Decolourization of acid orange 7 dye from wastewater by homogeneous ozone process

Thi Thom Dang^{1, 2*}, Van Manh Do^{1, 2}, Thanh Duong Dao³, Do Hung Phan¹, Hoai Chau Nguyen^{1, 2}, Van Tuyen Trinh^{1, 2}, Hung Viet Pham⁴

¹Institute of Environmental Technology, Vietnam Academy of Science and Technology

²Graduate University of Science and Technology, Vietnam Academy of Science and Technology

³University of Science and Technology of Hanoi, Vietnam Academy of Science and Technology

⁴Key Laboratory of Analytical Technology for Environmental Quality and Food Safety Control (KLATEFOS) VNU University, Vietnam National University, Hanoi

Received 6 June 2022; accepted 14 October 2022

Abstract:

The aim of this study is to evaluate the removal efficiency of acid orange 7 (AO7), which has a large range of uses the textile industry, by the homogeneous ozone process. The highest decolourization of AO7 solution, about 80%, was achieved at pH 3 after 1 h of treatment. The efficiency decreased with increasing initial pH, namely, efficiencies of 75, 60, 55, and 39% were achieved for pH 5, 7, 9, and 10, respectively, with an initial concentration of 100-107 ppm and initial O₃ concentration of 5.8-6.5 ppm. The decolourization process of AO7 by homogenous ozonation was assumed to follow the pseudo-first order kinetics and kinetic constants of the decolourization of AO7 confirmed the ability of ozonation to remove this dye. The rate constant of decolourization of AO7 was faster at pH 3 and 5 (k=3.10^-4 s^-1) and lower at pH 7, 9, and 10 (k=2.10^-4 s^-1).

Keywords: decolourization, acid orange 7, homogeneous ozone process.

Classification number: 2.2