Efficient degradation of pyruvic acid in water by catalytic ozonation with PdO/CeO2

PdO/CeO2 prepared at various calcination temperatures and Pd loading percentages significantly enhanced the degradation of pyruvic acid (PA) in water by catalytic ozonation compared to ozonation alone. The surface property of PdO/CeO2 was characterized with X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, BET surface area and zeta potential, and its relationship with the catalytic activity was examined and discussed in detail. Results indicate that PdO/CeO2 with 4.0% of Pd loading and calcined at 550 °C showed the highest catalytic activity in PA degradation by ozone. Complete PA (5 mg L−1) removal was quickly achieved in catalytic ozonation at 5 min and pH 4.7, in which PdO and CeO2 exerted a synergic effect. Moreover, PdO/CeO2 exhibited a persistently high activity throughout the semi-continuous ozonation of PA. It was observed that the surface contents of Ce(III) and Pd(II) were closely related to the catalytic activity and the optimal surface molar ratio of Ce(III)/Pd(II) was around 1:1. The positively charged surface of PdO/CeO2 also played an important role in catalyzing PA degradation by ozone.

Graphical abstractSynergetic effect of Pd and Ce oxides in catalytic ozonation of pyruvic acid.Figure optionsDownload full-size imageDownload high-quality image (179 K)Download as PowerPoint slideHighlights► PdO/CeO2 is an effective catalyst for ozonation of pyruvic acid in water. ► Surface Ce3+/Pd2+ molar ratio and metal charging states dominate catalyst activity. ► PdO/CeO2 catalysis is ascribed to the synergetic effect of Pd and Ce.