Extraction of gold(III), palladium(II), and platinum(IV) by 1-[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-ylmethyl]-1<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazole from hydrochloric acid solutions

The extraction of gold(III), palladium(II), and platinum(IV) with 1-[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole from hydrochloric acid solutions into toluene has been studied. The extraction follows the anion-exchange mechanism. The concentration constants and thermodynamic parameters of the extraction reaction have been calculated. The reagent is proposed for use in the extraction of the sum of precious metals.     

Spectrographic determination of gold and platinum metals in geological and other materials by fire-assay preconcentration

A method is described for the determination of gold, platinum, palladium, rhodium and iridium at microgram levels in geological and other materials by a combination of fire-assay preconcentration and emission spectrography. The noble metals are collected into 4-mg silver or platinum prills by a normal fire-assay technique. These prills are arced between graphite electrodes at 12 A d.c. No buffer is required to prevent ejection of the prill. Gold, platinum and palladium are determined in the silver prills and gold, palladium, rhodium and iridium in the platinum prills. Low, but reproducible, results are found for iridium. At the 0.08 ppm level an overall coefficient of variation of 11% is found. This technique is simple and rapid for the determination of the precious metals.     

Solvent extraction of gold with N-substituted benzoylthioureas

Summary Benzoylthioureas are excellent reagents for the solvent extraction of gold. Very effective separations of gold from platinum group metals and base metals are possible due to control of the extraction parameters. The best results, a fast extraction and low residual gold concentrations <1 g/l are obtained with N,N-Di-n-hexylbenzoylthiourea/toluene.     

Chelate von β-dicarbonylverbindungen und ihren derivaten—teil XLIV. Die extraktion von silber,gold, palladium und platin mit thiodibenzoylmethan1

The extraction of silver(I), gold(III), palladium(II) and platinum(IV) with thiodibenzoylmethane is reported, and methods for the extraction—photometric determination of silver and palladium in trace concentrations are described. Addition of EDTA allows a satisfactory selectivity to be achieved. The influence of foreign metals and complexing agents is discussed.     

Determination of palladium, platinum and gold by first derivative spectrophotometry

Summary The application of first-derivative spectrometry to the simultaneous determination of palladium(II), platinum(IV) and gold(III) is described. Light absorption of stable chlorocomplexes formed in 1 mol/l hydrochloric acid provides the basis of their determinations. A difference in the derivative amplitudes between two first-derivative zero crossing points of one metal A is read, corrected for the contribution of metal B and used for quantitation of metal C. Palladium (0.48–20 g ml^–1), platinum (0.16–24 g ml^–1) and gold (0.32–24 g ml^–1) have been determined with good precision and accuracy without any separations. Results are also presented for the simultaneous determination of the three precious metals in the presence of several major constituents.     

Selective extraction of palladium(II) with theophylline derivatives.

Theophylline derivatives with some kinds of alkyl chains were synthesized and used in extraction experiments involving metal ions. Theophylline derivatives have exhibited a high selectivity for palladium over other precious metals and base metals. The extraction of palladium from acidic chloride media has been investigated using theophylline derivatives (= RN) as extractants. Palladium(II) was found to be extracted with 7-octyltheophylline according to the following reaction: PdCl2 + 2RN <==> PdCl2(RN)2. The extraction equilibrium constant was determined to be K = 2.67 x 10(8) ( moldm(-3))(-2). In addition, the stripping of palladium was performed to an extent of 100% by a single batchwise treatment with a 1.0 mol dm(-3) ammonia solution. The stoichiometric relation in the extraction of palladium was supported by an analysis using mass spectrometry.     

A Short Review of the Separation of Iridium and Rhodium from Hydrochloric Acid Solutions by Solvent Extraction

Iridium and rhodium are among the platinum group metals. The properties, production processes, and aqueous chemistry of both metals are reviewed. The separation of Ir(IV) and Rh(III) from hydrochloric acid solution is dependent on the characteristics of the solvent extraction systems. In most of the extraction conditions, Ir(IV) is selectively extracted over Rh(III) by either amines or neutral extractants. Rh(I) can be selectively extracted over Ir(III) by neutral extractants after Rh(III) is reduced in the presence of a reducing agent. The separation of these two metals using cationic extractants has also been reported. Although selective extraction of one metal over the other is possible, more efficient solvent extraction systems need to be developed.     

Propiconazole and Penconazole as Effective Extractants for Selective recovery and concentration of platinum(IV) and palladium(II) from hydrochloric acid solutions formed in leaching of spent aluminoplatinum and aluminopalladium catalysts

Selective recovery and concentration of platinum(IV) and palladium(II) from hydrochloric acid solutions of varied composition was studied using commercial reagents propiconazole and penconazole as extractants. The ranges of hydrochloric acid concentrations for effective extraction and highly selective separation of platinum metals from Al(III) and Ni(II) with propiconazole (toluene with 15 vol % n-decanol as deluent) and penconazole (chloroform) were determined. The conditions for 10-fold selective concentration of platinum metals with recovery of more than 99.9% of metal ions into the organic phase were found. The conditions for quantitative (>99%) stripping of platinum(IV) with a hydrochloric acid solution of thiourea and palladium(II) with ammonia solution were determined. The results obtained can be used for optimizing the modes of selective recovery of platinum(IV) and palladium(II) from hydrochloric acid solutions formed in leaching of alumina-supported platinum-rhenium, platinum-nickel, and palladium catalysts.     

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]     

The tin-collection scheme for the determination of platinum-group metals, gold and silver

A comprehensive analytical scheme is presented for the determination of the six platinum-group metals, gold and silver. It is the result of the integration of separate procedures that have been described previously, in part, over the course of several years. The analytical scheme has been thoroughly tested in umpire and standards work on a wide variety of materials and, as a consequence, is of increasing interest to many laboratories. The precious metals are collected in molten tin when the sample is fused at 1200-1250 degrees with a flux containing stannic oxide, sodium carbonate, silica, borax and flour. The resultant tin alloy is dissolved and the precious metals are isolated by ion-exchange, solvent extraction and/or distillation procedures. With the exception of the usual facilities required in the fusion step of fire assaying, standard equipment can be used in the wet-chemical operations for the isolation and determination of the individual precious metals.     

Immobilization of 5-methylene-2-(2′-thiazolylazo)-anisole on silica and its application in preconcentration of palladium

5-Methylene-2-(2′ -thiazolylazo)-anisole can be immobilized on silica via a SiOSiC moiety. Distribution coefficient studies of platinum metals, gold and base metals show that the chelating silica is selective for palladium(II). The chelating silica is used to preconcentrate and separate palladium from synthetic solution containing traces of palladium and large amounts of copper. The capacity for palladium is about 0.07 mmol g^?1.     

电子废弃物中金元素的绿色溶解与提取

电子废弃物中含有Au、Pt、Pd、Ag等多种贵重金属,其处理处置的无害化、资源化成为目前一项重要课题。本文通过使用安全的试剂来溶解金,从而达到从含金废弃物中回收金的目的,说明利用配体与金形成配合物从而有效降低溶金电极电势的化学原理。普及科学原理,树立科学理念。介绍电子废弃物处置的常识,普及绿色化学的观念,避免新的污染与危险,树立环境保护的观念。     

Extraktiv-photometrische Bestimmung von Palladium als Palladium-Thioxan-Chlorid

Zusammenfassung Unter den Verbindungen [Pd · Thioxan₂ X₂] (X=Cl, Br, J) eignet sich das Chlorid zur extraktiv-photometrischen Bestimmung geringer Palladium-Mengen neben größeren Überschüssen an Gold und Platinmetallen, sowie neben den meisten Übergangsmetallen bei Verhältnissen Pd: Übergangsmetall=110000.

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Summary Within the compounds of the type [Pd · Thioxan₂X₂] (X=Cl, Br, J) the chloride may be used for extractive-photometric determination of small amounts of palladium in the presence of larger quantities of gold and platinum metals, and also of most of the transition metals (Pd: transition metal=110000).

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Der Deutschen Forschungsgemeinschaft danken wir für die Förderung der Arbeit durch Sachhilfen.     

Matrix elimination method for the determination of precious metals in ores using electrothermal atomic absorption spectrometry

Poly(N-(hydroxymethyl)methacrylamide)-1-allyl-2-thiourea) hydrogels, poly(NHMMA-ATU), were synthesized by gamma radiation using ⁶⁰Co γ source in the ternary mixture of NHMMA-ATU-H₂O. These hydrogels were used for the specific gold, silver, platinum and palladium recovery, pre-concentration and matrix elimination from the solutions containing trace amounts of precious metal ions. Elimination of inorganic matrices such as different transition and heavy metal ions, and anions was performed by adjusting the solution pH to 0.5 that was the selective adsorption pH of the precious metal ions. Desorption of the precious metal ions was performed by using 0.8 M thiourea in 3 M HCl as the most efficient desorbing agent with recovery values more than 95%. In the desorption medium, thiourea effect on the atomic signal was eliminated by selecting proper pyrolysis and atomization temperatures for all precious metal ions. Precision and the accuracy of the results were improved in the graphite furnace-atomic absorption spectrometer (GFAAS) measurements by applying the developed matrix elimination method performing the adsorption at pH 0.5. Pre-concentration factors of the studied precious metal ions were found to be at least 1000-fold. Detection limits of the precious metal ions were found to be less than 10 ng L⁻¹ of the all studied precious metal ions by using the proposed pre-concentration method. Determination of trace levels of the precious metals in the sea-water, anode slime, geological samples and photographic fixer solutions were performed using GFAAS clearly after applying the adsorption-desorption cycle onto the poly(NHMMA-UTU) hydrogels.     

Directed Self‐Assembly of Diblock Copolymer Thin Films on Prepatterned Metal Nanoarrays

The sequential layer by layer self‐assembly of block copolymer (BCP) nanopatterns is an effective approach to construct 3D nanostructures. Here large‐scale highly ordered metal nano­arrays prepared from solvent annealed thin films of polystyrene‐block‐poly(2‐vinylpyridine) (PS‐b‐P2VP) diblock copolymer are used to direct the assembly of the same BCP. The influence of initial loading concentration of metal precursor, the type of metal nanoparticle (gold, platinum, and silver), and the nanoparticle–substrate interaction on the directed assembly behavior of the upper BCP layer have been focused. It is found that the upper BCP film can be completely directed by the gold nanoarray with P2VP domain exclusively located between two adjacent gold nanowires or nanodots, which behaves the same way as on the platinum nanoarray. While the silver nanoarray can be destroyed during the upper BCP self‐assembly with the silver nanoparticles assembled into the P2VP domain. Based on the discussions of the surface energy of nanoparticles and the interplay between nanoparticle–substrate interaction and nanoparticle–polymer interaction, it is concluded that the effect of immobilization of nanoparticles on the substrate, together with entropy effect to minimize the energetically unfavorable chain stretching contributes to the most effective alignment between each layer.

     

Polythiophene-coated Fe3O4 nanoparticles as a selective adsorbent for magnetic solid-phase extraction of silver(I), gold(III), copper(II) and palladium(II)

We have developed a fast method for sensitive extraction and determination of the metal ions silver(I), gold(III), copper(II) and palladium(II). Fe₃O₄ magnetic nanoparticles were modified with polythiophene and used for extraction the metal ions without a chelating agent. Following extraction, the ions were determined by flow injection inductively coupled plasma optical emission spectrometry. The influence of sample pH, type and volume of eluent, amount of adsorbent, sample volume and time of adsorption and desorption were optimized. Under the optimum conditions, the calibration plots are linear in the 0.75 to 100 μg L^?1 concentration range (R²?>?0.998), limits of detection in the range from 0.2 to 2.0 μg L^?1, and enhancement factors in the range from 70 to 129. Precisions, expressed as relative standard deviations, are lower than 4.2 %. The applicability of the method was demonstrated by the successful analysis of tap water, mineral water, and river water.

Surface modification of phosphate ion to promote photocatalytic recovery of precious metals

Photocatalytic recovery,a novel precious metal recycling technology,dedicates to solving the environmental and energy consumption problems caused by traditional technologies.The activation of molecular oxygen (O₂) is one of the most critical steps in the whole process.Herein,we regulated the different adsorption intensity of oxygen on the surface by designing phosphate (PO₄^3-) modified titanium oxide(Ti O₂).The results show that the adsorption of oxyge...     

Extractive separation and spectrophotometric determination of palladium and platinum with dithizone in the presence of stannous chloride

The conditions [acid used, presence of chloride and tin(II)] for the extractive separation and spectrophotometric determination of palladium and platinum as the dithizonates Pd(HDz)(2) and Pt(HDz)(2) have been examined. In the absence of stannous chloride platinum does not undergo extraction. Conditions for the separation and determination of these metals in the presence of mercury, gold and copper, which are also extracted with dithizone into carbon tetrachloride or chloroform under the conditions suitable for palladium (1M sulphuric acid/0.1M hydrochloric acid), have been defined. The mercury and gold dithizonates are formed quickly and can be removed before the palladium and platinum compounds have had time to form. They can be decomposed with iodide. Copper dithizonate is decomposed by reduction with tin(II). The proposed procedure has been applied to the determination of palladium in technical platinum metal.     

Noble metals in polyoxometalates

Polyoxometalates containing noble metal ions, such as ruthenium, osmium, rhodium, palladium, platinum, silver and gold, are a structurally diverse class of compounds. They include both classical heteropolyanions (vanadates, molybdates, tungstates) in which noble metals are present as heteroatoms, as well as the recently discovered class of polyoxometalates with noble metal "addenda" atoms. The focus of this Review is on complexes that should, in principle, exist as discrete molecular species in solution, and which are therefore of interest for their reactivity, their future synthetic utility and potential applications, for example, in catalysis or nanoscience.