Solvent exchange in sulfoaluminate phases. Part II: monosulfate

The influence of organic solvent exchange techniques on the microstructure and the dimensional stability of monosulfate (3CaO.Al₂O₃.CaSO₄.12H₂O) was critically investigated. Monosulfate samples were treated with methanol, ethanol and isopropanol, and examined by different analytical techniques including X-ray diffraction, Fourier transform infrared spectroscopy, thermal gravimetric analysis and scanning electrom microscopy. Nitrogen surface area measurements (Brunauer–Emmett–Teller (BET) method) and length-change of the monosulfate samples in the solvents were also recorded. Evidence was obtained that indicates monosulfate was readily dehydrated from 12 water molecules to ten water molecules once it was treated by the investigated alcohols. The alcohol molecules, however, likely intercalated into the monosulfate structure, limiting an expected decrease in the interlayer distance of the monosulfate structure. Methanol had the greatest damaging effect on the monosulfate microstructure. Ethanol, however, resulted in higher long-term expansion owing to its intermediate molecular size and reactivity with monosulfate compared to methanol and isopropanol.