An Investigation of Iron(III)-Fulvic Acid Complexes by Mössbauer Spectroscopy and Chemical Methods
- H. Kodama ,
- M. Schnitzer and
- E. Murad
Three iron(III)-fulvic acid (FA) “complexes” were prepared in the laboratory. One of these was doped 50% with 57Fe and contained 1.54% total Fe. The other two “complexes” contained 0.80 and 4.70% Fe, respectively. At room temperature, Mössbauer spectra of the Fe(57Fe)-FA “complex” consisted of a paramagnetic doublet. The isomer shift (δ/Fe) was 0.30 mms−1 and the quadrupole splitting (ΔEQ) was 0.75 mms−1, typical of ferric iron. At 78 K the spectrum showed a magnetic component superimposed upon the quadrupole doublet. In the spectrum recorded at 4.2 K the magnetic contribution increased. An analysis of the Mössbauer data suggests that Fe(III) in laboratory-prepared Fe(III)-FA “complexes” occurs partly in the form of organic complexes and partly as inorganic species. Support for this view also comes from ESR data published in the literature. A study of the resistance of Fe in the “complexes” to base hydrolysis, showed that iron was associated with the FA by at least two, possibly three, different mechanisms and that the interaction products exhibited differing chemical stabilities.
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