National Engineering Laboratory for Efficient Utilization of Soil and Fertilizer Resources, College of Resources and Environment, Shandong Agricultural University, Tai'an, 271018, China.
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, 210046, China.
Environ Sci Pollut Res Int. 2018 Jun;25(16):15507-15517. doi: 10.1007/s11356-018-1728-5. Epub 2018 Mar 22.
Multi-walled carbon nanotubes (MWCNTs) are often used as adsorbent because of their strong adsorption capacity. However, due to the nature of MWCNTs, their ability to adsorb perfluorooctanoic acid (PFOA), a highly hydrophobic pollutant, is low. In this study, MWCNTs were modified by three nano metal oxides (nano iron oxide, copper oxide, and zinc oxide). The pristine (as the control) and modified MWCNTs were characterized by BET-N, TEM, FTIR, XPS, and XRD, which showed that nano metal oxides were well hybridized on the surface of MWCNTs. Radioactive-labeled PFOA (C-PFOA) was used to quantify it at trace level. Adsorption kinetics showed that intra-particle diffusion was the control step of PFOA adsorbing on metal oxides hybridized MWCNTs (MOHCNTs). Adsorption capacity of PFOA on the MOHCNTs was higher than that on the control due to electrostatic and hydrophobic interactions. In addition, PFOA formed inner-sphere complexes with metal oxide nanoparticles via ligand exchange. The alteration of PFOA adsorption capacity by increasing ionic strength was attributed to the aggregation degree of MWCNTs, electrostatic shielding, and/or salting out effect. The presence of Ca increased the adsorption, owing to not only its higher electrostatic shielding ability than Na but also its formation of bridge between PFOA and MOHCNTs. PFOA adsorption on MOHCNTs strongly depended on medium pH value. These results provide an innovative approach for removing trace PFOA from liquid medium.
多壁碳纳米管 (MWCNTs) 由于其强大的吸附能力，通常被用作吸附剂。然而，由于 MWCNTs 的性质，其对全氟辛酸 (PFOA) 的吸附能力较低，PFOA 是一种高度疏水的污染物。在这项研究中，MWCNTs 被三种纳米金属氧化物（纳米氧化铁、氧化铜和氧化锌）修饰。通过 BET-N、TEM、FTIR、XPS 和 XRD 对原始（作为对照）和修饰的 MWCNTs 进行了表征，结果表明纳米金属氧化物很好地复合在 MWCNTs 的表面上。放射性标记的 PFOA（C-PFOA）被用于定量检测痕量水平的 PFOA。吸附动力学表明，内扩散是 PFOA 吸附到金属氧化物复合 MWCNTs（MOHCNTs）上的控制步骤。由于静电和疏水相互作用，PFOA 在 MOHCNTs 上的吸附容量高于对照。此外，PFOA 通过配体交换与金属氧化物纳米颗粒形成内球络合物。离子强度增加导致 MWCNTs 的聚集程度、静电屏蔽和/或盐析效应改变了 PFOA 的吸附能力。钙离子的存在增加了吸附，这不仅是由于其比钠离子更高的静电屏蔽能力，还因为它在 PFOA 和 MOHCNTs 之间形成了桥。PFOA 在 MOHCNTs 上的吸附强烈依赖于介质的 pH 值。这些结果为从液体介质中去除痕量 PFOA 提供了一种创新的方法。
