Transport behavior of functionalized multi-wall carbon nanotubes in water-saturated quartz sand as a function of tube length.
Transport behavior of functionalized multi-wall carbon nanotubes in water-saturated quartz sand as a function of tube length.
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DOI：
10.1016/j.watres.2012.05.036
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发表时间：
2012-09-15
期刊：
影响因子：
12.8
通讯作者：
Pennell KD
中科院分区：
文献类型：
--
作者：
Wang Y;Kim JH;Baek JB;Miller GW;Pennell KD
通过一维柱实验研究了管长对4-乙氧基苯甲酸功能化多壁碳纳米管（MWCNTs）在饱和水多孔介质中迁移和沉积的影响。制备了水性MWCNTs悬浮液，得到了三种管长分布；0.02 - -1.3μm(短),0.2 - -7.5μm(媒介),0.2 - -21.4μm(长)。结果表明，随着管长的增加，MWCNT的保留率增加。然而，在所有实验条件下，在流出样品中检测到输送到柱上的MWCNT质量的76%以上，这表明功能化的MWCNT很容易通过40-50目渥太华砂运输。对废水样品中MWCNT长度分布的检测表明，长度大于8 μm的纳米管优先沉积。此外，测量的保留剖面显示，在柱入口附近的MWCNT沉积最大，对于长MWCNT沉积最为明显，并且随着行进距离的增加而急剧减少。扫描电子显微镜（SEM）图像显示，MWCNTs在整个柱长的砂表面沉积，而较大的MWCNTs束保留在颗粒交叉处和柱入口附近。基于洁净床过滤理论（CBFT）的数学模型无法准确模拟实测截留剖面数据，即使在改变权重函数并加入非均匀附着率系数表达式后也是如此。修正数学模型以考虑物理应变，极大地改善了MWCNT保留的预测，屈服应变率系数比相应的附着率系数大4个数量级。综上所述，这些实验和建模结果表明，在描述MWCNT在饱和水多孔介质中的输运时，颗粒应变和管长分布的潜在重要性，以及需要考虑的因素。
A series of one-dimensional column experiments was conducted to examine the effects of tube length on the transport and deposition of 4-ethoxybenzoic acid functionalized multi-wall carbon nanotubes (MWCNTs) in water-saturated porous media. Aqueous MWCNTs suspensions were prepared to yield three distributions of tube lengths; 0.02–1.3 μm (short), 0.2–7.5 μm (medium), and 0.2–21.4 μm (long). Results of the column studies showed that MWCNT retention increased with increasing tube length. Nevertheless, more than 76% of the MWCNT mass delivered to the columns was detected in effluent samples under all experimental conditions, indicating that the functionalized MWCNTs were readily transported through 40–50 mesh Ottawa sand. Examination of MWCNT length distributions in the effluent samples revealed that nanotubes with lengths greater than 8 μm were preferentially deposited. In addition, measured retention profiles exhibited the greatest MWCNT deposition near the column inlet, which was most pronounced for the long MWCNTs, and decreased sharply with travel distance. Scanning electron microscope (SEM) images showed that MWCNTs were deposited on sand surfaces over the entire column length, while larger MWCNT bundles were retained at grain intersections and near the column inlet. A mathematical model based on clean bed filtration theory (CBFT) was unable to accurately simulate the measured retention profile data, even after varying the weighting function and incorporating a nonuniform attachment rate coefficient expression. Modification of the mathematical model to account for physical straining greatly improved predictions of MWCNT retention, yielding straining rate coefficients that were four orders-of-magnitude greater than corresponding attachment rate coefficients. Taken in concert, these experimental and modeling results demonstrate the potential importance of, and need to consider, particle straining and tube length distribution when describing MWCNT transport in water-saturated porous media.
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影响因子：
13.3
作者：
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通讯作者：
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影响因子：
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影响因子：
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作者：
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