| Abstract [eng] |
In indoor environments, air quality is directly linked to human health, as airborne particulate matter, bacteria, fungal microorganisms and other bioaerosols can contribute to respiratory diseases, allergic reactions and the spread of infections. This problem is particularly intense in healthcare, educational and other public institutions where many people use the premises and air circulation does not always ensure sufficient reduction of microbiological contamination. For this reason, there is a growing demand for additional, effective and sustainable air purification technologies. One such technology is air ionization, which generates a stream of positive and negative ions that can interact with airborne particles and microorganisms. The objective of this master’s thesis is to optimize the material and configuration of air ionization electrodes to maximize ion generation for effective reduction of microbiological and particulate matter pollution in the air, while minimizing ozone production. During the study, an air ionizer was designed and manufactured, different electrode materials (tungsten, copper, carbon fibber) and their configurations were tested and the concentration of generated ions, ozone formation, reduction in microbiological air contamination and the number of particulate matter using different high voltages. Different ionizer polarities were applied in the experiments: positive, negative and bipolar. Microorganisms were assessed after incubation by counting the bacterial colonies that had grown on Petri dishes and the results were converted into concentrations of colony-forming units per milliliter and per cubic meter. Arithmetic means, standard deviations, normalized values, reduction efficiencies and exponential decay approximations were used for data analysis. A comparison of electrode materials and configurations revealed that carbon fibber electrodes are the most suitable for further testing. These electrodes were characterized by stable ion generation and a sufficiently high ion concentration at lower voltages, particularly when using negative and bipolar polarities. Voltages of 4 kV and 7 kV were selected for further studies, as they allowed for a comparison of the effects of lower and higher operating voltages. Ozone measurements showed that ozone concentration increases as voltage increases. At 4 kV, the ozone level remained low, while at 7 kV and 10 kV, the ozone concentration exceeded safe limits, therefore, for practical applications, it is necessary to consider the risk of ozone formation and select appropriate operating voltages. Tests to reduce microbiological air contamination showed that the concentration of microorganisms in the air decreased during ionization compared to the control test. After 40 minutes of exposure, the efficiency of all ionizer polarities exceeded 80 % and after 60 minutes, it approached 95–100 %. The highest efficiency was observed when applying a 7 kV voltage with negative polarity – 99,57 ± 0,18 %. In the experiment on the removal of particulate matter using a 7 kV voltage, the data were normalized and analysed based on the change in the number of particles over time. The results showed that ionization accelerates the decrease in the number of particulate matter and the coefficients of the exponential decay function allow for a comparison of the effects of different polarities. In summary, it can be stated that ionization technologies can be applied to reduce microbiological air contamination and the number of solid particles, however, their practical use must be evaluated not only in terms of air purification efficiency but also in terms of ozone formation. The results of the study show that carbon fibber electrodes are a suitable material for an ionizer and the negative polarity mode exhibits the highest efficiency in reducing microbiological air contamination. For safe operation, it is recommended to optimize the operating voltage so as to ensure sufficient ion generation while not exceeding safe ozone concentration limits. |
