| Abstract [eng] |
In this work, the synthesis conditions, chemical and physical properties of samples of calcium silicate hydrates (CaO/SiO2 = 1.5) modified with Cu2+, Co2+ or Cr3+ ions were investigated for their formation in a hydrothermal environment and their applicability in heavy metal ion adsorption processes was determined. In a temperature of 150°C in the 1,5CaO-SiO2∙nH2O-mH2O system, the starting materials reacted hard during hydrothermal synthesis, even after 72 h of isothermal curing. When the temperature was increased to 200°C, the starting materials started to react after a minimum residence time (1h) and calcium silicate hydrates were formed in different molar ratios depending on the heavy metal additive. During hydrothermal synthesis (200°C, 1h), it was found that all Cr3+ ions were intercalated into the calcium silicate hydrates structure, whereas Co2+ and Cu2+ ions formed separate compounds. Calcium silicate hydrates substituted with Cr3+ ions were thermally stable up to a temperature of 280°C, as the structure of the compounds formed by hydrothermal synthesis started to decompose in a higher temperature environment. The untreated samples of calcium silicate hydrates substituted with Cr3+ ions were suitable adsorbents for the adsorption of heavy metal ions and 194, 422 or 640 mg Cr3+, Co2+ or Cu2+/g can be removed from the aqueous medium by two processes (hydrothermal synthesis and adsorption). |
