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  • 學位論文

以商業用及新穎奈米磁性氧化鋁吸附處理含氟水溶液

Adsorption of Fluoride onto Commercial Activated Alumina and Novel Magnetic Fluoride Selective Nano-adsorbents from Aqueous Solutions

指導教授 : 張慶源

摘要


本研究以商業用之活性氧化鋁(γ- Al2O3)和兩種新穎奈米級磁性氧化鋁(分別以沉澱法合成之磁性氧化鋁(MAP)、及溶膠凝膠法合成之磁性氧化鋁(MASG))等三種鋁型吸附劑吸附處理含氟水溶液,研究內容包含了吸附劑之物理化學特性鑑定分析、等溫吸附行為、吸附動力學分析、小型管柱動力實驗等。此外,亦針對操作因子如pH值、離子強度、氟離子初始濃度、管柱實驗操作參數等對處理效果之影響進行探討。 以共沉澱法製備奈米級Fe3O4超順磁性顆粒、並以緩慢加酸法於Fe3O4表面包覆SiO2,得到(SiO2/Fe3O4)磁性載體;再分別經由沉澱法(Precipitation method)及溶膠凝膠法(Sol-Gel method)於磁性載體表面合成氧化鋁,可製備得奈米級磁性氧化鋁吸附劑(即MAP和MASG)。Fe3O4、磁性載體、MAP、及MASG之顆粒粒徑(dp,NMD)分別為:7 nm、31.3 nm、37.5 nm及33 nm;飽和磁化強度分別為59.24、8.16、8.69和8.73 emu/g,皆具有超順磁性;XRD之鑑定結果顯示MAP及MASG表面之鋁氧化物為三羥氧化鋁(Bayerite)結構。 等溫吸附試驗之研究結果顯示以Langmuir與Freundlich等溫吸附方程式皆能有效的模擬氟離子吸附在氧化鋁、MAP和MASG等三種吸附劑表面之行為。MAP和MASG對氟離子之吸附行為亦適用線性(linear)等溫吸附方程式模擬。單就單層飽和吸附量(qL)而言,MASG為本研究中所使用三種吸附劑中對氟離子吸附效果最佳者。假性二階動力程序(pseudo-second-order equation)及Elovich rate equation可有效的模擬MASG於CSTR中對氟離子之吸附動力。 小型吸附管柱貫穿實驗中,所求出之最適操作條件為:溶液之初始pH值為4、再生液(NaOH)強度為0.01N、及再生後之氧化鋁中和至pH=4以進行下一循環之吸附,此系統之吸附能力可維持長時間(14個完整循環以上)之穩定。當溶液之初始pH值越低,其吸附氟之能力越強,應是表面具有帶正電之官能基(S-OH2+)有效的增加,促進提升對氟離子的吸附容量。實驗中無法得到一氟離子完全貫穿之曲線,顯示氧化鋁具有緩衝之特性,並使溶出之Al3+可以持續生成氫氧化鋁膠羽,而達到氟吸附去除之目的,故此系統之吸附行為應可分為氧化鋁之吸附及氫氧化鋁膠羽之吸附,後者作用最顯著的地方應於高原遲緩期(plateau)處。 本研究期以表面複合模式(Surface complex formation model)為基礎,預測氧化鋁對含氟溶液之吸附貫穿曲線動力,但因模式仍於開發測試階段,目前尚無法進行貫穿曲線動態模擬。現階段以表面複合理論中兩性離子交換器之多重單價離子系統描述氧化鋁對氟離子之等溫吸附行為,並求出與等溫吸附相關之表面複合理論參數( 與m(H,F)),以作為將來預測氧化鋁對含氟溶液之吸附貫穿曲線動力之基礎。 半導體製造廠LSR系統中,WA樹脂塔進流廢水成分主要為氟離子,濃度約為54 mg/L,其餘陰離子包括Cl-、BrO3-、NO3-和SO42-等濃度分別為2.2、1.1、9.2和1.5mg/L,且pH值偏低(=3.6),初步認為此股廢水應適合以活性氧化鋁或磁性氧化鋁等鋁型吸附劑,進行溶液中氟之吸附去除處理,且其操作條件可以本研究小型管柱實驗所得之最適操作條件為基礎。

並列摘要


The adsorption process applied in the removal of fluoride from aqueous solutions was investigated in this study. Commercial activated alumina (γ-Al2O3) and two novel magnetic alumina adsorbents, which were synthesized by precipitation method (MAP) and sol-gel method (MASG), were used as the alumina-type adsorbents. The physicochemical characteristics of three adsorbents and factors affecting the adsorption equilibrium and kinetics were further examined in this study. The Langmuir and Freundlich isotherms were successfully used to predict the adsorption behavior of fluoride onto γ-Al2O3, MAP, and MASG, in which the monolayer adsorption capacity (qL) of MASG is the highest among three adsorbents. Furthermore, the linear isotherm also well described the adsorption behavior of fluoride onto both novel magnetic nano-adsorbents, MAP and MASG. Therefore, the novel magnetic nano-adsorbents, which were prepared by Fe3O4 coated with SiO2 and sequentially synthesized by means of precipitation and sol-gel methods in this study, can successfully be applied in the removal of fluoride from solutions. Regarding the adsorption kinetics of fluoride from solutions, among the tested kinetics models in this study (e.g. pseudo-first-order equation, pseudo-second-order equation and Elovich rate equation), both the pseudo-second-order equation and Elovich rate equation can well predict the adsorption kinetics of fluoride onto MASG in CFSTR. The removal of fluoride by commercial Al2O3 was also carried out in the fixed-bed adsorber. The optimal operating conditions were the pH value of 4 for the fed fluoride solution, the regeneration agent (NaOH) of 0.01 N, and the neutralization pH of 4 by means of 3.16×10-4 N HNO3. Under the optimal conditions, the removal efficiency of fluoride from solutions was not reduced for at least fourteen runs. In addition, the fluoride adsorption capacity increased with decreasing pH of fluoride solution and can be divided into two parts: adsorbed by alumina and by aluminum hydroxide, in which the former might be the major mechanism in the whole adsorption process and the latter mainly influenced the adsorption in the plateau area. The main composition and pH value of the aged scrubbing solution in the semiconductor manufacturing industries are fluoride of 40~ 60 mg/L, and 3.6, respectively. Therefore, on the basis of the data obtained from this study it is deduced that Al2O3, MAP and MASG possess high potential as the adsorbents for the application of adsorption process in the defluoridation from aged scrubbing solution.

參考文獻


顏雅侖,「錳鋅鐵氧化物磁性流體之製備及分散研究」,國立成功大學資源工程研究所碩士論文,2002。
Abe, I., S. Iwasaki, T. Tokimoto, N. Kawasaki, T. Nakamura and S. Tanada, “Adsorption of Fluoride Ions onto Carbonaceous Materials,” J. Colloid Interface Sci., 275, 35, (2004).
Bahena, J. L. R., A. R. Cabrear, A. L. Valdivieso and R. H. Urbina, “Fluoride adsorption onto alpha-Al2O3 and its Effect on the Zeta Potential at the Alumina-aqueous Electrolyte Interface,” Sep. Sci. Technol., 37(8), 1973, (2002).
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被引用紀錄


許紫菱(2006)。以奈米超順磁性二氧化鋯吸附處理陰離子溶液〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2006.00270
王曉娟(2005)。以商業用及超順磁活性氧化鋁吸附處理陰離子溶液以商業用及超順磁活性氧化鋁吸附處理陰離子溶液〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2005.01070

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