Synthesis and phase transformation of hydroxyapatite from Indonesian natural sources

Abstract

Hydroxyapatite (HAp) is an essential material for human bone growth. Several methods of hydroxyapatite synthesis that have been developed are hydrothermal, mechanochemical, and wet precipitation methods. Synthetic HAp applications may vary widely from bone repair, metal implant coating to artificial bone. This study used Padalarang lime and food grade phosphoric acid 85%. Wet precipitation method was proposed based on calculated the stoichiometric molar ratio of Ca/P corresponding for HAp and followed by heat treatment from 600, 700, 800, 900, 1000, 1100, 1200 and 1400°. Structural characterization and thermal analysis were done using X-ray diffraction (XRD) and Thermal Gravimetry / Differential Thermal Analaysis (TG/DTA). The XRD results showed that HAp undergoes phase transformation. Heat treatment from 600° – 900° gave slowly crystallization on HAp. At temperature 1100°, XRD pattern showed the similar crystalline with natural HAp. At temperature 1200 and 1400°, XRD pattern slightly appeared octocalcium phosphate (OCP) crystalline. The result of TG/DTA showed endothermic reactions at temperatures of 165.6, 264.2, 359.5 and 446.8° respectively and an exothermic reaction of 446.8 to 1200°. The largest mass loss was 6.12% during heat treatment until 1000°. Wet precipitation synthesis is the simple method to produce HAp from Indonesian natural sources. Variations of heat treatment give effect on phase transformation from amorphous HAp to crystalline HAp.