| Abstract |
Air pollution is one of the major environmental problems in developed countries, while along with the water pollution has the most visible and immediate impacts on human health. Air pollution is mainly generated in large urban centers and industrial areas, which fosters the illusion that concerns only a specific part of the population. This is only partially true as the production of electricity, public transportation, large and small scale industries, and domestic activities are other major sources of air pollutants further burdening the already polluted atmosphere. The daily and long time indoors presence of humans and their exposure to pollutants (often invisible), causes serious health effects. It is therefore an urgent need to develop technologies that will have the ability to process and degrade these pollutants.
For this purpose, we designed and constructed a prototype integrated setup for the decontamination of air using ozone. This setup is based on the high oxidation activity of ozone, which is responsible for the decontamination of indoor air. Ozone production to levels suitable for the decontamination of air is made by the “corona” effect followed by its excess concentration degradation to a level that guarantees limited to no harm to humans (under 0.05 ppm / 8 hour of exposure). The novelty of our device is based on the fact that the decontamination of an enclosed space, with microbial load by using ozone, takes place regardless of the presence of humans, since the excess of ozone concentration is degraded to levels imposed by the World Health Organization (WHO), i.e. below 0.05 ppm.
Therefore, the research aim of this work is focused on the subject of degradation of the ozone produced for the decontamination of air and deals with the synthesis and study of selected transition metals oxides (Cu, Ni and Mn) used as filters in this setup, for the rapid degradation of its excess concentration. We also examined whether these transition metals combined together in the form of an alloy improve their properties leading to better results, i.e. reduce the degradation time of ozone. Finally, we studied the contribution of the following parameters, Temperature, Humidity and Initial Ozone Concentration, with respect of required time to degradate the ozone, variables that affect the total operating time of the setup.
The method of co-precipitation was chosen for the synthesis of materials in the form of powder, a liquid chemical deposition technique. In the alloys’ composition, we observed that regardless of the initial ratio of the precursor solutions the preferred formation was the crystalline spinel CuNi0.5Mn1.5O4.
We examined the catalytic behavior of these materials on ozone using the prototype setup, which was designed and constructed for this purpose. It was observed that metal oxides were very reactive versus ozone. It was also shown that the combination of these transition metals in the form of the above spinel exhibits equally good results in the degradation of ozone, although it does not improve the total operating time of the setup. Conclusively, we concluded that the use of a structure in which manganese is in the oxidation state +4 outperforms all other metal oxides and spinel examined.
Finally, it was shown that the catalytic behavior, the parameters temperature and humidity show an independently and cumulatively effect. Those results were summarized in an empirical mathematical formulation, particularly useful for the estimation of the time required to degradate a particular ozone concentration to values safe for humans. These positive results set the stage for further study and development of this setup as an economic and effective indoor air pollutant decontamination prototype device.
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