Ceramics-Silikáty 52, (2) 95 - 101 (2008)

The sorption properties of synthetic pure gyrolite (CaO/SiO₂ = 0.66; 96 h; 200°C) for copper ions has been examined. It has been proved that stability and cation exchange capacity of gyrolite depend on concentration of copper ions in the Cu(NO₃)₂ solution. It should be emphasized that crystal structure of gyrolite is quite stable only in the solution when initial amount of Cu²⁺ ions is 1 g/l and its cation exchange capacity is equal to 54.32 mg Cu²⁺/g after 360 min of sorption at 25°C. In the solutions with higher initial concentrations c_Cu²⁺ = 5.0; 10.0; 20.0 g/l, the cation exchange reaction proceed intensively at the beginning of the adsorption process. The amount of adsorbed Cu²⁺ ions in the crystals lattice of gyrolite after 15 min is equal to: 94 mg Cu²⁺/g, when c_Cu²⁺ = 5.0 g/l; 580 mg Cu²⁺/g, when c_Cu²⁺ = 10.0 g/l; 1480 mg Cu²⁺/g, when c_Cu²⁺ = 20.0 g/l. Meanwhile, partial replacement (Ca²⁺ ↔ Cu²⁺) led to amorphization of the gyrolite crystals (lattice) and stimulate the formation of new compounds: gerhardite, gyrolite gel and C–S–H(I). The products of sorption were characterized by X-ray diffraction analysis, simultaneous thermal analysis and Fourier-transform infrared spectroscopy.