Photoassisted Electrochemical Treatment of Azo and Phtalocyanine Reactive Dyes in the Presence of Surfactants

Abstract

An electrochemical treatment (EC) was applied at different intensities to degrade the chromophoric groups of dyes C.I. Reactive Black 5 (RB5) and C.I. Reactive Blue 7 (Rb7) until uncolored species were obtained. Decolorization rate constants of the azo dye RB5 were higher than the phtalocyanine Rb7 ones. In addition, the EC treatment was more efficient at higher intensities, but these conditions significantly increased the generation of undesirable by-products such as chloroform. The combination of EC with UV irradiation (UVEC) drastically minimized the generation of chloroform. The photo-assisted electrochemical treatment was also able to achieve decolorization values of 99%. Finally, mixtures of dyes and surfactants were treated by EC and UVEC. In the presence of surfactants, the decolorization kinetic of dyes was slowed due to the competitive reactions of surfactants degradation. Both methods achieved total decolorization and in both cases, the generation of haloforms was negligible.

Sustainable Wastewater Treatment via Dye–Surfactant Interaction: A Critical Review

“…This is an efficient method of decolorization of textile effluents; however, the degraded dye molecules are not separated from the effluents, which still remains as a matter of environmental concern. The presence of surfactants in the effluents sometimes decreases the decolorization kinetics of dyes because of the competitive reactions of surfactant degradation but still achieves total decolorization …”

Reduction of Cost and Environmental Impact in the Treatment of Textile Wastewater Using a Combined MBBR-MBR System

“…In general, the acceptance limit for color differences in the textile industry is one unit (DE CMC (2:1) ≤ 1). This criterion is widely used in dyeing quality control to compare the color differences between two fabric samples [32].…”

LCA study of a new electrochemical and ultraviolet (EC-UV) combined system to decolourise and reuse textile saline effluents: Environmental evaluation and proposal to improve the production process

“…Among the different AOPs, our research group has demonstrated the effectiveness of the indirect electrooxidation assisted by UV irradiation (EC-UV) to treat effluents from the dyeing process with reactive dyes [15,16]. This kind of dyes requires the addition of high amount of salts to carry out the dyeing process.…”

“…Consequently, the treatment is performed without adding any chemicals and no sludge is generated. The irradiation with UV light of effluents previously treated in the electrochemical cell allows to avoid the emission of chlorinated by-products [15,16]. The EC-UV treatment was developed at industrial scale, optimized and installed in a Spanish textile mill.…”