Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521, USA.
Environ Sci Technol. 2012 Nov 6;46(21):11752-60. doi: 10.1021/es302453k. Epub 2012 Oct 11.
In this study, a systematic approach has been followed to investigate the fate and transport of single walled carbon nanotubes (SWCNTs) from synthesis to environmentally relevant conditions. Three widely used SWCNT synthesis methods have been investigated in this study including high pressure carbon monoxide (HiPco), SWeNT CoMoCat, and electric arc discharge technique (EA). This study relates the transport of three SWCNTs (HiPco-D, SG65-D, and P2-D) with different synthesis methods and residual catalyst content revealing their influence on the subsequent fate of the nanotubes. To minimize nanotube bundling and aggregation, the SWCNTs were dispersed using the biocompatible triblock copolymer Pluronic, which allowed the comparison in the transport trends among these SWCNTs. After purification, the residual metal catalyst between the SWCNTs follows the trend: HiPco-D > SG65-D > P2-D. The electrophoretic mobility (EPM) and hydrodynamic diameter of SWCNTs remained insensitive to SWCNT type, pH, and presence of natural organic matter (NOM); but were affected by ionic strength (IS) and ion valence (K(+), Ca(2+)). In monovalent ions, the hydrodynamic diameter of SWCNTs was not influenced by IS, whereas larger aggregation was observed for HiPco-D with IS than P2-D and SG65-D in the presence of Ca(2+). Transport of HiPco-D in the porous media was significantly higher than SG65-D followed by P2-D. Release of HiPco-D from porous media was higher than SG65-D followed by P2-D, though negligible amount of all types of SWCNTs (<5%) was released. Both transport and release patterns follow a similar trend to what was observed for residual metal catalysts in SWCNTs. Addition of NOM increased the transport of all SWCNTs primarily due to electrosteric repulsion. HiPco-D was notably more acidic than SG65-D followed by P2-D, which is similar to the transport trend. Overall, it was observed that the synthesis methods resulted in distinctive breakthrough trends, which were correlated to metal content. These findings will facilitate the safe design of environmental friendly SWCNTs by minimizing mobility in aquatic environments.
在这项研究中，我们采用系统的方法研究了单壁碳纳米管（SWCNTs）从合成到环境相关条件下的命运和迁移。本研究调查了三种广泛使用的 SWCNT 合成方法，包括高压一氧化碳（HiPco）、SWeNT CoMoCat 和电弧放电技术（EA）。本研究将三种具有不同合成方法和残留催化剂含量的 SWCNTs（HiPco-D、SG65-D 和 P2-D）的迁移与它们对随后纳米管命运的影响联系起来。为了最小化纳米管的缠结和聚集，使用生物相容性的三嵌段共聚物 Pluronic 对 SWCNTs 进行分散，这使得能够比较这些 SWCNTs 的迁移趋势。纯化后，SWCNTs 之间的残留金属催化剂遵循以下趋势：HiPco-D > SG65-D > P2-D。SWCNTs 的电泳迁移率（EPM）和水动力直径对 SWCNT 类型、pH 值和天然有机物（NOM）的存在不敏感；但受到离子强度（IS）和离子价（K(+)、Ca(2+)）的影响。在单价离子中，SWCNTs 的水动力直径不受 IS 的影响，而在 Ca(2+)存在下，HiPco-D 的 IS 比 P2-D 和 SG65-D 更大，观察到更大的聚集。多孔介质中 HiPco-D 的迁移明显高于 SG65-D，其次是 P2-D。HiPco-D 从多孔介质中的释放高于 SG65-D，其次是 P2-D，尽管所有类型的 SWCNTs（<5%）的释放量都可以忽略不计。迁移和释放模式都遵循与 SWCNTs 中残留金属催化剂观察到的相似趋势。添加 NOM 主要由于静电排斥作用而增加了所有 SWCNTs 的迁移。HiPco-D 的酸度明显高于 SG65-D，其次是 P2-D，这与迁移趋势相似。总的来说，研究结果表明，合成方法导致了独特的突破趋势，这与金属含量有关。这些发现将通过最小化在水生环境中的迁移性来促进环境友好型 SWCNTs 的安全设计。
