Adsorption of Fluoride, Chloride, Bromide, Sulfate and Nitrate onto Commercial and Superparamagnetic Activated Alumina from Aqueous Solutions
Date Issued
2005
Date
2005
Author(s)
Hsiao-Chuan
DOI
zh-TW
Abstract
本研究以商業用的活性氧化鋁（γ-Al2O3）和以溶膠凝膠法（sol-gel method）合成之修飾磁性氧化鋁（modified magnetic alumina via sol-gel method, MMASG）兩種鋁型吸附劑吸附處理含F-、Cl-、Br-、NO3-和SO42-水溶液。γ-Al2O3活化時採用0.01 N NaOH 再生及3.16×10-4 N HNO3 (稱為γ-Al2O3-N) 或HClO4 (稱為γ-Al2O3-P)中和至pH值等於4。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、完全攪拌槽吸附動力分析、小型管柱吸附動力實驗等。此外，亦針對操作因子如pH值和陰離子初始濃度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(參考林(2004) 之合成方法進行部份修正)於Fe3O4表面包覆SiO2，得到SiO2/Fe3O4磁性載體；再以溶膠凝膠法於磁性載體表面合成氧化鋁，可製備得修飾磁性氧化鋁吸附劑。Fe3O4、磁性載體及MMASG之飽和磁化強度分別為59.24、8.5和8.269 emu/g，皆具有超順磁性。X射線繞射(x-ray diffraction, XRD) 之鑑定結果顯示MMASG表面之鋁氧化物為三羥氧化鋁（bayerite）結構。
等溫吸附試驗之結果顯示以Langmuir與Freundlich等溫吸附方程式皆能有效的描述氧化鋁 (γ-Al2O3-N)、MASG (林(2004)所合成之磁性氧化鋁)和MMASG (本研究所合成之修飾磁性氧化鋁)等三種吸附劑吸附強鍵結的氟離子在鋁表面的行為。單就單層飽和吸附量（qL）而言，MMASG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。對於弱建結之Cl-、Br-、NO3-和SO42- 離子，Langmuir等溫吸附方程式也可描述良好。
假性二階動力程序（pseudo-second-order equation）及Elovich rate equation可有效的模擬γ-Al2O3-P 和MMASG於完全混合反應槽(completely stirred tank reactor, CSTR)中對含F-、Cl-、Br-、NO3-和SO42-離子之吸附動力。
小型γ-Al2O3-P管柱吸附貫穿實驗以 Yoon and Nelson 方程式描述半導體產業廢水中的個別五種單離子，皆有良好的適用性。所求得之參數值期望可用來評估應用於實廠廢水之吸附行為。以小型管柱吸附貫穿實驗模擬半導體實廠廢水(實驗條件為配製含 F- 、Cl-、Br-、NO3- 和 SO42-值為 54、2.2、1.1、10 和2 mg/L而初始pH值為4之水溶液)之吸附去除效果。結果顯示γ-Al2O3-P吸附可有效去除半導體廢水中之氟離子；對於弱鍵結之陰離子(如：Cl-、Br-及NO3-)而言，其吸附去除效果較差。則須進一步評估。
雖然MMASG因為顆粒很小不適用於管柱吸附，但由於MMASG與γ-Al2O3-N之等溫吸附平衡參數值比較，顯示MMASG對於強鍵結之氟離子及弱鍵結之陰離子之去除效果與γ-Al2O3-N在定性上一致。
The main species of the aged scrubbing solution in the semiconductor manufacturing industries are F-, Cl-, Br-, NO3- and SO42- with concentrations of about 54, 2.2, 1.5, 10 and2 mg/L respectively. The pH value of the solution is about 3.6. Therefore, on the basis of the results obtained from Lin (2004), the adsorption process applied in the removal of anions, including F-, Cl-, Br-, NO3- and SO42-, from the synthesized aqueous solutions was investigated in this study.
Commercial activated alumina activated using 0.01 N NaOH followed by 3.16×10-4 N HNO3 (noted as γ-Al2O3-N) or HClO4 (denoted as γ-Al2O3-P) and modified magnetic alumina adsorbent, which was synthesized employing sol-gel method (called as MMASG), were used as the alumina-type adsorbents. The physicochemical characteristics of two adsorbents and factors affecting the adsorption equilibrium and kinetics were further examined in the study.
The Langmuir and Freundlich isotherms were successfully used to predict the adsorption equilibrium behavior of the target anions onto γ-Al2O3-N and MMASG. The monolayer equilibrium adsorption capacity (qL) of MMASG is higher than that of γ-Al2O3-N. Besides, MMASG which was prepared by Fe3O4 coated with SiO2 and sequentially synthesized by sol-gel method in this study, can properly be applied in the removal of the said anions from solutions.
Regarding the adsorption kinetics of the target anions from solutions, among the kinetic models tested (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 the said anions onto γ-Al2O3-P and MMASG in a completely stirred tank reactor (CSTR).
The removal of anions by the commercial activated Al2O3-P was also carried out in a fixed-bed adsorber. The operating conditions were at pH value of 4 with various inlet concentrations for the fed anionic solutions. In addition, the adsorption patterns of anions can be divided into two types: inner-sphere (“chemical bond”) adsorption, such as F- and SO42-, and outer-sphere complex (ion pair) adsorption, such as Cl-, Br- and NO3-. Besides, Yoon and Nelson equation for breakthrough modeling can well predict the adsorption kinetics of anions onto γ-Al2O3-P in a fixed-bed adsorber.
This study takes into account for the practical data of the aged scrubbing solution in the semiconductor manufacturing industries. The results indicate that γ-Al2O3-P and MMASG possess proper potential as the adsorbents for the application of adsorption process in the defluoridation from aged scrubbing solution. As for the weak anions such as Cl-, Br- and NO3-, the applicabilities of the γ-Al2O3-P and MMASG are moderate.
Subjects
氟化物
氯化物
溴化物
硫酸根
硝酸根
吸附
活性氧化鋁
磁性氧化鋁
半導體LSR
Activated alumina
magnetic alumina
adsorption
defluoridation
adsorption isotherm
pseudo-first-order equation
pseudo-second-order equation
Elovich rate equation
precipitation method
sol-gel method
Type
thesis
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