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Adsorption of lead on multi-walled carbon nanotubes with different outer diameters and oxygen contents: Kinetics, isotherms and thermodynamics

查看全文 作　　者：Fei [1]Yu;Yanqing [1]Wu;Jie [2]Ma;Chi [1]Zhang 高影响力作者 机构地区：[1]School of Environmental Science and Engineering,Shanghai Jiao Tong University;[2]State Key Laboratory of Pollution Control and Resource Reuse,School of Environmental Science and Engineering,Tongji University高影响力机构 出　　处：《Journal of Environmental Sciences》索引2013年第25卷第1期,共9页高影响力期刊 基　　金：supported by the National High Technology Research and Development Program (863) of China (No.2007AA06Z334);the Scholarship Award for Excellent Doctoral Student granted by Ministry of Education and the Shanghai Jiao Tong University Innovation Fund for Postgraduates;the State Key Laboratory of Pollution Control and Resource Reuse Foundation (No. PCRRY11009);the Program for Young Excellent Talents at Tongji University (No. 2010KJ026) 摘　　要：The effects of different outer diameters and surface oxygen contents on the adsorption of heavy metals onto six types of multi-walled carbon nanotubes (MWCNTs) were investigated in an aqueous solution and lead was chosen as a model metal ion. The results indicated that the percentage removal and adsorption capacity of lead remarkably increased with decreasing outer diameter due to larger specific surface area (SSA). The SSA-normalized maximum adsorption capacity (qm /SSA) and SSA-normalized adsorption coefficient (Kd /SSA) were strongly positively correlated with surface oxygen content, implying that lead adsorption onto MWCNTs significantly increases with the rise of oxygen content and decreases with decreasing SSA. The calculated thermodynamic parameters indicated that adsorption of lead on MWCNTs was endothermic and spontaneous. When the oxygen content of MWCNTs increased from 2.0% to 5.9%, the standard free energy (△ G0 ) became more negative, which implied that the oxygenated functional groups increased the adsorption affinity of MWCNTs for lead. Through calculation of enthalpy (△ H0 ), G0 and free energy of adsorption (Ea ), lead adsorption onto MWCNTs was recognized as a chemisorption process. The chemical interaction between lead and the phenolic groups of MWCNTs could be one of the main adsorption mechanisms due to highly positive correlations between the phenolic groups and K d /SSA or q m /SSA. 关 键 词：多壁碳纳米管 吸附能力 氧含量 热力学 外径 动力学 等温线 铅
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