Synthetic Calcium Sulfates from Industrial Wastes

A promising analog of natural gypsum raw materials are synthetic calcium sulfates obtained from sulfuric acid and calcium carbonate materials derived from different wastes in the CaCO 3 -H 2 SO 4 -H 2 O system. Synthetic calcium sulfates have a significant advantage over natural ones, due to the fact that during synthesis it is possible to control the structure of the resulting crystals and particles. By controlling the technological parameters of the synthesis, crystals of an acicular, prismatic or lamellar shape with aggregates sizes from 200 to 600 μm were obtained. The main effects have deviations up to 50°С compared to natural gypsum. The possibility of obtaining calcium sulfate anhydrite in one technological stage at an ambient temperature of 45°C–95°С was worked out. The main advantage of the synthesis of calcium sulfates in the CaCO 3 -H 2 SO 4 -H 2 O system is the control of the structure of the resulting materials, depending on the requirements for them.