Influence of Cr3+, Co2+ and Cu2+ on the formation of calcium silicates hydrates under hydrothermal conditions at 200 °C

Abstract

This work aims to investigate the influence of Cr3+, Co2+ and Cu2+ on the formation of calcium silicates hydrates in CaO-SiO2-Al2O3-H2O system under hydrothermal conditions. The dry primary mixture with the molar ratio CaO/(SiO2+ Al2O3) = 1.5 and Al2O3/(Al2O3+ SiO2) = 0.05 was mixed with heavy metal nitrate solutions (metal ions concentration – 10 g/l) to reach the water/solid ratio of the suspension equal to 10.0. The hydrothermal synthesis was carried out in unstirred suspensions, under saturated steam pressure at 200°C temperature for 0–72 hours. It was determined that nature of metal ions have influence on both mineral composition and thermal stability of synthesis products. It was obtained that by increasing synthesis temperature up to 200°C, all Cr3+ and Co2+ ions were intercalated into the structure of synthesis products. Meanwhile Cu2+ ions participate in chemical reactions and as a result copper oxide were formed. The products of synthesis were characterized by STA, DSC, XRD and AAS analyses.

Keywords

• calcium silicate hydrates
• heavy metal ions
• hydrothermal synthesis
• metal oxides
• calcium chromate