Catalytic Ozonation of Oxalate with a Cerium Supported Palladium Oxide: An Efficient Degradation Not Relying on Hydroxyl Radical Oxidation

Abstract

The cerium supported palladium oxide (PdO/CeO2) at a low palladium loading was found very effective in catalytic ozonation of oxalate, a probe compound that is difficult to be efficiently degraded in water with hydroxyl radical oxidation and one of the major byproducts in ozonation of organic matter. The oxalate was degraded into CO2 during the catalytic ozonation. The molar ratio of oxalate degraded to ozone consumption increased with increasing catalyst dose and decreasing ozone dosage and pH under the conditions of this study. The maximum molar ratio reached around 1, meaning that the catalyst was highly active and selective for oxalate degradation in water. The catalytic ozonation, which showed relatively stable activity, does not promote hydroxyl radical generation from ozone. Analysis with ATR-FTIR and in situ Raman spectroscopy revealed that 1) oxalate was adsorbed on CeO2 of the catalyst forming surface complexes, and 2) O3 was adsorbed on PdO of the catalyst and further decomposed to surface atomic oxygen (*O), surface peroxide (*O2), and O2 gas in sequence. The results indicate that the high activity of the catalyst is related to the synergetic function of PdO and CeO2 in that the surface atomic oxygen readily reacts with the surface cerium-oxalate complex. This kind of catalytic ozonation would be potentially effective for the degradation of polar refractory organic pollutants and hydrophilic natural organic matter.

Mechanism of Catalytic Ozonation in Fe2O3/Al2O3@SBA-15 Aqueous Suspension for Destruction of Ibuprofen

“…Both samples exhibited a new band appearing at 913 and 938 cm −1 , respectively, which was assigned to a surface atomic oxygen species. 13,28,29 Oppositely, no surface atomic oxygen formed on the surface of SBA-15 and Fe 2 O 3 /SBA-15 with ozone aqueous solution (SI Figure S13). These results indicated that ozone was decomposed into a surface atomic oxygen when it was adsorbed on stronger Lewis acid sites of Al 2 O 3 @SBA-15, while the ozone adsorbed on Lewis acid sites of iron was not converted into the surface atomic oxygen.…”

“…12,13 These examples show irrefutably that our understanding of the catalytic ozonation in aqueous phase seems to be very poor.…”

Synergistic Effect of Copper and Cobalt in Cu-Co-O Composite Nanocatalyst for Catalytic Ozonation

“…16 It was applied here to get insights on the interaction between ozone and the catalyst. Figure 9( increased signicantly for Cu-Co-O composite in presence of ozone.…”

Role of Fe/pumice composition and structure in promoting ozonation reactions

“…The pH of the solution has a remarkable effect on ozone decomposition to generate • OH [45]. As shown in Fig.…”