Carbonate-containing apatite (CAP) synthesis under moderate conditions starting from calcium carbonate and orthophosphoric acid

Abstract

The synthesis of carbonate-containing apatite (CAP) from calcium carbonate and orthophosphoric acid under moderate conditions was investigated. In all cases, complete precipitation of orthophosphate species was observed. The reaction temperature influenced strongly the decomposition of calcium carbonate and therefore the composition of formed products. The reaction temperature of 80 °C was found to be effective for the complete decomposition of calcium carbonate particles after 48 h of reaction. Infra-red spectroscopy (IR), nuclear magnetic resonance (NMR), thermogravimetry/mass spectroscopy (TG-MS) coupling, and X-ray diffraction (XRD) characterizations allowed the identification of the composition of formed products. By increasing the reaction temperature from 20 °C to 80 °C, the content of A-type CAP increased and that of B-type CAP decreased, according to the favorable effect of temperature on the formation of A-type CAP. The total amount of carbonate content incorporated in CAP's structure, which was determined by TG-MS analysis, increased with the reaction temperature and reached up to 4.1% at 80 °C. At this temperature, the solid product was mainly composed of apatitic components and showed the typical flat-needle-like structure of CAP particles obtained in hydrothermal conditions. These results show an interesting one-step synthesis of CAP from calcium carbonate and orthophosphoric acid as low cost but high purity starting materials.

Hydroxyapatite starting from calcium carbonate and orthophosphoric acid: synthesis, characterization, and applications

“…The low-intensity peak at 630 cm -1 was attributed to hydroxyl groups. As expected, characteristic peaks of carbonate groups inserted in the apatitic structure were found at 1545, 1450, 1415, 880, and 870 cm -1 [32]. The intensity of the carbonate bands of the product synthesized at 13 bar was much higher than that of the product synthesized at atmospheric pressure.…”

“…The slight next weight losses in the temperature range of 175-360°C may be attributed to the dehydration/condensation of DCPD (dicalcium phosphate dehydrate, or brushite, CaHPO 4 Á2H 2 O) and DCPA (dicalcium phosphate anhydride, or monetite, CaHPO 4 ) [31]. Residual calcium carbonate was thermally decomposed around 610°C, followed by the decarbonation of carbonated apatite (CAP) around 720°C [31,32]. In parallel with these apparent weight losses, a continuous weight loss was observed with the increase of the temperature up to 1310°C, which was assigned to the partial transformation of OHanions of Ca-HA to molecular water and bivalent oxygen.…”

“…After 48 h of reaction, the powder was recovered by filtration and drying steps. Details of the synthesis process were reported [32]. Figure 8 compares IR spectra of two solids obtained under atmospheric pressure and under 13 bar.…”

“…The bioactivity test was then carried out for CAP synthesized under high-CO 2 pressure. Details of this test were described elsewhere [32]. As shown in Fig.…”

Carbonated hydroxyapatite starting from calcite and different orthophosphates under moderate hydrothermal conditions: Synthesis and surface reactivity in simulated body fluid

“…[1][2][3]. This explains the interest in the development of Ca-HA and substituted Ca-HA in the biomaterials field, due to their biocompatibility and bioactivity [4,5]. Substituted Ca-HA is formed when calcium, phosphate, and/or hydroxyl groups of Ca-HA structure are replaced by other metals and functional groups.…”