LASER-ASSISTED PHOTOCHEMICAL WASTE-WATER TREATMENT

Existing UV-emitters on the basis of mercury are lamps have a quantum yield which is too low in the spectral range 1 < 250 nm to be of inter est for most photolytic decomposition reactions. At present the only r adiation sources available in that spectral range are excimer lasers o r excimer lamps. Here we present a method based on an excimer laser. I ts intense pulsed radiation could be a powerful alternative to common mercury lamps. As model substances dyes for colouring textiles and was tewaters of dyehouses containing also auxiliary materials were used. T he waters were treated with laser radiation of different wavelengths ( 193 nm - ArF, 248 nm - KrF) frequently under addition of hydrogen pero xide or ozone as oxidizers. It was found that with the 193 nm radiatio n at the same energy dose and a substantially lower amount of added ox idizers the decolourization effect was greater than at 248 nm. The red uction of TOC was also faster. The HPLC spectra of the reaction produc ts at the two laser wavelengths showed good agreement, so that the adv antage of the shorter-wavelength radiation is the simplier achievement of the activation energies necessary for oxidation or decomposition r eactions. (C) 1997 IAWQ. Published by Elsevier Science Ltd.