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Caffeine degradation by high frequency discharge in solutions
Korečková, Svatava ; Mravcová, Ludmila (referee) ; Kozáková, Zdenka (advisor)
The bachelor thesis deals with the degradation of caffeine in solutions by a high frequency discharge generated directly in the solution. The influence of experimental conditions such as the initial pH and conductivity of the solution, caffeine concentration or electrode geometry was studied. The prepared caffeine solutions had a concentration of 10–100 ppm and their initial pH was adjusted with electrolytes (NaCl, Na3PO4, Na2HPO4 and NaH2PO4). All experiments were performed in a batch plasma reactor consisting of a 400 ml beaker and two electrodes. UV-VIS spectrophotometry was used to determine the amount of degraded caffeine. It was found that the experimental conditions (electrical conductivity, power, type of electrode used, electrolyte used) have an effect on the degradation of caffeine. The most suitable electrolyte appears to be NaCl and the initial specific electrical conductivity set in the range of 400–500 S·cm–1.
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Alkaloid decomposition by electric discharges in liquids
Jonisová, Lenka ; Kozáková, Zdenka (referee) ; Krčma, František (advisor)
Plasmachemical processes are one of the methods used for wastewater treatment. Sewage and household wastewaters include a variety of organic substances that must be removed to reuse water in industry or households. The aim of this diploma thesisisthe observation of alkaloids decomposition by plasma chemical process. The theoretical part is focused on plasma generation in liquids and characterization of selected alkaloids. The decomposition of caffeine and quinine in direct current electrical discharge in liquid with diaphragm configuration is investigated in this work. The experiments were carried out in a batch reactor divided into two parts by a diaphragm made from ceramic material ShapalTM-M (thickness 3.0 mm, pin-hole diameter 1.0 mm). The stainless steel electrodes of 5×12 cm size were used. The mean electric power was set to 135 W for an operation time of 60 minutes in each experiment. Caffeine solutions (total volume of 4 L) were prepared in concentrations of 10, 25 and 50 ppm, quinine solutions in concentrations of 5, 10 and 15 ppm. The initial conductivity was adjusted by sodium chloride at three different values – 400, 750 or 1000 µS•cm-1. The experimental part consisted also of using analytical methods necessary for compound quantification. Hydrogen peroxide formation during the electrical discharge was determined by colorimetric method based on generation of yellow complex with titanium(IV) sulfate reagent. The caffeine concentration was measured by UV spectrometric method at wavelength 273 nmand thenHPLC/MS analysis was performed. Quinine degradation was monitored by UV-VIS spectrometry and fluorescent measurements. The plasma generation in water solutions induces formation of hydroxyl radical, hydrogen peroxide, oxygen, hydrogen and other reactive species. Hydrogen peroxide is produced and then utilized in degradation of organic compounds and thus lower concentration of H2O2was measured in solution with caffeine and quinine than in solution without alkaloids. However, the situation is different between cathode chamber and anode chamber. There is only negligible amount of H2O2used on degradation in cathode chamber. In contrary, the considerable degradation of caffeine and quinine and diminished concentration of H2O2 was observed in anode chamber.
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Caffeine degradation by direct current discharge in solutions
Šindelková, Kateřina ; Mravcová, Ludmila (referee) ; Kozáková, Zdenka (advisor)
The work deals with electric discharges generated in liquids. The theoretical part focuses on the formation of plasma discharges in liquids, the characterization of caffeine and analytical methods that can be used in the determination of caffeine in solutions. Ignition of an electric discharge in a liquid produces physical and chemical processes, such as the formation and action of UV radiation, shock waves and reactive particles. These changes can then be used in various applications, such as the degradation of undesirable substances in wastewater. The experimental part deals with the decomposition of caffeine in aqueous solutions. The influence of experimental conditions on the degradation of caffeine is monitored. Specifically, it is the effect of concentration, pH, conductivity and power used. The experiments were performed in a reactor consisting of two electrodes and a 200 ml vessel. Electric discharge, forming non-thermal plasma directly in the solution, was created in an orifice of the main electrode, the second electrode was plane. Caffeine solutions were prepared in concentrations from 10 ppm to 100 ppm. The electrical conductivity and pH of all solutions were adjusted with NaCl, NaH2PO4, Na2HPO4 and Na3PO4 electrolytes. The electrical power was set in the range from 60 to 85 W. The degradation of caffeine was determined by an analytical method, UV-VIS spectrophotometry. All measured data are processed in the results. It was found that experimental conditions, except of the discharge polarity, do not significantly affect the degradation of caffeine. Caffeine was decomposed better with the positive polarity of the main electrode, but its decomposition degree after the experiment with the negative polarity was not very effective. In determining the effect of electrical conductivity on the decomposition itself, it was only found that the electrical conductivity was increased during the experiment, with one exception. As for the effect of pH, its values were decreased during the decomposition with the connection of the positive polarity. On the contrary, the pH values were increased in the case of the negative polarity.
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Caffeine degradation by high frequency discharge in solutions
Korečková, Svatava ; Mravcová, Ludmila (referee) ; Kozáková, Zdenka (advisor)
The bachelor thesis deals with the degradation of caffeine in solutions by a high frequency discharge generated directly in the solution. The influence of experimental conditions such as the initial pH and conductivity of the solution, caffeine concentration or electrode geometry was studied. The prepared caffeine solutions had a concentration of 10–100 ppm and their initial pH was adjusted with electrolytes (NaCl, Na3PO4, Na2HPO4 and NaH2PO4). All experiments were performed in a batch plasma reactor consisting of a 400 ml beaker and two electrodes. UV-VIS spectrophotometry was used to determine the amount of degraded caffeine. It was found that the experimental conditions (electrical conductivity, power, type of electrode used, electrolyte used) have an effect on the degradation of caffeine. The most suitable electrolyte appears to be NaCl and the initial specific electrical conductivity set in the range of 400–500 S·cm–1.
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Caffeine degradation by direct current discharge in solutions
Šindelková, Kateřina ; Mravcová, Ludmila (referee) ; Kozáková, Zdenka (advisor)
The work deals with electric discharges generated in liquids. The theoretical part focuses on the formation of plasma discharges in liquids, the characterization of caffeine and analytical methods that can be used in the determination of caffeine in solutions. Ignition of an electric discharge in a liquid produces physical and chemical processes, such as the formation and action of UV radiation, shock waves and reactive particles. These changes can then be used in various applications, such as the degradation of undesirable substances in wastewater. The experimental part deals with the decomposition of caffeine in aqueous solutions. The influence of experimental conditions on the degradation of caffeine is monitored. Specifically, it is the effect of concentration, pH, conductivity and power used. The experiments were performed in a reactor consisting of two electrodes and a 200 ml vessel. Electric discharge, forming non-thermal plasma directly in the solution, was created in an orifice of the main electrode, the second electrode was plane. Caffeine solutions were prepared in concentrations from 10 ppm to 100 ppm. The electrical conductivity and pH of all solutions were adjusted with NaCl, NaH2PO4, Na2HPO4 and Na3PO4 electrolytes. The electrical power was set in the range from 60 to 85 W. The degradation of caffeine was determined by an analytical method, UV-VIS spectrophotometry. All measured data are processed in the results. It was found that experimental conditions, except of the discharge polarity, do not significantly affect the degradation of caffeine. Caffeine was decomposed better with the positive polarity of the main electrode, but its decomposition degree after the experiment with the negative polarity was not very effective. In determining the effect of electrical conductivity on the decomposition itself, it was only found that the electrical conductivity was increased during the experiment, with one exception. As for the effect of pH, its values were decreased during the decomposition with the connection of the positive polarity. On the contrary, the pH values were increased in the case of the negative polarity.
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Alkaloid decomposition by electric discharges in liquids
Jonisová, Lenka ; Kozáková, Zdenka (referee) ; Krčma, František (advisor)
Plasmachemical processes are one of the methods used for wastewater treatment. Sewage and household wastewaters include a variety of organic substances that must be removed to reuse water in industry or households. The aim of this diploma thesisisthe observation of alkaloids decomposition by plasma chemical process. The theoretical part is focused on plasma generation in liquids and characterization of selected alkaloids. The decomposition of caffeine and quinine in direct current electrical discharge in liquid with diaphragm configuration is investigated in this work. The experiments were carried out in a batch reactor divided into two parts by a diaphragm made from ceramic material ShapalTM-M (thickness 3.0 mm, pin-hole diameter 1.0 mm). The stainless steel electrodes of 5×12 cm size were used. The mean electric power was set to 135 W for an operation time of 60 minutes in each experiment. Caffeine solutions (total volume of 4 L) were prepared in concentrations of 10, 25 and 50 ppm, quinine solutions in concentrations of 5, 10 and 15 ppm. The initial conductivity was adjusted by sodium chloride at three different values – 400, 750 or 1000 µS•cm-1. The experimental part consisted also of using analytical methods necessary for compound quantification. Hydrogen peroxide formation during the electrical discharge was determined by colorimetric method based on generation of yellow complex with titanium(IV) sulfate reagent. The caffeine concentration was measured by UV spectrometric method at wavelength 273 nmand thenHPLC/MS analysis was performed. Quinine degradation was monitored by UV-VIS spectrometry and fluorescent measurements. The plasma generation in water solutions induces formation of hydroxyl radical, hydrogen peroxide, oxygen, hydrogen and other reactive species. Hydrogen peroxide is produced and then utilized in degradation of organic compounds and thus lower concentration of H2O2was measured in solution with caffeine and quinine than in solution without alkaloids. However, the situation is different between cathode chamber and anode chamber. There is only negligible amount of H2O2used on degradation in cathode chamber. In contrary, the considerable degradation of caffeine and quinine and diminished concentration of H2O2 was observed in anode chamber.
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