Degradation of azo dye by three clean advanced oxidation processes: Wet oxidation, electrochemical oxidation and wet electrochemical oxidation—A comparative study

Abstract

This work compared the degradation behaviors of an azo dye, cationic red X-GRL, by three clean advanced oxidation processes: wet oxidation (WO), electrochemical oxidation (EO) and wet electrochemical oxidation (WEO). It was found that the WO process was readily to remove color while the EO process was prone to decompose pollutants. Integrated with the advantage of two processes, the WEO process posed synergetic effects for both efficient removal of color and COD. Even at the low temperature of 120 °C, the color could be almost completely removed at 60 min, and the COD removal was about 43.2% at 120 min, which was greatly protomted from that by WO at similar conditions (about 7.8%). And it demonstrated a better performance under a reduced temperature and a wider dye concentration range, representing the most promising alternative for environmental application among the three processes. The main degradation products for three processes were detected and a simplified five-stages degradation pathway was suggested, which indicated that the WEO process mineralized much more completely than the other two processes.