Evolutive follow-up of the photocatalytic degradation of real textile effluents in TiO2 and TiO2/H2O2 systems and their toxic effects on Lactuca sativa seedlings

Abstract

Textile industry wastes raise a great concern due to their strong coloration and toxicity. The objective of the present work was to characterize the degradation and mineralization of textile effluents by advanced oxidative processes using either TiO2 or TiO2/H2O2 association and to monitor the toxicity of the products formed during 6 h irradiation in relation to that of the in natura effluent. The results obtained demonstrated that the TiO2/H2O2 association was more efficient in the mineralization of textile effluents than TiO2 alone, with high mineralized ion concentrations (NH4+, NO3-, and SO42-) and significant organic matter reduction rates (represented by the COD and TOC). The toxicity of the degradation products to lettuce seeds (Lactuca sativa) was not significant, since percent germination was not significantly affected and neither was root and sprout percent growth. However, while the TiO2/H2O2 association was more toxic in the first hours of irradiation and less so in the end of the 6 h irradiation, the toxicity of TiO2 increased only slightly in the end of the experiments. Comparatively, the photogenerated products of both the TiO2 and the TiO2/H2O2 association were less toxic than the in natura effluent. © 2009 Sociedade Brasileira de Química.