g-C3N4/rGO/TiO2光催化材料降解模拟污水中氨氮

以自制的g-C₃N₄和氧化石墨烯（GO）及TiO₂为原料，通过静电吸附组装、水热还原等反应过程制备以还原氧化石墨烯（rGO）为光生电子传输介质的g-C₃N₄/rGO/TiO₂光催化材料，并通过冷场发射扫描电镜（SEM）、X射线衍射光谱（XRD）、紫外-可见光漫反射光谱（UV-Vis-DRS）、光电流密度测试等方法对催化剂形貌结构和光学性能进行了表征.选择含氮浓度为50mg/L的氨氮溶液作为模拟原水，调节氨氮溶液的pH值至9~10，研究了该光催化材料在氙灯照射下的氨氮去除效果.结果表明，g-C₃N₄/rGO/TiO₂光催化材料的SEM照片显示其为TiO₂包覆结构，复合材料的XRD图谱同时出现了TiO₂和g-C₃N₄的衍射峰，DRS光谱则体现出复合材料在可见光区的光吸收能力明显增强；对氨氮的去除实验表明原材料GO：g-C₃N₄=1：10的复合光催化材料有较好的光催化降解氨氮的性能，氨氮平均去除率为97%.通过采用电子顺磁共振（EPR）测定反应过程中的活性自由基，推测降解机理为：复合光催化剂在氙灯照射下生成的超氧阴离子自由基和羟基自由基直接在材料表面对吸附的NH₃进行氧化，而rGO则作为光催化材料的传输介质起到了传导光生电荷的作用.

The photocatalytic property of g-C3N4/rGO/TiO2 photocatalyst for ammonia nitrogen degradation in simulated wastewater

Using self-made g-C₃N₄, graphene oxide (GO) and TiO₂ as raw materials, the g-C₃N₄/rGO/TiO₂ photocatalyst with reduced graphene oxide (rGO) as photo-generated electron transport medium was successfully prepared through electrostatic adsorption and hydrothermal reduction processes, and the morphologies, structures and optical properties of the catalysts were characterized by SEM, X-ray diffraction (XRD), UV-Vis-DRS and photocurrent density test. Ammonia nitrogen solution with nitrogen concentration of 50mg/L was used as the simulated raw water, and the pH of ammonia nitrogen solution was adjusted to 9~10. The photocatalytic property of this photocatalyst for ammonia nitrogen removal was studied under the irradiation of a xenon lamp. The SEM results showed that g-C₃N₄/rGO/TiO₂ photocatalytic material was coated with TiO₂ as the coating layer, the XRD pattern of the composite exhibited both diffraction peaks of TiO₂ and g-C₃N₄, and the DRS spectrum showed that the optical absorption capacity of the composite photocatalyst was significantly enhanced in the visible region. Experiments on ammonia nitrogen removal showed that the composite photocatalyst with raw material GO:g-C₃N₄=1:10possessed best photocatalytic performance in ammonia nitrogen degradation, and the average removal rate of ammonia nitrogen was 96.80%. From the results of the electron paramagnetic resonance (EPR), it was speculated that the degradation mechanism was that the superoxide anion radical and hydroxyl radical generated by the composite catalyst oxidize the adsorbed NH₃ directly on the surface of the material under light irradiation, and rGO played a conduction role as the photocatalytic material's photo-generated charges transmission medium.