Optimization of phosphate recovery from monkfish, Lophius vomerinus, processing by-products and characterization of the phosphate phases

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% H3PO4 concentration (v/v), four extractions and solvent to feed ratio (v/w) of 5:1 at ambient temperature of 17 degrees 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 degrees 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 degrees 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. (c) 2018 Society of Chemical Industry