Synthesis of Hydroxyapatite Nanoparticles from Phosphorus Recovered from Animal Wastes

Abstract

Phosphorus (P) loss from agricultural soils and its adverse impact on the ecosystem have resulted in renewed calls on resource recovery. In this study, we tested five methods of purification of P extracted from common animal wastes (chicken litter and dairy cow, horse, sheep, and swine manures) to fabricate hydroxyapatite nanoparticles (HANPs), a potential nanofertilizer. Crystallization of HANPs from P extracts from swine manure and chicken litter was achieved with no purification of the extract but the yield and purity were compromised. All synthesized HANPs from partially purified P were carbonated apatite in which columnar hydroxyls are replaced by carbonate, which is ideal for enhancing the solubility. The TEM and XRD analyses were carried out to verify the nanodimension and phase crystallinity of HANPs. The concentration of heavy metals in HANPs decreased by 3–5 log orders compared to waste during purification and crystallization. Overall, these results suggest that the recovery and recycling of P from animal wastes and synthesis of pure HANPs are feasible and together contribute to the efforts on recycling a nonrenewable resource as well as protecting the environment.