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Diaphragm discharge in organic dye solutions with focus on electrolytic decomposition
Davidová, Jaroslava ; Brablec, Antonín (referee) ; Kozáková, Zdenka (advisor)
This Diploma thesis is focused on physical and chemical effects which contribute to the decomposition of organic dyes by diaphragm discharge generated in water solutions. Due to the application of DC high voltage source in continuous regime, there is an effect of electrolysis contributing to the dye decomposition by diaphragm discharge. The aim of this work was to find out when the electrolysis is running (or when is the moment of discharge breakdown) and which factors influence the breakdown. The other goal was decomposition of selected textile and food organic dyes by electrolysis itself. In the theoretical part, theory about creation of electrical discharges in aqueous solutions is noted and various types of underwater discharges are described. Background researches about underwater electrical discharges used in the world are mentioned as well as the use of diaphragm discharges and various ways how to remove organic dyes from wastewater. Finally, theories of electrolysis, UV-VIS spectroscopy and basis of other analytical methods useful for detection of organic molecules are described. Experimental part is oriented to experiment procedure which was carried out in a reactor with separated electrode areas. Separation was made by dielectric diaphragm with a pinhole in the centre. Its initial diameter was 0.4 mm. Used chemicals and course of experiments are described in this part, too. First, the breakdown moment in the reactor was investigated (i. e. determination, when only electrolysis was operating) by formation of hydrogen peroxide and measurement of dynamic (time resolved) electrical characteristics. Next, decomposition of selected dyes by electrolysis was carried out. As the decomposition was related to decolorization 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 an effect on breakdown of diaphragm discharge. These factors are kind of used electrolyte, initial conductivity of solution, kind of dye, temperature of solution and type of reactor (or solution volume). From the result, the most important factor is initial solution conductivity. After the determination of the breakdown moment, the electrolysis of organic dyes was performed. The applied current was 10 mA, initial conductivity was 500 µS/cm and used electrolyte was NaCl. Moreover comparison of dye decomposition in dependence on the different applied power was realized. From this comparison one can assume, there is no significant contribution of electrolysis (the efficiency is approximately 15 %) to the diaphragm discharge in aqueous solution.
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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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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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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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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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Diaphragm discharge in organic dye solutions with focus on electrolytic decomposition
Davidová, Jaroslava ; Brablec, Antonín (referee) ; Kozáková, Zdenka (advisor)
This Diploma thesis is focused on physical and chemical effects which contribute to the decomposition of organic dyes by diaphragm discharge generated in water solutions. Due to the application of DC high voltage source in continuous regime, there is an effect of electrolysis contributing to the dye decomposition by diaphragm discharge. The aim of this work was to find out when the electrolysis is running (or when is the moment of discharge breakdown) and which factors influence the breakdown. The other goal was decomposition of selected textile and food organic dyes by electrolysis itself. In the theoretical part, theory about creation of electrical discharges in aqueous solutions is noted and various types of underwater discharges are described. Background researches about underwater electrical discharges used in the world are mentioned as well as the use of diaphragm discharges and various ways how to remove organic dyes from wastewater. Finally, theories of electrolysis, UV-VIS spectroscopy and basis of other analytical methods useful for detection of organic molecules are described. Experimental part is oriented to experiment procedure which was carried out in a reactor with separated electrode areas. Separation was made by dielectric diaphragm with a pinhole in the centre. Its initial diameter was 0.4 mm. Used chemicals and course of experiments are described in this part, too. First, the breakdown moment in the reactor was investigated (i. e. determination, when only electrolysis was operating) by formation of hydrogen peroxide and measurement of dynamic (time resolved) electrical characteristics. Next, decomposition of selected dyes by electrolysis was carried out. As the decomposition was related to decolorization 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 an effect on breakdown of diaphragm discharge. These factors are kind of used electrolyte, initial conductivity of solution, kind of dye, temperature of solution and type of reactor (or solution volume). From the result, the most important factor is initial solution conductivity. After the determination of the breakdown moment, the electrolysis of organic dyes was performed. The applied current was 10 mA, initial conductivity was 500 µS/cm and used electrolyte was NaCl. Moreover comparison of dye decomposition in dependence on the different applied power was realized. From this comparison one can assume, there is no significant contribution of electrolysis (the efficiency is approximately 15 %) to the diaphragm discharge in aqueous solution.
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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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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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