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Influence of electrolysis on the degradation of dye water solutions
Olexová, Barbora ; Možíšková, Petra (referee) ; Kozáková, Zdenka (advisor)
The basic subject of this thesis is to investigate the influence of electrolysis on degradation of organic dyes in aqueous solutions. Electrolysis is a physically-chemical process, during which - under the influence of direct current - chemical reactions proceed inside the system. By choosing efficient conditions it is possible to achieve fundamental changes in the structure of organic compound’s molecules and on the basis of that for example their gradual degradation. This effect can be used in the process of wastewater treatment. The main task of the thesis is to analyse the influence of variously chosen chemical and physical conditions on the rate of degradation of azo dyes, which is the largest group of organic dyes used in industry and from this reason in great amounts contained both in mill residues and sewage water. Azo dyes have been selected for this experiment for their good solubility in water. Other advantage is that their degradation is accompanied by visible decoloration of the solution and their concentration in solution can be easily determined by UV-VIS spectrometry. Concretely two direct azo dyes - C.I. Direct Blue 106 and C.I. Direct Red 79 - have been chosen. The experiment was carried out in a simple reactor consisted of a bath with a stirrer into which two electrodes were installed and attached to the source of direct voltage. Every series of measurement proceeded at constant current which values were varied in range from 100 mA to 1 000 mA. The electric voltage ranged from 7 V to 22 V. Several samples were taken away from the solution during the experiment and the decrease of dye concentration was evaluated in every series. This evaluation validated the hypothesis that the dyes contained in the solution really degraded. This process was also connected to the expected bleaching of the solution. Decoloration of aqueous solution of dye is caused by disruptions in the structure of the dye molecule which is loosing its characteristic sections that cause colourfulness (a conjugate system of double bonds and presence of appropriate substitutes). A total amount of measured series was 16 with various input conditions (Fe and Pt electrodes, electrolytes NaCl, Na2SO4, and NaNO3 and their different concentrations, different current values) which more or less influenced the rate of degradation of investigated substances. It was found out that the blue dye is more likely to be electrolytically degraded. Chemical structure of its molecules, which is smaller and less branched than molecules of the used red dye, could be the source of that. The greatest degradation of the blue one proceeded at two chosen maximum values of constant current 800 mA and 1 000 mA. It could be assumed that current enhancement through the system induces higher dye concentration decrease. Degradation of the blue dye proceeded faster by using electrodes made of stainless steel than the platinum electrodes. The most suitable electrolyte was shown to be sodium chloride. When higher concentration (or conductivity) of electrolyte was used higher efficiency of degradation process was observed.
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Organic dye decomposition by AOP´s methods
Olexová, Barbora ; Dzik, Petr (referee) ; Kozáková, Zdenka (advisor)
This diploma thesis is focused on the study of the influence of advanced oxidation processes on degradation of organic dyes. The field of AOP – very effective physically-chemical methods of wastewater treatment – includes application of strong oxidation agents, UV and ionizing radiation and electrical discharges. For this thesis, two of these methods were chosen – the application of oxidation agent (ozone) and UV radiation. Along with electrolysis, which is mentioned rather marginally in this thesis (it is the subject of the previous thesis), these phenomena are products of electrical discharge in water, where they participate in the processes of degradation in a different way. For all measurement series, two direct azo dyes were chosen as model substances – C.I. Direct Blue 106 and C.I. Direct Red 79. The ozonizer, in which either oxygen or synthetic or technical air were loaded as carrier gases, was used for degradation of dyes by ozone. The generated ozone was loaded into the bubbling vessel with dye solution of different initial concentration (10–130 mg.dm-3), which was followed by other bubbling vessel with KI solution for the next analytical determination of the amount of generated ozone. The other parameters changed were the gas flow (1–2 dm3.min-1), ozonizer output (minimal and maximal), type of dye, pH value of the solution (neutral or acid) and additional electrolyte (NaCl, Na2SO4 or any). The reactor for the study of the influence of UV radiation on degradation of dyes was an UV sterilizer into which the equivalent volume of dye solution was added. The possibilities of experimental settings were limited and only the type of dye, an additional electrolyte and pH value of the dye solution were adjusted (as in the case of ozone). Several series of samples were measured with various input conditions which more or less influenced the degradation of investigated dyes in this experiment. It was found that for both used methods the Direct Blue 106 dye was more degradable (with significantly better results for ozone than for UV radiation). The degradation of Direct Red 79 dye proceeded only by ozone treatment, in the case of the application of UV radiation no degradation occurred. By investigation of the influence of initial concentration of dye on its degradation, it was confirmed that with the initial concentration enhancement the final concentration rises as well, whereas in low concentrations (10–50 mg.dm-3) the initial concentration has no effect. The addition of an electrolyte had an accelerating effect on dye degradation in both methods (NaCl and also Na2SO4 showed similar results though the degradation proceeded in different ways). The addition of HCl accelerated the degradation only in the case of UV radiation; during the application of ozone the pH level of the system did not have any influence on the degradation. Oxygen and synthetic air had the strongest effect on ozone degradation (comparable results); in the case of technical air the final dye concentration was higher up to 30 %. The gas flow of 1.5 dm3.min-1 was stated as optimal with the ozonizer output 30 W (maximal). At minimal power the ozonizer produced very low amount of ozone.
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Biodegradace azobarviv působením hub bílé hniloby
Bírošíková, Paulína
White rot fungi, belonging to wood decay fungi have the ability to degra-de complex aromatic structures such as lignin or pollutants with an aromatic structure (tetracyclines, endocrine disruptors) via extracellular ligninolytic enzymes. Azo dyes are synthetic dyes containing aromatic rings with bonded substituents lin-ked by an azo group. Fungi are able to degrade these structures, whereas decrease of dye is observed, called decolorization. The aim of this bachelor's thesis is to de-termine the degradation ability of three types of azo dyes (methylene red, tartrazine and azorubin) using ten types of white rot fungi. Cultivation of individual fungi with the dyes was carried out for twenty-four days, during which the absorbance was monitored using a UV/VIS spectrophotometer at intervals of every other working day. The colour loss was calculated from the measured values and the decoloriza-tion values were expressed graphically as a percentages. The selected fungi showed the greatest decolorization of tartrazine on the second day of the experiment, an average of 89%, except for the fungus Fomes fomentarius, for which dye decoloriza-tion was not observed. In contrast, the least degraded dye was azorubin, an average of 37% at the end of the experiment for most fungi species. Methylene red showed the most stable decolorization trend, with an average of 77% at the end of the me-asurement. The effect of decolorization was influenced by the structure of the azo dyes and the efficiency of specific fungal species.
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Boron-doped diamond electrodes: Utilization for determination of reducible organic compounds
Vosáhlová, Jana ; Schwarzová, Karolina (advisor) ; Dejmková, Hana (referee)
In this study the possibilities of utilization of boron-doped diamond (BDD) electrodes for electrochemical reduction of organic compounds and their determination in aqueous media were investigated. For this purpose BDD electrodes have several advantages (relative wide potential window in cathodic region, low sensitivity towards oxygen evolution) but are not frequently used. For the study were selected biologically active organic compounds with typical reducible groups. Vanillin (natural essential oil, synthetic aroma; reducible aromatic aldehyde) is not reducible at BDD electrode. Azidothymidine (antiviral drug; reducible azido group) shows voltammetric signal in Britton -Robinson buffer at pH 6.0 - 8.0, but its analytical utilization is difficult due to the close positioning to the decomposition of the supporting electrolyte. The height and potential of the reduction signal of 5-nitroquinoline (environmental pollutant; reducible nitro group on the aromatic nucleus and at higher potentials reducible heterocycle) is significantly influenced by the boron concentration in BDD film. Reduction of quinoline skeleton is visible in the range of pH6.0 - 11.0 in BR buffer. For differential pulse and DC voltammetry (reduction of nitro group) in BR buffer pH 5.0 limits of detection 0.2 µmol.l-1 and 2.7...
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Organic dye decomposition by AOP´s methods
Olexová, Barbora ; Dzik, Petr (referee) ; Kozáková, Zdenka (advisor)
This diploma thesis is focused on the study of the influence of advanced oxidation processes on degradation of organic dyes. The field of AOP – very effective physically-chemical methods of wastewater treatment – includes application of strong oxidation agents, UV and ionizing radiation and electrical discharges. For this thesis, two of these methods were chosen – the application of oxidation agent (ozone) and UV radiation. Along with electrolysis, which is mentioned rather marginally in this thesis (it is the subject of the previous thesis), these phenomena are products of electrical discharge in water, where they participate in the processes of degradation in a different way. For all measurement series, two direct azo dyes were chosen as model substances – C.I. Direct Blue 106 and C.I. Direct Red 79. The ozonizer, in which either oxygen or synthetic or technical air were loaded as carrier gases, was used for degradation of dyes by ozone. The generated ozone was loaded into the bubbling vessel with dye solution of different initial concentration (10–130 mg.dm-3), which was followed by other bubbling vessel with KI solution for the next analytical determination of the amount of generated ozone. The other parameters changed were the gas flow (1–2 dm3.min-1), ozonizer output (minimal and maximal), type of dye, pH value of the solution (neutral or acid) and additional electrolyte (NaCl, Na2SO4 or any). The reactor for the study of the influence of UV radiation on degradation of dyes was an UV sterilizer into which the equivalent volume of dye solution was added. The possibilities of experimental settings were limited and only the type of dye, an additional electrolyte and pH value of the dye solution were adjusted (as in the case of ozone). Several series of samples were measured with various input conditions which more or less influenced the degradation of investigated dyes in this experiment. It was found that for both used methods the Direct Blue 106 dye was more degradable (with significantly better results for ozone than for UV radiation). The degradation of Direct Red 79 dye proceeded only by ozone treatment, in the case of the application of UV radiation no degradation occurred. By investigation of the influence of initial concentration of dye on its degradation, it was confirmed that with the initial concentration enhancement the final concentration rises as well, whereas in low concentrations (10–50 mg.dm-3) the initial concentration has no effect. The addition of an electrolyte had an accelerating effect on dye degradation in both methods (NaCl and also Na2SO4 showed similar results though the degradation proceeded in different ways). The addition of HCl accelerated the degradation only in the case of UV radiation; during the application of ozone the pH level of the system did not have any influence on the degradation. Oxygen and synthetic air had the strongest effect on ozone degradation (comparable results); in the case of technical air the final dye concentration was higher up to 30 %. The gas flow of 1.5 dm3.min-1 was stated as optimal with the ozonizer output 30 W (maximal). At minimal power the ozonizer produced very low amount of ozone.
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Influence of electrolysis on the degradation of dye water solutions
Olexová, Barbora ; Možíšková, Petra (referee) ; Kozáková, Zdenka (advisor)
The basic subject of this thesis is to investigate the influence of electrolysis on degradation of organic dyes in aqueous solutions. Electrolysis is a physically-chemical process, during which - under the influence of direct current - chemical reactions proceed inside the system. By choosing efficient conditions it is possible to achieve fundamental changes in the structure of organic compound’s molecules and on the basis of that for example their gradual degradation. This effect can be used in the process of wastewater treatment. The main task of the thesis is to analyse the influence of variously chosen chemical and physical conditions on the rate of degradation of azo dyes, which is the largest group of organic dyes used in industry and from this reason in great amounts contained both in mill residues and sewage water. Azo dyes have been selected for this experiment for their good solubility in water. Other advantage is that their degradation is accompanied by visible decoloration of the solution and their concentration in solution can be easily determined by UV-VIS spectrometry. Concretely two direct azo dyes - C.I. Direct Blue 106 and C.I. Direct Red 79 - have been chosen. The experiment was carried out in a simple reactor consisted of a bath with a stirrer into which two electrodes were installed and attached to the source of direct voltage. Every series of measurement proceeded at constant current which values were varied in range from 100 mA to 1 000 mA. The electric voltage ranged from 7 V to 22 V. Several samples were taken away from the solution during the experiment and the decrease of dye concentration was evaluated in every series. This evaluation validated the hypothesis that the dyes contained in the solution really degraded. This process was also connected to the expected bleaching of the solution. Decoloration of aqueous solution of dye is caused by disruptions in the structure of the dye molecule which is loosing its characteristic sections that cause colourfulness (a conjugate system of double bonds and presence of appropriate substitutes). A total amount of measured series was 16 with various input conditions (Fe and Pt electrodes, electrolytes NaCl, Na2SO4, and NaNO3 and their different concentrations, different current values) which more or less influenced the rate of degradation of investigated substances. It was found out that the blue dye is more likely to be electrolytically degraded. Chemical structure of its molecules, which is smaller and less branched than molecules of the used red dye, could be the source of that. The greatest degradation of the blue one proceeded at two chosen maximum values of constant current 800 mA and 1 000 mA. It could be assumed that current enhancement through the system induces higher dye concentration decrease. Degradation of the blue dye proceeded faster by using electrodes made of stainless steel than the platinum electrodes. The most suitable electrolyte was shown to be sodium chloride. When higher concentration (or conductivity) of electrolyte was used higher efficiency of degradation process was observed.
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