Extraction of mercury(II) from aqueous thiocyanate solutions with 5-(4-pyridyl)nonane in benzene, and its subsequent atomic-absorption spectrometric determination

Tracer ( approximately 10(-8)M) mercury(II) can be quantitatively extracted with 5-(4-pyridyl)nonane in benzene from aqueous thiocyanate solutions that are up to 6M in HCl, 1M in H(2)SO(4) or 0.25M in HNO(3), in a single extraction. Optimal conditions for the extraction are given, based on a critical study of the relevant factors such as the effects of the acids, thiocyanate, salting-out and complexing agents and the reagent concentration. The mechanism underlying these extractions is discussed on the basis of the results obtained from partition and slope-analysis data. The extraction of the metal as Hg(PyN)(2)(SCN)(2) is indicated. The extracted mercury can be stripped from the non-aqueous layer with various aqueous solutions, including nitric acid (2M), sodium citrate ( 1M) and sodium thiosulphate (0.1 M). Common salts do not depress the extraction. Distribution coefficients and separation factors of several elements relative to mercury(II) are reported for media that contain the optimal concentrations of the mineral acids and are in 0.2M in potassium thiocyanate. The data have been applied for the determination of mercury in soil and water samples by atomic-absorption spectrometry.     

Solvation of thiocyanate complexes of tungsten(VI) by 5-(4-pyridyl) nonane from aqueous hydrochloric acid solutions

5-(4-Pyridyl)nonane has been evaluated as a solvent for trace amounts (<5·10^–5 M) of tungsten(VI) from aqueous chloride-thiocyanate solutions. Remarkable enhancements in metal extractability are observed on the addition of SCN^– to aqueous hydrochloric acid solutions. Extremal partition coefficients are obtained from 0.1 M HCl in 0.2 M KSCN. Diminutions of the metal extractability are produced by relatively high (>0.5 M) SCN^– concentrations and increased concentration of the supporting acid. Slope analysis data, under optimal parameters, indicates the most probable composition of the extractable species as WO₂(SCN)₂·2P_YN. Neutral anions do not have any significant effect on the D values. Behaviour of a number of metal ions has been checked using optimal aqueous conditions of extraction. The investigation shows that the reagent has a great potential for the preconcentration of a number of metal ions including the common toxins.     

Liquid-liquid extraction of cadmium(II) from aqueous thiocyanate solutions with liquid anion-exchangers

An investigation has been made on the system liquid anion-exchanger-Cd(II)-NCS⁻. The influence of the acidity and thiocyanate concentration of the aqueous phase on the extraction has been studied. Using various methods of analysis, it has been shown that the complex anion present in the organic extracts is Cd(NCS) ₄ ²⁻ . Details are given concerning the removal of traces of Zn(II) from Cd(II)-containing solutions, and the quantitative separation of Cd(II) from Cr(III).     

Extraction of molybdenum(VI) by 4-(5-nonyl)pyridine in benzene from aqueous mineral acid solutions containing thiocyanate ions

Extraction of Mo(VI) by 4-(5-nonyl)pyridine (NPy) in benzene from mineral acid solutions containing thiocyanate ions has been investigated at room temperature (23±2°C). From mineral acid (HCl, HNO₃, and H₂SO₄) solutions alone Mo(VI) is not extracted quantitatively while the presence of small amounts of KSCN in the system augments the extraction by a large factor. Stoichiometric studies indicate that ion-pair type complexes (NPyH)₂·[MoO₂(SCN)₄] are responsible for the extraction. Separation factors determined at fixed extraction conditions (0.1M Npy/C₆H₆–0.1M acid +0.2M KSCN) reveal that Ag(I), Cu(II), Co(II), Zn(II), Hg(II) and U(VI) are co-extracted while a clean separation from alkali metals, alkaline earths and some transition metals like Ln(III), Zr(IV), Hf(IV), Cr(III), Cr(VI) and Ir(III) is possible. Some of the complexing anions like oxalate, citrate, acetate, thiosulfate or ascorbate do not affect the degree of extraction of Mo(VI) allowing it to be recovered from diverse matrices.     

4-(5-nonyl)pyridine extraction of platinum from different aqueous solutions

The partition of tracer-level (<10^?7 mole/l) platinum between various 4-(5-nonyl)-pyridine phases and aqueous nitric, hydrochloric, and sulphuric acid phases has been studied radiometrically as a function of the amine and acid concentrations. The effects of saltingout agents and some anions on the extraction of the metal are reported. The extraction data is compared with that of gold and conditions are established for the separation of daughter¹⁹⁹Au from neutron irradiated platinum. The distribution coefficients of various metal ions are given for the 4-(5-nonyl)pyridine-10M HCl system and their factors for separation from platinum estimated.     

Solvent extraction of thiocyanate complexes of cobalt(II) by 2-benzylpyridine/benzene from aqueous acid solutions

Selective separation of Co(II) from aqueous acidic solutions containing thiocyanate ions has been achieved by using 2-benzylpyridine (BPy) dissolved in benzene. Optimum conditions of extraction by 0.1M BPy are: 0.05M (HCl, HNO₃) or 0.01M H₂SO₄+1 M KSCN. Ascorbate and sulfate ions do not affect the extraction of cobalt(II), whereas acetate, citrate and oxalate ions lower the extraction. Separation of cobalt(II) from Mn, Cr, Hf, Fe, Y, Ce, Cd, Sr, Cs and several rare earth elements can be achieved in a single extraction. Slope analysis by log-log plot reveals that neutral cobalt-thiocyanate species is extracted with the probable formula of the extracted complex as Co(BPY)₃ (SCN)₂.     

The extraction of manganese (II) from aqueous thiocyanate solutions with liquid anion-exchangers

Summary Manganese(II) is efficiently extracted from acidified thiocyanate solutions by alamine and, even more effectively, aliquat dissolved in e.g. toluene or CCl₄. The metal-containing species present in the organic extracts is Mn(NCS) ₄ ^2– .

---

Extraktion von Mangan (II) ans wäßrigen Thiocyanatlösungen mit flüssigen Anionen-Austauschern

Zusammenfassung Mit Hilfe von Alamin oder besser Aliquat, gelöst z.B. in Toluol oder Tetrachlorkohlenstoff, kann Mangan(II) mit gutem Erfolg aus sauren Thiocyanatlösungen extrahiert werden. Mn ist in den organischen Extrakten als Mn(NCS) ₄ ^2– enthalten.

     

Liquid-liquid extraction of cobalt thiocyanate with trhsooctylamine

Cobalt forms a coloured complex with triisooctylamine and thiocyanate in carbon tetrachloride. The green organic phase has maximum absorbancc at 627.5 mμ and Beer's law is obeyed in the range 0–10 mg Co. The molar extinction coefficient is 1895. The distribution coefficient at room temperature is 5.6. A composition of the coloured species is proposed.     

Liquid-liquid partition of cobalt between trilaurylamine N-oxide and aqueous thiocyanate solutions

In an attempt to gain an understanding of factors affecting the extraction of cobalt by trilaurylamine oxide, the equilibria between HX+SCN^– (where X=NO ₃ ^– , Cl^–, SO ₄ ^2– ) and benzene solutions of trilaurylamine oxide have been studied. Cobalt is quantitatively extracted by the oxide from aqueous 0.01–1M KSCN in 0.01M concentration of the acids. The extraction mechanism and the possible compositions of the extracted species are discussed. The effect of several anions on the extraction of the element from optimal aqueous solutions are reported and separation factors for a number of metal ions are given. The solvent has a potential for the group preconcentration of toxic metal ions from dilute aqueous solutions.     

Studies on extraction of thorium by the N-oxides of 5-(4-pyridyl)nonane and trioctylamine from different mineral acid solutions and its separation from rare earth elements and yttrium

The N-oxides of 5-(4-pyridyl)nonane and trioctylamine have been evaluated for use in the extraction of thorium from different mineral acid solutions. The influence of the concentration of the solvents and salting-out agents has been investigated. The possible mechanism of extraction is discussed in the light of the results of extraction isotherms, loading-ratio data and log-log plots of reagent concentration vs. distribution ratio. Separation factors for a number of metal ions are reported and a method for the separation of thorium from rare earth elements and yttrium is also suggested.     

Diphenyl(2-pyridyl)methane as a solvent for thiocyanate complexes of zinc in aqueous mineral acids

Summary Tracer (10^–8 M) zinc can be quantitatively extracted with 0.1M diphenyl(2-pyridyl)methane (DPPM) in benzene from neutral and acidic aqueous thiocyanate solutions in a single extraction. In all cases, extraction times of 1–5 min are sufficient for equilibration. The effects of the concentration of the mineral acids, the reagent, complexing and salting-out agents and phase-volume ratios on the metal extraction are reported. The metal is predominantly extracted through solvation, and the extraction of the metal as Zn(SCN)₂(DPPM)₂ is indicated. Among the common salts only sodium chloride exerts a slight depressing effect on extraction when present in high concentration. The metal can be stripped from the organic phase with aqueous oxalate, citrate or acetate solutions in a single operation. Distribution coefficients and separation factors for a number of metal ions, relative to zinc, are reported for 0.2M potassium thiocyanate media that contain the optimal concentration of mineral acid. The method can be employed for the simultaneous preconcentration of toxic metals such as zinc, copper and mercury from neutral aqueous solution in water pollution studies.

---

Diphenyl(2-pyridyl)methan als Lösungsmittel für Zink-Rhodanidkomplexe in wäßrigen Mineralsäuren

Zusammenfassung Zinkspuren (10^–8 M) lassen sich mit einer benzolischen, 0,1 M Lösung von Diphenyl(2-pyridyl)methan (DPPM) aus neutralen oder sauren, wäßrigen Rhodanidlösungen durch eine einzige Extraktion ausschütteln. Jedenfalls sind 1–5 min hinreichend für die Einstellung des Gleichgewichtes. Der Einfluß der Konzentration der Mineralsäure, des Reagens, des Komplexbildners und des Aussalzmittels sowie des Volumenverhältnisses der Phasen auf die Metallextraktion wurde beschrieben. Die Extraktion erfolgt vorherrschend durch Solvatation und zwar als Zn(SCN)₂(DPPM)₂. Unter den gewöhnlichen Salzen beeinträchtigt nur NaCl in hoher Konzentration die Extraktion in geringem Maß. Das Metall kann aus der organischen Phase mit wäßrigen Oxalat-, Citrat- oder Acetatlösungen in einem Arbeitsgang rückextrahiert werden. Die Verteilungskoeffizienten und Trennungsfaktoren für einige Metallionen in bezug auf Zink in 0,2M Kaliumrhodanid bei optimaler Mineralsäurekonzentration wurden angegeben. Das Verfahren eignet sich für die gleichzeitige Anreicherung toxischer Metalle, wie Zn, Cu und Hg aus neutraler Lösung bei der Untersuchung der Gewässerverunreinigung.

     

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.     

Liquid-liquid extraction of uranium(VI) from aqueous acidic solutions using Alamine, TBP and CYANEX systems

Liquid-liquid extraction of uranium(VI) (UO₂ ²⁺) from aqueous acidic (HCl and HNO₃) solutions into a co-existing organic phase containing Alamine 308 (triisooctyl amine), TBP (tri-n-butyl phosphate) or CYANEX 302 (bis(2,4,4-trimethylpentyl) monothiophosphinic acid) and diluent (toluene) was studied at isothermal conditions (298.2 K) at aqueous phase acidity varying in the range 0.5-6 mol/dm³. All solvent systems exhibit a maximum distribution ratio restricted in the acidity range 3-4 mol/dm³. An obvious difference in extraction behavior through amine system has been observed for two acids, HCl and HNO₃, distinguishing the divergent interactions attributed to the different mechanism of complexation depending on the acidic medium. The high degree of separation of UO₂ ²⁺ from HNO₃ solution is feasible through a complex formation with extractants ranging in the order CYANEX 302 > TBP > Alamine 308. The results were correlated using various versions of the mass action law, i.e., a chemodel approach and a modified version of the Langmuir equilibrium model comprising the formation of one or at least two U(VI)-extractant aggregated structures.     

Palladium(II) complexes with 5-methyl-5-(4-pyridyl)-2,4-imidazolidenedione

Two new palladium(II) complexes with 5-methyl-5-(4-pyridyl)-2,4-imidazolidenedione(mpyh) were synthesized: cis-[Pd(mpyh)₂Cl₂]·H₂O and cis-[Pd(mpyh)₂Br₂]·2H₂O. The molecular formulae of the complexes were confirmed by elemental analysis, IR, ¹H NMR spectra and DTA study. The ligand is coordinated to the palladium ion with N-atom of the pyridine ring. The spectroscopic data indicate a square planar geometry with two N-pyridine atoms and two halogene anions in cis position. The final product of the thermal decomposition of cis-[Pd(mpyh)₂Cl₂]·H₂O is metallic Pd, whereas for cis-[Pd(mpyh)₂Br₂]·2H₂O the residue consists of metallic Pd and C. The cytotoxic effects of the complexes were examined in vitro on some human tumor cell lines. The cis-[Pd(mpyh)₂Cl₂]·H₂O proved to be more active as compared to the cis-[Pd(mpyh)₂Br₂]·2H₂O.     

4-(5-Nonyl)pyridine as an extractant for cobalt thiocyanate complexes from mineral acid solutions

The partition behaviour of cobalt into 4-(5-nonyl)pyridine (NPy) in benzene from aqueous hydrochloric, nitric and sulfuric acid media containing variable amounts of potassium thiocyanate is described. Cobalt is quantitatively extracted by NPy from 0.1–1M KSCN solutions at 0.01 M concentration of the mineral acids. The extraction mechanism and the possible compositions of the extracted species are discussed. The effects of foreign salts on the extraction of cobalt from three mineral acid solutions are reported. Several elements including those which are of some interest in connection with the separation of cobalt were tested for extraction from 0.01 M solutions of mineral acids 0.3 M with respect to KSCN and their factors for separation from cobalt were estimated.     

The extraction of Cr(III) from aqueous thiocyanate solutions and its separation from Co(II) and Ni(II)

For the system liquid anion-exchanger—Cr(III)−NCS⁻, an investigation has been made of the dependence of the percentage extraction of Cr(III) on parameters such as standing time of the Cr(III)−NCS⁻ solution, temperature, pH and type of exchanger. Quantitative extraction of e.g. 4·10⁻⁴ M Cr(III) by 0.1M Aliquat in CCl₄ is easily achieved at room temperature, using 4.75M KNCS−0.05N HCl as aqueous phase. At high Cr(III) concentrations, the complex anion present in the organic phase is Cr(NCS) ₆ ³⁻ ; when working with dilute metal ion solutions, the species extracted is Cr(NCS)₄ (H₂O) ₂ ⁻ . Separations of mixtures containing 10⁻²−10⁻⁴ M Co(II), Ni(II) and Cr(III) have successfully been accomplished.     

Liquid-liquid extraction of rhodium(III) from hydrochloric acid solutions with 1,2,4-triazole derivative

Liquid-liquid extraction of rhodium(III) from hydrochloric acid solutions with a 1,2,4-triazole derivative was studied. Optimal conditions for its recovery were found. Rhodium(III) was shown to be recovered in extraction system by ion-exchange reaction at the time of phase contact not longer than 5 min. When phase contact time increased, rhodium(III) is extracted by a mixed mechanism with simultaneous insertion of two extractant molecules into the inner coordination sphere of rhodium(III) ion. Composition of coordination species of recovered compounds was established by electronic, IR, ¹H and ¹³C NMR spectroscopy and functional analysis, the structure of the coordination species is proposed.     

Liquid-liquid extraction of zinc(II) as its ethyl xanthate

A method for quantitative extraction of zinc with potassium ethyl xanthate into carbon tetrachloride is described. The optimum conditions are: pH 5-6 and Zn(II) to reagent ~1:8 mole ratio. The effects of other ions on the extraction of Zn(2+) have been investigated, and its separation from As(3+), Pb(2+), Cu(2+) and Fe(3+)is described. The possibility of repeated use of the solvent (still loaded with xanthate after the zinc has been stripped) for further extractions (after addition of a little extra xanthate) has been explored. Various stripping agents have been examined, and the optimum conditions found.     

Liquid-liquid extraction behaviour of mercury(II) as bromide,iodide and thiocyanate

The liquid-liquid extraction behaviour of mercury(II) as bromide, iodide and thiocyanate has been investigated in different oxygenated and non-oxygenated solvents. The effects of the molarity of acids, their sodium or potassium salts, the concentration of Hg(II) ions, the temperature and masking anions have been studied. The possibilities of separation of Hg(II) from Zn(II), Cd(II) Tl(I), Tl(II) and Au(III) in these extractions are discussed.     

Liquid-liquid extraction of uranium(VI) from nitric acid solutions with bis(octylsulfinyl)ethane (BOSE)

The liquid-liquid extraction behavior of uranium(VI) from aqueous nitric acid with bis(octylsulfinyl)ethane (BOSE) in 1,1,2,2-tetrachloroethane has been studied over a wide range of conditions. The extracted species appears to be UO₂(NO₃)₂·2BOSE. It was found that the extraction increases with increasing nitric acid concentration up to 7 mol/l and then decreased. Extraction also increases with increasing extractant concentration. The influence of temperature and salting-out agent concentration on the extraction equilibrium and stripping of uranium(VI) was also investigated and the enthalpy of the extraction reaction was obtained.