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Conditions have been developed for the direct titration of vanadium(V) and chromium(VI) with hydrazine sulphate, barium diphenylaminesulphonate being used as indicator and osmium tetroxide as catalyst. 相似文献
6.
The determination of vanadium(V) and molybdenum(VI) by a Landolt-type reaction with bromate, iodide and ascorbic acid is reported. For the determination of vanadium(V) the molybdenum(VI) is masked with citrate-citric acid buffer, which also controls the pH. Molybdenum(VI) is determined in the presence of thiourea as masking agent for vanadium(V). 相似文献
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Summary New specific methods have been developed for the detection of chromium(VI) and of vanadium(V), based on the formation of a purple color with primaquin in concentrated sulfuric acid solution. The identification limits and dilution limits have been determined to be 0.05g, 11 000 000 for chromium(VI) and 0.1g, 1500 000 for vanadium(V) respectively.
Neue spezifische Methoden zum Nachweis von Cr(VI) und V(V) mit Primachin
Zusammenfassung Die neu ausgearbeiteten Methoden sind spezifisch und beruhen auf der Bildung einer Purpur-Färbung mit Primachin in konz. Schwefelsäure. Die Nachweisgrenzen und Verdünnungsgrenzen betragen 0,05g bzw. 11 000 000 für Cr(VI) und 0,1g bzw. 1500 000 für V(V).相似文献
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The metal anions of vanadium (V) and chromium (VI) in aqueous solution can be effectively adsorbed by Zr(IV)-impregnated collagen
fiber (ZrICF). The maximum adsorption capacity of V(V) takes place within the pH range of 5.0 to 8.0, while that of Cr(VI)
is within the pH range of 6.0 to 9.0. When the initial concentration of metal ions was 2.00 mmol L−1 and the temperature was 303 K, the adsorption capacity of V(V) on Zr-ICF was 1.92 mmol g−1 at pH 5.0, and the adsorption capacity of Cr(VI) was 0.53 mmol g−1 at pH 7.0. As temperature increased, the adsorption capacity of V(V) increased, while that of Cr(VI) was almost unchanged.
The adsorption isotherms of the anionic species of V(V) and Cr(VI) can be fit by the Langmuir equation. The adsorption rate
of V(V) follows the pseudo-first-order rate model, while the adsorption rate of Cr(VI) follows the pseudo-second-order rate
model. Furthermore, ZrICF shows high adsorption selectivity to V(V) in the mixture solution of V(V) and Cr(VI). Practical
applications of ZrICF could be expected in consideration of its performance in adsorption of V(V) and Cr(VI). 相似文献
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We have considered the possibility of the sorption-spectrometric determination of molybdenum(VI) with phenylfluorone and chromium(VI) with diphenylcarbazide from a single sample by consecutive sorption from different media onto fiber materials filled with an AV-17 anion exchanger. The dependences of analytical signals of molybdenum and chromium on the sorption conditions (pH of the initial solution, NaCl concentration, sizes of the support disc, agitation time) have been studied in the batch mode. The conditions of analytical signal registration have been determined and the analytical ranges have been established (0.01–0.06 μg/mL for Cr and 0.02–0.2 μg/mL for Mo). It has been demonstrated that molybdenum and chromium can be determined at their ratios from 1: 1 to 5: 1 from a single sample after chromium sorption from 0.1 M HCl and molybdenum sorption at pH 4 by diffuse-reflection spectroscopy or visual test. The selectivity of molybdenum and chromium determination in the presence of interfering ions has been studied. 相似文献
10.
Contribution of air oxygen to photooxidation of alkanes by vanadium(V) and chromium(VI) oxocomplexes
In photochemical oxygenation of cyclohexane by KVO3–CF3COOH or K2Cr2O7–Bu4NBr–H2O–CH2Cl2 in air the source of oxygen atoms in the product cyclohexanol and cyclohexanone is air dioxygen rather than a metal oxo-complex. In the absence of dioxygen the products of alkane oxygenation are not formed in either of the above systems. At pH=3, Cr(VI) does oxidize cyclohexane to cyclohexanol even in argon atmosphere.
KVO3–CF3COOH K2Cr2O7–Bu4NBr–H2O–CH2Cl2 , . . , pH=3, Cr(VI) .相似文献
11.
S. Akyil M. A. A. Aslani S. Ölmez M. Eral 《Journal of Radioanalytical and Nuclear Chemistry》1996,213(6):441-450
In this paper, we studied the continuous adsorption of uranium on a composite ion exchanger. The experimental study was carried out at optimum conditions of uranium uptake found in the previous study. For these conditions first the adsorption isotherm was determined. This isotherm shows non-linear sorption according to the Langmuir model. Then we investigated uranium adsorption at different time intervals at temperatures of 30°C and 60°C, respectively. 相似文献
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Hydrazine sulphate is proposed as a primary standard reagent for the direct titrimetric determination of vanadium(V) and chromium(VI) alone and in mixtures with potentiometric and photometric end-points, in 9–12 M phosphoric acid medium. The methods proposed possess advantages over those currently available. The use of phosphoric acid as a reaction medium not only accelerates the hydrazine-vanadium(V) reaction very much but also makes it follow an accurate stoichiometric path. 相似文献
13.
Diffuse reflectance spectroscopy has been used for the study of the sorption of malonate and glycolate complexes of uranium(VI) and iron(III), present simultaneously in solution, onto the solid phase of fiber materials filled with an AB-17 anion exchanger. In the form of malonate complexes uranium(VI) is determined in 0.5 M HCl on substrate discs with immobilized Arsenazo III, while iron(III) is determined on substrate discs with potassium thiocyanate in 0.5 M HCl. The dependence of the analytical signals on the concentrations of U(VI) and Fe(III) is linear in the ranges 0.02–0.16 μg/mL; the detection limit is 0.01 μg/mL. The possibility of analysis of U(VI) and Fe(III) mixtures in ratio from 1: 5 to 5: 1 in the presence of 2-fold concentrations of Zr(IV), Th(IV), and Ti(IV), 5-fold concentrations of Bi(III), 10-fold concentrations of Cu(II), 20-fold concentrations of La(III), 100-fold concentrations of Ni(II) and Zn(II), and 200-fold concentrations of Co(II) and Ca(II) has been demonstrated. Standard color scales in the concentration range from 0.02 to 0.2 μg/mL have been used for the visual determination of uranium(VI) and iron(III). 相似文献
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The possibility of the sorption-spectrometric determination of zirconium(IV) and chromium(VI) from a single sample using a two-layer support made of polyacrylonitrile fiber filled with a PANF-KU-2 cation exchanger and PANF-AV-17 anion exchanger is studied. After sorption zirconium is determined with Arsenazo III on PANF-KU-2 and chromium is determined with 1,5-dipehnylcarbazide on PANF-AV-17. The sorption of zirconium and chromium is studied in the dynamic mode from solutions of HCl, HNO3, and H2SO4 and the optimal conditions of the simultaneous sorption of zirconium on PANF-KU-2 and chromium on PANF-AV-17 from 0.25 M HCl is chosen. Diffuse reflection spectra of zirconium and chromium complexes have are on the solid phase and the conditions of zirconium determination are optimized. Calibration curves are linear in the range of zirconium and chromium concentration 0.005–0.025 μg/mL; the detection limits are 0.002 μg/mL. The selectivity of zirconium and chromium determination is tested in the presence of interfering ions. A procedure is developed for their determination from a single sample at zirconium to chromium ratios from 3: 1 to 1: 3. 相似文献
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A flow injection analysis (FIA) method is presented for the simultaneous determinations of iron(III)-vanadium(V) and of iron(III)-chromium(VI) using a single spectrophotometric detector. In the presence of 1,10-phenanthroline (phen), iron(III) is easily reduced by vanadium(IV) to iron(II), followed by the formation of a red iron(II)-phen complex (lambda(max) = 510 nm), which shows a positive FIA peak at 510 nm corresponding to the concentration of iron(III). On the other hand, in the presence of diphosphate the reductions of vanadium(V) and/or chromium(VI) with iron(II) occur easily because the presence of diphosphate causes an increase in the reducing power of iron(II). In this case iron(II) is consumed during the reaction and a negative FIA peak at 510 nm corresponding to the concentration of vanadium(V) and/or chromium(VI) is obtained. The proposed method makes it possible to obtain both positive (for iron(III)) and negative (for vanadium(V) or chromium(VI)) FIA peaks with a single injection. 相似文献
16.
K. G. Varshney A. Agrawal S. C. Mojumdar 《Journal of Thermal Analysis and Calorimetry》2007,90(3):721-724
Pyridine based thorium(IV) phosphate (PyThP) has been synthesized by drop-wise addition of the thorium(IV) nitrate with constant
stirring into a mixture of pyridine and phosphoric acid. This material has been characterized using X-ray, IR spectra, TG,
DTG and SEM studies in addition to its ion exchange capacity, elution and pH titrations. The material has been found amorphous
and fibrous in nature on the basis of X-ray diffraction and SEM studies. TG has revealed the changes incurred in the material
on thermal treatment and IR spectral studies have shown the presence of various groups in its structure. 相似文献
17.
K. G. Varshney A. Agrawal S. C. Mojumdar 《Journal of Thermal Analysis and Calorimetry》2007,90(3):731-734
Both temperatures, T
C, (T
C —Curie temperature) and heat of the phase transition: ferroelectric-paraelectric, ΔH, in the BaxSr1−xTiO3 materials have been studied by means of the microcalorimetric method. The determined parameters were verified by either temperature
dependence of the dielectric permittivity (Curie-Weiss law) or thermodynamic method. The effect of strontium content on T
C has been discussed. It was found that microcalorimetry is useful tool studying phase transition phenomena in ferroelectric
perovskites. 相似文献
18.
The reaction between CrVI and 12-tungstocobaltate(II) was carried out in 2.0 mol dm–3 HCl and followed a simple second order rate law. The reaction was catalysed by hydrogen ion due to the formation of active H2CrO4 and was inhibited by chloride ion as, in its presence, conversion of the active species into inactive chlorochromate occurs. Chromium(V) and chromium(IV) were generated in situ by the use of CrVI—VIV or CrVI—2-ethyl-2-hydroxybutyric acid and CrVI—i-PrOH reactions respectively, and the oxidation of 12-tungstocobaltate(II) by these atypical oxidation states, was also studied. The rate constants for the oxidation of 12-tungstocobaltate(II) by CrVI, CrV and CrIV were found to be in the ratio 1:1.2:5.2 respectively. The ionic strength did not affect the reaction, while decrease in the solvent polarity increased the rate of the reaction. The activation parameters were also determined and the values H
, G
and S
were found to be 52.4 ± 6 kJ mol–1, 100.8 ± 7 kJ mol–1, –151.7 ± 10 J K–1 mol–1 respectively, supporting the mechanism proposed. 相似文献
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The effect of sorbent consumption and the kinetics and mechanism of sorption of uranium(VI) compounds on the surface of FIBAN A-6 fibrous anion exchanger from aqueous uranyl acetate solutions have been studied in the presence of sulfuric acid or sodium hydrocarbonate. The degree of sorption of uranium(VI) compounds by FIBAN A-6 anion exchanger has been found to be as high 97.0–99.5% at an interfacial contact time of 3–7 min and a sorbent consumption of 2–5 g/dm3. Diffusion and chemical kinetics models have been employed to show that the sorption kinetics of uranyl sulfate and carbonate complexes corresponds to the mixed diffusion mechanism and is described by a pseudo-second-order equation. The sorption isotherms of uranium(VI) compounds have the pattern of L-type isotherms according to the Giles classification and are satisfactorily described by the Langmuir, Freundlich, and Dubinin–Radushkevich equations. It has been found that, within 40 min, the sorbent may be regenerated by 65–82% with a 1 M NaHCO3 solution. 相似文献