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1.
Summary The cation-exchange behaviour of Mg(II), Ca(II), Sr(II), Ba(II), Mn(II), Cd(II), Co(II), Ni(II), Zn(II), Cu(II) and Fe(III) in succinate media at various concentrations and pH, was studied with Dowex 50 WX8 resin (200–400 mesh) in the NH 4 + form. As examples separations of Cd(II)/Co(II), Cd (II)/Ni(II), Fe(III)/Cu(II)/Ni(II) and Mg(II)/Ca(II)/Sr(II)/Ba(II) have been achieved.This work was supported by C.N.R. of Italy.  相似文献   

2.
Infrared photodissociation spectroscopy of mass‐selected heteronuclear cluster anions in the form of OMFe(CO)5 (M=Sc, Y, La) indicates that all these anions involve an 18‐electron [Fe(CO)4]2− building block that is bonded with the M center through two bridged carbonyl ligands. The OLaFe(CO)5 anion is determined to be a CO‐tagged complex involving a [Fe(CO)4]2−[LaO]+ anion core. In contrast, the OYFe(CO)5 anion is characterized to have a [Fe(CO)4]2−[Y(η2‐CO2)]+ structure involving a side‐on bonded CO2 ligand. The CO‐tagged complex and the [Fe(CO)4]2−[Sc(η2‐CO2)]+ isomer co‐exist for the OScFe(CO)5 anion. These observations indicate that both the ScO+ and YO+ cations supported on [Fe(CO)4]2− are able to oxidize CO to CO2. Theoretical analyses show that [Fe(CO)4]2− coordination significantly weakens the MO+ bond and decreases the energy gap of the interacting valence orbitals between MO+ and CO, leading to the CO oxidation reactions being both thermodynamically exothermic and kinetically facile.  相似文献   

3.
The redox system K4Fe(CN)6 adsorbed into anion exchanger particles (Dowex 1×2 of typically 200 µm diameter) and impregnated with 1‐butyl‐3‐methyl‐imidazolium tetrafluoroborate ionic liquid (BMIM+BF4?) in contact to a 50 µm diameter platinum microelectrode show well‐defined Fe(III/II) voltammetric responses. Processes are studied at the ionic liquid sphere | electrode | gas interface in the presence of dry or 80 % relative humidity argon gas flow. Due to the hygroscopic nature of BMIN+BF4? currents are sensitive to humidity levels. Pulsed and continuous microwave activation (2.45 GHz) is shown to occur locally at the tip of the platinum microelectrode due to focusing of microwave energy. Impedance experiments reveal the presence of a thin active film of ionic liquid.  相似文献   

4.
Summary Highly sensitive and selective test for vanadium(V) detection, with desferrioxamine B, is proposed. The method is based on reddish-violet complex fixation on cation-exchange resin. Detection limit of 1.01×10–10 g V(V)-ion is achieved by application of Dowex HCR(NH4 +) resin. Among 89 foreign substances investigated (diverse ions, complexing, oxidizing and reducing agents), Fe(II/III)-(under atmospheric conditions) and Co(II)-ion are the only interfering species.
Mikronachweis von Vanadin(V) mit Desferrioxamin B mit Hilfe der Harz-Tüpfeltechnik
Zusammenfassung Eine hochempfindliche und selektive Reaktion für den Nachweis von V(V) mit Desferrioxamin B wurde vorgeschlagen. Der dabei entstehende rot-violette Komplex wird an ein Kationenaustauscher-Harz gebunden. Die Nachweisgrenze 1,01×10–10 g V(V) wird mit Dowex HCR(NH4 +)-Harz erreicht. Unter 89 geprüften Fremdsubstanzen (div. Ionen, Komplexbildner, Oxydations- und Reduktionsmittel) sind Fe(II, III) und Co(II) die einzigen störenden Substanzen.


Presented at 9th International Symposium on Microchemical Techniques, Amsterdam, August 28–September 2, 1983.  相似文献   

5.
Summary: Three pyridine strong base anion exchangers as beads were obtained by quaternization reactions of a 4-vinylpyridine : 8% divinylbenzene copolymer of gel type. These resins possess methyl / ethyl / butyl radicals as substituents on N+ atoms and have exchange capacities of 4.80 mEq/g and 2.10 mEq/mL. For pyridine strong base anion exchangers, the behaviours in the retention processes of Cr(VI) as oxyanions and Ga(III) as [GaCl4] complex anion were evaluated with the bath method. All the resins exhibited retention properties, but the retained amounts of the metal cations are different as a function of the alkyl length as substituent on N+ atoms and the complex anion nature. Thus, Cr(VI) oxyanions are best retained by the resin with  CH3 as substituent on N+ atoms while [GaCl4] complex anion by the resin with  C4H9 as substituent on N+ atoms. By aminolysis reaction of an ethylacrylate : acrylonitrile : divinylbenzene copolymer as beads of macroporous type with NH2OH · HCl in the presence of C2H5OH a new chelating ion exchanger was performed which contains both amidoxime and hydroxamic acid functional groups. This ion exchanger has the retention property for different metal cations but its retention capacities values are strongly dependent of the nature of metal cation and the counterion as well as pH of the solution. Thus, in the static conditions Zn(II) cation with NOequation/tex2gif-stack-1.gif anion as counterion is retained with the best result at pH = 5. As an example, for the aqueous metal cation solution of 10−2 M concentration for Zn(NO3)2 the resin possess at equilibrium a retention capacity of 6.70 mmol Zn/g dry resin and for Cu(II) from Cu(NO3)2 solution of same concentration, the retention capacity is 0.22 mmol Cu/g dry resin and Fe(III) from Fe(NO3)3 solution is not retained.  相似文献   

6.
Four organic salts, namely benzamidinidium orotate (2,6‐dioxo‐1,2,3,6‐tetrahydropyrimidine‐4‐carboxylate) hemihydrate, C7H9N2+·C5H3N2O4·0.5H2O (BenzamH+·Or), (I), benzamidinium isoorotate (2,4‐dioxo‐1,2,3,4‐tetrahydropyrimidine‐5‐carboxylate) trihydrate, C7H9N2+·C5H3N2O4·3H2O (BenzamH+·Isor), (II), benzamidinium diliturate (5‐nitro‐2,6‐dioxo‐1,2,3,6‐tetrahydropyrimidin‐4‐olate) dihydrate, C7H9N2+·C4H2N3O5·2H2O (BenzamH+·Dil), (III), and benzamidinium 5‐nitrouracilate (5‐nitro‐2,4‐dioxo‐1,2,3,4‐tetrahydropyrimidin‐1‐ide), C7H9N2+·C4H2N3O4 (BenzamH+·Nit), (IV), have been synthesized by a reaction between benzamidine (benzenecarboximidamide or Benzam) and the appropriate carboxylic acid. Proton transfer occurs to the benzamidine imino N atom. In all four acid–base adducts, the asymmetric unit consists of one tautomeric aminooxo anion (Or, Isor, Dil and Nit) and one monoprotonated benzamidinium cation (BenzamH+), plus one‐half (which lies across a twofold axis), three and two solvent water molecules in (I), (II) and (III), respectively. Due to the presence of protonated benzamidine, these acid–base complexes form supramolecular synthons characterized by N+—H...O and N+—H...N (±)‐charge‐assisted hydrogen bonds (CAHB).  相似文献   

7.
The retention of gallium(III) on Dowex 50-X8 resin in 0.6 M HCl-dioxan media was studied as a function of the dioxan content. The ion-exchange in complexing medium (HC1) and in non-complexing medium (H2SO4) was studied; the determination of the distribution coefficients indicated the reactions occurring in the different media. Solvent uptake by Dowex 50-X8 (H+ and Ga(III) forms) from 0.6 M HCl-dioxan mixtures and the solvent composition in the resin were determined. The influence of the weak dielectric constant of dioxan proved to be most important; however, specific solvation phenomena were evident.  相似文献   

8.
A significant synergic effect between a metal–organic framework (MOF) and Fe2SO4, the so‐called MOF+ technique, is exploited for the first time to remove toxic chromate from aqueous solutions. The results show that relative to the pristine MOF samples (no detectable chromate removal), the MOF+ method enables super performance, giving a 796 Cr mg g−1 adsorption capacity. The value is almost eight‐fold higher than the best value of established MOF adsorbents, and the highest value of all reported porous adsorbents for such use. The adsorption mechanism, unlike the anion‐exchange process that dominates chromate removal in all other MOF adsorbents, as unveiled by X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), is due to the surface formation of Fe0.75Cr0.25(OH)3 nanospheres on the MOF samples.  相似文献   

9.
The crystal structures of 2‐hydroxy‐5‐[(E)‐(4‐nitrophenyl)diazenyl]benzoic acid, C13H9N3O5, (I), ammonium 2‐hydroxy‐5‐[(E)‐phenyldiazenyl]benzoate, NH4+·C13H9N2O3, (II), and sodium 2‐hydroxy‐5‐[(E)‐(4‐nitrophenyl)diazenyl]benzoate trihydrate, Na+·C13H8N3O5·3H2O, (III), have been determined using single‐crystal X‐ray diffraction. In (I) and (III), the phenyldiazenyl and carboxylic acid/carboxylate groups are in an anti orientation with respect to each other, which is in accord with the results of density functional theory (DFT) calculations, whereas in (II), the anion adopts a syn conformation. In (I), molecules form slanted stacks along the [100] direction. In (II), anions form bilayers parallel to (010), the inner part of the bilayers being formed by the benzene rings, with the –OH and –COO substituents on the bilayer surface. The NH4+ cations in (II) are located between the bilayers and are engaged in numerous N—H...O hydrogen bonds. In (III), anions form layers parallel to (001). Both Na+ cations have a distorted octahedral environment, with four octahedra edge‐shared by bridging water O atoms, forming [Na4(H2O)12]4+ units.  相似文献   

10.
The behavior and conditions of liquid‐liquid extraction‐separation of Fe(III) by ammonium thiocyanate‐H2O‐n‐propyl alcohol system in the presence of NaCl were studied, and the possible reactive mechanism of extraction of Fe(III) was deduced. The study showed that, in the presence of a given amount of NaCl, phases were separated thoroughly between n‐propyl alcohol and water. In the process of phase separation, the complex [Fe(SCN)n](3‐n) formed by NH4SCN and Fe(III) was quantitatively extracted into the n‐propyl alcohol phase. The extracted Fe(III) exists in the n‐propyl alcohol phase mainly as the forms of Fe(SCN)2+ and Fe(SCN)3. Also, the relationship between extraction yield of Fe(III) and the amount of NH4SCN agreed well with the quadratic equation E = 0.54 + 58.14x ? 8.39x2 (E and x represent the recovery rate of Fe(III) and the volume (mL) of 0.1 M NH4SCN respectively). The quadratic R‐Square is 0.9990. With this method, Fe(III) can be completely separated from Co(II), Ni(II), Mn(II), Al(III), Bi(III) and Cd(II) at pH 1.0?2.0. The present method was applied in determining Fe(III) in samples with satisfactory results such as relative standard deviation from 2.06% to 2.89% and recovery rate in the range of 98.4?101.4%.  相似文献   

11.
The title compounds, 2‐chloroanilinium dihydrogen phosphate (2CADHP) and 4‐chloroanilinium dihydrogen phosphate (4CADHP), both C6H7NCl+·H2PO4, form two‐dimensional supramolecular organic–inorganic hybrid frameworks. In 2CADHP, the dihydrogen phosphate anions form a double‐stranded anionic chain generated parallel to the [010] direction through O—H...O hydrogen bonds, whereas in 4CADHP they form a two‐dimensional supramolecular net extending parallel to the crystallographic (001) plane into which the cations are linked through strong N—H...O hydrogen bonds.  相似文献   

12.
Chromium may exist in environmental waters as Cr(III) and Cr(IV), the latter being the toxic and carcinogenic form. Since atomic absorption spectrometry (AAS) and inductively coupled plasma atomic emission spectrometry can only yield information on total Cr concentration, a polymer resin bearing O,O-donor chelating groups such as the maleic acid-functionalized XAD(CO)CHCHCOOH resin was synthesized to selectively retain Cr(III) at pH 4.0-5.5. The dynamic breakthrough capacity of the resin for Cr(III) at pH 5.0 was 7.52 mg g−1, and the preconcentration factor extended to 250-300. Chromium(III) in the presence of 250-fold Cr(VI)—which was not retained—could be effectively preconcentrated on the NH4+-form of the resin and determined by AAS or diphenylcarbazide (DPC) spectrophotometry. When Cr(VI) was reduced to Cr(III) with Na2SO3 solution brought to pH 1 by the addition of 1 M H2SO4, and preconcentrated on the resin, total Cr could be determined. The developed method was validated with a blended coal sample CRM-1632. Since the adsorption behavior as a function of pH of possible interferent metal ions, e.g. Ni(II), Co(II), Cu(II), Cd(II), Zn(II), Pb(II) and Fe(III), was similar to that of Cr(III), selective elution of Cr(III) from the resin was realized using a mixture of 1 wt.% H2O2+1 M NH3. The eluate containing Cr as chromate could be directly analyzed by diphenyl carbazide spectrophotometry without any adverse effect from the common interferents of this method, i.e. Fe(III), Cu(II) Hg(II), VO3, MoO42− and WO42−. Various synthetic waste solutions typical of electroplating bath effluents containing Cr, Cu, Ni, Zn, Na, Ca, cyanide (and chemical oxidation demand (COD), achieved by glucose addition) were subjected to pretreatment procedures such as hypochlorite oxidation (of cyanide) and catalytic oxidation (of COD) with peroxodisulfate. Chromium determination gave satisfactory results. The combined column preconcentration—selective elution—diphenylcarbazide spectrophotometric determination was also successfully applied to the determination of Cr in artificial and real seawater.  相似文献   

13.
3′:5′‐Cyclic nucleotides play an outstanding role in signal transduction at the cellular level but, in spite of comprehensive knowledge of the biological role of cyclic nucleotides, their structures are not established fully. Two hydrated sodium salts of thymidine 3′:5′‐cyclic phosphate (cdTMP, C10H12N2O7P), namely sodium thymidine 3′:5′‐cyclic phosphate heptahydrate, Na+·C10H12N2O7P·7H2O or Na(cdTMP)·7H2O, (I), and sodium thymidine 3′:5′‐cyclic phosphate 3.7‐hydrate, Na+·C10H12N2O7P·3.7H2O or Na(cdTMP)·3.7H2O, (II), have been obtained in crystalline form and structurally characterized, revealing one nucleotide in the asymmetric unit of (I) and eight different nucleotides in (II). All the cyclic nucleotide anions adopt a similar conformation with regard to nucleobase orientation, sugar conformation and 1,3,2‐dioxaphosphorinane ring puckering. In (I), no direct inter‐nucleotide hydrogen bonds are present, and adjacent nucleotide anions interact via water‐mediated and Na+‐mediated contacts. In contrast, in (II), direct thymine–phosphate N—H...O inter‐nucleotide hydrogen bonds occur and these are assisted by numerous inter‐nucleotide C—H...O contacts, giving rise to the self‐assembly of cdTMP anions into three different ribbons. Two of these three ribbons run in the same direction, while the third is antiparallel.  相似文献   

14.
Fe(III) and PAN form Fe(PAN),OH complex in CHCl3 extract which shows absorption maxima at 550 nm and 775 nm (log ε550,= 4.06, log ε775 = 4.08). In the Fc(III)-PAN-Triton X-100 system, two complex species Fe(PAN)2+ and/or Fe(PAN)2OH may be formed. Fe(PAN)2+ possesses a strongly absorbing peak at 550 nm (log ε550 = 4.36). In this paper the effect of Triton X-100 micelles on the Fe(III)-PAN color reaction has been investigated in detail. We consider that the high density of ether linkages in Triton X-100 micelles concentrate hydrous Fe(III) ions and change their existing state. Moreover, the micelles not only raise the reactivity of Fe(III), but also enhance the rate of the color reaction.  相似文献   

15.
The static secondary ionization mass spectrometry (SIMS) spectrum of tri-n-butyl phosphate (TBP) on a variety of basalt and quartz samples is affected by the chemical composition of the mineral surface. When TBP is adsorbed on Fe(II)-bearing surfaces, the compound undergoes concomitant H? abstraction and reduction, followed by the elimination of two C4H8 molecules to form an ion at m/z 137+. When TBP is adsorbed to quartz or other nonreducing surfaces, it merely undergoes protonation and elimination of three C4H8 molecules to form H4PO 4 + . When TBP is adsorbed to Fe(III)-bearing surfaces, it undergoes H? abstraction and elimination of two C4H8 molecules, to form an ion at m/z 153+. These conclusions are supported by model studies that employed FeO, Fe203, TBP, and tributyl phosphite. The results show that the SIMS spectrum is very sensitive to the mode of TBP adsorption on the mineral surface.  相似文献   

16.
The electrochemical electron-transfer rate constants for the redox systems Fe(IV)L3+/Fe(III)L3 (L=N,N-disubstituted dithicarbamate ion) and Fe(III)L3/Fe(II)L3? with a variety of substituents were measured at a platinum electrode in acetonitrile with the galvanostatic double-pulse method. It is known that each of the Fe(III) complexes exists both in a highspin state 6A1 and a low-spin state 2T2 in equilibirium of which position is widely changed by a subtle change in substituent. The standard rate constants for Fe(IV)L3+/Fe(III)L3 were larger or smaller than those for Fe(III)L3/Fe(II)L3? according as the Fe(III)L3 complexes are predominantly low- or high-spin complexes. Since the Fe(IV) and Fe(II) complexes are low-and high-spin complexes respectively, these findings suggest that electrochemical electron-transfer reactions accompanied by a spin-state change are slower than those without it. Such spin-state effect on electrode reactions has rarely been discussed so far.  相似文献   

17.
RuCl3 further catalyzes the oxidation of iodide ion by K3Fe(CN)6, already catalyzed by hydrogen ions. The rate of reaction, when catalyzed only by hydrogen ions, was separated graphically from the rate when both Ru(III) and H+ ions catalyzed the reaction. Reactions studied separately in the presence as well as absence of RuCl3 under similar conditions were found to follow second‐order kinetics with respect to [I?], while the rate showed direct proportionality with respect to [Fe(CN)6]3?, [RuCl3], and [H+]. External addition of [Fe(CN)6]4? ions retards the reaction velocity, while changing the ionic strength of the medium has no effect on the rate. With the help of the intercept of the catalyst graph, the extent of the reaction that takes place without adding Ru(III) was calculated and it was in accordance with the values obtained from the reaction in which only H+ ions catalyzed the reaction. It is proposed that ruthenium forms a complex, which slowly disproportionates into the rate‐determining step. Arrhenius parameters at four different temperatures were also calculated. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 545–553, 2004  相似文献   

18.
Cyanide (CN), thiocyanate (SCN), and copper(I) cyanide (Cu(CN)43−) are common constituents in the wastes of many industrial processes such as metal finishing and gold mining, and their treatment is required before the safe discharge of effluent. The oxidation of CN, SCN, and Cu(CN)43− by ferrate(VI) (FeVIO42−; Fe(VI)) and ferrate(V) (FeVO43−; Fe(V)) has been studied using stopped-flow and premix pulse radiolysis techniques. The rate laws for the oxidation of cyanides were found to be first-order with respect to each reactant. The second-order rate constants decreased with increasing pH because the deprotonated species, FeO42−, is less reactive than the protonated Fe(VI) species, HFeO4. Cyanides react 103–105 times faster with Fe(V) than with Fe(VI). The Fe(V) reaction with CN proceeds by sequential one-electron reductions from Fe(V) to Fe(IV) to Fe(III). However, a two-electron transfer process from Fe(V) to Fe(III) occurs in the reaction of Fe(V) with SCN and Cu(CN)43−. The toxic CN species of cyanide wastes is converted into relatively non-toxic cyanate (NCO). Results indicate that Fe(VI) is highly efficient in removing cyanides from electroplating rinse water and gold mill effluent.  相似文献   

19.

Equilibrium reactions of iron(III) with phosphate were studied spectrophotometrically by UV-Vis in the pH range of ~ 1.0-2.20. The STAR-94 Program was used to determine the number of absorbing species as well as the stoichiometries and formation constants of the complex species. Some literature values were further confirmed and new values of different stoichiometries were obtained. The kinetics and mechanism of Fe(III) with phosphate were studied in acidic medium. The reactive phosphate species were found to be only H3PO4 and H2PO? 4 and for Fe(III) were only Fe3+, FeOH2+ and Fe(OH)+ 2. The observed rate constants were pH as well as Tphos (total concentration of phosphate) dependent, i.e. Kobs,i = A i + B i Tphos + C i T2 phos (at a given pH).  相似文献   

20.
Six ammonium carboxylate salts are synthesized and reported, namely 2‐propylammonium benzoate, C3H10N+·C7H5O2, (I), benzylammonium (R)‐2‐phenylpropionate, C6H10N+·C9H9O2, (II), (RS)‐1‐phenylethylammonium naphthalene‐1‐carboxylate, C8H12N+·C11H7O2, (III), benzylammonium–benzoate–benzoic acid (1/1/1), C6H10N+·C7H5O2·C7H6O2, (IV), cyclopropylammonium–benzoate–benzoic acid (1/1/1), C3H8N+·C7H5O2·C7H6O2, (V), and cyclopropylammonium–eacis‐cyclohexane‐1,4‐dicarboxylate–eetrans‐cyclohexane‐1,4‐dicarboxylic acid (2/1/1), 2C3H8N+·C8H10O42−·C8H12O4, (VI). Salts (I)–(III) all have a 1:1 ratio of cation to anion and feature three N+—H...O hydrogen bonds which form one‐dimensional hydrogen‐bonded ladders. Salts (I) and (II) have type II ladders, consisting of repeating R43(10) rings, while (III) has type III ladders, in this case consisting of alternating R42(8) and R44(12) rings. Salts (IV) and (V) have a 1:1:1 ratio of cation to anion to benzoic acid. They have type III ladders formed by three N+—H...O hydrogen bonds, while the benzoic acid molecules are pendant to the ladders and hydrogen bond to them via O—H...O hydrogen bonds. Salt (VI) has a 2:1:1 ratio of cation to anion to acid and does not feature any hydrogen‐bonded ladders; instead, the ionized and un‐ionized components form a three‐dimensional network of hydrogen‐bonded rings. The two‐component 1:1 salts are formed from a 1:1 ratio of amine to acid. To create the three‐component salts (IV)–(VI), the ratio of amine to acid was reduced so as to deprotonate only half of the acid molecules, and then to observe how the un‐ionized acid molecules are incorporated into the ladder motif. For (IV) and (V), the ratio of amine to acid was reduced to 1:2, while for (VI) the ratio of amine to acid required to deprotonate only half the diacid molecules was 1:1.  相似文献   

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