Background: Fish-processing by-products represent an increasing proportion of wastes globally. Valorizing offers a sustainable alternative by harnessing high-value products through process development. This study aimed to develop and optimize a demineralization process to recover minerals from fish bones with subsequent recovery of phosphates from the resulting solution.
Results: The demineralization process was optimized under the following conditions: 5% H3 PO4 concentration (v/v), four extractions and solvent to feed ratio (v/w) of 5:1 at ambient temperature of 17 °C. This resulted in an ossein containing 2.0 ± 1.2 g kg-1 DM ash and 71.5 ± 3 g kg-1 DM hydroxyproline and mineral liquor. The phosphate precipitation from the mineral liquor was further optimized resulting in > 99% total P recovery at 75 °C reaction temperature and 1 mol L-1 Ca(OH)2 to mineral liquor ratio(v/v) of 0.95:1 for a reaction time of 17 min, per 150 mL starting mineral liquor. The precipitate contained 215.2 ± 3.0 g kg-1 DM dicalcium phosphate dihydrate (DCPD) with a net contribution of 17.2% P from the fishbones, and 25 ± 0.2 g DM of octacalcium phosphate (OCP) was precipitated from 150 mL starting mineral liquor at 25 °C reaction temperature, (1.2:1) 1 mol L-1 Ca(OH)2 to mineral liquor ratio (v/v) and reaction time of 17 min. The X-ray spectra confirmed the DCPD structure and Fourier transform infrared spectroscopy (FTIR) spectra indicated OCP precipitation.
Conclusion: This work successfully illustrated the recovery of minerals from fish bones and the subsequent production of different high-quality phosphates from fish-processing by-products, thus indicating a potential source for high-value products. © 2018 Society of Chemical Industry.
Keywords: FTIR; X-ray diffraction; dicalcium phosphate; monkfish (Lophius vomerinus); octacalcium phosphate; response surface methodology (RSM).
© 2018 Society of Chemical Industry.