A simple geochemical model for predicting Sb(V) partitioning: From iron oxides to complex soil systems

Area of Science:

• Environmental Geochemistry
• Soil Science
• Environmental Chemistry

Background:

• Antimony (Sb(V)) is a global environmental pollutant whose soil partitioning behavior is critical for understanding its environmental transport.
• Existing geochemical models have significant limitations in accurately predicting Sb(V) partitioning in complex soil environments.

Purpose of the Study:

• To develop and validate a robust geochemical model for predicting Sb(V) partitioning at the solid-liquid interface in soils.
• To integrate surface complexation models (SCM) for Sb(V) adsorption on iron oxides with soil organic matter (SOM) and phosphate (P(V)) interactions.

Main Methods:

• Batch adsorption experiments were conducted on goethite and ferrihydrite to develop SCM for Sb(V).
• A multi-surface speciation model (MSM) was constructed by integrating SCM sub-models, considering the presence of P(V) and SOM.
• Model performance was evaluated across twelve different soils under various hydrochemical conditions.

Main Results:

• The SCM successfully depicted bidentate and monodentate complexation of Sb(V) on iron oxides.
• The developed MSM accurately predicted Sb(V) adsorption across all studied soils.
• Simultaneous consideration of P(V) and SOM yielded the best model performance, and the competitive effect of reactive organic matter (RO-) was quantitatively estimated.

Conclusions:

• The advanced yet simple MSM provides a reliable approach for predicting Sb(V) partitioning in complex soil systems.
• Understanding the interplay between Sb(V), iron oxides, SOM, and P(V) is essential for accurate environmental transport modeling.
• This study offers a valuable tool for environmental risk assessment and management of antimony contamination.