The need for the development of controlled-release green fertilizers has increased dramatically over the last few decades due to widespread water quality problem originated primarily from nutrients leached from agricultural soils. Nanosized hydroxyapatite (HANP) is a potential controlled-release fertilizer. To increase P release efficiency, the solubility of HANP particles can be tuned by doping carbonate to the crystal lattice. Here we synthesized carbonated HANPs by chemical precipitation through an aqueous solution of calcium hydroxide and phosphoric acid at different temperatures. CO<sub>2</sub> gas was bubbled to increase the concentration of carbonate in the solution. The FTIR, nano-FTIR coupled with AFM, FE-SEM, XRD, and DS-TGA techniques were used to characterize the products. Crystalizing HANP particles from the same reactants over different temperatures revealed that the temperature affects not only morphology of precipitated particles but also the carbonate content in the crystal structure. Under the synthetic conditions used, a relative preference of forming an A-type of carbonate in HANP was found, which was dependent on the temperature of crystallization, an observation not reported in the literature so far.

Carbonated hydroxyapatite: Effect of crystallization temperature on carbonate content

2019 Fall National Meeting

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