Catalytic Ozonation by Copper Modified Sepiolite for the Degradation of Oxalic Acid in Water

ABSTRACT Copper modified sepiolite (Cu-SEP) with high catalytic activity was successfully prepared and used in ozonation to remove oxalic acid from water. The influence of Cu-SEP dosage, initial pH, ozone dosage and initial oxalic acid concentration on the removal of oxalic acid in heterogeneous catalytic ozonation was investigated, and XRD, FTIR, SEM, TEM and XPS were employed to characterize the Cu-SEP to clarify its working mechanism in ozonation. The experimental results showed that under the optimal condition, the removal of oxalic acid could reach 95.8%. Cu element successfully replaced Mg in the sepiolite lattice to form the Cu-SEP, it existed mainly in the form of Cu2+. Cu-SEP contained abundant surface hydroxyl groups, which played an important role in the catalytic ozonation process. With the combination of free radical quenching experiment, the possible mechanism of Cu-SEP catalyzed ozonation to degrade oxalic acid was proposed. After ozonation, Cu-SEP retained the original structure, and exhibited excellent stability and reusability.