun des éléments.

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In honour of the 70th birthday ofFritz Feigl.     

Microseparation of platinum metals by electrophoresis

Summary An electrophoretic study of the platinum metals, as Pt²⁺, Pt⁴⁺, Os⁴⁺, Ir⁴⁺, Ru³⁺, Rh³⁺, Au³⁺ and Pd²⁺ reveals that quite a large number of electrolytes effectively separate microgram amounts of ternary and quaternary mixtures of the ions into distinct zones. The voltages are maintained at 100 and 200 V for a period of three hours. The sequences of separation are tabulated.

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Zusammenfassung Die elektrophoretische Untersuchung der Platinmetalle Pt²⁺, Pt⁴⁺, Os⁴⁺, Ir⁴⁺, Ru³⁺, Rh³⁺, Au³⁺ und Pd²⁺ ergab, daß zahlreiche Elektrolyte zur Auftrennung von Mikrogrammengen ternärer und quarternärer Mischungen dieser Ionen in scharfe Zonen geeignet sind. Die Spannung wurde dabei auf 100 bis 200 V für 3 Stunden gehalten. Die Reihenfolge der Trennung wurde in Tabellen angegeben.

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Résumé Une étude par électrophorèse des métaux de la mine du platine, tels que Pt²⁺, Pt⁴⁺, Os⁴⁺, Ir⁴⁺, Ru³⁺. Au³⁺ et Pd²⁺, montre qu'un grand nombre d'électrolytes sépare en zones nettement distinctes des ions en mélanges ternaires et quaternaires, en quantités micro. On maintient la tension à 100 et 200 V pendant 3 heures. On présente sous forme de tableaux l'ordre de la séparation.

     

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.     

Selective complexing agents for the trace enrichment of platinum metals

Summary N,N-Dialkyl-N-benzoylthioureas act as selective complexing agents for the enrichment of platinum metals even from strongly interfering matrices. In combination with chromatographic separation techniques of GFAAS as detection method metal determinations in the g- and ng/kg range are possible. A review of the investigations so far been carried out is given.     

Functional, mesoporous, superparamagnetic colloidal sorbents for efficient removal of toxic metals

γ-Fe(2)O(3) incorporated mesoporous silica particles of 50-100 nm size have been synthesized which are functionalized with chelating agents of metal ions. These particles are water dispersible but aggregate in response to the external magnetic field and have been used for high performance and selective removal of Cd, Pb, Hg and As.