Decolorization of Reactive Dyes from Aqueous Solution Using Combined Coagulation-Flocculation and Photochemical Oxidation (UV/H₂O₂)

Abstract

Removal of reactive dyes from wastewater is a great environmental concern. Attempts were made to study the performance of a coupling process of coagulation-flocculation (CF) and photochemical oxidation (PCO) for the removal of two reactive dyes (Reactive Black 5 (RB 5) and Reactive Orange 12 (RO 12)) from aqueous solution. The CF experiments were conducted using alum as coagulant and polyacrylamide as coagulant aid whereas the PCO tests were carried out using H₂O₂ in the presence of UV light irradiation. Effects of various process parameters such as pH, coagulant dose and coagulant aid dose on the CF process, and H₂O₂ dose and UV exposure time on the PCO method have been studied. The study reveals that only the CF process is not sufficient to treat the dye solution. The CF step could remove 52.30% and 41.38% of RB 5 and RO 12, respectively. At the best conditions of process parameters, the combined CF-PCO method results in color removals of 87.10% and 82.53% for RB 5 and RO 12, respectively. The combined process of CF and UV/H₂O₂ may be a useful treatment technique for wastewater contaminated with reactive dyes.