Wrapping carbon nanotubes with poly (sodium 4-styrenesulfonate) for enhanced adsorption of methylene blue and its mechanism
Wrapping carbon nanotubes with poly (sodium 4-styrenesulfonate) for enhanced adsorption of methylene blue and its mechanism
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DOI：
10.1016/j.cej.2014.06.020
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发表时间：
2014-11
影响因子：
15.1
通讯作者：
Zhao-yang Zhang;Xuecheng Xu
中科院分区：
文献类型：
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作者：
Zhao-yang Zhang;Xuecheng Xu
提高碳纳米管(CNTs)的吸附性能以开发性能优良的吸附剂具有重要的现实意义。表面修饰或制备碳纳米管杂化材料是一种很有前途的方法。本论文将碳纳米管非共价包裹在聚4-苯磺酸钠(PSS)中，得到碳纳米管/聚对苯磺酸钠杂化材料。杂化产物在水中分散良好，但在亚甲基蓝(MB)吸附后立即聚集。吸附等温线和吸附动力学结果表明，CNT/PSS的吸附容量是未处理的CNT的两倍以上，吸附动力学也比未处理的CNT快得多。用XPS研究了碳纳米管与多孔硅的相互作用以及亚甲基蓝在碳纳米管/多孔硅上的吸附机理。结果表明，碳纳米管通过π-π电子-供体-受体相互作用包裹在碳纳米管表面，-SO3-−基团可以接受碳纳米管共轭体系中的π-电子。因此，杂化材料中的碳纳米管不仅可以通过π-π相互作用吸附MB，而且还可能有助于PSS的-SO3NMe2基团和MB的二甲氨基(-−)之间的静电吸引。考虑到-NMe2基团的季胺化作用，静电吸引作用相当强，其吸附的MB多于π-π相互作用。结果表明，与π-π相互作用相比，静电吸引在吸附方面具有优势，这是因为它节省了碳纳米管表面MB平面的倾斜取向，并且减弱了相邻MB分子之间的静电斥力。静电吸引是CNT/PSS吸附增强和聚集的主要原因。
Improving the adsorption performance of carbon nanotubes (CNTs) to develop superior adsorbents is of practical interest. Surface modification or making CNTs-based hybrids is a promising way. In this paper, CNTs were noncovalently wrapped with poly (sodium 4-styrenesulfonate) (PSS) to obtain CNT/PSS hybrid. The hybrid was well-dispersed in water, but aggregated immediately upon adsorption of methylene blue (MB). Adsorption isotherms and kinetics indicated that CNT/PSS exhibited more than two times higher adsorption capacity and much faster adsorption kinetics than pristine CNTs. XPS was used to study the interaction between CNT and PSS and the adsorption mechanism of MB on CNT/PSS. The results suggested that CNTs were wrapped with PSS by π–π electron-donor–acceptor interactions and –SO3−groups could accept the π-electrons from the conjugated system of CNTs. Therefore, CNTs in the hybrid may not only adsorb MB by π–π interactions but also contribute to the electrostatic attraction between –SO3−groups of PSS and dimethylamino (–NMe2) groups of MB. The electrostatic attraction was rather strong in view of the quaternization of –NMe2groups, and it adsorbed more MB than π–π interactions. We showed that electrostatic attraction has advantages over π–π interactions in adsorption because of space-saving tilted orientation of MB plane on CNTs surface and weakened electrostatic repulsion between adjacent MB molecules. The electrostatic attraction was responsible for both enhanced adsorption and the aggregation of CNT/PSS.