Papers by Keyword: Bactericidal Ability

Abstract: Thin films with the high content of Ti coated on the stainless steel (SS) sieves were successfully prepared through the sol gel method. Photocatalytic reaction on the TiO₂-coated SS sieves with UVA (ultraviolet light with the range of 315-400 nm) radiation is effective to destroy three selected bacterial strains with log-phase period. As a result, bactericidal ability was achieved to 77% in aqueous media. Amount of bacterial numbers, 3.4×10⁷ CFU/ml can be removed in this study, compared with our previous study, 1.85×10³ CFU/ml in the air media. Good contribution of bactericidal ability in 385 nm UVA radiation or heavy metals including Fe, Mn, Cr, Ni and Ti from the SS sieve was obtained as the range of 30-76%. The percentage of 10-17% contribution of bactericidal ability was increased with the photocatalytic reaction additive. It concluded the performance of bactericidal ability in aqueous solution is ascribed to the combination of UVA radiation, heavy metals on the sieve and photocatalytic reaction. The SS sieve coated with TiO₂ particles can be applied as a disinfectant for the effluent of wastewater treatment plant or water supply system in the future.

Abstract: The magnetic photocatalysts can provide both a high specific surface area and an alternative for recovering used catalyst from treated water by the application of a magnetic field. In this study, the Fe3O4 nanoparticles were synthesized by co-precipitation. After chemical co-precipitation of ferric and ferrous solution under alkaline condition, the suspension of magnetite nanoparticles were then mixed with TEOT (Titanium (Ⅳ) ethoxide) for sol-gel coating. The separated MPCs (magnetic photocatalyst nanoparticle) were then dried and calcined in 400oC. Magnetic properties of MPCs were identified by superconducting quantum interference device magnetometer (SQUID). The bactericidal ability of synthesized MPCs was evaluated by counting the residual numbers of E. coli after irradiation under a light intensity of 1.0 mW/cm2 at 365 nm. The results show that the MPCs were both anatase and had good crystallinity with clear peaks and insignificant noises after calcination. The SQUID test also reveals that calcination only affects the magnetic susceptibility of the MPC nanoparticles slightly (< 8%). The bactericidal ability of the synthesized MPCs was compared with the commercial TiO2 nanoparticle DegussaTM P25; P25 provided a faster inactivation rate for E. coli in water than MPCs did at the same dosage. The calculated photocatalytic bactericidal rate by P25 is about 3.6 times faster than that by MPCs synthesized in this work. However, the bactericidal rate of magnetic TiO2 synthesized in this work was 5 times than that of other MPCs in the literature. The particles size and surface area of MPCs from this work were about 135 nm and 210 m2/g, respectively. The MPCs from this work have much smaller size and larger surface area; hence there are more active sites for bactericidal reaction.