# 효율적 제철폐수의 처리를 위한 희토류 화합물과 칼슘화합물의 운전인자 연구

• Lee, Chang-Yong (Department of Environmental Engineering, Kongju National University) ;
• Lee, Sang-Min (Department of Environmental Engineering, Kongju National University) ;
• Kim, Wan-Joo (Department of Chemical Engineering, Seoul National University of Technology) ;
• Choi, Ko-Yeol (Department of Chemical Engineering, Seoul National University of Technology)
• 이창용 (공주대학교 환경공학과) ;
• 이상민 (공주대학교 환경공학과) ;
• 김완주 (서울산업대학교 화학공학과) ;
• 최고열 (서울산업대학교 화학공학과)
• Accepted : 2006.08.18
• Published : 2006.10.10
• 54 0

#### Abstract

The behavior of rare earth compounds such as $La_{2}O_{3}$, $CeO_{2}$, and $Ca(OH)_{2}$ on the removal of fluoride and heavy metals in the steel wastewater has been investigated. The removal mechanism of fluoride by rare earth elements has been known to be the formation of insoluble compounds between $F^{-}$ and cations such as $La^{3+}$ and $Ce^{4+}$ produced by the dissociation of rare earth compounds (To reduce the running cost of the fluoride wastewater treatment facility, their fluoride removal efficiencies were compared with those of inexpensive rare earth minerals such as natural lanthanide and cerium compound used as a glass polishing agent). All of the rare earth oxides used in this study showed a higher removal efficiency of fluoride than $Ca(OH)_{2}$ in the wastewater. In the case of artificial HF solution, the removal efficiency of fluoride showed in the order: $CeO_{2}$-mineral < $CeO_{2}$ < $Ca(OH)_{2}$ < $La_{2}O_{3}$-mineral < $La_{2}O_{3}$. However, the removal efficiency of fluoride in the wastewater increased in the following order: $Ca(OH)_{2}$ < $CeO_{2}$ mineral < $CeO_{2}$ < $La_{2}O_{3}$ mineral < $La_{2}O_{3}$. All agents showed high efficiencies for the removal of Mn and total Cr in the rare earth compounds. In the case of $Ca(OH)_{2}$, fluoride removal decreased with increasing pH while. However, the rare earth compounds showed a higher fluoride removal in higher pH condition, the optimum pH condition seemed to be around 7 considering both water quality and fluoride removal. Under the pH 7 condition, the $Ca(OH)_{2}$ was superior to rare earth compounds in Mn removal and the lanthanide was superior to others in total Cr removal.

#### Keywords

rare earth minerals;fluoride;stainless steel wastewater;$Ca(OH)_{2}$;heavy metals

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