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1.
Seifert S Simon F Baumann G Hietschold M Seifert A Spange S 《Langmuir : the ACS journal of surfaces and colloids》2011,27(23):14279-14289
The adsorption of poly(vinyl formamide) (PVFA) and the statistic copolymers poly(vinyl formamide-co-vinyl amine) (PVFA-co-PVAm) onto zinc and iron metal particles as well as their oxides was investigated. The adsorbates were characterized by means of XPS, DRIFT spectroscopy, wet chemical analysis, and solvatochromic probes. Dicyano-bis-(1,10-phenanthroline)-iron(II) (1), 3-(4-amino-3-methylphenyl)-7-phenyl-benzo-[1,2-b:4,5-b']difuran-2,6-dione (2), and 4-tert-butyl-2-(dicyano-methylene)-5-[4-(diethylamino)-benzylidene]-Δ(3)-thiazoline (3) as solvatochromic probes were coadsorbed onto zinc oxide to measure various effects of surface polarity. The experimental findings showed that the adsorption mechanism of PVFA and PVFA-co-PVAm strongly depends on the degree of hydrolysis of PVFA and pH values and also on the kind of metal or metal oxide surfaces that were employed as adsorbents. The adsorption mechanism of PVFA/PVFA-co-PVAm onto zinc oxide and iron oxide surfaces is mainly affected by electrostatic interactions. Particularly in the region of pH 5, the adsorption of PVFA/PVFA-co-PVAm onto zinc and iron metal particles is additionally influenced by redox processes, dissolution, and complexation reactions. 相似文献
2.
The adsorption of Zn2+ ions on amorphous Fe(OH)3 and -Fe2O3, as a function of pH, has been investigated. In the pH region corresponding to the formation of positively charged Zn-hydroxy complexes, an abrupt increase in adsorption was observed. The influence of EDTA and glycine on the adsorption of Zn2+ by -Fe2O3 has also been investigated. Strong suppression of the adsorption of Zn2+ was observed for high [EDTA or Gly]/[Zn2+] concentration ratios. The results of the adsorption of Zn2+ in the presence of an organic ligand were explained by the formation of Zn-EDTA or Zn-glycine complexes and also by the occupation of adsorption sites by the free organic ligand. 相似文献
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The flow injection analysis systems have been developed for the simultaneous determination of iron(III) and copper(II) and of iron(III) and palladium(II) based on the photochemical reactions of their thiocyanato-complexes. In the first system, a sample solution was injected in to nitric acid solution and mixed with ammonium thiocyanate solution, followed by spectrophotometric monitoring of the thiocyanato-complexes formed. Another aliquot of the same sample solution was injected and the thiocyanato-complexes formed in the same way were irradiated by UV light before spectrophotometric monitoring. In another system, the absorbance of thiocyanato-complexes formed by each sample injection was monitored with two flow cells aligned with the same optical path before and after UV irradiation. The difference in the extent of photochemical decomposition of the thiocyanato-complexes enabled simultaneous determinations of iron(III) and copper(II) and of iron(III) and palladium(II) at levels of several μg ml−1 to some tens μg ml−1 in their admixtures. Sample throughputs are 40 and 20 h−1 by the former and latter systems, respectively. 相似文献
5.
Several series of unidimensional coordination polymers of formula [Zn(C(n)H(2n+1)trz)(3)](Cl)(2)·xH(2)O (n = 18, 16, 13, 11, 10, trz = 4-substituted-1,2,4-triazole), [Zn(C(18)H(37)trz)(3)](ptol)(2)·xH(2)O, [Fe(C(n)H(2n+1)trz)(3)](X)(2)·xH(2)O (n = 18, 16, 13, 10; X = Cl(-) or ptol(-), where ptol(-) = p-tolylsulfonate anion), and [Fe(C(18)H(37)trz)(3)](X)(2)·xH(2)O (X = C(8)H(17)PhSO(3)(-) and C(8)H(17)SO(3)(-)) are reported with their thermal, structural, and magnetic properties. Most of these materials exhibit thermotropic lamellar mesophases at temperatures as low as 410 K, as confirmed by textures observed by polarized optical microscopy. The corresponding phase diagrams deduced by differential scanning calorimetry are also reported. All iron-containing materials present a spin crossover phenomenon that occurs at temperatures ranging from 242 to 360 K, only slightly below the mesophase temperature domain, and remains complete and cooperative, even for the longer alkyl substituents. The use of stable diamagnetic Zn(II) analogues proves to be very useful to characterize the comparatively less stable and less crystalline Fe(II) analogues. 相似文献
6.
Hydrothermal synthetic method has been used to prepare complex [ZnL]n (1) (H2L = 4-[(1H-imidazol-4-yl)methylamino]benzoic acid) as spherical microparticles. Slow morphological changes from small spindle-shaped particles to smoother spherical particles in the growth process of complex 1 were observed. Subsequently complex 1 was used as precursor as well as sacrificial template to synthesize hexagonal ZnO nanomaterials by calcination in air. The structure of the final products and the formation process were characterized by measurements of X-ray powder diffraction (XRPD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The formation mechanism of the final nanorods was proposed on the basis of the structural change of complex 1 in the calcination process. The photocatalytic properties of complex 1 and prepared ZnO have also been studied, and the results showed that all these nano-/micromaterials have photocatalytic properties and ZnO formed under lower calcinated temperature has higher photocatalytic activity. 相似文献
7.
《印度化学会志》2021,98(12):100243
This study introduces varying concentrations of graphene oxide (GO) as a filler into zinc chromate in forming composite coatings to improve the corrosion protection of mild steel. The purity of synthesized GO was inferred through the application of complementary characterization techniques, including FT-IR, XRD, Raman, SEM-EDX, and TEM analyses. GO doped zinc chromate coatings were deposited on the surface of mild steel through the brushing method. Electrochemical studies, i.e., electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PD) were conducted to elucidate the anticorrosion properties of the coated mild steel exposed to 0.5 M HCl solution. It was revealed that the highest anticorrosion protection was attained at low doping amount of 0.5% of GO with a corrosion rate of 0.036 mpy. Surface analyses revealed that incorporating GO into zinc chromate coating can effectively improve the anticorrosion properties and adhesion strength. 相似文献
8.
The development and use of 'green' electrode materials is extremely attractive for the routine use of disposable metal sensors. Bismuth is an environmentally-friendly element and a bismuth film electrode was proposed as an alternative to mercury film electrodes. Compared with bismuth, stannum is a more 'environmentally friendly' material. The stannum-bismuth composite film electrode prepared by the in situ electrodeposition of stannum and bismuth on the glassy carbon substrate is reported for the first time. Compared with bismuth film and stannum film electrodes, the stannum-bismuth composite film electrode revealed better electroanalytical performance, and can be used as a possible alternative electrode for electrochemical stripping analysis of trace heavy metals. 相似文献
9.
A procedure is described for the estimation of metallic iron, ferrous oxide, and ferric oxide when present together. The sample is treated with bromine dissolved in ethanol, and filtered. Iron in the filtrate is titrated iodometrically, and corresponds to the metallic iron present in the mixture. The oxide residue is dissolved in hydrochloric acid under a carbon dioxide atmosphere. The iron(II) formed, equivalent to FeO present, is titrated with a standard vanadate solution, and the total iron(III) (FeO + Fe2O3) in the titrated solution is then estimated iodometrically. 相似文献
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L. K. Shpigun Ya. V. Shushenachev P. M. Kamilova 《Journal of Analytical Chemistry》2007,62(7):623-631
Flow-injection methods are developed for the spectrophotometric analysis of binary copper(II) and zinc(II) mixtures. They are based on measurements of a differential kinetic signal caused by ligand-exchange reactions that occur in the flow between the complexes of these metals with the same chromogenic reagent (4-(2-pyridylazo)-resorcinol or zincon) and aminopolycarboxylic acids. Two different approaches are used for the kinetic separation (or masking) of these metals followed by the on-line processing of the recorded signal by regression analysis. One of them is monitoring an indicator reaction in the stopped-flow mode, and the other is recording the separated peaks in the flow-injection system with two reaction zones reaching the detector over certain periods. The optimum detection conditions were found (c min = 0.03 μg/mL), which allow the detection of the studied metal ions in mixtures in a ratio of no more than 1: 5 with a relative error of no more than 5%, good precision (RSD < 10%, n = 6, P = 0.95), and high throughput (90 h?1). The developed procedures were tested in the analysis of model mixtures and pharmaceutical preparations. 相似文献
12.
The thermal transitions of Na2S2O8 and K2S2O8 have been studied by means of a derivatograph in the presence of CuO or ZnO at various molar mixtures. A slight shift in the DTG peak of the first decomposition stage (persulfate into pyrosulfate) to higher temperature was noticed as the amount of oxide increases.The second decomposition stage (pyrosulfate into sulfate) was shown to proceed via the formation of double salts of alkali metal copper(II) sulfates and alkali metal zinc(II) sulfates, namely, Na2Cu(SO4)2, K2Cu(SO4)2, Na2Zn(SO4)2 and K2Zn(SO4)2. The reaction has a close relation to the semiconductivity of both oxides. The melting points recorded for these double salts were respectively 532, 634, 467 and 462°.The results were confirmed by the IR spectra of the reaction products.The double salts slowly decompose into the metal oxide, alkali metal sulfates, and sulfur trioxide.
Zusammenfassung Die Wärmeübergänge von Na2S2O8 und K2S2O8 wurden in Gegenwart von CuO und ZnO in verschiedenen molaren Gemischen mittels eines Derivatographen untersucht. Mit steigendem Oxidanteil wurde eine kleine Verschiebung des DTG-Peaks der ersten Zersetzungsstufe (Persulfat zu Pyrosulfat) in Richtung der hhvöheren Temperaturen beobachtet.Es wurde gezeigt, daß die zweite Zersetzungsstufe (Pyrosulfat zu Sulfat) über die Bildung von Doppelsalzen des Alkalimetall-Kupfer(II) Sulfats und Alkalimetall-Zink(II)Sulfats, d.h. Na2Cu(SO4)2, K2Cu(SO4)2, Na2Zn(SO4)2 und K2Zn(SO4)2 verläuft. Die Reaktion ist eng mit dem Halbleiterverhalten beider Oxide verbunden. Die aufgezeichneten Schmelzpunkte dieser Doppelsalze waren in obiger Reihenfolge 532, 634, 467 und 462°.Die Ergebnisse wurden durch IR-Spektra der Reaktionsprodukte bestätigt.Die Doppelsalze werden langsam in Metalloxide, Alkalisulfate und Schwefeltrioxid zersetzt.
Résumé Les transitions thermiques de Na2S2O8 et K2S2O8 en présence de CuO et de ZnO ont été étudiées à l'aide d'un Derivatograph pour diverses compositions molaires des mélanges. L'augmentation de la teneur en oxyde provoque un faible déplacement vers les températures plus élevées du pic TGD de la première étape de décomposition (persulfate pyrosulfate).La deuxième étape de la décomposition (pyrosulfate sulfate) s'effectue avec formation de sels doubles entre le sulfate du métal alcalin et le sulfate de cuivre(II) ou le sulfate de zinc(II), notamment Na2Cu(SO4)2, K2Cu(SO4)2, Na2Zn(SO4)2 et K2Zn(SO4)2. La relation est en étroit rapport avec le caractère semi-conducteur des deux oxydes. Les points de fusion enregistrés pour ces sels doubles s'élè vent respectivement à 532, 634, 467 et 462°.Les résultats sont confirmés par les spectres d'absorption infrarouge des produits de réaction.Les sels doubles se décomposent lentement avec formation de l'oxyde métallique, du sulfate du métal alcalin et de trioxyde de soufre.
Na2S2O8 K2S2O8 ZnO . . , — — () — (II), : Na2Cu(SO4)2, K2Cu(SO4)2, Na2Zn(SO4)2 K2Zn(SO4)2. 532, 634, 467 462°. . , .相似文献
13.
Oxide surface coatings are ubiquitous in the environment, but their effect on the intrinsic metal uptake mechanism by the underlying mineral surface is poorly understood. In this study, the zinc (Zn) sorption complexes formed at the kaolinite, goethite, and goethite-coated kaolinite surfaces, were systematically studied as a function of pH, aging time, surface loading, and the extent of goethite coating, using extended X-ray absorption fine structure (EXAFS) spectroscopy. At pH 5.0, Zn partitioned to all sorbents by specific chemical binding to hydroxyl surface sites. At pH 7.0, the dominant sorption mechanism changed with reaction time. At the kaolinite surface, Zn was incorporated into a mixed metal Zn-Al layered double hydroxide (LDH). At the goethite surface, Zn initially formed a monodentate inner-sphere adsorption complex, with typical Zn-Fe distances of 3.18 A. However, with increasing reaction time, the major Zn sorption mechanism shifted to the formation of a zinc hydroxide surface precipitate, with characteristic Zn-Zn bond distances of 3.07 A. At the goethite-coated kaolinite surface, Zn initially bonded to FeOH groups of the goethite coating. With increasing aging time however, the inclusion of Zn into a mixed Zn-Al LDH took over as the dominant sorption mechanism. These results suggest that the formation of a precipitate phase at the kaolinite surface is thermodynamically favored over adsorption to the goethite coating. These findings show that the formation of Zn precipitates, similar in structure to brucite, at the pristine kaolinite, goethite, and goethite-coated kaolinite surfaces at near neutral pH and over extended reaction times is an important attenuation mechanism of metal contaminants in the environment. 相似文献
14.
Nagabhushana BM Chandrappa GT Nagappa B Nagaraj NH 《Analytical and bioanalytical chemistry》2002,373(4-5):299-303
The bidentate ligand diformylhydrazine (OHC-HN-NH-CHO), DFH, combines with iron(II) and iron(III) in alkaline media in the pH range 7.3-9.3 to form an intensely colored red-purple iron(III) complex with an absorption maximum at 470 nm. Beer's law is obeyed for iron concentrations from 0.25 to 13 microg mL(-1). The molar absorptivity was in the range 0.3258x10(4)-0.3351x10(4) L mol(-1) cm(-1) and Sandell's sensitivity was found to be 0.0168 microg cm(-2). The method has been applied to the determination of iron in industrial waste, ground water, and pharmaceutical samples. 相似文献
15.
Wish Thanasarakhan Saisunee Liawruangrath Sunanta Wangkarn Boonsom Liawruangrath 《Talanta》2007,71(5):1849-1855
A sequential injection analysis (SIA) spectrophotometric method for the determination of trace amounts of zinc(II) with 1-(2-pyridylazo)-2-naphthol (PAN) is described. The method is based on the measurement of absorbance of the zinc(II)–PAN chelate solubilized with a non-ionic surfactant, Triton X-100, no extraction procedure is required in the proposed method, yielding a pink colored complex at pH 9.5 with absorption maximum at 553 nm. The SIA parameters that affect the signal response have been optimized in order to get the better sensitivity and minimum reagent consumption. A linear relationship between the relative peak height and concentration was obtained in the concentration range of 0.1–1.0 μg ml−1. The limit of detection (LOD, defined as 3σ) and limit of quantification (LOQ, defined as 10σ) were 0.02 and 0.06 μg ml−1, respectively. The sample throughput about 40 samples/h was obtained. The repeatability were 1.32 and 1.24% (n = 10) for 0.1 and 0.5 μg ml−1, respectively. The proposed method was successfully applied to the assay of zinc(II) in three samples of multivitamin tablets. The results were found to be in good agreement with those obtained by flame atomic absorption spectrophotometric method and with the claimed values by the manufactures. The t-test showed no significant difference at 95% confidence level. 相似文献
16.
The direct spectrophotometric determination of iron(III) and iron(II) by flow injection analysis with acetohydroxamic acid and 1,10-phenanthroline as reagents is reported. The working ranges are 0.5–10 and 10–60 mg l?1, respectively. Results obtained for synthetic mixtures of Fe(III) and Fe(II) and for acid extracts of haematite samples were accurate. Interference studies indicate that the method is highly selective. 相似文献
17.
The iron(II) and iron(III) complexes with EDTA can be determined separately and in mixtures in acetate-buffered medium at pH 4.0. The Evalues are in the range ?0.105 to ?0.112 V vs. SCE. Linear calibration plots are obtained over the range 0–1.0 mM for each oxidation state. A sample-handling procedure for avoiding oxidation of iron(II) species is described. It is shown that the acetate buffer system does not affect the stability of the iron-EDTA complexes. 相似文献
18.
The H-point standard addition method (HPSAM) was applied to the simultaneous determination of zinc(II) and cobalt(II). This method is based on the difference in the absorbance of methylthymol blue complexes of Zn(II) and Co(II) at pH 6 using different wavelength pairs. The results showed that Zn(II) and Co(II) can be determined simultaneously with concentration ratios of 20:1 and 1:7.5. Under working conditions, the proposed method was successfully applied to the simultaneous determination of zinc and cobalt in synthetic, drinking water and vitamin samples. 相似文献
19.
Piero Mirti 《Analytica chimica acta》1974,69(1):69-77
N-Carboxymelhyl pyrrolidine-2-carboxylic acid (CMPCA) is suggested as an optically active titrant. The values of the acidity constants of the ligand were determined and the order of magnitude of the stability constants of the complexes formed by CMPCA with some metal ions was evaluated. In order to determine the best conditions for the spectropolarimetric titrations, the dependence of the molar rotation of CMPCA and its complexes on wavelength and pH was examined. The spectropolarimetric titrations ofcopper(II), nickel(II) and iron(III) ions were carried out successfully. 相似文献
20.
The H-point standard addition method (HPSAM) was applied to the simultaneous determination of zinc(II) and cobalt(II). This method is based on the difference in the absorbance of methylthymol blue complexes of Zn(II) and Co(II) at pH 6 buffered solution in different wavelength pairs. The results showed that Zn(II) and Co(II) can be determined simultaneously with concentration ratios of 20:1 and 1:7.5. Under working conditions, the proposed method was successfully applied to the simultaneous determination of zinc and cobalt in synthetic and real samples. 相似文献