Preparation of g-C3N4-PEI Quantum Dot Photocatalytic Flower and Its Performance Study for Degrading Tetracycline

This paper uses carbon nitride and PEI as precursors to prepare g-C3N4-PEI water-soluble photocatalytic materials and then uses that material and sodium alginate hydrogel to construct photocatalytic flowers. The main research content and conclusions are as follows: (1) Five samples of g-C3N4-PEI were prepared using different ratios of both g-C3N4 and PEI materials; the g-C3N4: PEI=1:5 sample has the best degradation performance with a TC removal rate of 73.546%. The UV-Vis, FTIR, fluorescence, and XPS characterizations showed that g-C3N4-PEI had the basic s-triazine ring, carbon, and nitrogen atom heterocycle (2p orbitals), graphitic C–N network, amino and hydroxyl groups. The optimal light absorption wavelength is 368(nm), and the quantum yield (λex = 340 nm) was 20.9%, using quinine sulfate as a standard. (2) Throughout the experiments, the flower's removal rate of TC was (absorption 50%, photodegradation 66.75%), higher than pure g-C3N4 (6.23% and 52.76%).本研究以氮化碳与聚乙烯亚胺（PEI）为前驱体，制备了g-C₃N₄-PEI水溶性光催化材料，随后以该材料与海藻酸钠水凝胶构建光催化花状结构。主要研究内容与结论如下： (1) 采用不同配比的g-C₃N₄与PEI原料，制备了5组g-C₃N₄-PEI样品；其中g-C₃N₄与PEI配比为1:5的样品降解性能最优，对四环素（TC）的去除率可达73.546%。通过紫外-可见吸收光谱（UV-Vis）、傅里叶变换红外光谱（FTIR）、荧光光谱及X射线光电子能谱（XPS）表征可知，g-C₃N₄-PEI具有典型的均三嗪环、碳氮杂环（2p轨道）、类石墨相C-N网络以及氨基与羟基官能团。以硫酸奎宁为标准参照物，该材料的最优光吸收波长为368 nm，当激发波长（λ_ex=340 nm）时，量子产率可达20.9%。 (2) 实验结果显示，该光催化花状结构对TC的去除可通过吸附与光降解两种途径实现，二者的贡献占比分别为50%与66.75%，其整体性能优于纯相g-C₃N₄（纯相g-C₃N₄的吸附与光降解去除率分别仅为6.23%与52.76%）。