The potential for using zeolite-siliceous rock (ZSR) and calcite (CaCO3) in the solid-phase synthesis of wollastonite, the increase in specific surface area and pore volume, as well as the content of amorphous silica resulting from acid activation, makes it relevant to study the synthesis of wollastonite based on ZSR treated with a hydrochloric acid solution. Under optimal temperature-time synthesis conditions (3 hours, 1175 °C), the yield of wollastonite using activated zeolite-siliceous rock is lower than when using untreated ZSR. This may be due to the fact that high porosity can hinder effective contact between the components, reducing the reaction rate during high-temperature sintering. The decarbonization of CaCO3 occurring during this process likely also plays a role, as the carbon dioxide released at a certain stage of heating can mechanically destroy the forming crystals, especially when the process proceeds very rapidly. The molar ratio of the components should be adjusted, as it becomes suboptimal due to the activation of the ZSR and the increase in amorphous silicon dioxide within it, resulting in the formation of local regions with uneven concentrations of one of the ingredients. This leads to the formation of calcium-rich silicates in regions with high CaO concentrations, as well as the presence of free quartz in regions with an excess of SiO2. The low yield of the final product may be due to the presence of other elements, such as aluminum and magnesium, which are capable of isomorphously substituting calcium in the crystal lattice. Thus, acid activation of the ZSR, taking into account energy and labor costs, is not feasible for the production of wollastonite based on this rock.
ZEOLITE-SILICEOUS ROCK, WOLLASTONITE, SOLID-PHASE SYNTHESIS, ACID ACTIVATION, POROSITY



