多壁碳纳米管氧化改性及其对酚类吸附性能的研究

针对目前有机废水(尤其是酚类废水)污染严重的问题, 通过混酸氧化法对多壁碳纳米管(multi-walledcarbon nanotubes, MWCNTs)进行氧化改性(MWCNT-O), 并研究其改性前后对苯酚、对甲苯酚、对甲氧基苯酚、对羟基苯甲醛和对硝基苯酚5种典型酚的吸附作用。结果表明: 298 K下, 与未改性的MWCNTs相比,MWCNTs-O对5种酚类物质的吸附量均有提升。5种酚类物质在MWCNTs-O表面的吸附量有差别, 顺序为对硝基苯酚>对甲氧基苯酚>对羟基苯甲醛>对甲苯酚>苯酚。吸附过程符合Langmuir吸附等温方程, 主要为单分子层化学吸附。对MWCNTs-O进行表面官能团测试、透射电镜分析和拉曼光谱分析, 发现氧化改性后材料表面的酸性含氧官能团增多, 缠绕度降低, 整体分散性增强, 石墨化程度有所提升。通过研究分子结构与吸附量之间的关系, 发现吸附量与酚类物质的电子能量(electronic energy, EE)有显著的相关性, MWCNTs-O表面垂直的π电子和酚类物质的π电子形成π-π共轭作用。因此, EE 可以作为酚类物质在MWCNTs-O表面平衡吸附量的预测性指标。

Adsorption of Phenol by Oxidized Multi-Walled Carbon Nanotubes

Organic compounds pollution, especially phenolic compounds, has been a serious problem recently.Multi-walled carbon nanotubes (MWCNTs) were oxidized by mixed acid oxidation method to remove phenoliccompounds by adsorption. Five typical phenolic compounds including phenol, p-cresol, p-methoxyphenol, phydroxybenzaldehydeand p-nitrophenol were selected and to be adsorbed on MWCNTs and MWCNTs-O,respectively. Results showed that compared with the unmodified MWCNTs, the adsorption capacity of fivephenolic compounds on MWCNTs-O increased significantly. The adsorption amount of five phenols on MWCNTs-O was different and the order was p-nitrophenol >p-methoxyphenol > p-hydroxybenzaldehyde > p-cresol > phenol.Adsorption isotherm data for the five phenols fitted Langmuir model well, which proved that phenolic compoundson MWCNTs was monolayer chemisorption. Surface functional groups analyzation of MWCNTs-O indicated thatacidic oxygen-containing functional groups increased. TEM and Raman spectroscopy showed the winding degreeof MWCNTs decreased, and overall dispersion and the degree of graphitization increased. π-π conjugation betweenvertical π electrons on MWCNTs-O and π electrons of phenolic compounds was formed and the electronic energy(EE) could be used as indicator for phenols adsorption on MWCNTs-O.