Catalytic ozonation by palladium–manganese for the decomposition of natural organic matter

In this study, magnetic nanoparticles of Fe3O4/SiO2/Pd-Mn were synthesized by wet deposition method for heterogeneous catalytic ozonation to remove the organic compounds in water. The as-synthesized Fe3O4/SiO2/Pd-Mn was characterized by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS) to clarify its chemical and physical properties. SEM images indicated that the particle size of Fe3O4/SiO2/Pd-Mn was about 50–100 nm. EDS results confirmed with the XRD findings, illustrating that Pd and Mn were successfully coated on the catalyst with the at% of 1.66 and 2.40%, respectively. The degradation efficiency of organics in water was examined by A254 and dissolved organic compounds (DOC). Under heterogeneous catalytic ozonation treatment, the decomposition efficiency of A254 and DOC of raw water, from Te-Chi reservoir, achieved 70 and 60%, respectively. The decomposition efficiency of A254 and DOC increased to 80 and 90% when the pH was adjusted to 11. The calculated DOC degradation rate constant (kd) for was 6.5 × 10−2 min−1 at pH 11 via heterogeneous catalytic ozonation method. Hydroxyl radicals were dominated for the removal of organic compounds in our heterogeneous catalytic ozonation system as an evidence of 7-hydroxycoumarin generation in radical scavenger experiments. In addition, the removal efficiency of THMFPs (Trihalomethane Formation Potentials) was 74 and 38% for Fe3O4/SiO2/Pd-Mn heterogeneous ozonation and sole ozonation, repectively, illustrating the enhanced oxidation ability. The endpoint of ozonation process can be controlled by the modeling results of Nernst simulating as ORPA254 = 27240 − 14755.3 ln[A254] − 2486.91 pH + 2.64 ln[THMFPs].