Vanadium sorption by mineral soils: Development of a predictive model

Area of Science:

• Environmental Science
• Soil Chemistry
• Geochemistry

Background:

• Vanadium toxicity in soils is influenced by its sorption behavior.
• Understanding vanadium sorption is crucial for assessing soil contamination and plant uptake.

Purpose of the Study:

• To investigate vanadate(V) sorption properties across 26 diverse mineral soils.
• To develop and optimize a predictive model for vanadium sorption based on soil properties and pH.
• To evaluate the adequacy of current environmental guidelines for vanadium.

Main Methods:

• Utilized Freundlich equation with a pH term to model vanadium sorption.
• Employed Vanadium K-edge XANES spectroscopy to identify vanadium speciation in selected soils.
• Measured pH-dependent vanadium solubility and calculated the Freundlich Sorption Strength (FSS).

Main Results:

• The developed model accurately predicted vanadium sorption for most soils (r² > 0.99 for 20/26 soils).
• Vanadium primarily sorbed as adsorbed vanadate(V) onto Fe and Al hydrous oxides.
• A strong correlation (r² = 0.85) was observed between FSS and oxalate-extractable Fe and Al.
• Calculated FSS values varied significantly, indicating potential issues with existing environmental guidelines.

Conclusions:

• The developed model provides a robust framework for predicting vanadium sorption in mineral soils.
• Soil iron and aluminum content are critical factors controlling vanadium sorption.
• Current environmental guidelines for vanadium may require revision due to the wide range of predicted sorption strengths and potential under- or overprotection.