Characterization of iron, manganese, and copper synthetic hydroxyapatites by electron paramagnetic resonance spectroscopy

• Published in: Soil Science Society of America journal Vol. 66; no. 4; pp. 1359 - 1366
• Main Authors: Sutter, B., Wasowicz, T., Howard, T., Hossner, L. R., Ming, D. W.
• Format: Journal Article
• Language: English
• Published: Legacy CDMS Soil Science Society 01.07.2002; Soil Science Society of America; American Society of Agronomy
• Subjects: Biological and medical sciences; Chemical elements; Copper; Copper - analysis; Crops; Culture Media - analysis; Durapatite - analysis; Ecological Systems, Closed; Electron Spin Resonance Spectroscopy; Fertilizers - analysis; Fundamental and applied biological sciences. Psychology; Iron; Iron - analysis; Life Support Systems; Man/System Technology And Life Support; Manganese; Manganese - analysis; Soil - analysis; Soils; Space exploration; Space life sciences; Nasa Discipline Life Support Systems; Nasa Center Jsc; NASA Center JSC; NASA Discipline Life Support Systems
• ISSN: 0361-5995; 1435-0661
• DOI: 10.2136/sssaj2002.1359

The incorporation of micronutrients (e.g., Fe, Mn, Cu) into synthetic hydroxyapatite (SHA) is proposed for slow release of these nutrients to crops in NASA's Advanced Life Support (ALS) program for long-duration space missions. Separate Fe3+ (Fe-SHA), Mn2+ (Mn-SHA), and Cu2+ (Cu-SHA) containing SHA materials were synthesized by a precipitation method. Electron paramagnetic resonance (EPR) spectroscopy was used to determine the location of Fe3+, Mn2+, and Cu2+ ions in the SHA structure and to identify other Fe(3+)-, Mn(2+)-, and Cu(2+)-containing phases that formed during precipitation. The EPR parameters for Fe3+ (g=4.20 and 8.93) and for Mn2+ (g=2.01, A=9.4 mT, D=39.0 mT and E=10.5 mT) indicated that Fe3+ and Mn2+ possessed rhombic ion crystal fields within the SHA structure. The Cu2+ EPR parameters (g(z)=2.488, A(z)=5.2 mT) indicated that Cu2+ was coordinated to more than six oxygens. The rhombic environments of Fe3+ and Mn2+ along with the unique Cu2+ environment suggested that these metals substituted for the 7 or 9 coordinate Ca2+ in SHA. The EPR analyses also detected poorly crystalline metal oxyhydroxides or metal-phosphates associated with SHA. The Fe-, Mn-, and Cu-SHA materials are potential slow release sources of Fe, Mn, and Cu for ALS and terrestrial cropping systems.