This study reports a microwave-assisted synthesis of carbonated hydroxyapatite-based calcium phosphate powders using thermally treated green mussel shells (Perna viridis) as a sustainable calcium-rich precursor. The novelty of this work lies not merely in the formation of carbonated hydroxyapatite (CHA), but in the short-time conversion of thermally treated green mussel shells into phase-tailored calcium phosphate powders using low microwave power in solutions containing HPO₄³ ⁻. Green mussel shells were valuable because they are a common coastal biowaste in Indonesia and contain a high concentration of calcium carbonate, making them a viable alternative to other natural calcium sources such as eggshells and fish bones. The powdered shells were calcined at 900 °C for 5 h, producing a recoverable calcium-rich feedstock dominated by Ca(OH)₂ due to post-calcination hydration of CaO, as confirmed by X-ray diffraction (XRD)-Rietveld refinement and SEM/EDX analysis. The calcined powder was then reacted with phosphate solutions at a nominal Ca/P molar ratio of 1.67 under microwave powers of 30–80 W for 3 min. The H₃PO₄-mediated system produced calcium phosphate mixtures containing high fractions of monetite and brushite, together with a lower amount of A-type CHA with crystallite sizes of 173–174 nm. Conversely, the (NH₄)₂HPO₄-mediated system promoted the formation of nanocrystalline B-type CHA with carbonate substitution below 5 wt% and crystallite sizes of 5–6 nm. SEM observations revealed agglomerated microstructures composed of plate-like and interconnected sheet-like particles, forming porous aggregates approximately 1–3 µm in size. The formation of nanocrystalline carbonate-substituted apatite is significant for new materials research because carbonate incorporation, nanoscale crystallinity, and porous morphology are closely related to bioresorbability, osteoconductivity, and similarity to biological apatite. Therefore, this work demonstrates a sustainable waste-to-biomaterial route to producing mussel shell-derived calcium phosphate powders with potential applications in bone substitutes, scaffold fillers, and biomedical coatings.
Pusparizkita et al. (Thu,) studied this question.