The effect of hydrothermal treatment conditions and silica source on the formation of cuspidine

The influence of temperature and duration on the formation of cuspidine during hydrothermal synthesis was investigated in the CaO-SiO2 center dot nH(2)O and CaO-silica gel waste-CaF2-H2O systems. The reaction was carried out in the temperature range of 95-200 degrees C for 4-48 h. In the system with amorphous silica, cuspidine was determined to form at 130 degrees C within 12 h. At higher temperatures (150-200 degrees C) its formation started earlier (within 4 h). Portlandite reacted completely in the temperature range of similar to 170-200 degrees C; meanwhile, a part of fluorite remained unreacted up to 200 degrees C. The surface area of the obtained synthetic cuspidine sample (200 degrees C, 12 h) was 56.9 m(2) g(-1). In the CaO-silica gel waste-CaF2-H2O system, cuspidine formed within 4 h and it was the main compound in the synthesis products with an admixture of katoite, which formed due to the presence of aluminium ions in the waste material. The SEM images showed that synthetic cuspidine samples from both systems exhibited a scaffold-like structure. The mineralogical composition of the synthesised products remained stable up to 48 h. The synthetic products were investigated by XRD, STA, FT-IR, BET and SEM analysis methods.

Automated summary

The influence of temperature and duration on the formation of cuspidine during hydrothermal synthesis was investigated in two different systems. Cuspidine was found to form at 130 degrees C within 12 h in the CaO-SiO2 center dot nH(2)O system, and at higher temperatures (150-200 degrees C) its formation started earlier (within 4 h). Synthetic cuspidine samples from both systems exhibited a scaffold-like structure. The mineralogical composition of the synthesized products remained stable up to 48 h.