Preparation of Graphite Phase g-C 3 N 4 Supported Metal Oxide Activator and Its Performance in Activating Peroxodisulfate Degradation of Methyl Orange.

In order to improve the catalytic activity and recycling performance of semiconductor activators, and improve the activation pathway of persulfate, graphitic carbon nitride (g-C ₃ N ₄ ) was prepared by calcining melamine, and a composite activator Ag ₂ O/g-C ₃ N ₄ based on g-C ₃ N ₄ supported metal oxide was prepared using a precipitation method. The morphology, structure, and basic properties of the composites were characterized using SEM, XRD, FT-IR and XPS. The activation efficiency of the Ag ₂ O/g-C ₃ N ₄ composite activator on peroxodisulfate (PDS) was explored. The results showed that Ag ₂ O in the composite activator was highly dispersed on the surface of g-C ₃ N ₄ and did not change the molecular structure of g-C ₃ N ₄ significantly. Under different activation systems, the degradation process of MO was best fitted under the pseudo-second-order reaction kinetic model, compared to the separate g-C ₃ N ₄ or Ag ₂ O activated PDS systems; the activation of the PDS system with Ag ₂ O/g-C ₃ N ₄ had the best effect on MO degradation; and the composite activator Ag ₂ O/g-C ₃ N ₄ showed better activation performance. Under the conditions that the mass combined ratio of Ag ₂ O in the activator was 12%, the initial concentration of PDS was 4 mmol/L, the initial concentration of the activator was 1.25 g/L, and the initial pH was 3, the degradation degree of MO reached 99.4% after 40 min reaction. The free radical quenching experiment proved that the active substances that could degrade MO in the system were SO ₄ ^- · and ·OH, and the effect of SO ₄ ^- · was greater than that of ·OH. The degradation degree of MO in the reaction system remained above 80% after four cycles of use, and the crystal structure of Ag ₂ O/g-C ₃ N ₄ did not change significantly before and after the reaction. The above results show that Ag ₂ O/g-C ₃ N ₄ is an efficient and stable composite activator with good application potential in the treatment of dye wastewater by activating PDS.