Powders Synthesized from Calcium Carbonate and Water Solutions of Potassium Hydrosulfate of Various Concentrations

Powders with a phase composition including syngenite (K2Ca(SO4)2·H2O) and/or calcium sulfate dihydrate (gypsum, CaSO4·2H2O) were synthesized from the powder of calcium carbonate (CaCO3) and water solutions of potassium hydrosulfate (KHSO4) of various concentrations (0.5 M, 1 M, and 2 M). A molar ratio of starting salts, KHSO4/CaCO3 = 2, was used to provide the formation of syngenite (K2Ca(SO4)2·H2O). But when using a 0.5 M water solution of potassium hydrosulfate (KHSO4), the phase composition of the synthesized powder was presented by calcium sulfate dihydrate (gypsum, CaSO4·2H2O). When using 1 M and 2 M water solutions of potassium hydrosulfate (KHSO4), the syngenite (K2Ca(SO4)2·H2O) was found as the predominant phase in synthesized powders. According to estimations made from thermal analysis data, powders synthesized using 1.0 M and 2.0 M water solutions of potassium hydrosulfate (KHSO4) contained no more than 7.9 and 1.9 mass % of calcium sulfate dihydrate (gypsum, CaSO4·2H2O), respectively. The phase composition of products isolated from mother liquors via water evaporation consisted of syngenite (K2Ca(SO4)2·H2O) and potassium sulfate (arcanite, K2SO4). Synthesized powders can be used in preparation of biocompatible bioresorbable materials with phase compositions in the K2O-CaO-SO3-H2O system; as matrix of thermo- or photo-luminescent materials; as components reducing the setting time and increasing the strength of sulfate cements; in the fertilizing industry; and also as components of Martian regolith simulants.