Investigation of the role of surface chemistry and accessibility of cadmium adsorption sites on open-surface carbonaceous materials.
Investigation of the role of surface chemistry and accessibility of cadmium adsorption sites on open-surface carbonaceous materials.
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DOI：
10.1021/la703638h
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发表时间：
2008-09
期刊：
影响因子：
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通讯作者：
Zhanming Gao;T. Bandosz;Zongbin Zhao;Mei Han;Changhai Liang;J. Qiu
中科院分区：
文献类型：
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作者：
Zhanming Gao;T. Bandosz;Zongbin Zhao;Mei Han;Changhai Liang;J. Qiu
用浓硝酸氧化直流电弧放电法（ADCNTs）和化学气相沉积法（CVDCNTs）制备的碳纳米管，以改变其表面化学性质。采用SEM、TEM、FTIR、XPS、电位滴定和氮气吸附等方法对材料进行了表征。初始和氧化材料被用来作为吸附剂的镉从水溶液中具有不同的pH值。Langmuir和Freundlich吸附模型应用到拟合的等温线数据，这两个模型拟合实验数据非常好。酸氧化导致含氧基团的数量增加，而吸附剂的质地没有剧烈变化。尽管存在小体积的微孔，但纳米管结构可以被认为是无孔的。碳质材料中缺乏发达的微孔，消除了内表面扩散问题，并使绝大多数表面基团可用于吸附镉。这些中心的可用性取决于溶液的pH值，其控制质子化水平。尽管溶液的pH值在一定程度上影响镉的形态，但在本研究中采用的pH范围内，表面化学是吸附的主要力量，而材料的质地也影响纳米管的镉吸附性能。
Carbon nanotubes fabricated by the dc arc discharge method (ADCNTs) and chemical vapor deposition method (CVDCNTs) were oxidized with concentrated HNO 3 to modify their surface chemistry. The materials were characterized using SEM, TEM, FTIR, XPS, potentiometric titration, and nitrogen adsorption. The initial and oxidized materials were used as adsorbents of cadmium from aqueous solutions with different pH. Langmuir and Freundlich adsorption models were applied to fit the isotherm data, and both models fit the experimental data very well. The acid oxidation resulted in an increase in the number of oxygen-containing groups without drastic changes in the texture of the adsorbents. Although the small volume of micropores is present, the nanotube structure can be considered as nonporous. The lack of developed microporosity in carbonaceous materials eliminates the inner surface diffusion problems and makes the vast majority of surface groups available for adsorption of cadmium. The availability of these centers depends on the pH of the solution, which controls the protonation level. In spite of the fact that the pH of the solution affects the speciation of cadmium to some degree, the surface chemistry is the predominant force for adsorption at the pH range adopted in the present study, while the texture of materials also affects the nanotube's cadmium-adsorbing performance.