Decolorization and Degradation of Erioglaucine (Acid Blue 9) Dye in Wastewater

Abstract

Erioglaucine (CAS No. 3844-45-9) is a widely used acid aminotriphenylmethane dye of an intense blue color. Erioglaucine containing wastewater streams are not affected by activated sludge treatment plants. Therefore, pretreatment is necessary before discharging. In the industry the standard procedure is to use NaOCl for this purpose. Experiments showed that wastewater treated with this method could contain between 100 and 200 mg l⁻¹ of adsorbable organic chlorine (AOX) compounds of a questionable ecotoxicological relevance. Alternative treatment methods with reagents containing H₂O₂ have been investigated. The experimental results are assessed in terms of color and DOC reduction, H₂O₂ consumption, and enhancement of biodegradability. A combination of activated carbon and H₂O₂ proved not to be a viable alternative. Treatment with Fentons reagent (H₂O₂ and Fe²⁺) was found to be effective in terms of color removal as well as enhanced biodegradability. In the optimum operating range of pH and H₂O₂/Fe²⁺ ratio 5 ml of a 35% H₂O₂ solution are sufficient for the treatment of 1g Erioglaucine. Between 10 and 40°C, the reaction is completed in less than 4h. The environmental effects of the Erioglaucine degradation with Fentons reagent are small compared with the NaOCl treatment. Therefore, oxidation of Erioglaucine containing wastewater with NaOCl should be replaced by a treatment with Fentons reagent. The assumption is that the results obtained for Erioglaucine also apply to other structurally related aminotriphenyl dyes.

Keywords:

• Erioglaucine
• Acid Blue 9
• decolorization
• sodium hypochlorite
• Fentons reagent
• pharmaceutical industry
• H2O2
• NaOCl
• biodegradability