| Abstract
| - The effectiveness of Fe chelates as Fe sources and carriers in soil can be severely limited by theadsorption of Fe chelates or chelating agents in the solid phase. To study this phenomenon, well-characterized peat, Ca-montmorillonite, and ferrihydrite were used as model compounds, and theadsorption of Fe−EDDHA and Fe−EDDHMA chelates were studied. Sorption isotherms for themeso and racemic isomers of these chelates on the soil materials are described. The variability ofsorption with pH in peat and ferrihydrite was also determined because both have variable surfacecharge at different pH values. In montmorillonite, at low concentrations, the retention of Fe fromthe Fe−EDDHMA chelate is greater than the one of the Fe−EDDHA chelate. As well as theconcentration increased, the inverse situation occurs. The behavior of both meso and racemic isomersof chelates in contact with Ca-montmorillonite is similar. The Fe−meso-EDDHA isomer was highlyadsorbed on ferrihydrite, but the racemic isomer is not significantly retained by this oxide. ForFe−EDDHMA isomers, the racemic isomer was more retained by the oxide, but a small sorption ofthe racemic isomer was also observed. Results suggest that Fe−EDDHA chelates were more retainedin peat than Fe−EDDHMA chelates. The most retained isomer of Fe−EDDHA was the meso isomer.For Fe−EDDHMA, the adsorption was very low for both racemic and meso isomers. Keywords: Iron chelates; EDDHA; EDDHMA; sorption; montmorillonite; ferrihydrite; peat; HPLC
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