Valorization of sea waste: a one-step synthesis route to biomimetic calcite and aragonite nanoparticles from Sargassum spp. ash

Sargassum spp. ash obtained by calcination at 850 °C was used as a calcium and magnesium precursor for the one-step synthesis of biomimetic calcium carbonate particles that simultaneously precipitate Mg-calcite and aragonite phases at the micro and nanoscale. X-ray diffraction with Rietveld refinement confirmed a mineralogical composition that closely replicates the skeletal mineralogy of the natural crustose coralline algae (CCA) Neogoniolithon rhodolith, while SEM and TEM characterization revealed coexisting carbonate particles of varying sizes with morphologies characteristic of each polymorph. This approach demonstrates the valorization of marine biomass as a precursor and provides a chemically controlled route to CCA-mimetic carbonates with potential as functional substrates in crystal engineering and biomaterial synthesis.