Preparation of Graphite Phase g-C3N4 Supported Metal Oxide Activator and Its Performance in Activating Peroxodisulfate Degradation of Methyl Orange

Abstract

In order to improve the catalytic activity and recycling performance of semiconductor activators, and improve the activation pathway of persulfate, graphitic carbon nitride (g-C3N4) was prepared by calcining melamine, and a composite activator Ag2O/g-C3N4 based on g-C3N4 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 Ag2O/g-C3N4 composite activator on peroxodisulfate (PDS) was explored. The results showed that Ag2O in the composite activator was highly dispersed on the surface of g-C3N4 and did not change the molecular structure of g-C3N4 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-C3N4 or Ag2O activated PDS systems; the activation of the PDS system with Ag2O/g-C3N4 had the best effect on MO degradation; and the composite activator Ag2O/g-C3N4 showed better activation performance. Under the conditions that the mass combined ratio of Ag2O 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 SO4-· and ·OH, and the effect of SO4-· 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 Ag2O/g-C3N4 did not change significantly before and after the reaction. The above results show that Ag2O/g-C3N4 is an efficient and stable composite activator with good application potential in the treatment of dye wastewater by activating PDS.