Effect of calcium silicates on immobilization of fluorine in aqueous solution

Immobilization of fluorine in aqueous solution with 2CaO . SiO2 (C2S) and 3 CaO . SiO2 (C3S), and the effect of C2S and C3S on the fluorine immobilizat ion with 3CaO . Al2O3 (C(3)A) and 12CaO . 7Al(2)O(3) (C(12)A(7)) have been studied. The hydration products are identified by X-ray diffraction method and the fluorine-substituted compounds are confirmed by electron microprobe analysis. It is found that C3S appears more effective to immobilization of fluorine than C2S and (OH-) site in calcium silicate hydrates is substitut ed with F- ion. The behavior of fluorine immobilization by calcium aluminat es changes with the addition of calcium silicates because calcium silicates affect the formation of Ca3Al2(OH)(12-x)F-x, which is the most effective c alcium aluminate hydrate in view of the incorporation of F- ion. The fluori ne immobilization with C(12)A(7) can be promoted in the presence of appropr iate amount of C2S or C3S.