Efficient Degradation of Ketoprofen by MnO 2 -Modified Biochar via Heterogeneous Catalytic Ozonation

In recent years, biochar catalysts have shown high efficacy in catalytic ozonation for water treatment, as they promote O ₃ transformation to degrade organic pollutants. However, current challenges persist in catalytic ozonation systems: variations in pyrolysis conditions and precursors can compromise long-term operational stability, while complex aqueous environments often result in suboptimal degradation efficiency. This study prepared modified biochar with different pyrolysis temperatures and MnO ₂ loading ratios via oxygen-limited pyrolysis and co-precipitation, among which MBC900(1:20) exhibited the highest catalytic activity, achieving 88% degradation of ketoprofen (KTP) — 34% higher than the sum of ozonation alone and adsorption alone. Characterization revealed that the modified biochar possessed a rougher surface, increased specific surface area (SSA) with a shift toward micro/mesopores, amorphous MnO ₂ (mainly Mn ⁴⁺ ), and additional Mn–O bonding. Catalytic performance was enhanced with higher O ₃ dosage, catalyst loading, and temperature, but decreased with higher initial KTP concentration, while pH and H ₂ PO ₄ ^– concentration showed an initial increase followed by a decline in degradation efficiency. Mechanistic studies identified ^• OH as the dominant oxidant, leading to a mineralization rate of 44%—17% higher than O ₃ alone—with degradation occurring via hydroxyl radicals ( ^• OH) attack on the carboxyl group and benzene ring. This work offers an economical and eco-friendly approach for water pollution remediation.