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Isolation of fulvic acids from soil origin and fluorescence study
Rubínková, Eva ; Kozáková, Zdenka (referee) ; Fasurová, Naděžda (advisor)
Aim of this bachelor thesis was to find the optimal procedure and evaluation of soil fulvic acid (FA) isolation (soil type Eutric Cambisol, locality Vatín). Soil Cambisol contained higher amount of fulvic acid than humic acid (37,5%). Isolation and purifying of fulvic acid was made with 0,3 % yield. Fluorescence measurement by synchronous mode was used and compared with spectra of FA standard Elliot II. SFS spectra were similar. The main fluorophore of FA sample at excitation 358 and emission 448 nm from SFS spectra was determined.
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Study of influence of organic dye structure on their decomposition in the diaphragm discharge in liquids
Pajurková, Jana ; Fasurová, Naděžda (referee) ; Kozáková, Zdenka (advisor)
The main goal of presented thesis is to study the influence of organic dyes structure on its degradation in diaphragm discharge in liquids. Diaphragm discharge is a kind of non-thermal plasma that can be generated in liquids by the application of high voltage. In plasma channels (so-called streamers), many physical and chemical processes are formed. High electrical field, shock waves and last but not least emission of electromagnetic waves in the range of visible and ultra-violet radiation appear among physical processes. The most important chemical process is generation of active species. These species initiate chemical reactions and could attack molecules of organic compounds contained in water solution. The reason why organic dyes were chosen in this study is its visible destruction, because it is related to its decolouration. Further, UV-VIS spectroscopy for the determination of concentration during the experiment can be used. Organic dyes are good models of organic substance often contained in waste water and for which removal classical biological, chemical and physical methods aren’t sufficient. Selected dyes were mostly from the group of azo-dyes: Acid Red 14, Acid Red 18, Acid Yellow 23, Direct Blue 53, Direct Red 79, Direct Red 80, Direct Yellow 29, Food Yellow 3 and further, Acid Blue 74 (indigotic dye) and Direct Blue 106 (oxazine dye). Experiments were carried out in a special batch discharge reactor with the anode and the cathode spaces divided by a non-conductive barrier, where the diaphragm with a pin-hole was placed. Measurement showed different removal in the anode and cathode space. We have supposed it was caused by different streamers features and energetic conditions. Dyes were decomposed with higher efficiency in the anode space where the final concentration reached 40 % of the initial concentration while it remained about 90 % in the cathode space. In this thesis the influence of dyes structure on the dye decomposition by electrical discharge was investigated. Dyes consisted of small molecules and dyes with many substitutes bounded on aromatic ring were decomposed more easily than dyes consisted of big molecules. The shift of characteristic wavelength on both directions (to shorter as well as longer wavelength) was observed during the experiments especially when the Direct dyes were decomposed. This phenomenon was probably due to the formation of intermediate product, which have different characteristic wavelength than the primary compound. In general, colourfulness is given by long conjugated systems of double bonds with substitutes bounded on an aromatic ring. Each change in the molecule structure provides the colour change and this could be the possible reason of the shift of characteristic wavelength. The other task was the comparison of degradation process efficiency by the mean of electrolysis and diaphragm discharge. Results showed that electrolysis (30 W) was more convenient for degradation of dyes consisted of small molecules while diaphragm discharge (130170 W) suited for complex molecules. For degradation of small molecules, oxidation on the anode assumed to be the most effective process that is initiated by electrolysis. For degradation of big molecules, attack of active species produced by the discharge is necessary.
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Study of electrolytic influence on organic dye decomposition in the diaphragm discharge in liquids
Davidová, Jaroslava ; Rašková, Zuzana (referee) ; Kozáková, Zdenka (advisor)
This Bachelor thesis is focused on study of chemical and physical influences which are proceed in diaphragm discharge in water solution. These processes could be used in water treatment. If DC non-pulsed voltage is applied, a significant influence of electrolysis must be taken into account. The main goal of this thesis is the estimation of electrolytic contribution to processes in the discharge. Theoretical part describes basic theory about creation of electrical discharges in water and electrolysis with emphasis on processes leading to destruction of organic compounds. Production of reactive particles (radicals, hydrogen peroxide, ozone, etc.) and electrochemical reactions on electrodes mainly belongs among these processes. This part describes analytical method (UV-VIS spectroscopy) which was used for determination of organic dyes concentration as well. Experimental part is oriented to experiment procedure which was carried out in an apparatus with separated anode and cathode area. Separation was made by dielectric diaphragm with a pinhole in the centre. Its initial diameter was 0.25 mm. Electrolytic decomposition was carried out at constant current of 30 mA and supplied power was about 14–32 W. Two Saturn dyes (Direct Blue 106 and Direct Red 79) were selected for experiments. As the decomposition was related to decoloration of the solution, UV-VIS spectroscopy in the range of 350–700 nm was used for determination of dye concentration. Next part focused on results presents various factors which had remarkable effect on decomposition of organic dyes. These factors were: various polarities of electrodes, conductivity and pH of solution, applied power, kind of electrolyte and structure of organic dye. The electrolysis had the significant influence on decomposition of small organic molecules. Decomposition was running mainly in the anode area where so called negative discharge was created. Optimal conditions were set by NaCl electrolyte with concentration providing initial conductivity of 500 S·cm-1. By the NaNO3 electrolyte half decomposition efficiency was achieved and in Na3PO4 electrolyte, the decomposition even didn’t run. The decomposition in the anode area was stimulated by the low pH value, which was decreasing during electrolysis. Generally, higher decomposition was achieved by the discharge than by pure electrolysis but the electrolysis had higher efficiency. In pure electrolysis, high rate of removal can be achieved by the application of a relatively low power. When bigger organic molecules were decomposed, the efficiency was higher by applying the discharge.
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