Effect of Salinityon the Fe-Based Catalyst Performanceduring Intermittent Operation of the Ozonation Process

The catalytic ozonation process (COP) is an effective method for wastewater treatment. Previous studies have shown that Fe-based catalysts can yield good results in full-scale ozonation treatment of high-salinity wastewater, which is typically difficult to treat. However, chloride ions (Cl^–) affect the service life and performance of the catalyst during the stoppage of COP operations in actual practice. Therefore, a wet–dry cyclic test device was constructed to simulate the corrosion behavior under saline conditions. The results demonstrated that the Fe-based catalyst formed a relatively dense thick film structure after repeated wet–dry cycles, which led to enhanced durability, with a decreased corrosion current of ≥100 μA·cm^–2, and a slight enhancement in catalytic performance, with a maximum increase of approximately 6% in total organic carbon removal. However, long-term dry storage under high Cl^– conditions (50,000 mg/L) resulted in cavity formation within the material, leading to an increased risk of losing the effective catalyst layer. Overall, dry storage was a good low-cost option under low Cl^– conditions, whereas wet storage (with ozone aeration) was a better choice under high Cl^– conditions as it consumed less alloy and could prolong the service life of the catalyst. This study not only clarifies the formation mechanism of the thick film structure and changes in catalytic performance and durability of Fe-based catalysts after wet–dry cycles but also provides a scientific foundation for optimizing catalyst storage conditions. Additionally, the study offers a valuable insight for the economic and sustainable development of Fe-based catalysts for COP by proposing suitable storage conditions and a low-cost detection method.