METHOD FOR TREATING FLUORINE-CONTAINING LIQUID WASTE

摘要

PROBLEM TO BE SOLVED: To provide a method for treating fluorine-containing liquid waste, in which calcium fluoride and metal hydroxide, which are precipitated at a step of neutralizing fluorine-containing liquid waste containing a fluorine ion and a heavy metal ion, are separated from each other and the former is used satisfactorily in the iron industry as a slag formation promoting agent or an alternative raw material of fluorite being a raw material of hydrofluoric acid and the latter is used satisfactorily in the iron industry as a raw material for stainless steel.

SOLUTION: The method for treating fluorine-containing liquid waste comprises the steps of: adding a calcium-containing substance to the fluorine-containing liquid waste containing the fluorine ion and the heavy metal ion to precipitate calcium fluoride-based particles (a particle precipitation step); adding a polymer flocculant to the calcium fluoride-based particle-precipitated liquid to produce flocks of calcium fluoride-based particles; and subjecting the flock-produced liquid to solid-liquid separation to recover calcium fluoride-based particles as a solid portion. A part of the recovered solid portion is returned at the particle precipitation step to further precipitate calcium fluoride on the precipitated calcium fluoride-based particles and increase the particle size thereof and the calcium fluoride-based particles having the increased particle size are recovered as the solid portion by the solid-liquid separation.

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