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標題: 奈米碳管吸附水中二價鋅離子之研究
Adsorption of Zinc(II) from Water with Purified Carbon Nanotubes
作者: 邱煥宗
Chiu, Huantsung
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
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。
不同pH值(1-12)下,吸附量隨pH上升而提高。但在過酸或過鹼的情況下,H+與OH-會與金屬離子產生競爭吸附,而使吸附量降低。在不同溫度(5oC-45oC)下,改質碳管吸附容量隨溫度上升而增加。將結果代入熱力學式子中,改質單壁及改質多壁碳管之焓(△Ho)分別為0.237及0.618 kcal/mol,說明吸附屬於吸熱反應,吸附過程以表面離子交換為主。經由初始濃度60mg/l之鋅金屬溶液吸附後碳管,以pH值為1之硝酸溶液在25oC下進行脫附再生,結果發現改質碳管經第十次再生後,仍具有相當高的再生率(76%)。綜合本研究結果,碳管對於處理水中二價鋅離子具有良好的應用潛力。

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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