Sorption of molybdenum(VI) from mineral salt solutions

Changes in the ionic forms of molybdenum and conditions of sorption on the anionite AV-17 × 8 from mineral salt solutions at concentrations of 0.05–2 N and pH of medium 1–6 were revealed.     

Extraction of phosphorus(V), molybdenum(VI), and tungsten(VI) from fluoride solutions

The influence of titanim(IV) and silicon(IV) on the extraction of phosphorus(V), molybdenum (VI), and tungsten(VI) fluoride complexes by tributyl phosphate was studied.

     

The sorption of molybdenum(VI) by ionites from solutions in hydrochloric acid

The sorption of molybdenum(VI) by KU-2 × 8 and AV-17 × 8 ionites from solutions in hydrochloric acid (1 × 10⁻⁵−6 N) was studied. Changes in the sorption of molybdenum(VI) by cationite and anionite were observed. The isoelectric point of molybdenum in solutions in hydrochloric acid was determined from sorption and electrical migration measurements.     

Extraction of molybdenum(VI) from fluoride niobium-tantalum solutions with a high content of titanium(IV)

Distribution of molybdenum(VI) (0.05 M) upon extraction with tributyl phosphate from fl uoride solutions with a content of titanium(IV), niobium(V), and tantalum(V) of up to 3.0, 0.7, and 0.7 M, respectively, was studied.     

Recovery of tungsten(VI) and molybdenum(VI) with N′,N′-dialkylhydrazides of aliphatic carboxylic acids from acid solutions

Russian Journal of Applied Chemistry - Recovery of tungsten(VI) with solutions of N′,N′-dialkylhydrazides of 2-ethylhexanoic and octanoic acids in kerosene from sulfuric acid and...     

Anderson-type heteropolyanions of molybdenum(VI) and tungsten(VI)

The previously reported preparation of some Anderson-type molybdopolyanions containing divalent metal ions (Zn, Cu, Co or Mn) as a heteroatom has been reinvestigated. The molybdopolyanions of Zn(II) and Cu(II) were confirmed, although the Cu(II) polyanion was not stable and could not be recrystallized. On the other hand, the polyanions of Co(II) and Mn(II) could not be reproduced. Another type of heteropoly compound, [X(H₂O)_6-x(Mo₇O₂₄)]⁴⁻ [X = Cu(II), Co(II) or Mn(II)], was isolated as solids, which are not stable thermally. The mixed-type Anderson polyanions, [Ni(II)Mo_6-xW_x,O₂₄H₆]⁴⁻, which have been questioned as mixtures of species with different x values, were also reinvestigated using IR, UV absorption and MCD spectra. They are single species, but not mixtures, although some positional isomers may be present for the compounds where x = 2-4. The possibility of oxidation of the heteroatom with the Anderson structure maintained was examined. The oxidation of [Ni(II)Mo₆O₂₄H₆]⁴⁻ by the S₂O²⁻₈ ion in aqueous solution gave the Waugh-type [Ni(IV)Mo₉O₃₂]⁶⁻ polyanion, whereas the oxidation of [Ni(II)W₆O₂₄H₆]⁴⁻ gave no heteropoly compound.     

Column chromatographic separation of molybdenum (VI) from alloys with poly-(dibenzo-18-crown-6) from a hydrochloric acid medium

A very simple column chromatographic separation method has been developed for molybdenum (VI) using poly-(dibenzo-18-crown-6). The separations are carried out from hydrochloric acid medium. The adsorption of molybdenum (VI) on a poly-(DB-18-C-6) was quantitative from 2.5 to 10.0M HCl. Amongst the various eluents tested, 0.5M ammonium hydroxide was found to be an efficient eluent. Molybdenum (VI) was separated from a large number of elements in binary form, as well as from multicomponent mixtures. The method was applied for the analysis of molybdenum from various alloy samples. The method is very simple, rapid, selective and reproducible. The reproducibility of the procedure is +/-2%.     

Complexometric determination of molybdenum(VI)

In acidic medium molybdenum(VI) forms a stable complex on boiling with excess of DCTA and hydroxylamine hydrochloride. Molybdenum can then be determined by back-titration of the excess of DCTA either with zinc chloride at pH 5-5.5 or with thorium nitrate at pH 3-4.5, Xylenol Orange being used as indicator in both cases. A simple method for the determination of molybdenum in the presence of moderate amounts of tungsten is also described.     

Spectrophotometric determination of molybdenum(VI)

Molybdenum(IV) gives a red colour with ammonium thiocyanate in 5-8M hydrochloric acid medium, the Sandell sensitivity index being 0.018 ppm Mo(VI)/cm(2). Molybdenum(VI) in 4-7M hydrochloric acid medium forms a red complex with ethyl xanthate and ammonium thiocyanate and this can be extracted into acetophenone. Beer's law is obeyed over the range of 1.2-13.8 ppm, and the Sandell indices at 370 and 470 nm are 0.0016 and 0.0068 ppm/cm(2) respectively. The colour is stable for 40 hr. Most cations do not interfere.     

Homonuclear molybdenum(VI) and heteronuclear molybdenum(VI) copper(II) peroxo complexes containing amino acids

Summary MoO₃·H₂O reacts with two equivalents of glycylglycine (H₂Gg) or aspartic acid (H₂Asp) in an excess of aqueous H₂O₂ at ambient temperature to give [MoO(O₂)₂-(H₂Gg)₂(H₂O)] (1) and [MoO(O₂)₂(H₂Asp)(H₂O)] (2), respectively. An equimolar mixture of Cu powder and MoO₃·H₂O, on interaction with H₂Gg or H₂Asp in the presence or absence of H₂O₂, results in formation of [CuMoO(O₂)(Gg)₂(H₂O)₂] (3), [CuMoO₂(Gg)₂-(H₂O)₄] (4) and [CuMoO₂(Asp)₂(H₂O)₄] (5), respectively. These novel complexes have been characterized by elemental and thermogravimetric analysis, and e.s.r., electronic and i.r. spectral data.     

Reactions of tungsten(VI) and molybdenum(V) chlorides,and tungsten(VI) and molybdenum(VI) oxychlorides,with azoxybenzene

Reactions of W^VI and Mo^V chlorides with azoxybenzene yield ionic species of W^VI and Mo^VI oxychlorides in which the cation is a protonated azobenzene. The reaction between MoCl₅ or MoOCl₄ and azoxybenzene gives, after extraction with methylene chloride—ethanol mixture, the complex [trans-MoOCl₄(OC₂H₅)]^? [C₁₂H₁₀N₂H]⁺. In contrast, WOCl₄ reacts with azoxybenzene to give a stable non-ionic adduct in which the organic moiety is coordinated through its oxygen atom trans to the WO bond. Several complexes of substituted azoxybenzene having similar structures are described.     

纳米TiO2分离富集Mo(Ⅵ)和Re(Ⅶ)

本文研究了纳米TiO2吸附剂对Mo(VI)、Re(VII)的吸附行为,考察了溶液的pH值、吸附时间、温度等因素对吸附的影响。结果表明：纳米TiO2对Mo(VI)的吸附在pH 1～8条件下,吸附率超过99%,2 mL 0.05mol/L NaOH溶液可将吸附的Mo(VI)离子完全洗脱,解吸率能达到97%。在pH 1～10范围内,纳米TiO2不吸附Re(VII), 从而达到Mo(VI)、Re(VII)分离。在2℃～50℃温度范围内,Mo(VI)的吸附过程符合Langmiur等温式,纳米TiO2对Mo(VI)的最大吸附容量从11.51mg g-1增加到14.19 mg g-1;纳米TiO2分离钼后,溶液剩余的铼,用活性炭吸附,在pH1～10范围内, Re(VII)的吸附率可达99%,用浓氨水进行洗脱,洗脱率可达96%;吸附过程可用准二级反应动力学模型描述,是以化学吸附为控制步骤的吸附过程;吸附等温线与Freundlich模型有较好的拟合。     

Kinetic-spectrophotometric determination of molybdenum (VI) and tungsten (VI) in mixtures

A simple kinetic-spectrophotometric method is described for the determination of molybdenum(VI) and tungsten(VI) in mixtures, without prior separation. The method is based on the catalytic effect of molybdenum(VI) and tungsten(VI) on the oxidation of 2,4-diaminophenol dihydrochloride (DAP) by hydrogen peroxide in acidic medium. The reaction was followed spectrophotometrically by measuring the rate of change in absorbance with time at 500 nm. A partial inhibition in the catalytic activity of each catalyst, when the other one is present, at all ratios of Mo(VI) W(VI) mixtures studied was observed. On the other hand, the catalytic activity of tungsten(VI) dropped to zero whilst that of molybdenum(VI) decreased slightly, in the presence of citrate ions. Two sets of experiments were carried out, the first in the absence and the other in the presence of citrate, and the resolution of Mo(VI)/W(VI) mixtures was achieved by solving two simultaneous equations. Various molar ratios of Mo(VI) W(VI), at the 10^–6 M level, from 0.2 1 to 5 1 can be determined with satisfactory precision and accuracy. The selectivity of the method was investigated and the method was applied successfully to the determination of molybdenum and tungsten in each other's presence in steel.     

Radiochemical separation of rhenium(VII) from tungsten(VI)

The absorption of rhenium(VII) and tungsten(VI) ions on Al₂O₃ from HCl, HClO₄, HNO₃, H₂SO₄, H₃PO₄, NaOH, NH₄OH, NaCl, NaF, and Na-tartarate solutions by batch equilibration, as well as by passage through a chromatographic column, has been studied. The results show that rhenium(VII) can be effectively separated from tungsten(VI) using any of the acid or salt solutions investigated. The experimental data allowed to develop a simple procedure for the radiochemical separation of rhenium isotopes from an irradiated WO₃ sample.     

Solvent extraction of uranium(VI) and separation of vanadium(V) from sulfate solutions using Alamine 336

The present scientific study on uranium(VI) solvent extraction and vanadium(V) separation from sulfate solutions using Alamine 336 as an extractant diluted in kerosene was established. The preliminary experiments indicating the uranium extraction process will follow the solvation as well as ion-exchange mechanisms. In the present acid region (0.1–1.0 mol dm⁻³ H₂SO₄) it showing the ion-exchange type mechanism. Time (1–120 min) and temperature (25–55 °C) not influencing the present extraction system. Other experimental parameters like loading capacity of Alamine 336, stripping of uranium from loaded organic phase, recycling of Alamine 336 and separation of uranium(VI)/vanadium(V) was studied.