Solvent extraction of tetrachloronitridotechnetate(VI) ion with tetraphenylarsonium chloride

Radiochemical and spectrophotometric studies on the solvent extraction of tetrachloronitridotechnetate(VI) ion with tetraphenylarsonium chloride into chloroform have been reported. Analysis of the dependence of the distribution ratio for technetium species on the concentration of hydrogen ion (0.1–1.0M) revealed that an equilibrium between tetrachloronitridotechnetate(VI) ion and [(H₂OCl₃NTc–O–TcNCl₃(H₂O)]^2– is established in the aqueous phase. However, formation of di(-O) dimer was suggested, when the concentration of hydrochloric acid is less than 0.2M. The extraction constant for technetium and formation constant for -oxo technetium nitrido complex were evaluated.     

Solvent extraction and photometric determination of molybdenum (VI) with 2-aminobenzenethiol

A new extractive photometric method is described for estimation of molybdenum with 2-aminobenzenethiol. The green complex in chloroform has its absorbance maximum at 700 nm and is stable for 2 hr when extracted from a solution of optimum pH range 1.4-2.8. The extraction is quantitative. The sensitivity is 0.0075 microg cm (2). Beer's law is obeyed over the range 0.25-10 ppm with optimum range 0.5-4.5 ppm. The molar absorptivity is 7.08 x 10(4) 1.mole(-1). cm(-1). The overall stability constant is 2.0 x 10(8) at 25 +/- 0.1 degrees.     

Thermal decomposition of the solvent extracted molybdenum (VI) complexes from hydrochloric acid solutions with trioctylamine and trioctylmethylammonium chloride

The complexes of molybdenum(VI) with trioctylamine (TOA, R₃N) and trioctyl methylammonium chloride (TOMAC, R₃R'NCl) were prepared by drying in vacuo the organic solutions for the extraction of molybdenum(VI) from hydrochloric acid solutions at low and higher acidities, respectively, by TOA and TOMAC in benzene. The resulting complexes were examined by thermal analysis (TG and DTA) in air and under the atmosphere of nitrogen, and their thermally decomposed products such as volatile matters and residues by gas chlomatography, X-ray diffraction study and infrared spectrophotometry. It was found that their complexes decompose thermally to MoO₃ by cracking of alkyl groups combined with molybdenum(VI) ion. Accordingly the thermal decomposition process of those complexes is discussed and the probable structure of the complexes is proposed on the basis of the results obtained.

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Zusammenfassung Komplexe von Molybdän(VI) mit Trioktylamin (TOA, R₃N) und Trioktylmethylammoniumchlorid (TOMAC, R₃R'NCl) wurden hergestellt, mittels TG und DTA in Luft und in Stickstoffatmosphäre untersucht. Die thermischen Zersetzungsprodukte der Komplexe (flüchtige Substanzen und Rückstände) wurden mittels Gaschromatographie, Röntgendiffraktion und IR-Spektroskopie untersucht. Es wurde gezeigt, daß die Komplexe thermisch zu MoO₃ zerfallen, indem die an das Molybdän(VI)-Ion gebundenen Alkylgruppen abgekrackt werden. Die Ergebnisse der thermischen Zersetzungsprozesse wird diskutiert und auf der Basis der erhaltenen Ergebnisse die wahrscheinliche Struktur der Komplexe dargelegt.

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Dedicated to Professor Dr. H. J. Seifert on the occasion of his 60^th birthday

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The author wishes to thank Dr. H. Watanabe and Mr. T. Takahashi for assistance with experimental work, and also the Koei Chemical Co., Ltd. for samples of TOA and TOMAC.     

Solvent extraction of uranium(VI) with benzyloctadecyldimethylammonium chloride (BODMAC) from highly concentrated chloride solution

The ²²²Rn emanation fraction (EF) released from the technically enhanced naturally occurring radioactive material (TE-NORM) wastes at certain sites of petroleum and gas production was determined. The samples were analyzed by γ-ray spectrometry to determine the activity concentration of the ²²⁶Ra content, of which the ²²²Rn emanation fraction was calculated. The results showed that the ²²²Rn emanation fraction differs in the oil and gas production sites and it is independent of the activity concentration of ²²⁶Ra. This revised version was published online in August 2006 with corrections to the Cover Date.     

Solvent extraction of molybdenum(VI) with 1-Phenyl-2-methyl-3-hydroxy-4-pyridone

Summary The extraction of molybdenum(VI) from aqueous hydrochloric or perchloric acid solution by 1-phenyl-2-methyl-3-hydroxy-4-pyridone (HX) dissolved in chloroform has been studied. Molybdenum(VI) is quantitatively extracted from aqueous solution in the range 0.001–1M hydrogen ion concentration. Outside this range, the extraction of molybdenum decreases and at 10M acid concentration or at pH>6 practically all the molybdenum remains in the aqueous phase. Molybdenum can be stripped with 10M HCl. The composition of the extracted molybdenum(VI) species was found to be MoO₂X₂. This complex, dissolved in chloroform, has a maximum absorbance at 317 nm and a molar absorptivity of 2.5×10⁴ 1 · mole^–1 · cm^–1. Owing to this property, molybdenum can be determined spectrophotometrically directly in the organic phase.

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Zusammenfassung Die Extraktion von Mo(VI) aus wäßriger Salzsäure oder Perchlorsäure mit 1-Phenyl-2-methyl-3-hydroxy-4-pyridon (HX) in chloroformischer Lösung wurde untersucht. Sie erfolgt quantitativ bei 0,001–1-molarer H-Ionenkonzentration. Außerhalb dieses Bereiches fällt die Extraktionsrate ab und aus 10-m Säure bzw. bei pH>6 bleibt praktisch alles Molybdän in der wäßrigen Phase. Mit 10-m Salzsäure kann man Mo abtrennen. Die Zusammensetzung der extrahierten Mo-Verbindung entspricht der Formel MoO₂X₂. Dieser in Chloroform gelöste Komplex hat ein Absorptionsmaximum bei 317 nm und eine molare Extinktion von 2,5 · 10⁴l · Mol^–1 cm^–1. Demzufolge läßt sich Molybdän unmittelbar in der organischen Phase spektrophotometrisch bestimmen.

     

Liquid ion-exchange extraction study of hexacyanoferrate(III) with trioctylmethylammonium chloride (aliquat-336)

Liquid-liquid ion-exchange extraction of various anions including hexacyanoferrate(III) with a chlorobenzene solution of trioctylmethylammonium chloride (TOMA-Cl; Aliquat-336 chloride) is described. The ion-pair extraction constant of TOMA-Cl (K^Q.Cl_ex = 10⁴) and the ion-exchange extraction constants of TOMA-Cl for each anion (K^Cl.X_ex) are reported. The order of selectivity of anion extraction is Fe(CN)^3-₆ (log K^Q.X_ex = 22.41) > ClO^-₄(8.47) > PAR^- (7.80) > I^-(7.32) > NO^-₃(5.81) > Br^-(5.34) > Cl^-(4.00).     

Extraction of chromium(VI) with blue tetrazolium chloride and tetranitrotetrazolium blue chloride

The optimum conditions for extraction of microquantities of chromium(VI) as an ion-association complex with blue tetrazolium chloride (BTC) and tetranitrotetrazolium blue chloride (TNBT) has been determined. The extracted species was a 1: 2 of the BTC and TNBT cation and the chlorochromate anion. Beer’s law was obeyed in the range of 0.04–0.8 μg/mL Cr(VI) for BTC and 0.1–1.6 μg/mL Cr(VI) for TNBT. The molar absorptivities were ?₂₅₅ = 7.77 × 10⁴ L/(mol cm) (for BTC) and ?₂₇₅ = 2.04 × 10⁴ L/(mol cm) (for TNBT). Sandell’s sensitivity of the systems were found to be 6.69 × 10^?4 μg/cm² (for BTC) and 2.55 × 10^?3 μg/cm² (for TNBT). Limit of detection (LOD) is 8.55 ng/mL and limit of quantitation (LOQ) is 0.028 μg/mL Cr(VI) for BTC. For TNBT, LOD is 0.031 μg/mL and LOQ is 0.103 μg/mL. The characteristic values for the extraction equilibrium and the equilibrium in the aqueous phase have been determined. A sensitive method for determination of trace of chromium(VI) in plants has been developed.     

Solvent extraction of dioxouranium(VI) with dialkyldithiophosphoric acids

The extraction of dioxouranium(VI) species from acidic aqueous solutions into benzene, in the presence of dialkyldithiophosphoric acids occurs with moderate partition coefficients, increasing with the length of the alkyl chain. The mechanism involves the formation of neutral [UO₂[S₂P(OR)₂]₂] species soluble in benzene, the partition is strongly affected by complexation in the aqueous phase, when the alkyl chain is short. Distribution coefficients and extraction constants have been determined under various conditions.     

Potentiometric studies of the complexes of chromium(VI), molybdenum(VI) and tungsten(VI) with some Azoxine S dyes

The equilibrium constants of the complexation reactions of Cr(VI), Mo(VI) and W(VI) with 8-hydroxyquinoline-5-sulphonic acid (OXS), 7-phenylazo-8-hydroxyquinoline-5-sulphonic acid (PAZOXS), 7-(4-sulphophenylazo)-8-hydroxyquinoline-5-sulphonic acid (SPAZOXS) and 7-(4-sulphonaphthylazo)-8-hydroxyquinoline-5-sulphonic acid (SNAZOXS) have been determined by potentiometric pH titration. The values in the case of chromate are different from those for molybdate and tungstate. The order of stabilities is OXS > PAZOXS > SPAZOXS > SNAZOXS.     

Liquid-liquid extraction of molybdenum(VI) and uranium(VI) by LIX 622

The order of extraction of Mo(VI) from 1M acid solutions by 5% (v/v) LIX 622 (HL) in benzene is HCl>HNO₃>HClO₄>H₂SO₄, and extraction decreases with increasing concentration of HCl and H₂SO₄, and increases slightly with increasing concentration of HNO₃ and HClO₄. The extracted species is shown to be MoO₂L₂ as established by IR data of organic extracts and the extracted species in the solid form. Extraction is almost quantitative at and above 10% LIX 622, and is found to be independent of [Mo(VI)] in the range of 10^–4 to 10^–3 M. The diluents CCl₄, CHCl₃ and C₆H₆ are found to be superior to solvents of high dielectric constant for extraction of Mo(VI). Extraction of uranium(VI) by 10% (v/v) LIX 622 in benzene was found to increase with increasing equilibrium pH (3.0 to 6.0), and becomes quantitative at pH 5.9. Tributyl phosphate acts as a modifier up to 2% (v/v). Thorium(IV) is almost not extracted by LIX 622 or its mixture. Separation of Mo(VI) and U(VI) is feasible.     

Solvent extraction of W(VI) with rhodamine-B in nitrobenzene

A rapid and selective method has been developed for the extraction of W(VI) with rhodamine-B in nitrobenzene. The extraction coefficient value for the extraction between aqueous solution and nitrobenzene showed a maximum value of E=63 at a pH of 5.0. The stoichiometry of metal to reagent has been determined by the method of substoichiometric extraction and slope ratio method.     

Solvent extraction and spectrophotometric determination of uranium (VI)

Summary Solvent extraction of uranium-sodium diethyldithiocarbamate with ethylmethyl ketone and separation from titanium, zirconium, thorium, lanthanum and cerium has been described. It has been found that 11.75 to 47.00 mg of uranium can be extracted from a binary mixture containing 4.78 to 19.04 mg of titanium, 9.12 to 36.48 mg of zirconium, 116.0 to 460.0 mg of thorium, 6.95 to 27.8 mg of lanthanum or 7.06 to 28.24 mg of cerium at pH 3.0. The pH range between which the separations may be carried out successfully is 2.0 to 3.5. The following cations interfere in the separations: Cu^II, Fe^III, Co^II, Bi^III, Ni^II, Cr^VI, Te^IV, Se^IV, Ag^I, Hg^II, As^III, Sn^IV, Pb^IV, Cd^II, Mo^VI, Mn^II, V^V, Zn^II, In^III, Tl^I, W^VI, Os^VIII and Nb^V.

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Zusammenfassung Uran kann durch Extraktion als Diäthyldithiocarbamidat mit Methyläthylketon von Ti, Zr, Th, La oder Ce getrennt werden. Der günstigste pH-Bereich liegt zwischen 2,0 und 3,5. Die Trennungen wurden mit folgenden Mengen durchgeführt: U (11,75–47,00 mg); Ti (4,78 bis 19,04 mg), Zr (9,12–36,48 mg) Th (116,0–460,0 mg), La (6,95–27,8 mg), Ce (7,06–28,24 mg). Folgende Ionen verursachen Störungen: Cu^II, Fe^III, Co^II, Bi^III, Ni^II, Cr^VI, Te^IV, Se^IV, Ag^I, Hg^II, As^III, Sn^IV, Pb^IV, Cd^II, Mo^VI, Mn^II, V^VI, Zn^II, In^III, Tl^I, W^VI, Os^VIII sowie Nb^V.

     

Specific extraction of chromium(VI) using supercritical fluid extraction

In some situations, it is no longer sufficient to give a total concentration of a metal. Instead, what is required to understand the potential toxicity of a sample is the concentration of metal species or oxidation state. When developing species specific methods, the major concern is that the integrity of the species ratio is not changed. In other words, the sample preparation or the analytical method will not convert metal ions from one oxidation state to another. Normal extraction techniques and chromatography methods have shown some tendencies to change species ratios. An ideal extraction method would extract the metal efficiently while retaining the metal's oxidation state. The properties of supercritical fluids should approach the ideal of retention of oxidation states. For example, the need for speciation of chromium is obvious since Cr(III) is considered an essential element while Cr(VI) is thought to be toxic and carcinogenic. This paper presents the results of a species specific extraction of Cr(VI) using two different carbamate derivatives as the chelator. Supercritical fluid extraction (SFE) coupled with a fluorinated dithiocarbamate and a methanol modifier allows extraction of 1 ppm Cr(VI) from a solid matrix with a recovery level of 88.4+/-2.57% using the NIST standard sample. The optimized conditions using the HP 7680 supercritical fluid extractor were: 0.1 ml of methanol, 0.05 ml of pure water, and 0.01 g of chelate via a saturation chamber.     

Uranium(VI) extraction with benzyloctadecyldimethylammonium chloride (BODMAC) from chloride and sulfate solutions

Summary The solvent extraction of uranium(VI) from concentrated chloride solutions by quaternary salt benzyloctadimethylammonium chloride (BODMAC, R₄NCl) in three diluents was studied. The composition of the extracted species was R₄N^. UO₂Cl₃and (R₄N)₂^. UO₂Cl₄in the three diluents investigated. The dependence of the distribution ratios on the concentration of hydrochloric acid, extractant, salting-out agents and temperature was investigated. The extraction efficiency of BODMAC strongly depends on the nature of the diluent. The presence of Mg(SO₄)₂basically alters the sequence of diluent extraction efficiency.     

Solvent extraction of chromium(VI) from base metal ions with diphenyl-2-pyridylmethane as a liquid anion exchanger

The extraction of chromium(VI) from aqueous hydrochloric, nitric and sulfuric acid solutions by diphenyl-2-pyridylmethane(DPPM) dissolved in chloroform has been studied. Chromium(VI) is quantitatively extracted from hydrochloric acid solutions in the range 0.1–1M. With increasing acid concentration, the extraction of chromium diminishes and in concentrated acid solutions practically all the chromium remains in the aqueous phase. The quantitative back-extraction of chromium from the organic phase is possible with HCl or HNO₃ at concentrations higher than 5M through the use of reducing agents. The composition of the extracted chromium(VI) species was studied in solution. The complexes (DPPMH)⁺HCrO ₄ ⁻ and (DPPMH)₂Cr₂O ₇ ⁻ are extracted for tracer and macro amounts of chromium(VI) respectively. The data have been utilized for the separation of chromium(VI) from base metal ions.     

Studies on the extraction of chromium(VI) by ketones

A study of the extraction of chromium(VI) from aqueous media by ketones was made. Extraction of chromium was found to be most efficient from aqueous hydrochloric acid solutions. A mechanism for the extraction of chromium(VI) from aqueous hydrochloric acid solutions by methyl isobutyl ketone is proposed involving the formation of a receptor in the organic phase, the exchange of the chloride ion of the receptor for the anionic chromium(VI) species of the aqueous phase, and the solvation of the extracted chromium species. The differences in the abilities of various ketones to extract chromium(VI) from aqueous hydrochloric acid solutions, and the differences in the extraction of chromium (VI) from various aqueous acids by methyl isobutyl ketone are attributed to the differences in the formation of receptors.     

Spectrophotometric study of the complexation and extraction of chromium(VI) with cyanine dyes

Solvent extraction of chromium(VI) ion associates with symmetric cyanine dyes including the heterocyclic radicals of 1,3,3-trimethyl-3N-indoline, benzooxazol, benzothiazol and quinoline has been studied by means of spectrophotometric method. In the acidic medium in the presence of chloride ions, extractable by aromatic hydrocarbons and esters of acetic acids, chromium(VI) ion associates are formed. The molar absorptivities of ion associates are 2.5-3.6x10(5) l mol(-1) cm(-1) in dependence on extractant and dye. The absorbance of the coloured extracts obeys the Beer's law in the range 0.01-2.1 mg l(-1). The extraction of chromium is the highest during extraction from the sulphuric acid medium in the range 0.05-03 M H(2)SO(4). It was found that the Cr(VI):Cl:R molar ratio is 1:1:1. A novel procedure of chromium(VI) extraction and spectrophotometric determination in various types of soils and sewage doped with chromium(VI) was examined.     

Enhancement of phenols on ion-pair extraction of chromium(VI) with tetraphenylarsonium

The effect of phenols on the ion-pair extraction of chromium(VI) as chromate anion (HCrO ₄ ^– ) with tetraphenylarsonium cation (TPA⁺) has been investigated. By using TPACl, chromate is extracted as an ion-pair, TPA⁺·HCrO ₄ ^– , into organic solvents, but its extractability into nonpolar solvents such as carbon tetrachloride is very low. The addition of several phenols greatly enhances the extractability, e.g., the distribution ratio of chromium(VI) between carbon tetrachloride and water rises 5500-fold in the presence of 0.020M 3,5-dichlorophenol in the organic phase. The enhancement was larger when using more acidic phenols and less polar solvents. From the analysis of the extraction data for the 3,5-dichlorophenol-carbon tetrachloride system, it was shown that one molecule of chromate is extracted together with one TPA⁺ and 1–3 phenol molecules and the extraction constants were determined. The UV spectrum indicated the extracted species including chromate ester to the TPA⁺·ArOCrO ₃ ^– ·mArOH (m=1,2).