Understanding the Efficiency of Catalytic Ozonation for the Degradation of Synthetic Dyes in Water: A Study of Degradation Mechanism and Pathways

Dyes in wastewater are an environmental issue due to the persistent nature of these compounds. This comparative study examined the efficiency of ozonation and catalytic ozonation using Fe 3+ /O 3 for the degradation of two selected dyes, Methylene Blue (MB) and Methyl Orange (MO). For MB, ozonation alone achieved 65% degradation within the maximum reaction time of 15 min, whereas 100% degradation was obtained with the Fe 3+ /O 3 method in the same time. On the other hand, for MO, ozonation alone resulted in 85% degradation within 15 min, while the Fe 3+ /O 3 method achieved 100% degradation in 10 min. The effect of Fe 3+ dose was also investigated, and 3 ppm was found to be the most efficient. The scavenger effect highlighted that • OH radicals were the dominant species for degradation. For MB, the highest degradation rate was observed at pH 9, which is attributed to catalyzed ozone decomposition, thereby enhancing the generation of • OH radicals to a higher concentration. For MO, the degradation rate was highest at pH 5. LC-MS analysis was performed to explore MB degradation products formed during Fe 3+ /O 3 treatment. Five main degradation products were observed, with the main pathway involving the generation of P1, P2, and P3. Based on the results, the Fe 3+ /O 3 method is considered efficient for wastewater treatment. This study highlights the Fe 3+ /O 3 method as a sustainable solution for the degradation of dyes from textile wastewater.