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1.
175, 181Hafnium(IV) was extracted by HDBP in 2-ethylhexanol from 1–10M solutions of HClO4, HCl and HNO3, and 1–8M H2SO4. As with low polar organic phase diluents, the acidity dependence of the distribution ratio of Hf, D, passes through a minimum for HClO4, HCl, and H2SO4 whereas only an increase of D can be observed with increasing HNO3 concentration. From the slope analysis the following complexes were found to be extracted (HDBP=HA): HfA4 at <4M HClO4 and <5M HCl, lg Kextr=9, HfX4(HA)4 (X=ClO 4 , Cl or NO 3 ) at >5M HClO4, >7M HCl and 1–10M HNO3, Hf(SO4)A2(HA)3–4 at <3M H2SO4, and Hf(SO4)2 (HA)4 at >6M H2SO4. Coextraction of sulphate with hafnium from H2SO4 solutions was evidenced in experiments with macro concentrations of Hf(IV) and35SO 4 2− . Part XX: Coll. Czech. Chem. Commun., 40 (1975) 3617.  相似文献   

2.
The surface oxides produced from potentiostatic and galvanostatic oxidation of Pt electrodes in HClO4 and H2SO4 are examined using X-ray photoelectron spectroscopy. The oxide I species produced as the initial oxidation product by successively more anodic potentiostatic oxidation in 0.2 M HClO4 is found to have a Pt2+ oxidation state, a binding energy characteristic of neither PtO, Pt(OH)2 or PtO2, and a limiting thickness of 8 Å. Galvanostatic oxidation in HClO4 and H2SO4 is found to produce PtO2·H2O as an unlimiting growth oxide or a limiting growth oxide layer depending on the concentration of the acid electrolyte. The incorporation of the acid electrolyte anion in the surface layer is shown to have an effect on which type of oxide layer is produced. X-ray decomposition and chemical modification by Ar+ stripping are shown to produce chemical artifacts complicating any interpretation of a Pt oxide surface layer.  相似文献   

3.
An assumption has been made that in the presence of electrosorbing cations potential oscillations should be observed in the course of galvanostatic oxidation of hydrogen on platinum electrode. The reality of this assumption has been proved in the presence of Cd2+, Cu2+, Sn2+, Bi3+, Ag+ ions using different base electrolytes (H2SO4, HCl, HClO4). Some features connected with these oscillation phenomena were considered.  相似文献   

4.
Corich core–Ptrich shell/C prepared by thermal decomposition and chemical reduction methods were treated by 20% H2SO4 aqueous solution and used as the electrocatalysts for the oxygen reduction reaction (ORR). The particle size range of Corich core–Ptrich shell (molar ratio of 0.92:1) on carbon powder support decreased from 3–8 to 1–6 nm when the time for the electrocatalysts immersed and treated with 20% H2SO4 aqueous solution increased from 0 to 4 h. Using Corich core–Ptrich shell (molar ratio of 0.92:1)/C treated with 20% H2SO4 from 0 to 4 h as the working electrode, the open circuit potential of ORR in 0.5 M HClO4 aqueous solution increased from 0.9995 to 1.0155 V, and the current density, mass activity, and specific activity at the overpotential of 0.1 V increased from 0.619 mA cm?2, 6.184 A g?1, and 18.614 μA cm?2 to 0.912 mA cm?2, 15.544 A g?1, and 23.413 μA cm?2, respectively.  相似文献   

5.
A new ion chromatographic (IC) system, in which n-tetradecylphosphocholine (TDPC, a phosphobetaine type of zwitterionic surfactant) was used as the stationary phase, pure water as the mobile phase, and conductivity as the method of detection, has been developed for the determination of inorganic acids. Five model acids, HCl, HNO3, HClO4, H2SO4, and H3PO4, were separated to baseline and eluted in the order H3PO4 > HCl > HNO3 > H2SO4 > HClO4. When peak areas were plotted against the concentrations of the acids in samples, linear calibration curves were obtained. Ultimate determination limits were approximately 1 mmol L–1, but the discrimination of the method between solutions of different concentration was better than 10 μmol L–1 for those model analytes. Salts of divalent cations could also be separated, but they were eluted faster than the acids. No separation was observed for the salts of monovalent cations. This newly proposed approach is applicable to the simultaneous determination of the inorganic acids (produced by reactions of NOx, SOx, and HCl with water) in aerosols.  相似文献   

6.
Polymerization of methyl acrylate in HClO4 and HNO3 was studied in the temperature range 10–15°C. The kinetics of the polymerization were found to be very simple, involving initiation and termination by cobaltic ions. Kinetic studies on polymerization of acrylonitrile in HClO4 and HNO3 revealed that water oxidation, and monomer oxidation were side reactions as in the case of methyl methacrylate. Experimental evidence favored the simultaneous initiation by Co3+ and CoOH2+ species. In H2SO4, certain unusual features were encountered. At low [Co3+], linear termination as well as termination by mutual combination occurred. Another interesting aspect was that CoSO4+ initiated at low [Co3+]. This was unlike the case of other monomers in H2SO4. The rates of polymerization and rates of cobaltic ion disappearance were measured with respect to changes in [M], [Co3+], [H+], temperature, etc. The various rate constants were evaluated.  相似文献   

7.
Transients of the open-circuit potential observed in the reaction of methanol with oxygen (Oads) preliminarily adsorbed on smooth polycrystalline platinum (pcPt) are measured in 0.05 M HClO4, 0.5 M HClO4, 0.05 M H2SO4, 0.05 M H2SO4 + 0.45 M Na2SO4, and 0.05 M H2SO4 + 0.45 M Cs2SO4. It is shown that the solution pH has a weak effect on the transient characteristics (when the reversible hydrogen electrode potential scale is used). This confirms the chemical nature of rate-controlling stages in the reaction mechanism. The changes in the reaction rate, observed upon going from one electrolyte to another, are preferentially associated with the involvement of solution ions in the formation of activated surface complexes that include CH3OH, Oads, and supporting-electrolyte components.  相似文献   

8.
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.  相似文献   

9.
Electrodes of supported Pt, modified with Cr, have shown an increase in electrochemical activity for oxygen reduction in phosphoric acid fuel cells over supported Pt only electrodes. To clarify the role of chromium and its chemical nature at the electrode surface, we have characterized a series of PtxCr(1-x) bulk alloys (x = 0.9, 0.65, 0.5, 0.2) by electrochemical and ex-situ surface science methods. In this paper we report the surface characterization of native and post-electrochemical electrodes by XPS, cyclic voltammetry in 0.05 M H2SO4 and 85% H3PO4, and analysis of 0.05 M H2SO4 electrolyte following electrochemical treatment. The surface Cr(1 to 2 nm) was oxidized to Cr3+ oxide for surfaces at open circuit and those exposed to potentials < + 1.3 V vs DHE in 0.05 M H2SO4 and < + 1.55 V vs. DHE in 85% H2PO4. In 0.05 M H2SO4 the Cr component was electrooxidized to solube Cr6+ species at potentials > +1.3 V with the extent of Cr dissolution dependent on initial alloy stoichiometry. Alloys with Cr content 0.5 are capable of producing (dependent on time spent at potentials above +1.3 V in 0.05 M H2SO4) very porous Pt-rich surfaces. Loss of Cr was also observed in 85% H3PO4 for the alloys with Cr content 0.5, although at the more positive potential limit of +1.55 V. For the Pt0.2Cr0.8, treatment in 85% H3PO4 at +1.4 V and above led to the appearance of Pt4+ and Cr6+ species, apparently stabilized in a porous phosphate overlayer up to 5 nm thick (dependent on time spent at potentials above this limit). The enhancement reported for supported Pt+Cr oxygen cathodes is discussed in the light of these results.  相似文献   

10.
Certified reference materials (JMS-2 and JMS-1 – Marine sediment, LKSD-1 Lake Sediment, and STSD-1 Stream Sediment) and bottom sediment were analysed for arsenic by hydride generation atomic absorption spectrometry (HG-AAS) after digestion by different methods (microwave digestion, digestion in aluminium block, dry digestion) and different combinations of acids (HNO3, HCl, HClO4, H2SO4). The study revealed that both wet and dry digestion can be used to digest the reference materials and bottom sediment. Exceptionally satisfactory results were produced by the application of aqua regia, HNO3 + HCl + HClO4, and HNO3 + HCl mixtures. Addition of Mg(NO3)2 during dry digestion caused an increase in arsenic recovery in the reference materials and improved the accuracy of arsenic determination in the bottom sediments.  相似文献   

11.
Tracer concentrations of Hf(IV) were extracted by 60% TBP solution in benzene from 5M HClO4, 5M HCl, 6M HNO3 and 8M H2SO4 solutions, and by 1·10?4 M TOPO solution in benzene from 2M HClO4 and 2M HCl solutions in the presence of a variety of organic solvents miscible with the aqueous phase. Whereas for TBP these solvents caused an increase of HF(IV) extraction, an opposite effect was observed for TOPO. The results were discussed from the point of view of various solute-solvent and solvent-solvent interactions.  相似文献   

12.
Solvent extraction of Cr(VI), Mo(VI), W(VI) and Hf(IV) with 1-phenyl-3-methyl-4-caproyl-pyrazolone-5 (PMCP) in methyl isobutylketone (MIBK), xylene and chloroform (CHCl3) from mineral acid solutions was studied. Chromium(VI) is not extracted from any of the acids studied (HCl, H2SO4 and HClO4). Molybdenum(VI) is quantitatively extracted by the reagent in xylene and CHCl3 from HClO4 and HNO3 solutions. It is also extracted quantitatively by the reagent in MIBK from HCl, HNO3 and H2SO4 solutions but the participation of the diluent as extractant is considerable. Tungsten(VI) is quantitatively extracted in xylene from 9M HClO4 solution. MIBK used as diluent also affects its extraction with PMCP. Hafnium(IV) is not extracted from H2SO4 solutions while it extracts more than 99% at 3M HNO3 and above. The extracted species likely are: MoO2(PMCP)2, WO2(PMCP)2 and Hf(PMCP)4, respectively.  相似文献   

13.
Polymerization of methyl methacrylate initiated by cobaltic ions in perchloric, nitric and sulfuric acids was studied in the temperature range 15–25°C. In all three acids, water oxidation occurred as a side reaction. In HClO4 and HNO3 media monomer oxidation was shown to be an additional complicating feature. Rates of cobaltic ion disappearance, monomer disappearance, and chain lengths of polymers were measured with variations in [M], [Co3+], [H+], initially added [Co2+], and temperature. In HClO4 and HNO3 experimental results favored simultaneous initiation by Co3+ and CoOH2+ species, while in H2SO4, Co3+ ions alone were the active entities. An appropriate kinetic scheme to fit all the experimental observations is proposed. The various rate constants were evaluated.  相似文献   

14.
The substoichiometric extraction of Hg2+ using diethyldithiocarbamic acid and 203Hg tracer was studied. Chloroform was employed to remove the complexes from the aqueous media which were 0.5M H2SO4 or 1 M HClO4 and 0 to 5 M NaCL. - Systems containing Cl? allowed extraction of Hg2+ for all DDC/Hg molar ratios, the extracted complexes being HgCl(DDC) and Hg(DDC)2. Their exchange constant was determined. - In the absence of Cl?, no extraction could be effected in either system if the DDC/Hg molar ratio was < 1; the H2SO4 system remained clear, whereas a precipitate of HgClO4(DDC) formed in the HClO4 system. For molar ratios > 1, the extraction of Hg2+ increased linearly with the addition of DDC, the extracted complex being Hg(DDC)2.  相似文献   

15.
In situ near-infrared (NIR) spectroelectrochemical studies during growth and dedoping/redoping of polyaniline (PANI) in the range between 1200 to 3000 nm are carried out in 1 M aqueous solutions of HCl, H2SO4, and HClO4 acids andp-toluene sulfonic acid (PTSA). The results show three characteristic absorption bands around 1440, 1900, and 2500 nm. The band at 2500 nm is characteristic of mobile charge carriers. The PANI prepared in HClO4 keeps memory of the size of the doping anion (ClO4 ) and can be redoped only with the same or smaller anions (Cl and SO4 2– or HSO4 ) while it cannot be redoped to any significant extent by a larger anion (PTSA).  相似文献   

16.
Summary Systematic studies on the anion-exchange behaviour of thorium in malic acid solution on Amberlite IRA-401 have been carried out. Acids such as HNO3, HCl, H2SO4, HClO4 and salts such as NH4Cl, (NH4)2SO4, NaClO4, NaCl and NaNO3 have been tested as eluants for thorium, their efficiency being evaluated in terms of their distribution coefficients. HNO3 is the best eluent for thorium. Methods have been developed for the separation of thorium from several elements in malic acid media using selective adsorption or selective elution. The proposed method is applied to the analysis of thorium in monazite where HClO4 is a better eluant than HNO3. The method is simple and the accuracy about ±3%.  相似文献   

17.
The adsorption of methylviologen dications (MV2+) on single‐crystalline Au electrodes in both H2SO4 and HClO4 was examined. MV2+ strongly interacted with sulfate and bisulfate anions adsorbed on the Au(111) electrode surface in 0.05 M H2SO4 under a controlled potential of 1.25 V vs. the reversible hydrogen electrode (RHE). A characteristic non‐Faradaic current was observed at 1.10 V vs. RHE. When adsorption of MV2+ was carried out in 0.1 M HClO4, the electrochemical response of MV2+ was less than that obtained in H2SO4. The results show that the formation of a highly ordered sulfate/bisulfate adlayer plays an important role in the formation of condensed MV2+ layers. Examination of polycrystalline Au and Au(100) electrodes revealed a poor electrochemical response due to the surface roughness of the Au substrate, but the electrochemical detection was applicable to polycrystalline Au electrodes. A systematic investigation of the structural dependency of viologen derivatives showed that molecular size is important for electrostatic interactions with a highly ordered sulfate/bisulfate adlayer. The findings of the present study demonstrate successful detection of MV2+ at a concentration of ≤1 pM with a non‐Faradaic current.  相似文献   

18.
Kinetics of oxidation of L-ascorbic acid (H2A) by sodium perborate (SPB) and peroxy disulphate (PDS) have been investigated in aqueous acid and micellar media. Reaction kinetics indicated first-order dependence on both |oxidant| and |H2A|. Increase in ionic strength (μ) increased reaction rate only in H2SO4 media. Rate of SPB oxidation of H2A has been accelerated by acidity in HNO3 and HCl media while a decreasing trend is observed in HClO4 and H2SO4 media. The results are interpreted by various theories of acidity functions. Reaction rate is enhanced by the addition of added |H2O2| indicating a H2O2 coordinated boron species to be active in the present system. In the absence of micelle, increase in |acid| altered the PDS(SINGLEBOND)H2A reaction rate marginally (a very small positive effect with HClO4 and negative effect with H2SO4). Most plausible mechanisms have been proposed on the basis of experimental results. Activation parameters evaluated for specific kinetic constants are in accord with outer sphere electron transfer mechanism. In SPB(SINGLEBOND)H2A system, addition of anionic micelle (Sodium lauryl sulfate) increased the rate, stabilizing the cationic species in the transition state in all the acid media. Although rate of PDS oxidation of H2A was catalyzed by TX and inhibited by SDS at critical micellar concentration (CMC) increase in |acid| (both HClO4 and H2SO4) beyond 9.6 × 10−4 M decreased the rate of oxidation. This trend was explained due to the repulsive interaction of coanion, HA, and negatively charged micellar species. © 1996 John Wiley & Sons, Inc.  相似文献   

19.
A simple separation method has been developed for thorium(IV) using poly-(dibenzo-18-crown-6) and column chromatography. The separation was carried out from ascorbic acid medium. The adsorption of thorium(IV) was quantitative from 0.001-0.01M ascorbic acid. The elution of thorium(IV) was quantitative with 4.0-8.0M HCl, 3.0-6.0M HClO4, 4.0-8.0M H2SO4 and 1.0-8.0M HBr. The capacity of poly-(dibenzo-18-crown-6) for thorium(IV) was found to be 1.379±0.01 m.mol/g of crown polymer. Thorium(IV) was separated from a number of cations in binary as well as in multicomponent mixtures. The method was extended to the determination of thorium in monazite sand. It is possible to separate and determine 5 ppm of thorium(IV) by this method. The method is very simple, rapid, selective and has good reproducibility (approximately ±2%).  相似文献   

20.
Different methods for the determination of several metals in soils by flame atomic absorption spectrometry (FAAS) were investigated. Different procedures for total dissolution of soil: I – HF+HClO4, H3BO3, HCl digestion (conventional heating), II – HF+HClO4, H3BO3 digestion followed by fusion with LiBO2 (conventional heating) and III – HF+HCl+HNO3, H3BO3 digestion (microwave heating), as well as a leaching procedure with HNO3+HClO4, HCl were tested and compared. For quality assessment, the certified reference material S-1 soil was used. For most of the investigated metals, the best accuracy and precision were achieved when the procedure I or III were used. The developed procedure was applied to the analysis of soil samples from crude oil refinery and dump of petroleum origin wastes regions.  相似文献   

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