Phytoremediatgion of wastewater containing azo dye by sunflowers and their photosynthetic response

Abstract

Azo dyes, as the largest group of synthetic dyes released from textile and dyestuff industries, have caused serious environmental problems. We investigated the removal ability and physiological response of sunflowers to simulated wastewater containing azo dyes with concentration similar to real wastewater or above. The percent decolorization of the three azo dyes within 4days varied greatly. For the same dyes, the percent decolorization was descending with the primary dye concentration increasing. The percent decolorization of Bismark browny, Evans blue and Orange G at same concentration was also descending. The average percent decolorization of the three azo dyes at 100mg/L within 4days was 62.64%. The physiological effects of the tested azo dyes on sunflowers were also very different. The stress effects of Bismark browny, Evans blue and Orange G at same concentration were also descending. All tested azo dyes reduced significantly normalized relative transpiration (NRT), net photosynthesis rate (Pn), transpiration intensity (Tr) and stomatal conductance (Gs) of sunflowers. The percent of decline of all the indicators such as NRT, Pn, Tr and Gs was less than 50% when concentration of azo dyes was 100mg/L. The result showed that sunflowers can survive in water containing 100mg/L all tested azo dyes. We conclude that sunflowers can be used for phytoremediation of wastewater containing azo dyes.