School of Environmental Science and Engineering, Sun Yat-sen University, 510006, Guangzhou, PR China; Agrosphere Institute (IBG-3), Forschungszentrum Jülich GmbH, 52425, Jülich, Germany.
United States Department of Agriculture, Agricultural Research Service, U. S. Salinity Laboratory, Riverside, CA, 92507, USA.
Environ Pollut. 2019 Apr;247:907-916. doi: 10.1016/j.envpol.2019.01.106. Epub 2019 Feb 1.
Multi-walled carbon nanotubes (MWCNTs) are increasing used in commercial applications and may be released into the environment with anionic surfactants, such as sodium dodecylbenzenesulfonate (SDBS), in sewer discharge. Little research has examined the transport, retention, and remobilization of MWCNTs in the presence or absence of SDBS in porous media with controlled chemical heterogeneity, and batch and column scale studies were therefore undertaken to address this gap in knowledge. The adsorption isotherms of SDBS on quartz sand (QS), goethite coated quartz sand (GQS), and MWCNTs were determined. Adsorption of SDBS (MWCNTs » GQS > QS) decreased zeta potentials for these materials, and produced a charge reversal for goethite. Transport of MWCNTs (5 mg L) dramatically decreased with an increase in the fraction of GQS from 0 to 0.1 in the absence of SDBS. Conversely, co-injection of SDBS (10 and 50 mg L) and MWCNTs radically increased the transport of MWCNTs when the GQS fraction was 0, 0.1, and 0.3, especially at a higher SDBS concentration, and altered the shape of retention profile. Mathematical modeling revealed that competitive blocking was not the dominant mechanism for the SDBS enhancement of MWCNT transport. Rather, SDBS sorption increased MWCNT transport by increasing electrostatic and/or steric interactions, or creating reversible interactions on rough surfaces. Sequential injection of pulses of MWCNTs and SDBS in sand (0.1 GQS fraction) indicated that SDBS could mobilize some of retained MWCNTs from the top to deeper sand layers, but only a small amount of released MWCNTs were recovered in the effluent. SDBS therefore had a much smaller influence on MWCNT transport in sequential injection than in co-injection, presumably because of a greater energy barrier to MWCNT release than retention. This research sheds novel insight on the roles of competitive blocking, chemical heterogeneity and nanoscale roughness, and injection sequence on MWCNT retention and release.
多壁碳纳米管（MWCNTs）在商业应用中越来越多地被使用，并且可能随着十二烷基苯磺酸钠（SDBS）等阴离子表面活性剂一起通过污水排放而释放到环境中。在具有受控化学异质性的多孔介质中，很少有研究考察 MWCNTs 在存在或不存在 SDBS 的情况下的迁移、保留和再迁移。因此，进行了批处理和柱规模研究来解决这一知识空白。确定了 SDBS 在石英砂（QS）、涂覆有针铁矿的石英砂（GQS）和 MWCNTs 上的吸附等温线。SDBS（MWCNTs > GQS > QS）的吸附降低了这些材料的动电电位，并使针铁矿产生电荷反转。在不存在 SDBS 的情况下，当 GQS 分数从 0 增加到 0.1 时，MWCNTs 的传输量大大减少。相反，当 GQS 分数为 0、0.1 和 0.3 时，SDBS（10 和 50 mg/L）和 MWCNTs 的共注入大大增加了 MWCNTs 的传输，特别是在更高的 SDBS 浓度下，并且改变了保留曲线的形状。数学模型表明，竞争阻塞不是 SDBS 增强 MWCNT 传输的主要机制。相反，SDBS 的吸附通过增加静电和/或空间相互作用，或者在粗糙表面上产生可逆相互作用，增加了 MWCNT 的传输。在砂（0.1 GQS 分数）中顺序注入 MWCNTs 和 SDBS 的脉冲表明，SDBS 可以将一些保留的 MWCNTs 从顶部迁移到更深的砂层中，但只有少量释放的 MWCNTs 在流出物中回收。因此，与共注入相比，SDBS 对 MWCNT 在顺序注入中的传输影响要小得多，这可能是因为 MWCNT 释放的能量障碍比保留的能量障碍大。这项研究为 MWCNT 保留和释放过程中竞争阻塞、化学异质性和纳米级粗糙度以及注入顺序的作用提供了新的见解。
