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Effect of pH on complexation of Fe(III) with fulvic acids
Author(s) -
da Silva Joaquim C. G. Esteves,
Machado Adélio A. S. C.,
Oliveira César J. S.
Publication year - 1998
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620170711
Subject(s) - chemistry , ionic strength , quenching (fluorescence) , fulvic acid , ligand (biochemistry) , analytical chemistry (journal) , stability constants of complexes , fluorescence , nuclear chemistry , chromatography , aqueous solution , humic acid , organic chemistry , fertilizer , biochemistry , physics , receptor , quantum mechanics
The interaction of Fe(III) with two samples of fulvic acids (FAs) extracted from a pinewood soil (FA2: horizon 0–10 cm; FA3: horizon 10–25 cm) was monitored by synchronous fluorescence (SyF) spectroscopy at four pH values (3, 4, 5, and 6). Spectral data were preprocessed by SIMPLISMA, a self‐modeling curve‐resolution method, and from the calculated quenching profiles, equilibrium parameters for the interaction of Fe(III) and FAs were obtained (conditional stability constants [ K c s] and ligand site concentrations). The calculated log K c s were ( I = 0.1 M KNO 3 ; standard deviation in parentheses): FA2, pH = 3, 4.9 (2), pH = 4, 4.7 (2), pH = 5, 5.1 (4), and pH = 6, 5.1 (1); FA3, pH = 3, 5.48 (1); pH = 4, 4.96 (7), pH = 5, 4.89 (1), and pH = 6, 5.1 (2), where I is the ionic strength. These results show that FA forms quite stable soluble complexes with Fe(III) in the acid pH range.