Analysis of Chemical Deposition in the Ca(OH)2–H3PO4–H2O System

Abstract

The possibility of regulating the structure and morphology of precipitates forming in the CaO–P₂O₅–H₂O system in the low concentration region during neutralization of acidic solutions with lime milk is studied. The effect of the main technological parameters (temperature and pH) on the crystallization of calcium phosphates from dilute CaO–P₂O₅–H₂O solutions, other conditions being equal, is determined. The formation of dicalcium phosphate under neutralization of the model acidic solutions in the range of pH 4.5–6.5 is reported; at higher pH values, the formation of tricalcium phosphate crystalline hydrate is observed. The formation of hydroxyapatite crystals is not established. It is demonstrated by the physicochemical analysis of the forming precipitates that an increase in the neutralization temperature facilitates an increase in the tricalcium phosphate crystallization rate at lower pH values.