REACTIVE CRYSTALLIZATION OF CALCIUM-PHOSPHATE

The reactive crystallization of calcium phosphate by equimolar calcium nitrate and potassium phosphate has been studied in batch and continu ous systems at conditions of reaction temperature 25 or 50 degrees, an d initial calcium or total phosphate concentration of 4.0 to 16.0 mmol dm(3). In the batch system at 25 degrees, the induction time, t(ind) [min], was correlated with the initial supersaturation of amorphous tr icalcium phosphate (ACP), Ca-3(PO4)(2) . nH(2)O, beta(I,ACP), and the initial pH by the following equation: t(ind) = 1.52 x 10(-11) beta(I,A CP)(-0.337) pH(15.9) In the case of the addition of a single component in the whey, the lactalbumin exerted a great influence on the inhibit ion of the reactive crystallization of calcium phosphate. In the conti nuous system, the pH and the calcium concentration changed stepwise wi th the reaction time and the reactive crystallization of calcium phosp hate showed remarkable morphological variations for the start-up of th e continuous system. At the steady state, two different precipitation phases, that is, dicalcium phosphate dihydrate (DCPD), CaHPO4 . 2H(2)O , and octacalcium phosphate (OCP), Ca8H2(PO4)(6) . 5H(2)O, were obtain ed finally.