Vliv polovodičových materiálů na fotokatalytické reakce

Abstract

The development and use of the advanced oxidation processes leads to the environmental protection by applying them in the wastewater decontamination and purification from endocrine disruptors and bacteria. The interest was focused on designing of a photocatalytic reactor and a way of immobilization of a powder catalyst by water-glass, which was the nanofiber powder catalyst NnF Ceram TiO2 produced by company Pardam s.r.o. The commercial TiO2 Evonik P25 was used for comparison. The catalysts were characterized using XRD, UV-Vis spectrometry, physical sorption of nitrogen by 77 K and surface analysis by TEM. Design and construction of the developed device was tested during degradation of hormones (17α-ethinylestradiol, 17α-stradiol, 17β-estradiol, estriol, estrone, progesterone) and bacteria (coliform bacteria, E. coli, Pseudomonas aeruginosa, Staphylococcus aureus). A source of the light was UV lamp with wavelength 368 nm. To the total degradation of chosen bacteria occurred after 24 hours in the presence of both catalysts. The decomposition of hormones was in accordance with pseudo-first-order law. The conversion all hormones was higher by using the TiO2 Evonik P25 catalyst in comparison with NnF Ceram catalyst. It was shown, that progesterone and all types of estradiols were decomposed in the most easiest way in the presence of both TiO2 Evonik P25 and NnF Ceram TiO2 catalysts. On the other hand the lowest conversion was reached by estrone and estriol. The crucial role in different photocatalytic activity of tested catalysts can be assigned to their various phase structure. The catalyst TiO2 -P25 is double-phase (composition 80 wt.% of anatase and 20 wt.% of rutile). Although the anatase phase is photocatalytically more active, the current presence of anatase and rutile may cause the synergic effect, which leads to reduction of recombination of electron-hole pairs. This is the reason of their better availability for photocatalytic reaction.The TiO2 based photocatalysts immobilized by water-glass seems to be promising for photocatalytic water purification. Designed photocatalytic device for hormones and bacteria degradation could find its application in commercial sphere using whirlpools or similar equipment for bathing, where people can pollute the water by hormones and bacteria.