Direct observation of solid-phase adsorbate concentration profile in powdered activated carbon particle to elucidate mechanism of high adsorption capacity on super-powdered activated carbon.
Direct observation of solid-phase adsorbate concentration profile in powdered activated carbon particle to elucidate mechanism of high adsorption capacity on super-powdered activated carbon.
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DOI：
10.1016/j.watres.2010.08.050
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发表时间：
2011
期刊：
影响因子：
12.8
通讯作者：
Naoya Ando;Y. Matsui;T. Matsushita;K. Ohno
中科院分区：
文献类型：
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作者：
Naoya Ando;Y. Matsui;T. Matsushita;K. Ohno
通过粉碎减小粉末活性炭（PAC）的粒度增加其对天然有机物（NOM）和聚苯乙烯磺酸盐（PSS，其用作模型吸附质）的吸附容量。壳吸附机制，其中NOM和PSS分子不完全渗透的吸附剂颗粒，而是优先吸附在颗粒的外表面附近已被提出作为这种吸附容量增加的解释。在这份报告中，我们提出了直接的证据来支持壳吸附机制。用聚焦离子束对吸附有PSS的PAC颗粒进行切片，并利用场发射扫描电子显微镜/能量色散X射线能谱仪（FE-SEM/EDXS）直接观察颗粒截面的固相PSS浓度分布。从硫的X射线发射，PSS浓度的指数，是在壳区域比在内部区域的颗粒。EDXS观测到的X射线发射曲线与壳层吸附模型分析PSS等温线数据预测的固相PSS浓度曲线并不完全一致，但考虑分析误差后，观测曲线与预测曲线并不一致。这些EDXS的结果提供了第一个直接的证据，PSS主要是吸附在PAC颗粒的外表面附近，因此，结果支持的命题，NOM和PSS的吸附容量的增加，随着粒径的减小是由于分子可以被吸附的外表面积的增加。
Decreasing the particle size of powdered activated carbon (PAC) by pulverization increases its adsorption capacities for natural organic matter (NOM) and polystyrene sulfonate (PSS, which is used as a model adsorbate). A shell adsorption mechanism in which NOM and PSS molecules do not completely penetrate the adsorbent particle and instead preferentially adsorb near the outer surface of the particle has been proposed as an explanation for this adsorption capacity increase. In this report, we present direct evidence to support the shell adsorption mechanism. PAC particles containing adsorbed PSS were sectioned with a focused ion beam, and the solid-phase PSS concentration profiles of the particle cross-sections were directly observed by means of field emission–scanning electron microscopy/energy-dispersive X-ray spectrometry (FE-SEM/EDXS). X-ray emission from sulfur, an index of PSS concentration, was higher in the shell region than in the inner region of the particles. The X-ray emission profile observed by EDXS did not agree completely with the solid-phase PSS concentration profile predicted by shell adsorption model analysis of the PSS isotherm data, but the observed and predicted profiles were not inconsistent when the analytical errors were considered. These EDXS results provide the first direct evidence that PSS is adsorbed mainly in the vicinity of the external surface of the PAC particles, and thus the results support the proposition that the increase in NOM and PSS adsorption capacity with decreasing particle size is due to the increase in external surface area on which the molecules can be adsorbed.