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This study compared photocatalysis reactions from titanium dioxide powder (Degussa P25), concentrations of 0.001, 0.005, 0.01, 0.05 and 0.1 g/L, with nano-titanium dioxide fibers for inactivation of Bacillus subtilis spores. The fibers were synthesized from titanium (IV) isopropoxide and polyvinylpyrrolidone using electrospinning technic and calcined at the temperatures of 400-640 °C to obtain anatase to rutile ratio of 100 : 0, 70 : 30, 50 : 50 and 30 : 70. The fiber concentrations of 0.1, 0.25, 0.5, 1, 1.5 and 2 g/L were studied and concurrently compared with the best concentration of Degussa P25. Finally, the usage repetition of fibers for 5 times was investigated. The fiber-regeneration was conducted by heating at 100, 350, and 570 °C for 1 hour before each re-use. The experiment was conducted for 4 hours under sunlight irradiation. The results revealed that Degussa P25 at a concentration of 0.005 g/L yielded 100 % efficiency within 90-120 min, while a 1.5 g/L of the fiber with anatase to rutile ratio of 70 : 30 gave the highest efficiency, 80-99 %, within 210 min. For the usage repetition, regeneration temperature of 570 °C slightly yielded better efficiency than that of 350 °C. Both temperatures could regenerate fibers for 3 times of usage. However, the regeneration temperature of 100 °C showed the least efficiency rate.
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