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

). Em relação à toxicidade apresentada pelos produtos formados durante a degradação perante as sementes de alface (Lactuca sativa) os dados sugerem que não foi apresentada toxicidade considerável, uma vez que não houve redução significativa da porcentagem de germinação nem influência na porcentagem de crescimento das raízes e radículas, contudo, a associação TiO 2 /H 2 O 2 apresenta maior toxicidade nas primeiras horas de irradiação e posterior redução da mesma ao final de seis horas, enquanto que o TiO 2 somente aumenta um pouco sua toxicidade no final dos experimentos. Porém, comparados ao efluente bruto, ambos apresentaram redução de toxicidade, ou seja, os produtos fotogerados apresentam-se menos tóxicos que o efluente inicial.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 TiO 2 or TiO 2 /H 2 O 2 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 TiO 2 /H 2 O 2 association was more efficient in the mineralization of textile effluents than TiO 2 alone, with high mineralized ion concentrations (NH 4 + , NO 3 -, and SO 4 2-) 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 TiO 2 /H 2 O 2 association was more toxic in the first hours of irradiation and less so in the end of the 6 h irradiation, the toxicity of TiO 2 increased only slightly in the end of the experiments. Comparatively, the photogenerated products of both the TiO 2 and the TiO 2 /H 2 O 2 association were less toxic than the in natura effluent.

Differential Degradation and Detoxification of an Aromatic Pollutant by Two Different Peroxidases

“…The toxicity of SRB dye before and after complete enzymatic degradation was measured using the phytotoxicity effect of the SRB dye samples on the germination of lettuce ( L. sativa ) seeds, as previously described [56] with slight modifications. Briefly, Whatman filter paper (No.…”

CaTiO3 Perovskite in the Photocatalysis of Textile Wastewater

“…Textile wastewater, polished by photocatalysis (240 min of irradiation), showed an increase of about 27% (from 55% to 82%) in the relative germination index when compared to the wastewater without treatment. Garcia et al (2009) reached 75% of germination after photocatalysis of textile wastewater with TiO2 P25 with the same irradiation time. The treated tannery wastewater also showed an increase in RG index (9%) compared to the wastewater Rev.…”

Fitotoxicidade e citogenotoxicidade da água e sedimento de córrego urbano em bioensaio com Lactuca sativa

“…Além de metais pesados vários contaminantes com potencial fitotóxico foram encontrados em estudos com solos e com sedimentos de corpos d'água em áreas urbanizadas, como hidrocarbonetos aromáticos policíclicos (HAP), compostos organoclorados e outros poluentes orgânicos (Garcia et al, 2009). Comumente, esses contaminantes são relatados em águas do escoamento superficial pela lavagem do solo de áreas agrícolas e do asfalto (Bollmann & Marques, 2006) e em efluentes de indústrias têxteis (Garcia et al, 2009).…”

“…Comumente, esses contaminantes são relatados em águas do escoamento superficial pela lavagem do solo de áreas agrícolas e do asfalto (Bollmann & Marques, 2006) e em efluentes de indústrias têxteis (Garcia et al, 2009). …”