Carbon nitride is a novel nonmetal semiconductor photocatalyst, which has developed into an ideal environmental treatment material in recent years. Graphite carbon nitride(g-C3N4) was prepared through pyrolysis melamine, and the structure, morphology and optical properties of samples were characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM) and UV-Vis diffuse reflectance spectra(UV-Vis DRS). The potential application of g-C3N4 in the simultaneous photocatalysis reduction of Cr(Ⅵ) and oxidation of sulfosalicylic acid(SSA) was further explored. And the effects of different conditions such as catalyst dosage, pH and initial concentration ratio of Cr(Ⅵ) with SSA on the simultaneous photocatalysis were also investigated. The results showed that when the catalyst dosage was 0.5 g·L-1, pH=2, the initial concentration ratio of Cr (VI) and SSA was 1:4(10 mg·L-1:40 mg·L-1), optimal simultaneous photocatalysis efficiency was achieved, which was more than 3 times higher than that of the separated photoreduction or photooxidation reactions. Within 3 hours, the reduction ratio of Cr(Ⅵ) and oxidation ratio of SSA could reach 98.9% and 93.4%, respectively. The mechanism of simultaneous photocatalysis was discussed. Cr(Ⅵ) was reduced by electrons and SSA was oxidized by the combined function of hole, O2·- and·OH under visible light.
Keywords: Cr(Ⅵ); g-C3N4; reaction mechanism; simultaneous photocatalysis; sulfosalicylic acid(SSA).