Simulating uranium sorption onto inorganic particles: The effect of redox potential

Area of Science:

• Environmental Chemistry
• Geochemistry
• Surface Science

Background:

• Uranium sorption onto inorganic particles is crucial for understanding its fate in aquatic environments.
• Existing empirical data limits predictive capabilities for uranium sorption under varying conditions.
• A mechanistic approach is needed to simulate uranium sorption influenced by environmental factors.

Purpose of the Study:

• To develop an analytical expression for simulating uranium sorption onto model inorganic particles.
• To predict the distribution coefficient (Kd) as a function of pH, redox potential (E), and ligand concentration.
• To apply a surface complexation model for uranium sorption on aluminol, iron hydroxide, and silanol sites.

Main Methods:

• Utilized a surface complexation model with a single type of surface site (>SuOH).
• Incorporated complexation and hydrolysis constants for solution and sorbed species.
• Correlated hydrolysis constants with surface complexation constants for specific sorption sites.
• Simulated sorption in the absence and presence of carbonates.

Main Results:

• Developed an analytical expression for Kd incorporating pH, E, and ligand concentration.
• Demonstrated high sensitivity of Kd values to the presence or absence of carbonates.
• Validated model predictions against literature data for uranium sorption on various adsorbents.
• Successfully simulated uranium sorption on different mineral surfaces (aluminol, iron hydroxide, silanol).

Conclusions:

• The proposed analytical expression effectively simulates uranium sorption dynamics.
• Environmental factors like pH, redox potential, and carbonate presence significantly influence uranium distribution.
• The model provides a valuable tool for predicting uranium behavior in aquatic systems and can be extended to other redox-sensitive elements.