EFFECT OF CU2+ ION ON THE STRUCTURAL STABILITY OF SYNTHETIC HYDROXYAPATITE

The reaction of synthetic hydroxyapatite, Ca5(PO4)3OH (HAP), with Cu2+ ions is investigated by means of pH, pCu and pCa measurements as a function of the time and temperature (30, 40, 45 and 60-degrees-C) and at different CU2+:Ca2+ molar ratios in the range 0.01-1.07. The solid phases separated after different times of reaction were investigated with XRD and IR techniques. The Cu2+ ions give rise to an acidic solution and promote HAP dissolution; HAP does not incorporate the Cu2+ ions and a new phase corresponding to the mineral Cu2(PO4)OH (Libethenite) crystallizes quantitatively. In the course of the reaction, with the ratio Cu2+:Ca2+ in the range 0.1-1, the pH decreases owing to the release of phosphoric acid, whereas it increases for the ratio 0.01. At physiological ionic strength, obtained with NaCl, the solid phase containing Cu is again libethenite, but the process is notably accelerated.