Development of a hybrid environmental purification unit by using of excimer VUV lamps with TiO2 coated titanium mesh filter

Abstract

A versatile photocatalyst-excimer-lamp hybrid unit for both air- and water-purification at practical scale was investigated. The unit consisted of a xenon filled quartz tube (20mm i.d.×300mm length) and TiO2 nanoparticles-modified Ti-mesh sheet (TMiP™). Emission at 172nm from a xenon excimer (Xe2∗) was able to produce reactive species by direct photolysis of water or air. At the same time, the emission was able to excite TiO2 on TMiP surface. Therefore, the unit decomposes organic contaminants by synergy of photocatalysis and photolysis. Air- and water-purification efficiency of the unit was examined by high concentration of acetaldehyde and phenol decomposition test, respectively. The disinfection activity of the units for waterborne pathogens was also investigated. For comparison, the purification units using excimer-lamp alone or UV lamps with TMiP and/or ozone treatment were evaluated in the same methods. The photocatalyst-excimer-lamp hybrid unit was able to decompose acetaldehyde and phenol effectively, compared with the other units. On the other hand, disinfection activity of the unit for waterborne pathogens was strongly affected by the kind of the waterborne pathogens. The difference of efficiency between organic pollutants and waterborne pathogens by the unit may be due to the molecular or bacterial size and the surface composition of bacteria and viruses, critical wavelength for disinfection, and the permeation ability of the outer wall of bacterial cells or virus particles for reactive species. Taken together, the photocatalyst-excimer-lamp hybrid unit has wide potentials for environmental purification by the synergy of photocatalysis and photolysis. These results would be attractive to develop a practical environmental purification system such as sewage water treatment.