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Mystery of Ageing of „Zero-Valent Iron“ (ZVI)
Wouafo, M. T. ; Donkeng Dazie, Joel ; Tchatchueng, J. B. ; Noubactep, Ch. ; Ludvík, Jiří
So called „zero-valent iron“, (ZVI), is used for water treatment, or, more generally for\nenvironmental remediation. In fact, the surface of the metallic iron powder in the presence of\nwater and oxygen cannot be considered as pure Fe0 but as a mixture of its corrosion products.\nThe remediation process occurs on the surface of these iron particles, hence, the degree of\n„corrosion“ is crucial for the process itself. Therefore, investigation of „aging“ of ZVI is an\nimportant prerequisite for deeper understanding of its activity.\nIn this work, the first results of the systematic study of aging of iron metal powder are\npresented. The investigation was performed in batch conditions in aqueous buffered solutions\npH 4, 4.7, 5.5 and in the presence of air oxygen. Increasing and then decreasing concentration\nof the Fe2+ ion in the solution appeared to be the important marker of aging process.\nIn the second part of the work, removal of Zn2+ ions using ZVI was investigated.\nElectrochemical techniques, namely polarography and its differential pulse form (DPP) were\nused for permanent monitoring of the presence of Fe2+ and Zn2+ ions in the studied solution.\nChanging concentrations of both ions revealed that at pH 5.5 the optimum aging time of ZVI\nfor removal of Zn2+ from aqueous solution is 6 hours.
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Silver Amalgam Electrodes in Electroanalysis of Selected Agrochemicals
Daňhel, Aleš ; Barek, Jiří (advisor) ; Vytřas, Karel (referee) ; Ludvík, Jiří (referee)
4 ABSTRACT Development and testing of novel non-toxic electrode materials, detection arrangements and analytical methods applicable in determination of selected agrochemicals is the main aim of this Ph.D. Thesis. New working electrodes based on silver solid amalgam paste (AgSA-PE) with organic pasting liquid and other based on crystallic silver amalgam (CAgAE) were developed, their electrochemical behaviour investigated and further used in voltammetric determination of widespread and toxic environmental pollutant 4-nitrophenol (4-NP). This analyte could be determined by DPV at AgSA-PE with limit of detection (LD) 1×10í6 mol lí1 and using CAgAE with LD 4×10í7 mol lí1 , both in 0.2 mol lí1 acetate buffer pH 4.8. Attempts to decrease LDs by utilization of adsorptive stripping voltammetry were not successful in either case. Crystallic silver amalgam was also successfully used for construction of microcylindric flow-through cell and tested for amperometric determination of nitrophenol mixture in HPLC-ED system. Both novel electrodes were found to be suitable alternatives to toxic mercury electrodes and the CAgAE seems to be promising working electrode for flowing systems. Method for sample preparation and voltammetric determination of broad-spectrum herbicide Glyphosate in contaminated soil samples was also...
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Porphyrazine film for use in electrochemical sensor
Merhoutová, Jana ; Nesměrák, Karel (advisor) ; Ludvík, Jiří (referee)
Porphyrazine film for use in electrochemical sensor Abstract: A water soluble N,N',N'',N'''-tetramethyltetra-3,4-pyridinoporphyrazine complex containing cobalt cation (II) as a central atom was used like a mediator for preparation of electrochemical sensor. Such effects on a sensor function like an electrode carrier material, the manner of porphyrazine deposition, pH and thickness of the layer, were studied by cyclic voltammetry method. The sensor was tested for hydrogen detection in water buffer solution consequently.
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New Electrochemical Methods for Determination of Nitro and Oxo Derivatives of Fluorene
Vyskočil, Vlastimil ; Barek, Jiří (advisor) ; Ludvík, Jiří (referee) ; Heyrovský, Michal (referee)
4. Conclusion This Thesis represents a contribution to the search for new analytical methods applicable on environmental and biological samples. The current state- of-art concerning the formation, occurrence, and biological activity of fluorene and its nitro and oxo derivatives was summarized in Chapter 1. Further experimental work was focused on assessment of new approaches in the detection of the studied compounds. Attention was paid mainly to nitrofluorenes, fluorenone and nitrofluorenones, namely 2-nitrofluorene, 2,7-dinitrofluorene, 9-fluorenone, 2-nitro-9-fluorenone, and 2,7-dinitro-9- fluorenone and the possibilities of their determination using polarographic and voltammetric methods. Interactions of calf thymus dsDNA with 2-nitrofluorene and 2,7-dinitrofluorene at the DNA/SPCPE were investigated and subtle DNA damage under conditions of direct DNA-analyte interaction at room temperature and damage to DNA bases under condition of electrogeneration of short-lived radicals of nitrofluorenes at human body temperature were found. The obtained results can be summarized as follows: ● Modern polarographic and voltammetric methods at mercury electrodes developed for determination of trace amounts of 9-fluorenone and 2,7-dinitro-9-fluorenone (and other NPAHs generally) in concentration ranges from 2×10-8 to...
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Deciding public universities according to the quality indicators
Ludvík, Jiří ; Urbánek, Václav (advisor) ; Bušovský, Ladislav (referee)
The thesis is focused on the system of funding public universities in the Czech Republic. At first, the basic characteristics of university education are presented and the connection between university education, externalities, human capital and economic growth is outlined. Then we proceed to define the system of funding public universities and the development of individual indicators in this process. Briefly, following the university education, also the demographic development is mentioned. The last part of the thesis analyzes the impact of introducing the qualitative criteria into public universities and the expert interviews are used to determine how these changes affect the actual public universities.
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Structural, Redox and Spectrometric Characterization of Energetic Material FOX-7 (2,2-dinitroethene-1,1-diamine) in Solution
Šimková, Ludmila ; Ludvík, Jiří
The investigation of energetic materials, especially organic nitro-amino-derivatives, always has attracted attention of physical chemists. However, published articles demonstrate lack of systematic study of molecules based on aliphatic backbones, rather than aromatic structures. This work represents the first systematic electrochemical and spectrometric characterization of 2,2-dinitroethene-1,1-diamine (FOX-7) in aqueous and aprotic solvent. Based on the results obtained from combination of electrochemistry with spectrometric methods, the actual structure of FOX-7 in various media was revealed, its reducibility described and radical intermediates as well as products were intercepted, isolated and characterized.
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Electrochemical Study of Oxazaborine Chromophores
Mikysek, T. ; Josefík, F. ; Vytřas, K. ; Ludvík, Jiří
This contribution describes a basic electrochemical study of a series of newly synthesized chromophores based on the oxazaborine core. The attention was focused on determination of the first oxidation and the first reduction potentials, their difference and the relationship to the calculated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies. The oxidation is mostly a two-electron irreversible process, the first reduction is also irrevesible, but involving one-electron. For better understanding of the relationship between the structure and redox properties, the approach using sigma (para) constants of Hammett type was applied, the difference between E(ox) and E(red) was correlated with the HOMO-LUMO gap.
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