Avaliação ecotoxicológica de Rodamina B e azul reativo QR-19 antes e após fotocálise heterogênea com sistema Pu/Bentonita/Nb₂O₅

Abstract

Textile sector effluents represent one of the primary sources of aquatic pollution due to their high organic load, intense coloration, and presence of recalcitrant compounds, such as synthetic dyes, notably Rhodamine B (RhB) and Reactive Blue QR-19 (QR- 19), which are widely used and resistant to degradation by conventional methods. In this context, heterogeneous photocatalysis using a bentonite/niobium pentoxide (Nb₂O₅) catalyst supported on rigid polyurethane foam emerges as a promising alternative for treating textile effluents. The present study aimed to evaluate the ecotoxicity of these dyes before and after photocatalytic treatment, employing test organisms from different trophic levels: Daphnia magna, Lactuca sativa, and Allium cepa. The assays assessed acute toxicity, phytotoxicity, and cytogenotoxicity, respectively. For Rhodamine B, assays with D. magna indicated that photocatalytic treatment did not reduce acute toxicity, with the same response level maintained before and after the process. In L. sativa, the crude sample caused inhibition of germination and root growth, with complete elimination of phytotoxicity following photocatalytic treatment. In A. cepa, no cytotoxicity was detected under any of the evaluated conditions; however, a slight increase in chromosomal alteration and mutagenicity indices was observed after treatment, possibly associated with the formation of intermediate by-products. For Reactive Blue QR-19, assays with D. magna indicated low acute toxicity, with a tendency toward reduction after treatment. In L. sativa, the dye showed no phytotoxicity under any of the evaluated conditions. Similarly, in A. cepa, no cytotoxicity was detected, with a tendency toward a reduction in chromosomal alteration and mutagenicity indices after treatment. The results demonstrate that decolorization does not necessarily imply a reduction in toxic potential, reinforcing the importance of ecotoxicology as an complementary tool in the environmental validation of textile effluent treatment processes.