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The immobilization of fluorine by calcium aluminum ferrites has been studied using 20 mass ppm F-containing aqueous solution. It is found that the rate of the F immobilization by Ca2(Al,Fe)2O5, is initially slower than that by 3CaO Al2O3, at the solid/liquid ratio of 1/200, but a similiar immobilization degree is obtained at later stage. The hydration product contributed to the F immobilization is the Ca3(Al,Fe)2(OH,F)12 phase, which is confirmed by the combination of XRD and electron microprobe analysis. For a ferrite phase of Ca2(Al(0.68)Fe(0.32)2O5, the hydration product has a chemical composition of Ca3Al(1.54)Fe(0.46)((OH)(1-x)F(x))12 (x=0 - 0.13). The F immobilization by 2CaO Fe2O3 does not occur to a significant extent, but the F immobilization by 12CaO 7Al2O3 is accelerated with the addition of 2CaO x Fe2O3 due to the formation of the Ca3(Al,Fe)2(OH,F)12 phase. It is also observed that F can be immobilized by the formation of ettringite (3CaO Al2O3 3CaSO4 32H2O, 3CaO Fe2O3 3CaSO4 32H2O) through the substitution of F(-) ion for the SO(2-)4 site.
The immobilization of fluorine by calcium aluminum ferrites has been studied using 20 mass ppm F-containing aqueous solution. It is found that the rate of the F immobilization by Ca2(Al,Fe)2O5, is initially slower than that by 3CaO Al2O3, at the solid/liquid ratio of 1/200, but a similiar immobilization degree is obtained at later stage. The hydration product contributed to the F immobilization is the Ca3(Al,Fe)2(OH,F)12 phase, which is confirmed by the combination of XRD and electron microprobe analysis. For a ferrite phase of Ca2(Al(0.68)Fe(0.32)2O5, the hydration product has a chemical composition of Ca3Al(1.54)Fe(0.46)((OH)(1-x)F(x))12 (x=0 - 0.13). The F immobilization by 2CaO Fe2O3 does not occur to a significant extent, but the F immobilization by 12CaO 7Al2O3 is accelerated with the addition of 2CaO x Fe2O3 due to the formation of the Ca3(Al,Fe)2(OH,F)12 phase. It is also observed that F can be immobilized by the formation of ettringite (3CaO Al2O3 3CaSO4 32H2O, 3CaO Fe2O3 3CaSO4 32H2O) through the substitution of F(-) ion for the SO(2-)4 site.
Immobilization of fluorine in aqueous solution by calcium aluminum ferrite and the mixture of calcium aluminate and gypsum
Ruhigstellen von Fluor in einer wässrigen Lösung durch Kalzium-Aluminium-Ferrit und einem Gemisch aus Kalziumaluminat und Gips
ISIJ International ; 42 ; 794-799
2002
6 Seiten, 9 Bilder, 1 Tabelle, 7 Quellen
Article (Journal)
English
Caesium immobilization in hydrated calcium-silicate-aluminate systems
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