Transforming waste fish bones into nanoparticles with ultrasound and aqueous organic acids

Abstract

Synthesizing materials from biomass has gained significant attention as a step towards achieving a circular economy. Seafood processing by-products (e.g., heads, fins, bones, and viscera) are currently disposed of using unsustainable practices including disposal in landfills and/or at sea. However, fish bones are made of 60% hydroxyapatite and therefore could be utilized as a sustainable feedstock for calcium phosphate materials. In this research, nano-hydroxyapatite particles were prepared from Atlantic salmon (Salmo salar) bones using ultrasound in combination with heat, ball milling, and aqueous acid treatment. The size of the synthesized hydroxyapatite nanoparticles can be tailored depending on the chosen conditions. The smallest particles (d = 29 nm) were produced using aqueous propanoic acid and 15 min ultrasound exposure, whereas heat pre-treatment and ultrasound treatment for 60 min led to more well-defined but larger particles (d = 69 nm). The presence of calcium propanoate on the surface of nanoparticles prepared with propanoic acid was detected by IR spectroscopy and X-ray diffraction. A simplified gate-to-gate life cycle assessment was used to demonstrate that this ultrasound process results in a 97% reduction in CO₂ emissions compared to other methods reported in the literature to date.