Stability analysis of hydroxyapatite in the system P-Ca-H2O aided prediction of the mechanisms of dephosphorization from the high phosphorus iron ore by hydrometallurgy process

Abstract

Stability of hydroxyapatite (HA) in the system P-Ca-H2 O at room temperature (298 K) and elevated temperature (363 K) were analyzed in terms of log [P]-pH diagrams to discuss the mechanisms of phosphorus removal from high phosphorus iron ore. The effects of system pH value and temperature on the concentrations of species in the P-Ca-H2 O system were elaborated according to thermodynamic calculation. Lower temperature contributes to improve the dissolution of HA and this effect is more obvious at pH values lower than 11.3. At higher pH values, it is easy to remove phosphorus from iron ores at elevated temperature, attributing to the predominance area of highly soluble PO4 3- and HPO4 2- expansion. On the basis of these thermodynamic analyses, a suitable dephosphorization method of acid leaching at room temperature was proposed for high phosphorus iron ore.