Heterogeneous oxidation of diclofenac in the presence of α-MnO₂ nanorods: influence of operating factors and mechanism

Diclofenac (DCF), one of the pharmaceutical and personal care products that has been widely detected in water, was selected as a model pollutant to evaluate the oxidation activity of α-MnO₂ nanorods. The results showed that the heterogeneous oxidation process is highly pH dependent, with higher degradation efficiency at lower pH values. The complete removal of DCF was obtained within 80 min at the solution pH value of 2.5. The oxidation kinetics of DCF can be modeled by Langmuir–Hinshelwood equation (R² > 0.999). The effects of various operating parameters, including initial solution pH, α-MnO₂ dosage, anions, and cations, on the oxidation efficiency were investigated in detail. A possible reaction pathway for DCF was proposed. In addition, it was demonstrated that the α-MnO₂ nanorods can be recycled without decreasing their oxidation activity after 10 cycles.