Activity and mechanism of photocatalytic degradation for 2,4-DCP over g-C 3 N 4

Abstract

Graphite carbon nitride (g-C3N4) photocatalyst was synthesized via thermal condensation at high temperatures using melamine as a starting material. The structure and properties of the catalyst was characterized by scanning electron microscopy (SEM),X-ray diffraction (XRD),UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), and attenuated total reflection infrared spectroscopy (ATR-IR).The results indicate that the as-synthesized g-C3N4 had a layered structure with a specific surface area of 15.34 m2·g-1 and possed strong visible light absorption capacity. Photocatalytic degradation of 2,4-dichlorophenol (2,4-DCP) using g-C3N4 under visible light irradiation (λ>420 nm) corresponds to the first order kinetics with a reaction rate constant of 0.0113 min-1.After 250 min,the mineralization rate of 2,4-DCP in the presence of 0.67 g·L-1g-C3N4 reached 60%. The degradation efficiency of 2,4-DCP was highly enhanced in weak acid. Trapping experiments and electron spin resonance (ESR) experiments show that superoxide radical (O2·-) was the main active species in the photocatalytic degradation of 2,4-DCP.The main degradation pathways of 2,4-DCP include dechlorination,aromatic ring opening and carbon chain rupture.