Metal-free activation of peroxymonosulfate by g-C3N4 under visible light irradiation for the degradation of organic dyes

Semiconducting carbon nitride materials (g-C3N4) were investigated as metal-free catalysts for the activation of peroxymonosulfate (PMS) under visible light irradiation to degrade organic dyes in aqueous solution. X-ray diffraction, scanning electron microscopy, N2 adsorption/desorption isotherms, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the properties of the material. The effect of several parameters including the concentration of catalyst, PMS and organic dye, and initial solution pH on its catalytic activity was also investigated. It was found that the obtained g-C3N4 can effectively activate PMS under visible light irradiation to generate strong sulfate radicals which was highly active for Acid Orange 7 (AO7) and other organic dyes degradation. The catalyst also presented a long-term stability during multiple runs. Based on intermediate detections, the degradation pathway of AO7 in the g-C3N4/PMS/Vis system was proposed. This study demonstrated a promising approach for the activation of green oxidant, PMS, by the newly-developed polymer photocatalysts for environmental remediation and oxidation catalysis.