| Abstract [eng] |
The influence of transition metal (Cr3+, Co2+, Cu2+) ions on the crystallization of calcium silicate hydrates compounds in CaO-SiO2-Al2O3-H2O and CaO-SiO2-H2O systems (CaO/SiO2 = 1,5) was investigated in this work. The project evaluated the influence of hydrothermal treatment duration, temperature, nature and concentration of metal ions for synthesized compounds and their properties. It was found, that in the system with Al3+ additive at 200 °C all Cr3+ ions are incorporated into the CSH/CSAH structure, while Cu2+ and Co2+ can participate in various chemical reactions to form coper oxide, copper hydroxide and monticellite. Therefore (due to the ability to interrupt into structure and its wide use), further experiments were performed only with the addition of Cr3+ ions. The structure and properties of the formed compound in the CaO-SiO2-H2O system were influenced by the concentration of Cr(NO3)3 solution as well as the duration of hydrothermal treatment duration and temperature. It was studied that at higher temperature (200 °C) all Cr3+ are incorporated into the structure of compounds formed during synthesis, even at the highest metal concentration (15 g/l). In addition, the higher concentration of chromium ions promotes reaction of raw materials and formation of amorphous structure compounds. Meanwhile, at lower temperature (150 °C) the raw materials react heavier and chromium containing compounds are identified: CaCr3O8 and Ca5Cr2SiO12, Ca5Cr3O12 and / or Ca5Cr3O4,5. These studies are described by XRD, STA, DSC, FT-IR, AAS and SBET instrumental analysis methods. Analysing the structure of the obtained compounds, it was found that the samples are dominated by cylindrical pores. Even more, higher concentration (15 g/) of Cr3+ increases the specific surface area of unburned samples, which significantly decreases after heat treatment. In addition, tasted samples can be uses in adsorption processes, because more than 85 % of metal ions are sorbed from the aqueous solution, which concentration – 1 g Cr3+/l. |
