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

Abstract

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.