Nanoparticle Stability in Dissolved Organic Matter: A Research Breakthrough

Researchers from the Kunming University of Science & Technology have discovered that the stability of iron and aluminum-based nanoparticles in dissolved organic matter-rich environments is more complex than previously thought. Using advanced spectroscopic analyses, the team demonstrated that different dissolved organic matter (DOM) fractions mediate different interfacial forces, leading to contrasting sedimentation behaviors of ferrihydrite and amorphous aluminum hydroxide nanoparticles.

Key Takeaways:

• The stability of nanoparticles in dissolved organic matter-rich environments is unpredictable when evaluated through classical XDLVO (Extended Derjaguin-Landau-Verwey-Overbeek) theories.
• Ferrihydrite nanoparticles preferentially adsorb aromatic humic components, leading to hydrophobic interactions and accelerated sedimentation, while amorphous aluminum hydroxide nanoparticles selectively bind high molecular weight protein-like substances, enhancing stability through steric hindrance.
• The XDLVO model fails to capture the selective adsorption and molecular rearrangement that occur during DOM-NP interaction, leading to differing sedimentation rates between ferrihydrite and amorphous aluminum hydroxide nanoparticles.
• Hydrophobic interactions and macromolecular steric effects dominate stability and DOM fractionation is dictated by NP surface chemistry.
• The findings demonstrate that different DOM fractions mediate different interfacial forces, and a new conceptual framework is needed to predict colloid transport and carbon cycling in organic-rich aquatic ecosystems.

Statistics:

• The sedimentation rate of ferrihydrite nanoparticles increased by 37-58% due to DOM-induced aggregation.
• The sedimentation rate of amorphous aluminum hydroxide nanoparticles decreased by 42-65% due to suppressed settling.
• The XDLVO model failed to capture the selective adsorption and molecular rearrangement that occur during DOM-NP interaction in 100% of study cases.

Sources:

• Deviation of nanoparticle aggregation from XDLVO theory as explained by dissolved organic matter adsorption and fractionation. Environmental Pollution, 2025;379:126511. (Elsevier Sci Ltd, 125 London Wall, London, England, www.elsevier.com, www.journals.elsevier.com/environmental-pollution/)
• Kunming University of Science & Technology, Yunnan Provincial Key Lab of Soil Carbon Sequestration and Pollution Control, Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, 650500, Yunnan, People's Republic of China.