Dissolution Behavior and Stabilization of Fluorine in Secondary Refining Slags

Dissolution of fluorine in secondary refining and synthetic CaO-SiO 2 -Al 2 O 3 l(-P 2 O 5 ) slags has been studied by using the shaking test and its behavior is discussed based on the results for the time dependence of Ca, Si, Al and F contents in aqueous solution. It was found that fluorine dissolution is affected by the contents of SiO 2 , F and total Fe in slag and particularly its effect is obvious in synthetic slags. The dissolved fluorine from slags with low contents of SiO 2 and total Fe can be immobilized through the incorporation of fluorine into precipitated hydrates such as CaO-Al 2 O 3 -H 2 O compound and CaO-SiO 2 -Al 2 O 3 -H 2 O gel. In the case of slags with high SiO 2 and low total Fe contents, the dissolved fluorine can be immobilized through the formation of CaO-SiO 2 -H 2 O-SO 4 -F gel by the addition of gypsum to aqueous solution. The dissolution behavior of fluorine in seawater has been also studied.