Gallium(III) adsorption on carbonates and oxides: X-ray absorption fine structure spectroscopy study and surface...

Area of Science:

• Geochemistry
• Environmental Science
• Surface Chemistry

Background:

• Gallium (Ga) is an element with potential environmental and industrial implications.
• Understanding its interaction with mineral surfaces is crucial for predicting its fate and transport.
• Previous studies have explored metal adsorption on mineral surfaces, but Ga-specific interactions require detailed investigation.

Purpose of the Study:

• To investigate the adsorption behavior of gallium (Ga) on various mineral surfaces.
• To characterize the structure of adsorbed Ga complexes using spectroscopic techniques.
• To develop a surface complexation model describing Ga adsorption equilibria.

Main Methods:

• Batch adsorption experiments were conducted to study Ga adsorption.
• X-ray Absorption Fine Structure (XAFS) spectroscopy was used to characterize adsorbed Ga complexes.
• A surface complexation model (Constant Capacitance Model) was applied to analyze adsorption data.

Main Results:

• Ga adsorption is dependent on solution pH and Ga concentration.
• At high surface loadings, Ga forms polymeric networks; at low loadings, it forms isolated octahedra.
• Ga coordination changes from 4 to 6 upon adsorption, forming surface complexes like MeOGa(OH)n(H2O)2-n.
• A surface complexation model successfully described Ga adsorption across a range of conditions.

Conclusions:

• Gallium adsorption on calcite, magnesite, silica, and manganese oxide is a complex process influenced by surface chemistry and solution conditions.
• The structure of adsorbed Ga varies with surface loading, impacting its reactivity.
• The developed surface complexation model provides a framework for predicting Ga behavior in natural systems.