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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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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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