Degradation of Acid Azo Dyes Using Oxone Activated by Cobalt Titanate Perovskite

Abstract

Chemical degradation by sulfate radicals from activation of Oxone is one of the most attractive advanced oxidation processes (AOPs) for treating toxic acid azo dyes. However, development of an effective and recyclable heterogeneous catalyst for activating Oxone is still highly desired. In this study, cobalt titanate perovskite (CoTiO3) was synthesized and employed as a heterogeneous catalyst for activating Oxone to degrade acid azo dyes, Acid Red 27 (AR), Acid Yellow 17 (AY), and Acid Blue 120 (AB). As CoTiO3 does not adsorb these azo dyes, and Oxone alone is ineffective to degrade them, the combination of CoTiO3 and Oxone tremendously improves degradation of acid azo dyes, validating that CoTiO3 can activate Oxone. The analyses of Co species before and after Oxone activation validate that the activation mechanism can attributed to Co2+ of CoTiO3, which transforms between Co2+ and Co3+ to activate Oxone. Through examining the effects of radical scavengers, the degradation of these azo dyes is primarily owing to sulfate radicals and derivative hydroxyl radicals to a lesser extent. In addition, CoTiO3-activated Oxone is much favorable at elevated temperature and under a neutral condition (pH = 7), while the addition of NaCl slightly slows the dye degradation kinetics by CoTiO3-activated Oxone. CoTiO3 can also be reused for multiple cycles (up to 5 cycles) and remains effective to activate Oxone. CoTiO3-activated Oxone exhibits the highest degradation efficiency for AR, followed by AB and finally AY, when AR, AB, and AY co-exist. This study demonstrates that CoTiO3 is a promising catalyst for activating Oxone to degrade typical acid azo dyes. The findings obtained here can provide further understanding and optimized parameters for using CoTiO3 to activate Oxone in treatments of acid azo dye-containing wastewater.