Substoichiometric extraction of gold(III). Determination of the extraction constant of gold dichloride diethyldithiocarbamate

The extraction constant of gold dichloride diethyldithiocarbamate has been determined (log K = 68.2 ± 0.2) by studying the competition from palladium in the substoichiometric extraction of gold with copper diethyldithiocarbamate in chloroform. Experimental conditions that allowed the equilibrium to be reached for any palladium concentration were chosen so that the influence of the palladium concentration on the extraction kinetics has also been studied. A program for the computation of any stability constant from extraction data for mixtures of three cations has been written.     

Solvent extraction of zinc by trilaurylamine N-oxide

The solvent extraction behaviour of zinc from aqueous hydrochloric acid solutions using trilaurylamine N-oxide in toluene has been studied. The distribution ratios have been studied as a function of concentration of acid and extractant. The effects of foreign agents such as nitrate, sulphate, chloride, acetate, citrate, oxalate, and ascorbic acid on the extraction of zinc from hydrochloric acid solution are also determined.     

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 gold in silver, copper, lead, selenium and anode slime by atomic-absorption spectrometry

A simple and sensitive combined solvent-extraction and atomic-absorption spectrometric method has been developed for the determination of gold in silver, copper, lead, selenium and anode slime. Samples are decomposed with hydrochloric and nitric acids, and gold is extracted as the trioctylmethylammonium-gold bromide complex and determined by atomic-absorption spectrometry by direct spraying of the extract into the flame. Optimal conditions for the extraction and determination of gold have been established. As little as 0.5 mug of gold in a sample can be determined. The extraction of gold from hydrochloric or hydrobromic acid solution with trioctylamine or trioctylmethylammonium chloride (or bromide) has also been investigated.     

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.     

Liquid-liquid extraction of zinc from aqueous thiocyanate solutions with 5-(-4-pyridyl)nonane in benzene

5-(4-Pyridyl)nonane dissolved in benzene has been applied to the extraction of zinc, down to very low concentration (< 10(-6)M), from aqueous thiocyanate solutions. The metal can be quantitatively extracted from neutral and acidic thiocyanate solutions (up to 5M HCl, 0.25M HNO(3) or 0.25M H(2)SO(4)) in a single extraction. Equilibration times of 5 min are sufficient for almost complete extraction. The optimum thiocyanate concentration range is 0.05-0.5M. Among the common anions chloride exerts a slight depressing effect on extraction from neutral solution when present in high concentration. The extraction mechanism and the composition of the extracted complexes of zinc are discussed. The metal is predominantly extracted by means of a solvate mechanism. The effect of chloride, nitrate, sulphate, acetate, citrate, oxalate and ascorbate ions on the extraction of zinc is described. Several elements, including those of interest in separation of zinc, have been tested for extraction from O.1M KSCN at the optimal concentrations of the mineral acids, and the separation factors estimated.     

Extraction of metal–dye ion-association complexes by thin ether-type polyurethane membranes

The extraction and transport of various gold(III) chloride–organic dye ion-association complexes in aqueous solution through thin ether-type polyurethane membranes have been studied. The effects of the presence of salt, acid, different starting and receiving solution compositions, and temperature on the sorption process were investigated. Methylene Blue, Rhodamine B and Brilliant Green, which represent organic dyes from the thiazine, xanthene, and triphenylmethane groups, respectively, were used for this study. Gold(III) chloride and the individual organic dyes were extracted and transported through the membrane only if the solution conditions favored the formation of a neutral species. The ion-association complexes of gold(III) chloride with Methylene Blue and Rhodamine B were extracted and transported by the polymer only when the formation of the complex was more efficient than the individual extraction and transport of each of the species. The extraction of Brilliant Green under all conditions studied was very high, however, no transport occurred. The overall sorption of this dye was found to be independent of the presence of gold regardless of solution composition. High temperature resulted in a very high rate of transport of the gold(III) chloride–organic dye ion-pair.     

Selective solvent extraction of chromium(VI) using 2-hexylpyridine

The extraction behaviour of trace and macroamounts of chromium(VI) from different mineral acid solutions by 2-hexylpyridine in chloroform has been investigated. In the chloride system, the extracted species is apparently (HPyH⁺)₂ (Cr₂O₇)²⁻ or HPy⁺(HCrO ₄ ⁻ ) for macro and trace amounts of chromium(VI), respectively. Among the common anions chloride and sulphate have little effect on extraction up to 1M concentration, while in the case of nitrate there is a continuous decrease in the extraction with the increase of salt concentration in the aqueous phase. The effect of ascorbate, acetate, citrate, oxalate, thiosulphate, thiocyanate ions on the extraction from 1M HCl was also examined. Separation factors of several elements relative to chromium(VI) have been described and the separation of chromium(IV) from a large number of elements has been achieved.     

The extraction of mercury by dithizone retained on silica gel

A silica gel-dithizone-chloroform phase is suitable for the quantitative batch extraction of certain metals. The extraction of mercury from a chloride phase by such a support has been investigated and the effect of varying acidity, free ligand acid concentration, and chloride ion concentration has been determined.     

Extraction of gold(III) with (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-yl-methyl)-pentan-3-ol from hydrochloric acid solutions

Extraction of gold(III) with (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)-pentan-3-ol from 3 M hydrochloric acid solutions (with chloroform as a diluent) has been studied. Optimal extraction conditions have been found. The reagent has been shown to extract efficiently metal ion from solutions containing 3 M hydrochloric acid due to formation of coordination bond between gold(III) and the N4 atom of the triazole ring. The coordination mechanism of gold(III) extraction has been proposed on the basis of the data obtained. Concentration constants of extraction have been calculated, and the thermodynamic parameters of extraction have been determined.     

Phosphonium ionic liquids as extractants for recovery of ruthenium(III) from acidic aqueous solutions

The aim of this work is to investigate extraction of ruthenium(III) from acidic aqueous solutions with phosphonium ionic liquids such as trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101), trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate (Cyphos IL 104) and tributyl(tetradecyl)phosphonium chloride (Cyphos IL 167) as extractants. The influence of HCl content in the feed solutions on extraction of Ru(III) was investigated. The research was performed for model solutions containing Ru(III) and a mixture of waste solutions containing Ru(III) and Rh(III). In addition, investigation of the type of extractant and its concentration in the organic phase on extraction of Ru(III) was carried out. Co-extraction of protons to the organic phase was determined. To the best of our knowledge, the extraction of Ru(III) with Cyphos IL 167 (tributyl(tetradecyl)phosphonium chloride) as an extractant has not yet been described in the scientific literature.     

The determination of copper at thin film electrodes by constant current stripping potentiometry

A comparison of the determination of copper by constant current stripping potentiometry (CCSP) at mercury and gold films has been carried out. The preferred solution conditions for the mercury film study were determined to be 0.1M ammonium acetate at pH 4.5 and 0.1M HCl for the gold film study. The influence of chloride on the stripping signal was investigated and it was found that for the mercury film conditions, well-formed stripping signals could be obtained up to a chloride concentration of 0.5 M which permitted the ready determination of copper in seawater. With the gold film, high chloride concentrations affected both the film stability and the glassy carbon surface and repeatable results were difficult to obtain. The optimized CCSP methods were applied to various aqueous samples including tap water, seawater, TCLP (acetic acid) extracts as well as TCLP extracts using groundwater and ocean water. Based on the results obtained for these various matrices, it was concluded that there are several advantages favoring the mercury film. The interference from organic components in the sample matrix on the general applicability of CCSP for the determination of copper at either a mercury or gold film is discussed.     

Study of liquid-liquid extraction of perrhenate with cyclohexanone in different media

A study has been made of the extraction of ReO(4)(-) from the following media: nitric, hydrochloric, sulphuric and phosphoric acids, and sodium nitrate, chloride, sulphate, carbonate and hydroxide solutions. The extraction curves were obtained and hydration and solvation numbers determined. It is concluded that in acidic medium the extraction follows a hydratosolvate mechanism; in neutral and alkaline medium only a solvate mechanism is observed. Similar investigations were carried out with molybdenum(VI). The separation of rhenium and molybdenum is discussed.     

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.     

Complexometric estimation of ferric iron

Summary Ferric iron has been determined alone or in presence of barium chloride, calcium chloride, magnesium sulphate, mercuric chloride, manganese sulphate, strontium nitrate, chromic sulphate or zinc sulphate by titrating it with EDTA, using potassium thiocyanate-p-anisidine indicator. In these complexometric titrations, the quantitative results obtained by using potassium thiocyanate-p-anisidinie indicator are comparable with those obtained with Bindschedler's green indicator; and the metallic salts mentioned above do not interfere in the estimation of ferric iron by this method.     

Extraction and separation studies of tellurium(IV) with tris-(2-ethyl hexyl) phosphate

A method is proposed for the extraction of microgram levels of tellurium(IV) from halide media with tris-(2-ethyl hexyl) phosphate dissolved in toluene as extractant. The optimum conditions have been evaluated from a critical study of acid concentration, extractant concentration, period of equilibration and effect of solvent. Tellurium ion from the organic phase is stripped with water and determined spectrophotometrically with stannous chloride. The method affords binary separation of tellurium from copper, bismuth, gold and selenium and is applicable to the analysis of alloy samples and synthetic mixtures. The method is fast, accurate and precise.     

Extraction and spectrophotometric determination of mercury with N-p-chlorophenylbenzohydroxamic acid (N-p-Cl-BHA)

Extraction and spectrophotometric studies of tracer amounts of mercury with N-p-chlorophenylbenzohydroxamic acid are described. The yellow color mercury complex was extracted from chloroform at pH 9.0. The spectral measurement was made at 388 nm and the molar absorptivity of the complex is 6.0 × 10² liters mol^?1 cm^?1. It gives a clean separation from many commonly occurring metal ions. Effects of pH, solvents, electrolytes, and reagent concentration on the extraction of mercury have been discussed. The mercury is determined in drug samples and industrial effluents. From the extraction data an attempt has been made to calculate the stability constant of mercury complex.     

Diethylenetetra-ammonium sulphatocerate as volumetric reagent: Iodine monochloride method

The method of preparation of diethylenetetra-ammoniuin sulphatocerate is described. This substance has been used as an oxidant to determine potassium iodide, ferrous ammonium sulphate, arsenious oxide, stannous chloride, hydrazinc sulphate, thallous chloride. hydroquinone and potassium ferrocyanide by a volumetric method, using iodine inonochloride as catalyst and preoxidizer. During these titrations, normality of the solution with respect to hydrochloric acid has been kept at about 6N. Chloroform is used as an indicator. It is 'coloured pink owing to the liberation of iodine during the titration and becomes very pale yellow at the end-point because of the formation of iodine monochloride.     

Optimization and validation of a capillary electrophoresis methodology for inorganic anions in atmospheric aerosol samples

Optimization and validation of a method for the determination of inorganic anions, such as chloride, nitrate, sulphate, fluoride and phosphate, in atmospheric particulate matter is described. Ultrasonic extraction followed by CE, using CTAB as EOF modifier, has been established for this separation using chromate as visualization reagent for the indirect UV/vis detection. Optimization of the experimental chemical conditions (pH, surfactant concentration, chromate concentration and acetonitrile concentration) and instrumental parameters (temperature, applied voltage and injection time) is described. Linear calibrations plots are obtained for the five ions, with detection limits in the high ng/mL range. A standard reference material, SRM 1648 Urban Particulate Matter, has been used to validate the proposed method. Satisfactory reproducibility and acceptable agreement to the matter atmospheric samples has been found (recoveries ranging from 86 to 96%). Application to real particulate matter atmospheric samples, collected on high volume samplers from the air quality surveillance network of Extremadura, southwest Spain, is shown.     

Studies on transport mechanism of Cr(VI) extraction from an acidic solution using liquid surfactant membranes

A mathematical model for analysing the extraction of Cr(VI) from aqueous acidic solution by emulsion liquid membrane using Aliquat 336 as extractant and NaOH as stripping agent has been presented. The existing models developed so far do not account for the existence of different forms of Cr(VI) ions in the aqueous phase depending on pH conditions. Accordingly, in the present model, reaction equilibrium has been considered instead of distribution coefficient to represent realistically the transport mechanism for this type of system through liquid surfactant membrane. Unlike other models, liquid–liquid equilibrium of sodium hydroxide-chloride of Aliquat 336 has also been considered. The carrier thus exists in the membrane phase in hydroxide and chloride forms and extraction of hexavalent chromium from the external phase proceeds by the two carriers. The validity of the model has been checked from comparison of the simulated curves and experimental data using chemical reaction equilibrium constant and D_eff/R² as fitting parameters.