Hydroxyapatite (HAp) was obtained from tilapia scales by two extraction methods: direct calcination and acid-base treatment. The physicochemical characteristics of the obtained HAps were evaluated by thermogravimetric analysis, X-ray fluorescence, X-ray diffraction, scanning electron microscopy, surface area, infrared spectroscopy, and basicity measurement at 298 K by CO 2 -pulse titration. Furthermore, the CO 2 capture capacity of the solids at high temperature was also determined. Both methods showed the presence of a HAp phase although significant differences in the properties of the solids were found. The HAp obtained by direct calcination, exhibited a lower crystallinity and a greater surface area and basicity than the HAp obtained by the acid-base treatment. These features were correlated with the solid's CO 2 capture capacity. In this work, CO 2 capture capacity values for HAp yielded by calcination ranged from 2.5 to 3.2 mg CO 2 /g captured at 973 K, and for the acid-base treatment-derived HAp, CO 2 capture capacity values between 1.2 to 2.5 mg CO 2 /g were recorded. These results reveal the potential of HAps extracted from tilapia scales as solids with high CO 2 capture capacity, thermal stability, and capture/release cycles reversibility.Keywords: fish scales; tilapia; hydroxyapatite; calcium; CO 2 capture
IntroductionMillions of tons of fish scales are discarded and wasted around the world. In Colombia, fish scales are considered worthless, unusable, and are often eliminated as waste. Consequently, the local fish industry generates large amounts of fish waste per year, of which tilapia scales have a considerable share. Ideas have been proposed on how to create value for fish scales and how to use this resource [1 -4]. The surface of fish scales is constituted by numerous high-value organic and inorganic components, such as hydroxyapatite