Powders Synthesized from Calcium Chloride and Mixed-Anionic Solution Containing Orthophosphate and Carbonate Ions

Low-crystalline hydroxyapatite was synthesized from an aqueous solution of calcium chloride (CaCl2), and a mixed-anionic (HPO42− и CO32−) aqueous solution prepared from potassium hydrophosphate trihydrate (K2HPO4 3Н2О), and potassium carbonate (K2CO3). The interaction of K2CO3 and K2HPO4 salts during synthesis from a mixed-anionic solution in the reaction zone without additional regulation provided the pH level necessary for the synthesis of hydroxyapatite. For comparison, as references, powders were also synthesized from an aqueous solution of CaCl2 and from aqueous solutions of either K2HPO4 or K2CO3. The phase composition of the powder synthesized from aqueous solutions of CaCl2 and K2HPO4 included brushite (CaНРО4·2H2O). The phase composition of the powder synthesized from aqueous solutions of CaCl2 and K2CO3 included calcite (CaCO3). The phase composition of all synthesized powders contained potassium chloride (sylvine, KCl), as a reaction by-product. After heat treatment at 1000 °C of the powder containing low-crystalline hydroxyapatite and KCl, powder of chlorapatite (Са10(РО4)6Cl2) was obtained. After heat treatment of a powder containing brushite (CaНРО4·2H2O) and KCl at 800 and 1000 °C, a powder with the phase composition including β-calcium pyrophosphate (β-Ca2P2O7), β-calcium orthophosphate (β-Ca3(PO4)2), and potassium-calcium pyrophosphate (K2CaP2O7) was obtained. Heat treatment of calcite (CaCO3) powder at 800 °C, as expected, led to the formation of calcium oxide (CaO). Synthesized powders, including biocompatible minerals such as hydroxyapatite, chlorapatite, brushite, monetite, calcium pyrophosphate, calcium potassium pyrophosphate, tricalcium phosphate, and calcite, can be used for the creation of biocompatible inorganic materials or composite materials with a biocompatible polymer matrix. The potassium chloride present in the synthesized powders can act as one of the precursors of biocompatible minerals, such as chlorapatite or calcium potassium pyrophosphate, or it can be treated as a removable inorganic porogen.