Solid Waste. Application of AlF3 Production Waste to Gyrolite Synthesis

The third chapter of the monograph begins with a literature review about the influence of foreign ions on the formation of synthetic gyroliteSynthetic gyrolite. As the next step, a detailed description of solid wasteSolid waste—silica gelSilica gel contaminated with aluminum and fluorine ionsFluorine ions—is presented. This waste is usually landfilled, which may lead to serious environmental issues. The application of silica gelSilica gel wasteWaste is limited because it contains ~10 wt% of F– ions; however, the high concentration of SiO2 (78.9 wt%) makes this wasteWaste a potential source of silica for the synthesis of silicates. Finally, the synthesis of gyrolite was performed by changing the molar ratio of the initialInitial mixture and raw materials. The results of the experimental part and the thermodynamic calculationsThermodynamic calculations of hypothetical crystallizationCrystallization reactions of calcium silicate hydratesCalcium silicate hydrates in the investigated system showed that the formation of gyrolite family compounds under hydrothermal synthesisHydrothermal synthesis conditions proceeds according to the following sequence: 0.66CaO + SiO2 + H2O → C–S–H(I)C-S-H(I) → Z-phaseZ-phase → gyrolite gel → gyrolite → truscottiteTruscottite. Also, it was determined that silica gel wasteWaste is a prospective SiO2 source for the synthesis of low-base calcium silicate hydratesCalcium silicate hydrates because the formation of gyrolite is two times shorter in comparison with pure mixtures. Meanwhile, calcium nitrateCalcium nitrate is not recommended as a source of calcium because, during synthesis, nitrate anionsAnions intercalate into the structure of gyrolite. As a result, the porosity of gyrolite decreases, which can negatively affect the properties of synthetic gyroliteSynthetic gyrolite.