Ultra-fast route to synthesizing biogenic carbonate hydroxyapatite: Consequence of a high-pressure solid-solid preparation technique

[Display omitted] •Solid (calcium)-solid (phosphate) reaction was proposed.•CO2 was used as reactant and reaction media at high-pressure.•The reaction was self-catalytic and ultrafast.•Carbonate contents similar to biological apatites were produced.•The product has high surface area and is an efficient ibuprofen delivery agent. We employed a high-pressure solid–solid preparation technique in CO2 to synthesize carbonate hydroxyapatite (CHAp) powders from solid calcium and phosphate precursors. The synthesis parameters were investigated and optimized to determine the best precursor and optimal synthesis conditions. The results showed that the technique is green and that the biogenic calcium from eggshells in supercritical CO2 yielded B-type CHAp with desirable and recommended carbonate contents (4.1–5.1 wt %). The biogenic calcium source also yielded product with excellent surface area (212.4m2/g) and pore volume (0.65 cm3/g) compared to the synthetic calcium source, which exhibited high ibuprofen loading (270.0 mg/g) and enhanced dissolution (100% in 6 h) in simulated gastric fluid. These results indicate that the CHAp has potential for medical and other related applications. Mechanism study revealed that the procedure is a self-catalytic reaction triggered by water in the reactants with short time, which can overcome the disadvantages of existing techniques commendably.