No.7（2004）14.Removal method of Fluorine from wastewater

Kenji OTSUKA, Akira HASEGAWA, Shigeru NAGASHIMA, Yukio KOSAKA

Water pollution control laws stipulate that the regulation value of fluorine is to be less than 8mgF/L. But it has proved to be too difficult to meet this in the treatment of wastewater, including tetrafluoroborate ion(BF4^-). The removal conditions of fluorine from wastewater was then studied using a coprecipitation method with the addition of aluminum ion(Al³⁺) and magnesium ion(Mg²⁺).. 

In order to decompose BF4^-, Al³⁺ was added into the wastewater, and was sitted for 60minutes' at room temperature. After the removal of aluminum hydroxide, Mg²⁺ was added into the filtrate. The solution was adjusted to pH 10-10.5 with a sodium hydroxide solution, and made to react to 10 minutes' of stirring. The fluorine in the solution was precipitated together with products of magnesium. By using the present procedure, it was found that less than 300mgF/L of fluorine (F of BF₄^-:100mgF/L, F-:200mgF/L) in the wastewater could be removed to a degree below the fluorine regulation value to less than 1mgF/L.

Keywords
Wastewater, Treatment, Tetrafluoroborate ion, Room temperature, Aluminum ion, Magnesium ion

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