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Adsorption of Zinc(II) from Water with Purified Carbon Nanotubes
|關鍵字:||吸附;Carbon nanotubes;二價鋅離子;次氯酸鈉;奈米碳管;脫附;再生率;Adsorption;Zn2+;pH effect;Temperatures effect;Desorption;Recovery;Kinetics;Thermodynamics||出版社:||環境工程學系||摘要:||
本研究以奈米碳管吸附水中二價鋅離子，研究結果顯示。經由次氯酸鈉氧化改質後，金屬催化劑及不定型碳被去除，碳管的開口率提高，增加更多的吸附位址，並產生有利於吸附之含氧及親水性官能基。在25oC下，Langmuir模式求取飽和吸附量，單壁次氯酸鈉改質碳管為43.66 mg/g，多壁次氯酸鈉改質碳管為32.68 mg/g。其吸附量遠大於粉狀活性碳(13.5 mg/g)及F-400碳(13 mg/g)。另外改質碳管吸附二價鋅離子，符合二階動力模式。
Commercial carbon nanotubes (CNTs) were treated by sorts of oxidative methods. CNTs which were treated by 70% sodium hypochlorite solutions oxidizer has the greatest adsorption capacity of zinc(II). It was then employed as adsorbent to study the adsorption characteristics of zinc(II) in water. The properties of CNTs such as purity, structure and nature of the surface were greatly improved after purification which made CNTs become more hydrophilic and suitable for adsorption of Zn2+ from water.
The adsorption capacity of Zn2 +onto CNTs increased with increasing pH value and temperatures. Parameters such as equilibrium constant (K0), standard free energy changes (ΔG0), standard enthalpy change (ΔH0) and standard entropy change (ΔS0) were obtained by adsorption thermodynamics at various temperatures (5-45oC). A pseudo-second-order rate model has been employed to describe the kinetic adsorption Zn2+ processes. Desorption studies revealed that Zn2+ can be easily removed from CNTs by acid solution within recovery above 76％ after the tenth times of desorption. A comparative study on the adsorption of Zn2+ from water between CNTs and commercial powdered activated carbon (PAC) was also conducted. The maximum adsorption capacities of Zn2+ calculated by the Langmuir model were 43.66, 32.68, 13.04 mg/g with SWCNTs, MWCNTs and PAC, respectively, at an initial Zn2+ concentration range 10-80 mg/l. The short contact time needed to reach equilibrium as well as the high adsorption capacity suggested that CNTs possess highly potential applications for the removal of Zn2+ from water.
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