Determination of the extraction constant of gold diethyldithiocarbamate dichloride by substoichiometric extraction

Radioactive gold(III) with radioactive palladium(II) as reference ion in a chloride medium was substoichiometrically extracted with zinc diethyldithiocarbamate in chloroform. A formula for calculation of the extraction constant of the gold(III) complex was derived, for which only the values of distribution ratios of gold and palladium between the two phases had to be measured experimentally. The extraction constant was found to be log K = 68.9 ± 0.4.     

Determination of crotonaldehyde in ethanol by differential pulse polarography

The extraction constant of gold bisdiethyldithiocarbamate chloride has been determined (log K' = 81.5± 0.7) by studying the competition from palladium in the extraction of gold with an excess of copper diethyldithiocarbamate in chloroform. Gold bisdiethyldithiocarbamate chloride is an ion pair which can dissociate: a dissociation constant of this compound has been determined by studying the influence of chloride concentration on the extraction of gold with the same reagent. In sulphuric acid medium, the low extraction ratio of gold observed cannot be attributed to extraction of gold bisdiethyldithiocarbamate sulphate as dependence on sulphate concentration has not been obtained. A program for the computation of this type of stability constant from extraction data for mixtures of cations and ligands is given.     

Flame atomic absorption spectrometric determination of trace amounts of palladium,gold and nickel after cloud point extraction

In this article, a sensitive cloud point extraction procedure for the preconcentration of trace amounts of palladium, gold and nickel prior to their determination by flame atomic absorption spectrometry has been developed. The cloud point extraction method is based on the complexation of Pd(II), Au(II), and Ni(II) ions with 1-(2-pyridylazo)-2-naphthol and entrapping in non-ionic surfactant Triton X-114. The main factors affecting cloud point extraction efficiency, such as pH of sample solution, concentration of 1-(2-pyridylazo)-2-naphthol and Triton X-114, equilibration temperature and time, were investigated in detail. Under the optimized conditions, calibration curves were constructed for the determination of palladium, gold and nickel according to the general procedure. Linearity was maintained from 0.01 to 1.0 μg/mL for palladium, 10.0 μg/mL to 1.5 μg/mL for gold, and 10.0 μg/mL to 0.5 μg/mL for nickel. Detection limits based on three times the standard deviation of the blank divided by the slope of analytical curve (3Sb/m) for Pd(II), Au(III), and Ni(11) ions were 3.4, 3.9, and 2.4 μg/mL, respectively. Seven replicate determination of a mixture of 0.5 μg/mL palladium and gold and 0.2 μg/mL nickel gave a mean absorbance of 0.174, 0.150, and 0.201 with relative standard deviation ±1.5, ±1.3, and ±1.8%, respectively. The high efficiency of cloud point extraction to carry out the determination of analytes in complex matrices was demonstrated. The proposed method has been applied for determination of trace amount of palladium, gold and nickel in certified reference material and water samples with satisfactory results.     

An investigation of the diethyldithio-carbamates of palladium, including the determination of their stability constants

The reaction of palladium with copper diethyldithio-carbamate has been studied and two complexes isolated: palladium diethyldithiocarbamate and palladium chloride diethyldithiocarbamate. The spectra of both complexes have been examined. The extraction constants and partition coefficients between chloroform and water have been determined, the former by the use of other strong complexing reagents as masking agents for palladium. The stability constants and the exchange constant for the two complexes have been calculated.     

Substoichiometric determination of traces of gold by radioactive isotope-dilution analysis

A radioactive isotope-dilution method for the determination of traces of gold has been developed. It is based on the solvent extraction of gold diethyldithiocarbamate from 0-5N sulphuric acid containing ascorbic acid, by means of a substoichiometric amount of zinc diethyldithiocarbamate in chloroform. The separation has been applied to the analysis of gold-doped semiconductor-grade silicon and of gold-bearing ores. Amounts of gold down to 5 x 10(-7)g 20 ml of test solution can be determined.     

Studies on the extraction of platinum metals with tri-iso-octylamine from hydrochloric and hydrobromic acid: separation and determination of gold, palladium and platinum

The extraction of Pd(II), Rh(III), Ir(III), Au(III) and Pt(IV) from hydrochloric and hydrobromic acid with 5% tri-iso-octylamine solution in carbon tetrachloride has been studied. The gold extract from hydrochloric acid is yellow and absorbs at 325 nm, the palladium compound is red and absorbs at 290 nm and 467 nm, and the platinum compound is blood-red and shows absorption at 268 nm. The gold, palladium and platinum extracts from hydrobromic acid are crimson. reddish brown and blood-red, with maximum absorption at 260, 345 and 300 nm respectively. Methods have been devised for the separation of gold from platinum and for its determination and also for the simultaneous determination of palladium and platinum.     

Determination of gold in water samples using electromembrane extraction

In this work, an electromembrane extraction (EME) technique was used for the extraction and determination of gold from water samples prior to UV-Vis spectrophotometry. An artificial neural network (ANN) combined with imperialist competitive algorithm (ICA) has been applied to optimize the EME. The effective parameters including pH of acceptor phase, extraction time (t), volume of sample solution (V), stirring rate (S), and voltage (E) were chosen as input variables and the extraction recovery of gold was considered as output variable. The mean of squared error (i.e., 0.0009) and determination coefficient (i.e., 0.9821) were applied to estimate the performance of the ANN model. The limit of detection was 4.5?µg L^?1 (S/N?=?3) on the optimized variables. The intra- and interday precisions (%) were found to be 6.7% and 2.6%, respectively. This technique was then applied for analysis of gold from environment water samples.     

The extraction of low-concentrations of gold(I) with 198Au as a radiotracer

The solvent extraction of gold from alkaline cyanide solution was studied by using ¹⁹⁸Au as a radiotracer. The influence of several variables on the gold extraction, including the concentration of gold, the molar ratio of extractants to gold(I), the volume percentage of cosolvent and the pH value of the aqueous phase, was investigated. The results indicated that the radioactive tracer technique is a quick, accurate, and convenient tool to investigate the extraction behavior of an element existing in low concentrations. The experimental results indicated that the studied amines, tetradecyldimethylbenzylammonium chloride, N1923 and tri-n-octylamine, could be used as extractants for the recovery of gold from aqueous alkaline cyanide solutions.     

Substoichiometric determination of traces of palladium by neutron-activation analysis

A highly selective, rapid one-step radiochemical separation procedure for palladium has been developed. It is based on the solvent extraction of palladium diethyldithiocarbamate from a 5M hydrochloric acid solution with a substoichiometric amount of copper diethyldithiocarbamate in chloroform. The separation has been applied to the determination of traces of palladium by neutron-activation analysis, in platinum, the rocks W-1 and PCC-1 and a biological material (kale). Amounts of palladium down to 10(-8) g have been determined.     

Application of the group substoichiometric separation of gold,mercuric, and cupric diethyldithiocarbamates to determining them by means of activation analysis

The substoichiometric method has been applied to group separation. By a single extraction gold and mercury were separated quantitatively, and copper substoichiometrically, at the same time. Zinc diethyldithiocarbamate has been used as the chelating agent. The group of elements was separated from 2N H₂SO₄ and 0.1N HClO₄ medium. This method of group separation was applied to the activation analysis of biological materials and metallic tin.     

The extraction of trace amounts of gold from different aqueous mineral acid solutions by diphenyl-2-pyridylmethane dissolved in chloroform

Diphenyl-2-pyridylmethane, a high molecular weight substituted pyridine has been examined and found to be a useful solvent extraction reagent. Its behaviour is similar to amines in that it forms salts with mineral acids. The acid ionization constant (pK_BH ⁺) determined spectrophotometrically has a value of 4.41±0.06 at 25 °C. A study of the partition behaviour of trace amounts of gold between mineral acid solutions and 0.1M diphenyl-2-pyridylmethane dissolved in chloroform indicates that the metal can be quantitatively extracted from dilute mineral acid solutions and also from concentrated hydrochloric acid media in a single extraction. Attempts have been made to gain an understanding of factors affecting the extraction of gold. Common anions have little effect on extraction in concentrations upto 1M. Separation factors of a number of metal ions relative to gold are reported for three mineral acid systems; and gold has been estimated in some synthetic samples using neutron activation technique by prior extraction with 0.1M solution of diphenyl-2-pyridylmethane dissolved in chloroform.     

Extractive radiometric titration as a method of checking the extraction of gold with diethyldithiocarbamates

The extraction of gold(III) by copper-, zinc-, and mercury diethyldithiocarbamates from acid medium was studied by means of extractive radiometric titration, using trichloromethane or benzene as the solvent. Two end-points corresponding to the molar ratios 1 Au∶1 DDC and 1 Au∶2 DDC were observed on the titration curve of trivalent gold when diethyldithiocarbamate ion (DDC) was used as the titrant. Two compounds are formed successively: $$Cl_2 Au^{III} DDC and \{ [Au^{III} (DDC)_2 ]^ + \cdot Cl^ - \} $$ . The first compound is completely extracted into trichloromethane or benzene; the extractibility of the second compound increases with increasing solvent polarity. Univalent gold forms only one compound with the diethyldithiocarbamate ion: AuDDC.     

Liquid-liquid extraction of palladium and gold by the sulphide podand 1,12-di-2-thienyl-2,5,8,11-tetrathiadodecane

The extraction properties of the sulphide podand 1,12-di-2-thienyl-2,5,8,11-tetrathiadodecane (TTD), an open-chain neutral polythioether with six sulphur donor atoms in 1,2-dichloroethane, chloroform and MIBK for Pd and Au in hydrochloric, nitric and perchloric acid media have been examined. The kinetic aspects of the extraction of palladium(II) from hydrochloric acid by TTD and dioctyl sulphide (DOS) were compared. The rate of Pd extraction with TTD is considerably higher than that with DOS, especially with chloroform. Combined use of a reducing agent and TTD enhances the extraction of gold(III) into 1,2-dichloroethane.     

Determination of mugram amounts of palladium in titanium alloys by x-ray fluorescence spectrometry after solvent extraction and collection on a filter paper

Palladium is separated from large amounts of titanium matrix and other elements by solvent extraction with diethyldithiocarbamate, and is collected into the small central area on a filter paper for subsequent x-ray fluorescence measurement. The palladium diethyldithiocarbamate chelate is extracted quantitatively into chloroform at pH 9.5 in the presence of large amounts of tartrate and EDTA. Palladium in the range 30–100 μg can be determined with coefficients of variation of 0-6–1.4%. The detection limit is 0.3 μg of palladium; up to 500 μg of copper does not interfere.     

Determination of gold by substoichiometric extraction with N-thioacetyl benzamide

Estimation of gold has been successfully carried out by substoichiometric radiochemical solvent extraction method using a newly designed organic moiety, N-thioacetyl benzamide as extractant and chloroform as solvent at aqueous pH 4. The interference effects of different closely related diverse ions like Fe(III), Cu(II), Co(II), Zn(II), Ni(II) etc. were also critically studied. The validity of this method has been verified by the study of recovery of gold in mud samples.     

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.     

Synergetic extraction and spectrophotometric determination of gold(III)

Summary A method is described for the synergetic extraction and subsequent spectrophotometric determination of gold(III). The gold--furil dioxime-pyridine complex extracted into chloroform has a characteristic yellow colour with an absorption maximum at 330 nm. Beer's law is obeyed in the concentration range [Au(III)]45g/ 10 ml organic phase. A scheme to separate gold from interfering elements by extraction with 4-methyl-2-pentanol in benzene has been proposed.

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Zusammenfassung Ein Verfahren zur synergetischen Extraktion und nachfolgenden spektrophotometrischen Bestimmung von Gold(III) wurde beschrieben. Die Komplexverbindung des Goldes mit-Furildioxim und Pyridin ist in chloroformischer Lösung gelb gefärbt. Ihr Absorptionsmaximum liegt bei 330 nm. Bis 45g Au(III)/10 ml organischer Phase wird das Beersche Gesetz befolgt. Die Trennung des Goldes von störenden Elementen durch Extraktion mit 4-Methyl-2-pentanol in Benzol wurde vorgeschlagen.

     

A high selective ion‐imprinted polymer grafted on a novel nanoporous material for efficient gold extraction

In this work, for the first time, an ion‐imprinted polymer was developed for selective extraction and determination of gold ions. To increase the sorbent efficiency, this polymer was coated on a novel nanoporous carbon‐based material, carbohydrate‐derived Max‐Planck Gesellschaft 1, which is also the first example of grafting imprinted polymer on nanoporous‐carbon material. These particles were applied successfully for preconcentration of ultratrace amount of gold ions, following determination by flame atomic absorption spectrometry. Some effective factors on the efficiency of gold ions extraction, such as concentration and volume of eluent, sample and eluent flow rates, and also effect of interfering ions especially palladium and platinum ions, were investigated. The LOD was determined to be 0.27 ng/mL. Furthermore, the precision of the method was calculated to be 2.14% under optimal conditions with recovery more than 97.3%. The technique was also used to determine the concentration of gold ions in mine stone samples with satisfactory results. The accuracy of this method was investigated by determination of gold ions concentrations in several reference materials with certified gold content.     

Extraction of palladium and platinum with trioctylphosphine oxide (TOPO) in various solvents from hydrochloric and hydrobromic acid media

The extraction of palladium and platinum with trioctylphosphine oxide (TOPO) in cyclohexane, chloroform, methyl isobutyl ketone (MIBK) and 2,2′-dichlorodiethyl ether (DCDE) from hydrochloric and hydrobromic acids in dependence on the concentration of the acids and the extractant has been investigated. The obtained relation have been discussed and the possibilities of the separation of palladium, platinum, gold and their simultaneous extraction have been pointed out.     

Extraction of palladium from nitric acid medium by commercial resins with phosphinic acid,methylene thiol and isothiouronium moieties attached to polystyrene-divinylbenzene

Summary Commercially available polystyrene-divinylbenzene (PS-DVB) resins functionalized with isothiouronium (Tulsion CH-95), phosphinic acid (Tulsion CH-96) and methylene thiol (Tulsion CH-97) moieties have been used for separating palladium from nitric acid medium. Extraction of palladium has been studied as a function of time, concentration of nitric acid and palladium. The distribution coefficients (K_d, ml/g) of palladium on sulfur based resins (Tulsion CH-95 and Tulsion CH-97) are higher (5000-10⁴ml/g in 0.1M nitric acid) than on Tulsion CH-96 resin and decrease with increasing concentration of nitric acid. The initial rate of extraction of palladium by Tulsion CH-95 and Tulsion CH-97 resins was very rapid and the time required for the establishment of equilibrium was a function of palladium concentration in the aqueous phase. The rate data could be fitted by a second order rate equation and the magnitude of rate constant for the extraction of palladium by these resins (~10²M^-1. min^-1) decreased in the order of: Tulsion CH-95 > Tulsion CH-97 > Tulsion CH-96. The extraction isotherms of Tulsion CH-95 were fitted by Langmuir adsorption model and the coefficients were obtained by regression. The extraction capacity of palladium on Tulsion CH-95 was found to be ~20 mg/g at 3M nitric acid. Column experiments have been conducted and the data were fitted using Thomas model. A column utilization of 75% was achieved for the extraction of palladium by Tulsion CH-95 resin.