Antimony sorption to schwertmannite in acid sulfate environments

Area of Science:

• Environmental Geochemistry
• Mineralogy
• Environmental Science

Background:

• Schwertmannite, an iron(III) oxyhydroxysulfate mineral, influences antimony(V) mobility in acidic sulfate environments.
• Understanding Sb(V) uptake mechanisms by schwertmannite is crucial for acid mine drainage and acid sulfate soil remediation.

Purpose of the Study:

• To investigate the mechanisms of aqueous antimony(V) sorption onto schwertmannite.
• To determine the role of schwertmannite in controlling Sb(V) mobility in acidic sulfate conditions.

Main Methods:

• Examined Sb(V) sorption to schwertmannite at environmentally relevant loadings and pH 3 in sulfate-rich solutions.
• Utilized Antimony K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy to analyze Sb(V) coordination and linkages.

Main Results:

• Sb(V) sorption occurred via edge and double-corner sharing linkages, indicating heterovalent Sb(V)-for-Fe(III) substitution within the schwertmannite structure.
• Sb(V) sorption was not limited by surface complexation sites and showed strong resistance to desorption by phosphate.
• Sorption of Sb(V) enhanced schwertmannite stability, reducing its dissolution rate.

Conclusions:

• Schwertmannite immobilizes Sb(V) by incorporating it into its crystal structure, not just surface complexation.
• This mechanism highlights schwertmannite's significant role in sequestering Sb(V) in acidic sulfate environments.
• The findings have implications for understanding and managing antimony contamination in acid mine drainage and soils.