Influence of Ce3+ on the Formation of α-Semi-Hydrate Gypsum

Abstract

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.

DOI: http://dx.doi.org/10.5755/j01.ms.18.4.3102