Characterization of hydroxyapatite from recycled fish scale and its application as a filler in a biodegradable food tray

Abstract

Fish scale waste can be used as a precursor of hydroxyapatite (HAp). In this work, HAp was extracted from white seabass (Lates calcarifer) scale waste by using an alkali heat treatment. The fish scale was pretreated with hydrochloric acid (HCl) concentrations of 0.1, 0.5, and 1 M. The pretreated fish scale was then treated with 2% sodium hydroxide (NaOH) solution at 70°C for 5 h and again (20% NaOH solution) for 1 h to extract HAp. The effects of each pretreatment on the properties of the extracted HAp were investigated. HAp produced after pretreatment with 1 M HCl had the smallest particle size (28.24 ± 5.20 μm), the highest degree of crystallinity (79%), the highest thermal stability, the largest BET surface area (90.80 m2/g), and the highest whiteness value (97.360 ± 0.01). 1 M HCl could eliminate more protein, collagen, and other organic compounds than lower HCl concentrations without destroying the crystalline domains of the fish scale. Waste L. calcarifer scale is therefore a potential source of HAp. Furthermore, in a preliminary study for further research, HAp extracted in the proposed procedure was used as a filler in a biodegradable starch foam.