Novel TiO 2 thin films/glass fiber photocatalytic reactors in the removal of bioaerosols

Abstract

The photocatalytic disinfection of aerosolized Escherichia coli, a pathogenic microorganism was investigated. The air disinfection system is a novel TiO 2 thin films/glass reactor filter and ultraviolet (UV) radiation air purification system, operating at a flow rate of 20 L/min. A special glass fiber reactor design allowed the UV lamp to be located in the center of the reactor. The photocatalyst reactor was then filled with TiO 2 coated glass fiber substrates to examine the photocatalytic efficiency of the TiO 2 filled reactor against aerosolized E. coli in cell concentrations of 10 5 CFU/mL. A slow sol–gel technique hydrolysis was used in this study to acquire fine and uniform TiO 2 nanoparticles of 10–30 nm. The TiO 2 thin films were obtained on glass fiber substrates by dipping method followed by thermal treatment. In an attempt to understand the structure and the morphology of TiO 2 sol–gel thin films, analyses by X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed. The SEM images showed that uniform anatase TiO 2 thin films were coated on fiber surfaces. A neublizer was applied to yield E. coli bioaerosol at a controlled humidity of 72%. Disinfection of E. coli under 254 and 365 nm light illumination was conducted to evaluate the photocatalytic ability of the TiO 2 thin films. The nano-TiO 2/glass fibers gel catalyst prepared in the laboratory showed good photocatalytic performance with the high degradation efficiency above 95% at both wavelengths. With the UV illumination switched off, the degradation efficiency dropped to below 60%. The improvement of the photocatalytic activity was ascribed to the fibers-based reactor with a screen mechanism which provided a huge surface area of TiO 2 thin films. These results will be useful and assist engineers to design photocatalyst reactors for the industrial applications of bioaerosol removal.