Study on Phase Evolution of Calcium Silicate Hydrate (C-S-H) During Solidification of Cr(VI) under Hydrothermal Conditions

In this paper, calcium silicate hydrate (C-S-H) was synthesized by hydrothermal method using CaO and quartz sand as raw materials. The solidification effect of Cr(VI) in C-S-H was studied using XRD, FTIR, and SEM. The leaching amount of Cr(VI) after solidification was determined by anatomic absorption spectrometer to analyze and calculate the solidification rate of Cr(VI). Results show that appropriately increasing the reaction temperature and prolonging the reaction time can help improve the crystallinity of C-S-H. A small Cr(VI) dosage of Cr/Si < 0.05 is beneficial for the crystallization of C-S-H, but when Cr/Si > 1.0, Cr(VI) ions inhibit the formation of C-S-H. When Cr/Si <0.15, the solidification efficiency of C-S-H on Cr(VI) decreases with increasing Cr(VI) content; The C-S-H with Ca/Si = 1 has the best solidification efficiency for Cr(VI).