Oxidation and incorporation of adsorbed antimonite during iron (II)-catalyzed recrystallization of ferrihydrite

The toxicity and mobility of antimony (Sb) are strongly influenced by the redox transformation of widely spread 2-line ferrihydrite (Fh) in natural soils and sediments. This study investigated the transformation and redistribution of adsorbed antimonite (Sb(III)) during Fe(II)-catalyzed recrystallization of Fh under anaerobic conditions. X-ray diffraction (XRD), transmission electron microscopy (TEM), and synchrotron based X-ray absorption spectroscopy (XAS) were utilized to characterize the mineralogy and morphology of generated minerals as well as the speciation of Sb and Fe. Chemical analysis and Sb L-III-edge XANES spectra demonstrated that a great part of Sb(III) (80%-90%) was oxidized to Sb(V) by reactive oxygen species (ROS) during the Fe(II)-catalyzed transformation of Fh. Chemical extraction results showed that the mobility of Sb was significantly reduced with 50%-70% of initially adsorbed Sb(III) transformed to phosphate-unextractable phase. Antimony K-edge EXAFS analysis showed the SbO6 octahedra were incorporated into secondary minerals by substituting the Fe atoms. Our findings shed new light on the understanding of the geochemical behavior of Sb(III) under anoxic conditions. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study investigated the transformation and redistribution of adsorbed antimonite (Sb(III)) during Fe(II)-catalyzed recrystallization of 2-line ferrihydrite under anaerobic conditions. The results showed that a great part of Sb(III) was oxidized to Sb(V) by ROS during the transformation process, reducing the mobility of Sb significantly. Antimony was transformed to phosphate-unextractable phase with 50%-70% of initially adsorbed Sb(III), and incorporated into secondary minerals by substituting the Fe atoms.