Solvation of thiocyanate complexes of mercury(II) by 2-hexylpyridine from aqueous mineral acid solutions

The extraction of trace amounts of mercury(II) by 2-hexylpyridine dissolved in benzene from aqueous mineral acid solutions has been studied. The replacement of chloride, nitrate and sulfate ions by the potentially ambidentate, linear and less basic thiocyanate group offers interestingly high extraction coefficients. The value of the distribution coefficients may be lowered by complexing mercury with oxalate, thiosulfate, acetate or citrate ions in the aqueous phase. The possible mechanism of extraction has been discussed in the light of the results of extraction isotherms and slope analysis data. Distribution coefficients and separation factors of several metal ions relative to mercury(II) are reported for the three mineral acid systems and the possible removal of mercury along with some other inorganic pollutants from aqueous solutions is suggested.     

Solvation of cobalt-thiocyanate complexes by 2-hexylpyridine from aqueous mineral acid solutions

A study of the distribution of cobalt between mineral acid solutions containing potassium thiocyanate and 0.1M 2-hexylpyridine in benzene has been undertaken. Cobalt can be quantitatively extracted as its thiocyanate complex from very dilute acid solutions containing 0.1–1M KSCN. Variation of the distribution coefficient D_Co in terms of the ligand concentration in the organic phase has allowed the formula of the extracted species to be determined as Co(HPy)₄ (SCN)₂. The effects of oxalate, acetate, fluoride, ascorbate, sulphate and thiosulphate ions on the extraction of cobalt from three mineral acid solutions have been reported. The extraction coefficients of several elements are given for the 0.1M 2-hexylpyridine in three systems containing 0.5M KSCN with 0.25M HNO₃, 0.05M HCl and 0.05M H₂SO₄ respectively; and their factors for separation from cobalt are estimated.     

Anion-exchange separations of metal ions in thiocyanate media

The analytical potential of a weak-base macroreticular anion-exchange resin for the quantitative separation of metal ions in thiocyanate media is investigated and demonstrated. Distribution data are given for the sorption of some 25 metal ions from aqueous mixtures of potassium thiocyanate (1.0M or less) and 0.5M hydrochloric acid. The magnitude of the distribution data suggests many possible separations, some of which were quantitatively performed by procedures which are fast, simple and require only mild conditions. Representative separations are removal of traces of iron(III) and copper(II) from water samples prior to the determination of water hardness (calcium and magnesium), separation of nickel(II) from vanadium(IV) and the separation of thorium(IV) from titanium(IV). Some multicomponent separations are the separation of rare earths(III) and thorium(IV) from scandium(III) and the separation of rare earths(III) from iron(III) and uranium(VI).     

Preparation and properties of a new chelating resin containing 1-nitroso-2-naphthol as the functional group

A macroreticular polystyrene-based chelating ion-exchanger containing 1-nitroso-2-naphthol as the functional group has been synthesized. The exchange-capacity of the resin for a number of metal ions such as copper(II), iron(III), cobalt(II), nickel(II), palladium(II) and uranium(VI) as a function of pH has been determined. The sorption and elution characteristics for palladium(II) and uranium(VI) have been thoroughly examined with a view to utilizing the resin for separation and concentration of uranium and palladium. Uranium(VI) has been separated from a mixture of ten other metal ions by sorption on the chelating resin and selective elution with 0.5M sodium carbonate. Palladium(II) has been separated from various metal ions by selective sorption on the resin in 1M hydrochloric acid medium.     

Liquid-liquid extraction with long-chain quaternary Ammonium Halides

The extraction of anionic chloro-complexes of certain metal ions using various long-chain quaternary ammonium halides in toluene and chloroform is described. The investigation has concerned itself mainly with coualt(II) and iron(III); a few extractions have also been carried out with indium(III) and gallium(in). The ion association of chloro-anionic complexes of iron, cobalt, indium and gallium in aqueous chloride media (hydrochloric acid or lithium chloride) with the quaternary ammonium ion in the organic phase is responsible for the extraction of the metal ion into the organic phase. Tlic extraction efficiency varies with the nature of the metal ion system involved as well as with the distribution of the quaternary compound and the size, shape and nature of the organic groups substituted in the quaternary compound.     

Extraction of arsenic(III) from chloride-iodide solutions by diphenyl(2-pyridyl)methane and benzene

The variation of the partition coefficient of arsenic(III) between chloride-iodide solutions and diphenyl(2-pyridyl)methane in benzene has been studied. The effect of the concentration of hydrochloric acid and iodide in the aqueous phase has been assessed. The partition coefficients are maximal for concentrated acid solutions which are 0.02-0.1 M in potassium iodide. Slope-analysis studies were used to elucidate the composition of the extracted species. Polymerization of the solvent species tends to decrease the distribution coefficients of arsenic with increasing concentration of diphenyl(2-pyridyl)methane, especially with trace concentrations of the element. Arsenic can be selectively separated from copper, cobalt, nickel, iron, chromium and antimony, which are usually associated with it in various ores.     

The use of 5-(4-pyridyl)nonane for the separation of chromium(vi) from fission products in hydrochloric acid media

The distribution of chromium(VI) between 5-(4-pyridyl)nonane in benzene and hydrochloric acid media has been studied as a function of the concentration of the acid, extractant, chromium(VI), chloride and a few other ions. The extraction mechanism and the composition of the extracted complexes of Cr(VI) have been proposed. The separation of Cr(VI) from uranium, thorium and fission products in 3M hydrochloric acid has been achieved.     

Solvent extraction of zinc by 2-hexylpyridine in benzene from aqueous mineral acid — Thiocyanate media

Solvent extraction of Zn(II) by 2-hexylpyridine (HPy) in benzene has been studied from aqueous mineral acid—thiocyanate media. The extraction, though dependent on the acidity of the aqueous phase, is poor from mineral acids (HCl, HNO₃ or H₂SO₄). Addition of 0.02M KSCN to the aqueous phase enhances the distribution ratio by a factor of almost one thousand. The stoichiometry of the extracted complex established by the usual slope analysis method indicates that an ionic type complex, e.g. Zn(SCN)₄·(HPyH)₂, is responsible for extraction. Complexing anions like acetate, oxalate or citrate at 1 M concentration mask the extraction of Zn(II) almost completely. Separation factors determined at optimal conditions (0.1M HPy in benzene −0.05M H₂SO₄+0.2M SCN⁻) indicate that Zn(II), along with Hg(II), can be separated in a single extraction from a number of metals, e.g. Cs(I), Sr(II), Ln(III), Y(III), Cr(III) and (VI). Other metals of interest like Cu(II), Co(II), Fe(III), Mo(VI), U(VI) and Tc(VII) are coextracted but the separation factors are large enough to allow separation in a multistage extraction process.     

Synthesis and extracting properties of triacylated ethyleneamines

Series of triacylated ethyleneamines for extraction of metal ions from hydrochloric acid media were synthesized. The effect of the length of the alkyl radical on the distribution of reagents among the organic and aqueous phases, stability of the reagents against hydrolysis in acid media, and extracting properties of the reagents with respect to rhodium(III) chloro complexes were studied.     

Extraction of metal ions from chloride solution with N,N-dioctylacetamide

N,N-Di-n-octylacetamide (DOAA) was prepared and shown to be an effective extractant for a number of metal ions from aqueous hydrochloric acid solution. Distribution ratios of 35 metal ions were measured for 1M DOAA in chloroform and hydrochloric acid solutions ranging from 0.10 to 9.0M. Extraction of uranium(VI) from solutions of hydrochloric acid and of nitric acid was compared. The effects of different diluents and varying concentrations of DOAA were studied in an attempt to elucidate the extraction mechanisms involved.     

Liquid-liquid extraction study of tellurium(IV) with N-n-octylaniline in halide medium and its separation from real samples

N-n-Octylaniline in xylene is used for extractive separation of tellurium(IV) from hydrochloric acid media. Tellurium(IV) is extracted quantitatively with the 3% reagent in xylene from 5.5 to 7.5 M hydrochloric acid. It is stripped from organic phase with 1:1 ammonia and estimated spectrophotometrically with pyrimidine-2-thiol (4'-bromoPTPT). The effects of metal ion, acids, reagent concentration, diluents and various foreign ions have been investigated. The log-log plots of distribution ratio (D(Te(IV))) versus N-n-octylaniline concentration indicate that the nature of extracted species is [(RR'NH(2)(+))(2) TeCl(6)(2-)](org). The method affords binary separation of tellurium(IV) from gold(III), selenium(IV), bismuth(III), copper(II), lead(II), antimony(III), germanium(IV) and is applicable to the analyses of synthetic mixture containing associated metal ions and alloy samples. The method is simple, selective, rapid and accurate.     

Anion-exchange separation of metal ions in dimethyl sulphoxide-methanol-hydrochloric acid

The effect of dimethyl sulphoxide on the anion-exchange behaviour of many metals m a methanolic system with hydrochloric acid was explored. Distribution coefficients for 26 elements were determined in a mixed solvent system of dimethyl sulphoxide-methanol-0.6M hydrochloric acid, in which the proportions of dimethyl sulphoxide and methanoi were varied. Lead(II) and silver(I) complexes are soluble in this system. Interesting effects were noted for gold(III), iron(III), molybdenum(VI) and uranium(VI). As a measure of the usefulness of the systems studied, 27 anion-exchange separations of two- to four-component mixtures of metal ions were carried out, each with quantitative results.     

Selective extraction of iron(III) from aqueous nitrate solution in the presence of cobalt(II), copper(II) and nickel(II) ions using bis(delta2-2-imidazolinyl)-5,5'-dioxime.

The feasibility of using bis(delta2-2-imidazolinyl)-5,5'-dioxime (H2L) for the selective extraction of iron(III) from aqueous solutions was investigated by employing an solvent-extraction technique. The extraction of iron(III) from an aqueous nitrate solution in the presence of metal ions, such as cobalt(II), copper(II) and nickel(II), was carried out using H2L in binary and multicomponent mixtures. Iron(III) extraction has been studied as a function of the pH, equilibrium time and extractant concentration. From the extracted complex species in the organic phase, iron(III) was stripped with 2 M HNO3, and later determined using atomic-absorption spectrometry. The extraction was found to significantly depend on the aqueous solution pH. The extraction of iron(III) with H2L increases with the pH value, reaching a maximum in the zone of pH 2.0, remaining constant between 2 and 3.5 and subsequently decreasing. The quantitative extraction of iron(III) with 5 x 10(-30 M H2L in toluene is observed at pH 2.0. H2L was found to react with iron(III) to form ligand complex having a composition of 1:2 (Fe:H2L).     

Liquid-liquid extraction of palladium(II) with N-n-octylaniline from hydrochloric acid media

N-n-Octylaniline in xylene is used for the extractive separation of palladium(II) from hydrochloric acid medium. Palladium(II) was extracted quantitatively with 10 ml of 2% reagent in xylene from 0.5-2 M hydrochloric acid medium. It was stripped from the organic phase with 1:1 ammonia and estimated spectrophotometrically with pyrimidine-2-thiol at 420 nm. The effects of metal ion, acids, reagent concentration and of various foreign ions have been investigated. The method affords binary separation of palladium(II) from iron(III), cobalt(II), nickel(II) and copper(II) and is applicable to the analysis of synthetic mixtures and alloys. The method is fast, accurate and precise.     

Preconcentration and separation of iron, zinc, cadmium and mercury, from waste water using Nile blue a grafted polyurethane foam

The present work describes a novel method for the incorporation of Nile blue A into polyurethane foam matrix. This foam material was found to be very suitable for the extraction of metal ions from aqueous solutions. The characterization of Nile blue A grafted foam and the effect of halide concentration, pH, shaking time, extraction isotherm and capacity have been investigated. This foam material was found to be suitable for the separation and preconcentration of iron (III), zinc (II), cadmium (II) and mercury (II) from waste water. The extraction was accomplished in (15-20) minutes. Iron was separated from acid medium (2-4 M HCl), zinc from (3-5 M HCl), cadmium from (4-6 M HCl) as thiocyanate complexes and mercury was separated from (1-2 M HCl) as chloride.     

Quantitative description and local structures of trivalent metal ions Eu(III) and Cm(III) complexed with polyacrylic acid

The trivalent metal ion (M(III)=Cm, Eu)/polyacrylic acid (PAA) system was studied in the pH range between 3 and 5.5 for a molar PAA-to-metal ratio above 1. The interaction was studied for a wide range of PAA (0.05 mg L(-1)-50 g L(-1)) and metal ion concentrations (2x10(-9)-10(-3) M). This work aimed at 3 goals (i) to determine the stoichiometry of M(III)-PAA complexes, (ii) to determine the number of complexed species and the local environment of the metal ion, and (iii) to quantify the reaction processes. Asymmetric flow-field-flow fractionation (AsFlFFF) coupled to ICP-MS evidenced that size distributions of Eu-PAA complexes and PAA were identical, suggesting that Eu bound to only one PAA chain. Time-resolved laser fluorescence spectroscopy (TRLFS) measurements performed with Eu and Cm showed a continuous shift of the spectra with increasing pH. The environment of complexed metal ions obviously changes with pH. Most probably, spectral variations arose from conformational changes within the M(III)-PAA complex due to pH variation. Complexation data describing the distribution of complexed and free metal ion were measured with Cm by TRLFS. They could be quantitatively described in the whole pH-range studied by considering the existence of only a single complexed species. This indicates that the slight changes in M(III) speciation with pH observed at the molecular level do not significantly affect the intrinsic binding constant. The interaction constant obtained from the modelling must be considered as a mean interaction constant.     

The Extractive-Spectrophotometric Determination of Iron(III) As a Mixed-Ligand Complex with N-Hydroxy-N,N′DI-p-Tolyl-p-Toluamidine and Thiocyanate

The extractive-photometric determination or iron(III) as a mixed-ligand complex with N -hydroxy-N, N′ -di-p -tolyl-p -toluamidine (HDTTA) and thiocyanate is described. The orange-red Waterinsoluble 1:1:2 (metal: HDTTA: SCN^?) ternary complex formed in 0.1–0.6 M hydrochloric acid solutions is quantitatively extractable into benzene. The wavelength of maximum absorption, molar absorptivity and sensitivity of the colour system are 460nm, 12000 l. mole^?1 cm^?1 and 0.0046 μg Fe/cm ²respectively. The influence or foreign ions on the determination of iron has been studied. This method has also been applied to determine the iron content of several alloys.     

Extraction of metal ions with a primary amine

This paper describes some experimental results obtained at the extraction of sulfate solutions of U(VI), Mo(VI), V(V), Ce(IV), Zr(IV), Fe(III), Al(III) with a benzene solution of Primene JMT. The aqueous solutions consist of metal sulfates (or other metal salts) in the presence of sulfuric acid with a concentration range of 0–2.1 mol·dm^–3, the concentration of amine in the organic phase being 0.1–0.3 mol·dm^–3. The presence of various species of metal ions in the aqueous phase is considered and the equilibrium concentration of substances extracted in the organic phase is determined. On the basis of the results of chemical analysis (concentration of metals and sulfate ions) the composition of the prevailing complexes in the organic phase is proposed.     

Tri-n-octylphosphine sulfide: : A selective organic extractant

Tri-n-octylphosphine sulfide (TOPS) has been investigated as the stationary phase in reversed-phase partition paper Chromatographie separations using nitric or hydrochloric acids as the mobile phase. TOPS has also been studied as an extractant for metal ions. Silver, mercury (II), and palladium (II) were found to have RF values of zero when nitric acid was used as the mobile phase. These same ions were also selectively extracted from aqueous nitric acid solutions. Gold(III), mercury(II), palladium (II), and platinum (IV) were found to have RF values of zero when hydrochloric acid was used as the mobile phase. However, only gold(III) and mercury(II) were extracted from aqueous hydrochloric acid solutions in liquid-liquid extraction systems. Several separations were successfully performed from 1 M nitric acid.     

Polymer Supported Schiff Base Complexes of Iron(III), Cobalt(II) and Nickel(II) Ions and their Catalytic Activity in Oxidation of Phenol and Cyclohexene

The polymer supported transition metal complexes of N,N′‐bis (o‐hydroxy acetophenone) hydrazine (HPHZ) Schiff base were prepared by immobilization of N,N′‐bis(4‐amino‐o‐hydroxyacetophenone)hydrazine (AHPHZ) Schiff base on chloromethylated polystyrene beads of a constant degree of crosslinking and then loading iron(III), cobalt(II) and nickel(II) ions in methanol. The complexation of polymer anchored HPHZ Schiff base with iron(III), cobalt(II) and nickel(II) ions was 83.30%, 84.20% and 87.80%, respectively, whereas with unsupported HPHZ Schiff base, the complexation of these metal ions was 80.3%, 79.90% and 85.63%. The unsupported and polymer supported metal complexes were characterized for their structures using I.R, UV and elemental analysis. The iron(III) complexes of HPHZ Schiff base were octahedral in geometry, whereas cobalt(II) and nickel(II) complexes showed square planar structures as supported by UV and magnetic measurements. The thermogravimetric analysis (TGA) of HPHZ Schiff base and its metal complexes was used to analyze the variation in thermal stability of HPHZ Schiff base on complexation with metal ions. The HPHZ Schiff base showed a weight loss of 58% at 500°C, but its iron(III), cobalt(II) and nickel(II) ions complexes have shown a weight loss of 30%, 52% and 45% at same temperature. The catalytic activity of metal complexes was tested by studying the oxidation of phenol and epoxidation of cyclohexene in presence of hydrogen peroxide as an oxidant. The supported HPHZ Schiff base complexes of iron(III) ions showed 64.0% conversion for phenol and 81.3% conversion for cyclohexene at a molar ratio of 1∶1∶1 of substrate to catalyst and hydrogen peroxide, but unsupported complexes of iron(III) ions showed 55.5% conversion for phenol and 66.4% conversion for cyclohexene at 1∶1∶1 molar ratio of substrate to catalyst and hydrogen peroxide. The product selectivity for catechol (CTL) and epoxy cyclohexane (ECH) was 90.5% and 96.5% with supported HPHZ Schiff base complexes of iron(III) ions, but was found to be low with cobalt(II) and nickel(II) ions complexes of Schiff base. The selectivity for catechol (CTL) and epoxy cyclohexane (ECH) was different with studied metal ions and varied with molar ratio of metal ions in the reaction mixture. The selectivity was constant on varying the molar ratio of hydrogen peroxide and substrate. The energy of activation for epoxidation of cyclohexene and phenol conversion in presence of polymer supported HPHZ Schiff base complexes of iron(III) ions was 8.9 kJ mol^?1 and 22.8 kJ mol^?1, respectively, but was high with Schiff base complexes of cobalt(II) and nickel(II) ions and with unsupported Schiff base complexes.