A new treatment method for wastewater containing concentrated fluoride and fluoroborate ions by hydrothermal treatment were developed.The treatment is an earth-mimetic method to produce natural minerals by hydrothermal treat-ment with Ca(OH)_2 as a mineralizer.Results of various analyses of the precipitate indicated that the recovered minerals were Ca_2B_2O_5 centre dot H_2O (parasibirskite) and CaF_2 (fluorite).By optimizing the conditions,it was possible to recover more than 98 percent of the boron and 99.9 percent of the fluorine from model wastewater samples containing fluoride (7000 mg L~(-1)) and fluoroborate (8000 mg L~(-1)) ions.Moreover,in the case of fluoroborate ions,the present treatment simultaneously caused the decomposition of the fluoroborate ion,the formation of each minerals,and the preventation of redissolution of parasibirskite.Therefore,the present hydrothermal mineralization treatment with the Ca(OH)_2 min-eralizer is an effective technique to recover boron and fluorine from wastewater.
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