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Adsorption of Humic Acid form Water with Carbon Nanotubes
|關鍵字:||Carbon nanotubes;奈米碳管;Adsorption;Desorption;Humic acid;Temperature effect;Kinetics;Thermodynamic analysis;吸附;脫附;腐植酸;活性碳;動力學;熱力學||出版社:||環境工程學系||摘要:||
本研究利用單壁奈米碳管(Single-walled carbon nanotubes，SWCNTs)和多壁奈米碳管(Multi-walled carbon nanotubes，MWCNTs)吸附去除水中腐植酸，奈米碳管吸附腐植酸的量隨著奈米碳管管徑減小、腐植酸分子量減少、溫度降低、水溶液pH下降而有增加的趨勢。在腐植酸(1k~5k)初始濃度0.2~30 mg TOC/l下利用Langmuir model 求出單壁奈米碳管 、多壁奈米碳管其飽和吸附量分別為121.95 mg TOC/g、107.53 mg TOC/g，比其他商業用之活性碳有較佳的吸附量如：F-400 carbon (18.02 mg TOC/g) 與PAC (42.37 mg TOC/g)。計算奈米碳管吸附腐植酸反應的活化能，顯示膜擴散為反應速率控制因子，根據熱力學參數的求取顯示奈米碳管吸附腐植酸的過程為自發、放熱反應。在脫附再生(Regeneration cycle, RC)實驗方面，奈米碳管和PAC吸附腐植酸(1k~5k)的吸附量隨著RC次數的增加而遞減，在RC=10時單壁奈米碳管之吸附量為49.15 mg TOC/g、多壁奈米碳管 27.47 mg TOC/g、PAC 11.77 mg TOC/g 。所以奈米碳管在吸附容量和脫附再生特性上均較活性碳好，雖然奈米碳管目前售價仍相當昂貴，但是其作為吸附劑的應用潛力卻不容忽視。
Commercial carbon nanotubes (CNTs) were employed as adsorbents to study adsorption of humic acid (HA) from water. The adsorption capacity of HA onto CNTs increased with decreasing outer diameter of CNTs (dp), molecular weight of HA, trmperature and pH value of water. The maximum adsorbed amounts of HA(1k~5k) onto SWCNTs and MWCNTs calculated by the Langmuir model at 25oC were 121.95 and 107.53 mg TOC g-1, which were much higher than that onto commercially available F-400 carbon (18.02 mg TOC g-1) and powdered activated carbon (42.37 mg TOC g-1).The activation energies for adsorption of HA onto CNTs indicated the film diffusion is the rate-controlling mechanism in the reaction. According to thermodynamic analysis, the adsorption of HA onto CNTs is an exothermic and spontaneous process. The adsorbed amount of HA(1k~5k) with CNTs and PAC decreased with the increase of regeneration cycle (RC). The adsorbed amounts of HA under RC=10 were 49.15 mg TOC g-1 with SWCNTs, 24.47 mg TOC g-1 with MWCNTs and 11.77 mg TOC g-1 with PAC. It is obvious that the adsorption capacity as well as the desorption property of CNTs are superior to that of PAC suggesting that CNTs possess highly potential applications in environmental protection.
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