An integrated permanganate and ozone process for the treatment of textile dyeing wastewater: Efficiency and mechanism

Abstract

Textile dyeing effluent has been the focus of considerable research because of its adverse effects on aquatic biota. Here, we present the first comprehensive study of a combined permanganate and ozone (KMnO4O3) technique to treat different kinds of textile dyeing wastewater. We investigated the effects of process parameters on TOC and COD removal and the toxicity of the wastewater after KMnO4O3 treatment. The synergistic mechanism involved in the KMnO4O3 process is also discussed. The results indicate that KMnO4O3 treatment is efficient in treating many kinds of textile dyeing wastewater. The TOC, COD, and toxicity were reduced by approximately 70%, 80%, and 34.4–95.5%, respectively, using a KMnO4 dosage of 1.5 mM, an O3 dosage of 10 mg/L, a pH value of 7, and a reaction time of 30 min. Furthermore, biodegradability was increased to 0.33–0.68. The combined use of KMnO4 and O3 provided synergetic and complementary advantages. On the one hand, oxidation of pollutants on suspended solid surfaces and in the aqueous phase was enhanced by the stirring action of O3 molecule bubbles. On the other hand, small molecular organic compounds and fine particles were coagulated by KMnO4 and its intermediate oxidations. X-ray photoelectron spectroscopy results indicate that the valence state of manganese changed after KMnO4O3 treatment, and the manganese intermediate catalysing O3 process contributed to the removal of 20% of COD and 19% of TOC. It was therefore determined that the KMnO4O3 treatment is a promising method for use in the treatment of textile dyeing wastewater.