Environmental aspects on the photodegradation of reactive triazine dyes in aqueous media

Reactive dyes are the most important in textile industry for dyeing cotton. In spite of the best technological developments of dyeing processes, complete dye exhaustion is not possible. Substantial amounts of dyes are lost resulting with the considerable amounts of intense colored wastewater that have an adverse environmental effect. Such wastewater should be adequately treated prior to the discharge in order to preserve the eco-balance in receiving waters.This study concerns the environmental aspects of the triazine reactive dye by assessing the ecological water quality parameters. The selected reactive dyes with triazine anchor and different chromophore groups are considered. Decolorization of dye solutions due to the destruction of chromophoric system under UV-C irradiation are monitored by UV–vis spectrophotometry. Dye degradation is also characterized by the decrease in total organic content due to the mineralization of dye solution. The corresponding changes in biodegradability and toxicity on Vibrio fischery of dye aqueous solution are monitored during the applied treatment processes. The values of determined ecological parameters are discussed and correlated with the structural characteristics of selected dyes. It was determined that dyes with larger spherical molecular structure, higher masses and fewer number of rings are more suitable to biodegradation. The initial toxicity of studied triazine dyes depends mainly on polarizibility and aromaticity of particular dye molecule.

► The photodegradation of nine triazine dye by UV-C irradiation was studied.
► The relationship between photodegradation parameters and dye structures was established.
► The relationship between biodegradability and dye structures was established.
► The relationship between toxicity and dye structures was established.