Photodegradation of pollutant pesticide by oxidized graphitic carbon nitride catalysts

Oxygen-doped graphitic carbon nitride (Og-CN) was synthesized by H2O2-treating of graphitic carbon nitride (g-CN), which was prepared by the condensation-polymerization of melamine and the exfoliation. The successful oxidation was confirmed by the decrease of photoluminescence intensity, the detection of oxygen-including bond and the slight increase of surface area. Og-CN was applied to the photocatalytic degradation of 2,4-dichlorophenoxyacetic acid in the aqueous phase under the UV and visible light irradiation and compared with the catalytic behavior of g-CN. The degradation efficiency of Og-CN was higher than that of g-CN, the UV light irradiation was more effective than the visible light irradiation, and Og-CN was stable in three photocatalytic cycles with only 4% decrease. The kinetics analysis indicated that the photoreactions of both Og-CN and g-CN follow the zerothorder reaction rather than the first-order reaction. On the photoreaction mechanism study, the active speciestrapping experiment, which was performed using 2,2,6,6-tetramethyl-1-piperdinyloxy free radical, t-BuOH and KI for scavenging O-2(degrees-), O degrees H and h+, respectively, confirmed the reactivity order of O-2(center dot-) > (OH)-O-center dot > h(+). Then the present research refers that Og-CN is a promising photocatalyst because it has extremely high total organic carbon removal (88 % of degraded 2,4-D after 120 min).

Automated summary

Oxygen-doped graphitic carbon nitride (Og-CN) was synthesized and applied as a promising photocatalyst for the degradation of 2,4-dichlorophenoxyacetic acid in aqueous phase. Og-CN showed higher degradation efficiency compared to untreated g-CN, with UV light irradiation being more effective than visible light and good stability in repeated photocatalytic cycles. The photoreaction mechanism study confirmed the reactivity order of O-2(center dot-) > (OH)-O-center dot > h(+).