Toxicity removal by Daphinia similis assay in BTEX contaminated groundwater using nanometric TiO₂/ZrO₂ film and black light

In this work, a photocatalytic tubular reactor, with a nanometric TiO₂/ZrO₂ film, immobilized on glass substrate, was developed in order to investigate the degradation of volatile organic compounds, such as, benzene, toluene, ethylbenzene and xylene (BTEX ) in groundwater sample, under black light irradiation (365nm). The BTEX compound were determined by solid phase microextraction (SPME) technique and analyzed by Gas Chromatography - Ionization Flame Detection (CG-FID). The efficiency of photocatalytic process was evaluated by determination of BTEX removal and toxicity, using Daphnia similis as organism-test. The influence of the initial concentration of BTEX in the degradation process was investigated. The degradation process of sample groundwater contaminated with BTEX (145μg/L) from gasoline, resulted in 90% of efficiency after 120 minutes of treatment. The toxicity (EC50-48 h) of the groundwater sample to Daphnia similis was 14.1% (10.5-19.0) for untreated samples. After 30 min of treatment, the EC50-48 h was of 84.3 (71-100%). The benzene efficiency removal was reduced in function of the increase of its initial concentrations that observation was not found for the other compounds studied. (paper)