热解法制备g-C_3N_4及其可见光降解有机污染物

Pyrolysis Synthesized g-C_3N_4 for Photocatalytic Degradation of Organic Pollutants under Visible Light Irradiation

在580℃下热解单氰胺的方法合成石墨型碳氮化合物g-C_3N_4,并采用X-射线衍射(XRD),扫描电子显微镜(SEM),紫外可见漫反射(UV-Vis DRS),红外光谱(FT-IR),光致发光光谱(PL)对该催化剂进行了表征.通过对罗丹明B(Rhodamine B,RhB)及水杨酸(Salicylic acid,SA)的降解来研究其催化活性,同时探讨了光催化降解RhB体系中g-C_3N_4的用量和溶液pH对RhB降解的影响.结果表明,在可见光(λ≥420nm)照射下,g-C_3N_4为1.2g/L,pH 5.35时,g-C_3N_4对RhB的光降解活性最好,150min后可使RhB褪色完全.在光催化反应条件下降解SA,45h时降解率达到35.09%.采用外加异丙醇、苯醌、EDTA等捕获剂试验,推测其催化机理主要为超氧自由基(O2·-)氧化历程.

g-C3N4 photocatalyst was synthesized by directly heating the low-cost cyanamide at 580℃, and characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, diffuse reflection spectroscopy （UV-Vis DRS）, Fourier transform infrared spectroscopy （FT-IR） and photoluminescence spectroscopy （PL）. Rhodamine B （RhB） and salicylic acid were used to evaluate the photocatalytic activity of g-C3 N4. The effect of g-C3 N4 amount and pH on the photocatalytic activity was researched. The results demonstrate that g- C3 N4 has the best degradation efficiency under the conditions of 1.2 g/L g-C3 N4 and pH 5.35. RhB is degraded completely by g-CaN4 after 150 minutes with visible light irradiation, while SA removed more than 35% during 45 h of visible light irradiation. The photodegradation mechanism for RhB is proposed based on trapping experiment by adding isopropanol, benzoquinone and ethylene diamine tetraaeetic acid. In the g-CaN4 photocatalysis system, the photodegradation of RhB is mainly attributed to superoxide radical.