Loss of phosphorus (P) from agricultural soils has an adverse impact on the ecosystem which have catalyzed renewed calls on resource recovery as well as to use of slow-release P fertilizers. In this study, we aimed to recover P from common animal wastes (chicken litter, dairy cow manure, horse manure, sheep manure, and swine manure) and fabricate into hydroxyapatite nanoparticles (HANPs), a potential slow release nanofertilizer. Among various purification methods tested, HANP synthesis did not require a high purity solution. Direct precipitation of HANPs without concentrating P or removing contaminant ions from waste digests was possible for animal wastes with high P content such as swine manure and chicken litter but the yield and purity were compromised. All synthesized HANPs from partially purified P are carbonated apatite in which columnar hydroxyls are replaced by A-type carbonate, which is an ideal candidate for better P release because the presence of carbonate in HANPs enhances the solubility. The HANPs showed a uniform size of particles with constant lattice fringe, indicative of relatively high purity. Overall, our results suggest that the recovery and recycling of P from animal wastes to synthesize HANPs is feasible and could contribute to efforts on protecting the environment.
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