Photodegradation of pollutant pesticide by oxidized graphitic carbon nitride catalysts

Abstract

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 zeroth-order reaction rather than the first-order reaction. On the photoreaction mechanism study, the active species-trapping experiment, which was performed using 2,2,6,6-tetramethyl-1-piperdinyloxy free radical, t-BuOH and KI for scavenging O2°-, O°H and h+, respectively, confirmed the reactivity order of O2•−>O•H>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).