Effect of the deposition of Ca2+on the Fe-based catalyst in the catalytic ozonation of high-salinity wastewater

Fe-based catalysts used for catalytic ozonation process (COP) were widely investigated. However, there was almost no research on engineering application of Fe-based catalyst for advanced treatment of high-salinity pharmaceutical wastewater. In this study, Fe shavings were used to form Fe-based monolithic catalyst pack-ing, which was effectively applied to a pharmaceutical factory. It was found that chemical oxygen demand (COD) removal decreased by similar to 20% after more than three years of operations. Regression analysis showed that ozone (O-3) dosage and hydraulic residence time (HRT) had significant impact on the catalytic performance. The characterization results of Fe-based catalyst demonstrated that calcium carbonate (CaCO3) was deposited on the surface of the Fe-based catalyst inside the packing, and partial gamma-FeOOH were converted into alpha-FeOOH. These phenomena impaired the catalytic capacity of Fe-based catalyst and further reduced the production of hydroxyl radicals (center dot OH). Besides, the increase in bulk density of Fe-based monolithic catalyst packing indicated that the packing has collapsed. By comparing the surface film properties of Fe-based catalyst in wastewater with different salinity, it was concluded that high-salinity wastewater would accelerate the corrosion of Fe-based catalyst. This study can provide a reference for the engineering application of catalytic ozonation technology in high-salinity wastewater.