Influence of Ce3+ on the Formation of α-Semi-Hydrate Gypsum
Influence of Ce3+ on the formation of α-semi-hydrate gypsum was investigated in this work. α-semi-hydrate gypsum is normally obtained by heat conversion of the dihydrate gypsum. The model system: CaSO4·2H2O–Ce2(SO4)3×8H2O was designed. The amount of Ce2(SO4)3×8H2O corresponding to 0.1; 0.5 and 1 % of Ce2O3 from the mass of dry materials (gypsum) was added to solution. Maleic anhydride (C4H2O3)was used as crystal modifier and 0.1 % of C4H2O3 from the mass of dry materials (gypsum) was added to solution. Water/gypsum of the suspension was equal to 2. The system was processed under hydrothermal conditions at 128°C ±2°C and 138°C ±2°C temperature; the duration of isothermal curing was 3 hours. The product obtained was treated at 400°C temperature. The X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) scanning electron microscopy (SEM) was used to characterize the product.The results showed that the larger amount of Ce3+in the system, the larger the remaining amount of un-dehydrated dihydrate gypsum in the final product, and the resulting crystals of α-semi-hydrate gypsum are tiny, indefinite and irregular in shape. Therefore, the results obtained lead to a conclusion that Ce3+ has a negative influence on the dehydration of dihydrate gypsum (or on the formation of α-semi-hydrate gypsum) and the morphology of α-semi-hydrate gypsum crystals.
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