Highly efficient catalytic ozonation for oxalic acid mineralization with Ag2CO3 modified g-C3N4: Performance and mechanism

Abstract

A series of Ag2CO3 doping g-C3N4 composites labeled as AgCNx-T (x represented the weight content of g-C3N4 and T referred to the hydrothermal temperature) were synthesized by a simple precipitation method. Various techniques such as BET, XRD, FTIR, SEM, and XPS were employed to explore the morphology structure and physicochemical properties of catalysts ascribed to the decoration of Ag2CO3 onto g-C3N4 and the results revealed that the hydrothermal temperature played an important role in the size dimension and crystallinity of Ag2CO3. It was worthy noted, the decorating of Ag2CO3 would provide more active sites on the catalyst surface, strengthen the regeneration and transmission of electrons, improve the utilization of O3, and promote the generation of reactive oxygen species, thus improving the catalytic ozonation performance. Amongst, the AgCN0.4-100 composite had the optimal performance with 99.99% of OA degradation efficiency and 93.19% of OA mineralization. Moreover, the AgCN0.4-100 exhibited satisfactory reusability for multiple consecutive cycles (≥5) with low Ag ion release (<0.3 mg L−1). The reactive species (O2•− and 1O2) were verified to take predominant roles in the reaction through the radical scavenger experiments and ESR spectra. Accordingly, an empirical kinetic model was established to predict OA concentration with the given operational parameters. Finally, the synergistic mechanism of OA degradation in catalytic ozonation system was also proposed, which possessed promising prospect in practical water treatment for environmental applications.