Abstract:CaCO3 is an inorganic chemical raw material that can remove Cd2+ from water. However, its surface activity is low, and its removal rate of Cd2+ is low. This limited its large-scale application in the field of removing Cd2+ in water. To improve the surface activity of CaCO3 and enhance its ability to remove Cd2+ from water, natural shell powder was used as CaCO3 raw material, and SiO2 was coated on its surface by carbonation method to prepare CaCO3@SiO2 composite materials with stronger ability to remove Cd2+ from water. Moreover, the reaction mechanism was studied. The results showed that the removal rate and attachment amount of Cd2+ in water were 99.84% and 199.68 mg/g by CaCO3@SiO2, respectively. Under the same conditions, the removal rate and attachment amount of Cd2+ by CaCO3 were 96.32% and 24.08 mg/g, respectively. Compared to CaCO3, the removal rate of Cd2+ by CaCO3@SiO2 increased by 3.52%, and the adsorption capacity increased by 6.29 times. This indicated that after being coated with SiO2, the ability to remove Cd2+ from water by CaCO3 was significantly enhanced. The results of mechanism research indicated that the main way to fix Cd2+ by CaCO3@SiO2 was through its negative charge adsorption on Cd2+ and the complexation of Si-OH with Cd2+ hydroxylates. The fixation of Cd2+ in the CaCO3 system was due to the increase of pH caused by CaCO3, which led to the formation of Cd(OH)2 precipitate and adsorption on the surface of CaCO3. The method used in this study improved the activity of CaCO3 and consumption of CO2 gas. This not only achieves the goal of "treating waste with waste" but also align with the "dual carbon" goal. Therefore, it has important application prospects.