Cu²⁺, Co²⁺ and Cr³⁺ adsorption by synthetic dibasic calcium silicate hydrates and their thermal stability in a 25–1000 °C temperature range

In this work, the adsorption capacity of Cu²⁺, Co²⁺ and Cr³⁺ by synthetic dibasic calcium silicate hydrate sample as well as its thermal stability was examined. The synthesis of dibasic calcium silicate hydrate was carried out in unstirred suspensions, when CaO/SiO₂ molar ratio of primary mixture was equal to 1.5 and the duration of isothermal curing at 175 °C temperature was 16 h. Afterwards, metal ions were incorporated into the synthesis products; the experiments were carried out at 25 °C temperature by stirring 5 g of synthetic dibasic calcium silicate hydrate in 500 mL of Co(NO₃)₂·6H₂O, Cr(NO₃)₂·9H₂O or Cu(NO₃)₂·3H₂O solutions containing 1 g of Co²⁺, Cr²⁺ or Cu²⁺ dm⁻³ for 30 min. It was obtained that after adsorption all metal ions (100 mg Me²⁺ g⁻¹) were intercalated into the structure of synthesis products. In situ X-ray diffraction study on the thermal stability of synthesized compounds was performed in a modular temperature chamber from RT to 1000 °C temperature. The obtained results were confirmed by XRD, STA, FT-IR, AAS and SEM methods.