g-C_3N_4协同光催化还原Cr(Ⅵ)及氧化磺基水杨酸

Simultaneous Photocatalytic Reduction of Cr(Ⅵ) and Oxidation of SSA by Carbon Nitride

氮化碳是一种新型非金属半导体光催化剂,近年来发展成为一种理想的环境治理材料.通过热解三聚氰胺的方法制备出石墨相氮化碳(g-C_3N_4),利用XRD、TEM和UV-vis DRS对它的结构、形貌及光电特性进行表征,并进一步对其在协同光催化还原Cr(Ⅵ)及氧化磺基水杨酸(SSA)中的应用进行了研究,考察了催化剂投加量、初始pH以及Cr(Ⅵ)与SSA初始浓度比等条件对协同光催化反应的影响.结果表明,催化剂投加量为0.5 g·L^(-1),pH=2,初始Cr(Ⅵ)与SSA浓度比为1∶4(10 mg·L^(-1)∶40 mg·L^(-1))时,协同光催化反应达到最优化,比单独光还原或光氧化污染物的能力提高3倍以上,此时Cr(Ⅵ)的还原率为98.9%,SSA的氧化率为93.4%.本文还深入探讨了协同光催化机制,g-C3N4在可见光激发下,光生电子还原Cr(Ⅵ),同步产生的空穴、O_2^(·-)和·OH共同氧化SSA.

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-C_3N_4 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 reach98.9% 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,O_2^（·-） and ·OH under visible light.