Filter cake-derived calcium carbonate polymorphs from sugar refinery for hydroxyapatite production as a sustainable material for biomedical application

Abstract

In this study, sugarcane filter cake (SFC) was refined to produce calcium carbonate (CaCO3) via the calcination method under a controlled environment. The obtained CaCO3 and orthophosphoric acid were used as calcium and phosphorus precursors respectively to synthesize hydroxyapatite (HA) through the wet precipitation method. Morphological investigation showed different morphologies of CaCO3 particles. The scanning electron microscopy (SEM) image showed high agglomeration of CaCO3 particles and the synthesized HA nanoparticles. Particle size analysis of CaCO3 and the HA nanoparticles revealed an average size of 0.9 μm and a crystallite size of 24.33 nm, respectively. X-ray diffraction (XRD) and Wide-angle x-ray scattering (WAXS) analysis confirmed the phase of calcium carbonate coexisting with both calcium hydroxide and calcium oxide, and a single phase of carbonated HA. The calcium to phosphorus (Ca/P) ratio of HA derived from calcinated filter cake was 1.66, which is close to the stoichiometric value of 1.67. The HA nanoparticles were biocompatible, with no evidence of toxicity to MC3T3-E1 cells. This study has demonstrated the feasibility of utilizing sugarcane filter cake as a sustainable raw material for CaCO3 and HA production. The as prepared HA is similar to biological apatite found in mammals and is potentially useful for hard tissue repair and other biomedical applications.