Uncommonly efficient degradation performance of photocatalytic ozonation towards tetracycline over synthesizing 3-D g-C3N4 nanosheet based on Si-O-Co framework

3D g-C3N4/Co-MCM-48 was successfully prepared by constructing mesoporous Si-O-Co framework as the template for loading g-C3N4 nanosheet. Excellent synergistic effect and stability in photocatalytic ozonation of tetracycline (TET) were observed owe to the ordered and unique catalyst structure. The results indicated that g-C3N4/Co-MCM-48 possessed better catalytic performance for TET degradation and had an apparent advantage compared with bulk g-C3N4. The highly dispersed Co atoms in the framework acted as reaction centers of ozonation and promoted separation of photo-induced carriers, which further improved the synergistic effect and produced abundant reactive oxygen species (ROSs). Meanwhile, the increase of specific surface area provided sufficient active sites for catalysis. The degradation rate of TET by simulated solar light/g-C3N4/Co-MCM-48/O3 was close to 100% within 8 min, and both the kinetic constant and synergy index of TET degradation were 7.8 and 4.9 times as much as that of simulated solar light/g-C3N4/O3. Effects of various initial pH and Co contents on the TET degradation were studied. In addition, g-C3N4/Co-MCM-48 revealed good stability in photocatalytic ozonation process by cycling for four times, and the pathway of TET degradation was also proposed in this study. It was suggested that g-C3N4/Co-MCM-48 was an excellent catalyst for the practical application of photocatalytic ozonation.