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1.
Cristalline Chromium(III) Phosphate Hexahydrate On precipitation of chromium (III) phosphate from a cold water solution, two further crystalline modifications of the previously described CrPO4 · 6 H2O with the same composition are obtainable. The three phases can be characterized by means of their X-ray diffraction patterns. The least stable of the three forms (γ-CrPO4 · 6H2O) is isomorphous with the corresponding hydrate of the chromium(III) arsenate and forms cubic crystals with a0 = 9.42 Å and 4 molecules in the unit cell. A structural explanation can be given for the most stable of the phases (α-CrPO4 · 6 H2O) which forms monoclinic crystals for the space group Cc with eight molecules in the unit cell and the dimensions a0 = 9.87, b0 6.89, c0 = 23.49 Å and β = 99.4·  相似文献   

2.
The formation of active chromium hydroxide, Cr(OH)3·3H2O, was studied through potentiometric titrations and turbidimetric measurements. UV-Vis and IR spectroscopies were also employed to characterize the synthesized solid. The rapid addition of NaOH solution to aqueous chrome alum (KCr(SO4)2·12H2O) solutions caused the immediate precipitation of the active material. Only monomeric Cr(III) species seemed to be participating in the precipitation process; neither chromium polymers nor complexes with anions (SO2−4, Cl, NO3, ClO4) influenced the fast formation of Cr(OH)3·3H2O. Titration studies allowed the determination of several hydrolysis and precipitation constants for Cr(III). Nevertheless, they cannot be used for the estimate of Cr(OH)03formation constant.  相似文献   

3.
Specific features of ion-exchange purification of washing water formed in zinc plating in an alkaline medium are considered. The parameters of extraction of zinc ions and regeneration of ion-exchange resins are optimized.  相似文献   

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6.
The dose-dependent formation of Cr(III) complexes and uptake of chromium by Arthrobacter oxydans — a Gram-positive bacterium from contaminated Columbian basalt rocks (USA) — were studied along with the testing under aerobic conditions of two bacterial strains of Arthrobacter genera isolated from the polluted basalts from the Republic of Georgia. Instrumental neutron activation analysis (INAA) was used to track the accumulation of chromium in the bacterial cells. To monitor and identify Cr(III) complexes in these bacteria, electron spin resonance (ESR) spectrometry was employed.  相似文献   

7.
A method for preparing sulfate-oxalate chromium-plating solutions by reducing Cr(VI) from industrial chromium-plating electrolytes to Cr(III) with a Na2SO3 solution is proposed.  相似文献   

8.
In the presence of traces of Cr(VI) or Cr(III) ions in ammonia or borate buffers containing the As(III) ions a catalytic hydrogen wave arises in the dc polarogram. It was established that the complex Cr(H2AsO3)n+3?n is formed in the solution, and that its reduced form adsorbed at DME is of catalytic activity. The wave can be employed for the determination of low concentrations (2×10?8×10?7M) of Cr(VI) and Cr(III) ions.  相似文献   

9.
The synthesis of MoVI bisphosphonates (BPs) complexes in the presence of a heterometallic element has been studied. Two different BPs have been used, the alendronate ligand, [O3PC(C3H6NH3)(O)PO3]4? (Ale) and a new BP derivative with a pyridine ring linked to the amino group, [O3PC(C3H6NH2CH2C5H4N)(O)PO3]4? (AlePy). Three compounds have been isolated, a tetranuclear MoVI complex with CrIII ions, (NH4)5[(Mo2O6)2(O3PC(C3H6NH3)(O)PO3)2Cr]·11H2O (Mo4(Ale)2Cr), its MnIII analogue, (NH4)4.5Na0.5[(Mo2O6)2(O3PC(C3H6NH3)(O)PO3)2Mn]·9H2O (Mo4(Ale)2Mn), and a cocrystal of two polyoxomolybdates, (NH4)10Na3[(Mo2O6)2(O3PC(C3H6NH2CH2C5H4N)(O)PO3)2Cr]2[CrMo6(OH)6O18]·37H2O ([Mo4(AlePy)2Cr]2[CrMo6]). In this latter compound an Anderson-type POM [CrMo6(OH)6O18]3? is sandwiched between two tetranuclear MoVI complexes with AlePy ligands. The protonated triply bridging oxygen atoms bound to the central CrIII ion of the Anderson anion develop strong hydrogen bonding interactions with the oxygen atoms of the bisphosphonate complexes. The UV–Vis spectra confirm the coexistence in solution of both POMs. Cyclic voltammetry experiments have been performed, showing the reduction of the Mo centers. In strong contrast with the reported MoVI BP systems, the presence of trivalent cations in close proximity to the MoVI centers dramatically impact the potential solid-state photochromic properties of these compounds.  相似文献   

10.
Ma  Hong-Rui  Li  Huan  Wu  Wei  Qiao  Xian-Rong 《Research on Chemical Intermediates》2017,43(4):2333-2350
Research on Chemical Intermediates - The presented work focused on extraction and separation of Fe(III) and Cr(III) from tannery sludge bioleachate using di(2-ethylhexyl) phosphoric acid (D2EHPA)...  相似文献   

11.
《Analytical letters》2012,45(10):2269-2275
Abstract

A simple fluorimetric determination of Cr(VI) in the presence of Cr(III) is described. This determination is based on the fluorescence, produced from the ion-association complex between the Crystal violet cation and the anionic complex, formed between Cr(VI) and excess of I?. This fluorescence is not observed when Cr(III) is used instead of Cr(VI). The fluorescence intensity is linear over the concentration range of 0–60 μg/1. The method was applied in potable and sea waters.  相似文献   

12.
Regression analysis was used to derive equations for estimaing thermodynamic stability constants for complexes of Cr2+ (log° 1[Cr2+L] = 0.53log° n [H n L]) and Cr3+ (log° 1[Cr3+L] = 0.88log° n [H n L]) from the known protonation constants of H n L ligands and for determining stability constants of Cr2+ and Cr3+ complexes from the available stability constants of Cu2+ complexes (log° 1[Cr2+L] = 0.76log° 1[Cu2+L] and log° 1[Cr2+L] = 0.60log° 1[Cr3+L], respectively). Parameters of the Panteleon–Ecka equation for calculating stability constants of Cr2+ complexes ( = 0.57) and Cr3+ complexes ( = 0.69) with two and three bidentate ligands were also determined. The ratio of logarithmic stability constants for complexes with the same metals but with different metal ionic charges was found to be approximately equal to the ratio of charges on the central ions. The stability constant of Cr(II) sulfate complex was calculated.  相似文献   

13.
The thermal stability of chromium(III) complexes with dithiocarbamate acid derivatives was studied. The general formula of these complexes is (RCS2)3Cr where: The thermal stability of these complexes was found to depend on the kind ofR and the decomposition occur in several stages.The final product of the decomposition of the complexes in the 20–600 temperature range investigated is chromium sulphide, Cr2S3 or with incomplete combusted sulfur atoms.
Zusammenfassung Die Thermostabilität von Chrom(III)-Komplexen mit sauren Derivaten von Dithiocarbamat wurde untersucht. Die allgemeine Formel dieser Komplexe ist (RCS2)3Cr. Es wurde festgestellt, da\ die Thermostabilität dieser Komplexe von der Art von R abhängt und die Zersetzung in mehreren Stufen verläuft.Das Endprodukt der Zersetzung der Komplexe im untersuchten Temperaturbereich von 20 bis 600 ist Chromsulfid, Cr2S3, oder solches mit überschüssigem Schwefel.

Résumé On a étudié la stabilité thermique des complexes du chrome(III) avec les dérivés de l'acide dithiocarbamique. La formule générale de ces complexes est (RCS2)3Cr où: On a trouvé que la stabilité thermique de ces complexes dépendait de la nature du radical et que la décomposition se déroulait en plusieurs étapes.Dans l'intervalle de température étudié, de 20 à 600, le produit final de la décomposition des complexes est le sulfure de chrome, Cr2S3, éventuellement accompagné de soufre résultant d'une combustion incomplÊte.

(III) - . — (RCS2)3 Cr, , R . 20–600 Cr2S3 .


The autors would like to thank Doc. dr h. J. F. Biernat for valuable discussions.  相似文献   

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The differential pulse single-sweep voltammetric technique with hanging mercury drop electrode was used for the determination of Cr(III). The determination was carried out in 0.2 mol/l sodium acetate as supporting electrolyte. The reduction peak of Cr(III) was recorded at –1.5 V vs. Ag/AgCl reference electrode. The relative standard deviation was 3% for Cr concentrations in the range of 0.4 mol/l. The determination of impurities (Cd, Cu, Pb and Zn) in fresh and overworked galvanic baths using anodic stripping voltammetry in the differential pulse mode is also described.  相似文献   

16.
《Analytical letters》2012,45(13-14):2877-2885
Abstract

The adsorption studies of Cr(VI) in presence of Cr(III) on the sulphide of Lead, Zinc and Copper has been studied. It has been found that in case of lead sulphide 100% adsorption of Cr(VI) took place at pH 4.0 and of Cr(III) at pH 7.0. While in case of zinc sulphide the 100% adsorption of Cr(VI) took place at pH 4.5 and of Cr(III) at pH 6.5. In case of copper sulphide 100% adsorption of Cr(VI) took place at pH 5.0 and of Cr(III) at pH 7.0. This difference in adsorption at different pH values forms the basis for the determination of these ions. The method is accurate.  相似文献   

17.
A new Au(III)-imprinted hydrogel (Au(III)-Imp) was prepared by the photopolymerisation of 4-acryloylmorpholine (AcM), 2-hydroxyethyl acrylate (HEA), and poly(ethylene glycol) diacrylate (cross-linking monomer, PEG-DA) in the presence of gold ions. In addition, non-imprinted hydrogel (N-Imp) was similarly prepared without Au(III) ions The Au(III)-Imp hydrogel was characterised by several techniques. To achieve the optimal conditions, effect of pH, time, and initial metal ion concentrations were investigated using a batch system. The pre-concentration factor for Au(III) ions was found to be at least 100. The analytical parameters of the method were determined and the method was also successfully applied to computer circuit board scrap samples. The reusability of the Au(III)-Imp hydrogel was also determined.  相似文献   

18.
A biological sludge – waste-activated sludge (WAS) – from a dairy filtering station was investigated for the removal of trivalent chromium from aqueous solution. Kinetic results revealed that chromium adsorption was instantaneous. The removal rate increases up to pH 4 for contact times beyond 20 min. The equilibrium state is attained in 30 min in all the considered systems. The reaction orders as well as the diffusion rate constant were determined. Values adsorption isotherms measured at pH 3 generally followed the Langmuir model. The maximum uptake capacity was 25.64 mg/g. Values of thermodynamic parameters show that chromium (III) sorption on WAS is an exothermic process.This study provides an opportunity for the removal of heavy metals such as chromium from aqueous solutions using a low-cost biosolid as adsorbent support.  相似文献   

19.
The production of reference materials for quality control of Cr(III) and Cr(VI) speciation in environmental samples is described. It concerns in the first place two lyophilized solutions containing Cr(III) and Cr(VI) at different concentrations, respectively representative for drinking water and filter leaching solutions, and in the second place filters loaded with welding dust. Twenty-four laboratories with experience in the field participated in an intercomparison exercise organized to validate the suitability of the reference materials and to gauge the state-of-the-art of Cr speciation throughout Europe. The outcome of this exercise is discussed.  相似文献   

20.
Speciation of Cr(III) and Cr(VI) can be attained by flow injection analysis with amperometric detection. Cr(VI) is reduced in an acidic medium to Cr(III) with a glassy carbon electrode at —0.1 V vs. Ag/AgCl and the current is recorded. Cr(III) is oxidised on-line to Cr(VI) with alkaline hydrogen peroxide solution. From the difference of the total chromium and Cr(VI), the amount of Cr(III) was obtained. A linear calibration curve for Cr(VI) was obtained for the concentration ranges 0.01-5.0ppm of Cr(VI) and we have calculated the limit of determination to be about 0.5ppb. We have studied the degree of reproducibility obtained using the solid electrodes under various conditions. The influence of flow rate, coil length, interfenences and the extent of reaction were studied.  相似文献   

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