Assessing the aggregation behaviour of iron oxide nanoparticles under relevant environmental conditions using a...

Area of Science:

• Environmental Science
• Nanotechnology
• Soil Science

Background:

• Iron oxide nanoparticles (Fe2O3NPs) are promising for soil and groundwater remediation.
• Nanoparticle aggregation significantly impacts mobility, reactivity, and environmental fate.
• Assessing nanoparticle stability under environmental conditions is critical.

Purpose of the Study:

• To characterize the behavior of Fe2O3NPs under environmentally relevant conditions using a multi-method approach.
• To investigate dissolved organic matter (DOM) as a green coating agent to prevent Fe2O3NP aggregation.
• To evaluate the stability of DOM-coated Fe2O3NPs under varying ionic strengths.

Main Methods:

• Multi-method characterization including size measurements and DLVO theory.
• Controlled experiments simulating soil conditions (pH, ionic strength, particle concentration).
• Investigation of nanoparticle coating with dissolved organic matter (DOM).

Main Results:

• Fe2O3NPs extensively aggregated (>1 μm) under specific soil conditions (pH 7, 10 mM NaCl, 2 mM CaCl2).
• DOM coating conferred negative surface charge, providing electrostatic stabilization and reducing aggregation.
• DOM-coated Fe2O3NPs showed enhanced stability in high ionic strength, but CaCl2 induced aggregation via charge neutralization and bridging.

Conclusions:

• DOM coating is an effective green strategy to stabilize Fe2O3NPs against aggregation.
• The presence of divalent cations like CaCl2 can overcome DOM-induced stabilization, impacting nanoparticle fate.
• Understanding these interactions is crucial for the environmental application of iron oxide nanoparticles.