ROD-LIKE IRON(III) OXYHYDROXIDE PARTICLES IN IRON(III)-POLYSACCHARIDE SOLUTIONS

摘要

The interaction of iron(III) with different anionic polysaccharides has been studied by pH-metric, UV-vis, Fourier transform infrared, viscometric, and conductometric methods. The formation of water-soluble compounds containing surprisingly high numbers of iron(III) ions even at physiological pH has been observed. The complex formation involves carboxylate, sulfonate, and probably alcoholic hydroxylate moieties. The metal binding starts in the acidic pH region with the complex precipitating at 3.5 less than or equal to pH less than or equal to 6. The precipitate dissolves at pH > 6. The compositions of the complexes formed at pH 7 were found to be L[Fe(OH)(3)](n), where L is the repeating unit of the polymer. The maximum value of n proved to be dependent not only on the coordination ability, but also on the molar mass of the ligands. Viscometric and conductometric data suggest that the structure-determining element of these complexes is the polysaccharide rather than an iron oxyhydroxide cluster. Their solution structure can be described as independent rod-like particles comprising an unfolded polysaccharide backbone and polymerized iron(III)-oxyhydroxide particles. [References: 40]