Analytical Sciences

Binding Characteristics and Dissociation Kinetics for Iron(II) Complexes with Seawater Extractable Organic Matter and Humic Substances in a Compost

Hisanori IWAI,* Masami FUKUSHIMA,* and Mitsuo YAMAMOTO**

*Laboratory of Chemical Resource, Division of Sustainable Resources Engineering, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
**Graduate School of Frontier Sciences & Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa 277-8564, Japan

A steel-slag/compost fertilizer can be useful in supplying complex Fe(II) species to barren coastal regions. Seawater extractable organic matter (SWEOM) was examined for use as a novel chelator of Fe(II) in the compost. The dissociation kinetics for Fe(II)-SWEOM were evaluated, based on the rate of ligand-exchange with ortho-phenanthroline. The ΔH^‡ for the Fe(II)-SWEOM (19 kJ mol⁻¹) was significantly smaller than the corresponding values for Fe(II) complexes with humic substances (27 kJ mol⁻¹), suggesting that the Fe(II)-SWEOM is kinetically less stable.

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