Extracellular azo dye oxidation: Reduction of azo dye in batch reactors with biogenic sulfide

Abstract

In this study, the sulfide-based reduction of azo dyes (Acid Blue 264) was investigated. Sulfate was reduced to sulfide with an ethanol-fed sulfate reduction reactor and the sulfide produced was used to reduce azo dyes in separate batch reactors using sulfide as the electron carrier. The Box-Behnken experiment design method was used to identify how operational parameters affect the decolorization efficiency. As independent variables, initial dye concentration, sulfide concentration and reaction time were selected while dye removal was considered as the response function. Based on the Box Behnken design, the higher regression coefficient (R-2=0.9397) shows that the experimental results are in good agreement with model predictions. At the initial dye concentration of 80 mg/L, the highest dye removal efficiency, about 82.39%, was obtained at the sulfide concentration of 50 mg/L and the reaction time of 25 h. This study showed that Box Behnken's model prediction was a suitable approach for identifying the best conditions for dye removal.