Abstract:

Series of products with different formation stages of titanate nanotubes (TNTs) are synthesized, with the hydrothermal reaction time of 1, 2, 3, 4 days. XRD, SAXS and N₂ adsorption/desorption have been chosen to detect the morphology and structure of various products. Afterwards, the adsorption behavior of Cd(Ⅱ) onto various products are also compared, and possible mechanism for the different adsorption capacities are detected based on their structures. XRD detection depictes that all products are monoclinic system. Results from SAXS and N₂ adsorption/desorption suggeste that the formation processes of TNTs are the disintegration of TiO₂→the formation of titanate nanotubes→the destruction of tubular structures. Among all products, TNTs-3d displayes the best defined structure. As for Cd(Ⅱ) adsorption, Langmuir-Freundlich model can better describe the adsorption isotherm, and the adsorption capacities rank as: TNTs-3d ≈ TNTs-1d > TNTs-4d > TNTs-2d. Further detection proves that gyration radius and pore volume play little role, while BET surface area and the average pore diameter possibly affect the adsorption capacity.

Key words: titanate nanotubes, SAXS, adsorption, Langmuir-Freundlich model

摘要：

在以 P25 二氧化钛为钛源, 水热反应时间为1, 2, 3, 4天条件下, 合成钛酸纳米管(TNTs)形成过程中的4种产物, 采用XRD, SAXS和N₂吸附/脱附等温线等手段进行表征。以Cd(Ⅱ)为代表污染物, 研究4种产物对Cd(Ⅱ)的吸附, 并着重分析4种产物的结构对其吸附能力的影响。粉末XRD结果表明, TNTs的4种产物均为单斜晶胞结构。SAXS和N₂吸附/脱附表征证实, 水热法制备TNTs经历二氧化钛源结构解体→钛酸纳米管形成→管状结构解体的过程, TNTs-3d具有最为规整的管状形貌。吸附等温线结果表明, Langmuir-Freundlich模型能够更好地拟合吸附等温结果, 且Cd(Ⅱ)的吸附量大小顺序为TNTs-3d ≈ TNTs-1d > TNTs-4d > TNTs-2d。进一步的分析表明, 样品的回转半径、孔体积对吸附量影响较小, 而比表面积和平均孔径可能会显著影响吸附容量。

关键词: 钛酸纳米管, SAXS, 吸附, Langmuir-Freundlich 模型