Modeling Pb(II) adsorption onto sandy loam soil.

Area of Science:

• Environmental Science
• Soil Science
• Geochemistry

Background:

• Lead (Pb(II)) is a toxic heavy metal pollutant.
• Soil contamination by heavy metals poses risks to ecosystems and human health.
• Understanding lead adsorption mechanisms in soil is crucial for remediation strategies.

Purpose of the Study:

• To investigate the adsorption behavior of Pb(II) onto hydrous sandy loam soil.
• To determine the influence of pH and surface loading on Pb(II) adsorption.
• To elucidate the surface acidity of the soil and model the adsorption process.

Main Methods:

• Batch equilibrium adsorption experiments were conducted.
• Electrophoretic mobility measurements were used to determine soil surface acidity.
• A surface complex formation model (SCFM) was applied to analyze adsorption data.

Main Results:

• Pb(II) adsorption increased with rising pH and surface loading.
• Soil surface acidity constants (pK(a1)(int) = 1.57, pK(a2)(int) = 3.43) were determined.
• Adsorption free energies for Pb2+ and Pb(OH)+ ions ranged from -5.74 to -10.00 kcal/mol.
• Specific chemical interactions were identified as the primary adsorption mechanism.

Conclusions:

• Hydrous sandy loam soil effectively adsorbs Pb(II), with adsorption enhanced by higher pH and loading.
• Surface complexation modeling accurately describes Pb(II) adsorption, highlighting the role of soil surface hydroxyl groups.
• The findings indicate that chemical interactions are dominant in lead sequestration by this soil type, informing soil remediation efforts.