A microwave-assisted hydrothermal method for rapidly synthesizing nanocrystalline carbonated hydroxyapatite from calcium resources in crab shell waste

Nanocrystalline carbonated hydroxyapatite (CHA) shows significant promise for bone replacement within biomedical applications. This study aimed to synthesize nanocrystalline CHA using calcium resources from crab shell waste through a microwave-assisted hydrothermal technique. In this way, the crab shells were initially pulverized and calcined at 900° C for 5 h, yielding Ca(OH)₂ powder. This powder was then dissolved in a prepared hydrothermal solution of diammonium phosphate and subjected to microwave irradiation for 3 min at power levels of 80, 240, and 400 watt. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) analyses confirmed the nanocrystalline CHA type B formed with a crystallinity index ranging from 79 % to 99.5 %. SEM images show the agglomerated morphology (0.5 μm-1 μm) of nanocrystalline CHA, with crystallite sizes ranging from 15 nm to 17 nm. Recycling calcium biogenic sources from crab shells as a powder feedstock using microwave-assisted synthesis is a rapid and environmentally friendly method for producing nanocrystalline CHA powder, which has potential applications in biomedical materials due to its high bioactivity and adsorption capacity.