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. [ABSTRACT FROM AUTHOR]