Skip to main content

The influence of phospholipids on the structure and composition of ferrihydrite colloids

Organophosphates (OP) are important nutrient components in soils and they readily interact with abundant iron phases. Ferrihydrite (FHY), a ubiquitous iron phase in soils, plays a major role in iron-mediated carbon storage. However, the influence of OP on FHY formation, transformation or stabilization is poorly understood. Here we investigated the effects that glycerol phosphate (GP; model organophosphate compound) has on the structure and properties of synthetic FHY. FHY-GP was synthesized by coprecipitation using variable initial molar P/Fe ratios (0.01 to 0.5). The solids displayed typical 2-line FHY X-ray diffraction pattern and chemical analyses showed that they all had a final P/Fe ratio of no more than 0.2. With increasing initial P/Fe ratio, we observed a sharp decrease in specific surface area from 290 to 3 m2 g-1 with an associated reduction in porosity. Analyses of solid products by small angle X-ray scattering revealed that the at high initial P/Fe ratios the solids formed were cluster with diameters of ~ 1.2 nm. Local structural and bonding environment analysis derived from infrared spectroscopy and Fe K-edge X-ray absorption spectroscopy, showed that with increasing P loading, the bonding configuration gradually transitioned from the initial binary binuclear to monodentate mononuclear geometry, while the average coordination number of edge-shared Fe polyhedral decreased from 3.2 to 1.3 and the corner-shared Fe polyhedral disappeared. These results indicated that during the formation of the FHY-GP, the Fe(III) polymerization was likely impeded by the GP, with an increasing P/Fe ratio strongly affecting the resulting FHY-GP structure.


Zhengzheng Chen1, Jeffrey Paulo H. Perez2, Roberts Blukis2, Glen J. Smales3, Brian R. Pauw3, Jessica A. Stammeier2, Jörg Radnik3, Liane G. Benning1
1GFZ German Research Center for Geosciences, Telegrafenberg, 14473 Potsdam, Germany;Department of Earth Sciences, Freie Universität Berlin, 12249 Berlin, Germany; 2GFZ German Research Center for Geosciences, Telegrafenberg, 14473 Potsdam, Germany; 3Bundesanstalt für Materialforschung und-prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany
GeoMinKöln 2022