抄録
Calcium aluminoferrite immobilizes hexavalent chromium in a liquid phase following hydration, even under the coexistence of a large quantity of sulfate ions. However, the rate of immobilization is reduced by the coexistence of sulfate ions. In addition, the rate of hexavalent chromium immobilization is significantly affected by the composition of calcium aluminoferrite. Calcium aluminoferrite simultaneously immobilized sulfate ions together with hexavalent chromium in a liquid phase. MASH rapidly decreased chromium in a liquid phase. Compared with MASH, MFSH showed a slower rate of chromium immobilization. Calcium aluminate tended to speed up the removal of chromium in a liquid phase after the generation of monosulfate was recognized. From this fact, it is considered that the reason why the rate of chromium immobilization slows down under the coexistence of sulfate ions is due to the generation reaction of ettringite, which hardly immobilizes chromium, predominantly proceeds in the initial stage of hydration through the interaction between C3A and sulfate ions. On the other hand, in the case of calcium aluminoferrite, the timing of the formation of AFm and the timing when hexavalent chromium is in a liquid phase drastically decreased and were not always corresponding. Judging from the fact that the rate of chromium immobilization of MFSH is slower than that of MASH, AFm, which is generated from calcium aluminoferrite system compounds, is slower in the rate of chromium immobilization compared with MASH.
