Abstract: In this work, the surface structure of CeO2/nitrogen-doped carbon composites was tuned by controlling the feeding order of cerium nitrate and melamine in their synthesis process. Upon the characterization by TEM, XRD, TG, Zeta potential, and N2 adsorption-desorption isotherms, the synthesized CeO2/N-doped carbon composites were confirmed to be mainly composed of CeO2 and a large amount of N-doped carbon with different structures. Interestingly, it was found that the feeding order had a great influence on the nitrogen content, CeO2 dispersion, surface charge distribution, pore structure as well as specific surface area of CeO2/N-doped carbon composites. Compared to the CeO2/N-doped carbon composites prepared first by adding melamine (MCe), the CeO2/N-doped carbon composites prepared first by adding cerium nitrate (CeM) in their synthesis process had a much higher nitrogen content, which promoted the CeO2 dispersion on N-doped carbon surface and led to the formation of a predominantly positively charged surface in this sample, despite their lower specific surface area and unfavorable pore structure. The removal of Congo red by adsorption was employed to investigate the correlation between the surface structure of adsorbents and their adsorption capacities. It was discovered that the pore structure and specific surface area of CeO2/N-doped carbon composites were not the predominant factors for the adsorption removal of Congo red. Since Congo red presented an anionic state in aqueous solution, the formed Congo red anions could adsorb onto the positively charged surface of the sample via an electrostatic adsorption interaction, achieving high efficient removal of Congo red from the dye waste solution. Therefore, CeM exhibited a higher removal efficiency of Congo red. The adsorption capacities of the CeO2/N-doped carbon composites were further investigated to reveal the effect of different adsorption conditions such as inorganic salt, Congo red concentration, pH value, adsorbent dosage, and adsorption temperature.

Key words: CeO2/N-doped carbon composites, Congo red, adsorption, feeding order

摘要： 本工作通过控制硝酸铈和三聚氰胺的投料顺序，调节了CeO2/氮掺杂碳复合材料的表面结构。通过透射电镜(TEM)、X射线衍射(XRD)和Zeta电位等表征技术，发现投料顺序对CeO2/碳氮复合材料的氮含量、CeO2分散性、表面电荷分布、孔的结构及比表面积产生显著影响。相对于先加入三聚氰胺制备的CeO2/碳氮复合材料(MCe)，先加入硝酸铈制备的CeO2/碳氮复合材料(CeM)尽管具有较低的比表面积和不太理想的孔结构，但由于其具有更高的氮含量，促进了CeO2在复合材料中的分散；此外，Zeta电位测试表明，CeM样品表面主要带正电荷，由于刚果红在溶液中主要以阴离子形式存在，能与带正电荷的样品表面形成静电吸附作用。因此，先加入硝酸铈所制备的CeO2/碳氮复合材料展现出更高的刚果红去除效率。

关键词: CeO2/碳氮复合材料, 刚果红, 吸附, 投料顺序