| Summary: | 碩士 === 國立臺灣大學 === 環境工程學研究所 === 93 === 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.
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