Influence of electrochemical pre-treatment in dyeing wastewater reuse for five reactive dyes

Abstract

In this study, the influence of an electrochemical pre-treatment was evaluated in dyeing wastewater reuse for five reactive dyes for cotton fabrics. The most proper dyeing method was established and the influence of alkali was also studied. Wastewater was treated in an electrochemical cell at 20 Lh−1 and 40 mA/cm2 for between 3 and 15 minutes before being reused. During the electrochemical treatment the evolution of the dye degradation was evaluated by COD measurements. From the results, it can be concluded that 70% of the wastewater can be satisfactorily reused by direct bath reuse with most of the reactive dyes obtaining DE (CMC (2:1)) values below 1 with respect to the reference. Differences of DE (CMC (2:1) can be improved up to 75% by applying an electrochemical pre-treatment. In DE (CMC (2:1)) values, DL* was found to be the most influential parameter. Finally, the influence of the level of dye degradation in the wastewater was observed as non-relevant in the direct reuse of the bath for most of the studied dyes.