| 摘要 |
PROBLEM TO BE SOLVED: To remove fluorine from desulfurized gypsum effectively utilized for a building material such as a gypsum board. SOLUTION: Fluorine-containing gypsum is cleaned with cleaning water with weak acidity or preferably, of pH in the range of 4 to 5 in which an aluminum compound such as aluminum sulfate (Al<SB>2</SB>(SO<SB>4</SB>)<SB>3</SB>-18H<SB>2</SB>O) is dissolved, so that fluorine is eluted from the gypsum into the cleaning water. The fluorine eluted into the cleaning water is subjected to flocculation precipitation with lime water (Ca(OH)<SB>2</SB>) or calcium carbonate (Ca(CO<SB>3</SB>)<SB>2</SB>), and is removed from the cleaning water. COPYRIGHT: (C)2005,JPO&NCIPI
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