Vishay Optoelectronics has introduced a number of high-power, ceramic-packaged UVA and UVB emitters, a low-power (2.5 mW) UVC emitter, and are poised to introduce a mid-power (12 mW) UVC emitter. While many believe that only UVC can be used to decontaminate water-based solutions, UVA light in combination with titanium dioxide photo catalyst can render harmful organic compounds into harmless end products such as carbon dioxide, water,and inorganic ions.
Titanium dioxide is a semiconductor with a bandgap of 3.2 eV, which corresponds to a wavelength of λ=387nm. UVA light generates electron-hole pairs in the semiconductor. Electrons e– and holes h+ can diffuse to the surface of the TiO2 where they generate radicals due to their oxidative effect. -OH radicals are formed which attack the pollutants present in the aqueous solution. In this way the organic substances are decomposed by the photocatalytic surfaces. The resulting main products are carbon dioxide and water.