Existing UV-emitters on the basis of mercury arc lamps have a quantum yield which is too low in the spectral range 1 < 250 nm to be of interest for most photolytic decomposition reactions. At present the only radiation sources available in that spectral range are excimer lasers or excimer lamps.
Here we present a method based on an excimer laser. Its intense pulsed radiation could be a powerful alternative to common mercury lamps.
As model substances dyes for colouring textiles and wastewaters of dyehouses containing also auxiliary materials were used. The waters were treated with laser radiation of different wavelengths (193 nm - ArF, 248 nm - KrF) frequently under addition of hydrogen peroxide or ozone as oxidizers.
It was found that with the 193 nm radiation at the same energy dose and a substantially lower amount of added oxidizers the decolourization effect was greater than at 248 nm. The reduction of TOC was also faster. The HPLC spectra of the reaction products at the two laser wavelengths showed good agreement, so that the advantage of the shorter-wavelength radiation is the simplier achievement of the activation energies necessary for oxidation or decomposition reactions.