Synthesis and characterization of natural hydroxyapatite extracted from pirarucu scales (Arapaima gigas)

Abstract

The hydroxyapatite belongs to the group of ceramic biomaterials being applied in the medical area due to its biocompatibility and osteoconductive properties, which makes it an option for treatments involving recovery of bone traumas. Fishing residues, bones and scales can be used as an inexpensive source for the production of calcium phosphates (hydroxyapatite). The objective of the study was the use of the non-toxic residue pi-rarucu scales to investigate the viability of extracting natural hydroxyapatite and characterizing it by physico-chemical and structural analyzes in order to prove its integrity. Firstly, thermal characterization was per-formed to establish the conditions of the heat treatment. With this, the scales were heat treated for the remov-al of the organic compounds. Thereafter, the material was homogenized, sieved and purified with reagents, because the sample could absorb impurities during the experimental procedure. The physical-chemical and structural characterizations were performed to accompany and prove the stages developed and examined. The results showed that the product obtained showed 99% of natural HAp phase and crystalline powders. In the infrared region, the peaks 3750-3500 cm-1 and 610-560 cm-1 were obtained referring to the OH- and PO4-3 ions respectively, referring to the functional groups hydroxyl and phosphate that constitute the chemical for-mula of hydroxyapatite and, by means of dispersive energy spectroscopy, the samples presented elemental percentages of calcium (37%), oxygenus (40%) and phosphorus (13%) that are compatible with the Ca/P molar ratio of the hydroxyapatite phase.