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Dispersion of Nanomaterials in Aqueous Media: Towards Protocol Optimization
Published on: December 25, 2017
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Ion release kinetics and particle persistence in aqueous nano-silver colloids
1Department of Chemistry, Division of Engineering, Institute for Molecular and Nanoscale Innovation, Brown University, Providence, Rhode Island, USA.
Environmental Science & Technology
|February 24, 2010
Summary
Pure nanosilver (nAg) releases silver ions through oxidation, influenced by pH, temperature, and organic matter. These silver nanoparticles are not persistent in oxygen-containing environments.
Area of Science:
- Environmental Science
- Materials Science
- Chemistry
Background:
- Nanosilver (nAg) behavior, including toxicity and persistence, is significantly affected by dissolved silver ions.
- Understanding ion release is crucial for assessing nanosilver's environmental impact.
Purpose of the Study:
- To synthesize pure, ion-free nanosilver colloids.
- To quantify the time-dependent release of dissolved silver from nanosilver.
- To investigate factors influencing silver ion release rates.
Main Methods:
- Synthesis of citrate-stabilized nanosilver colloids.
- Centrifugal ultrafiltration for separating dissolved silver.
- Atomic absorption spectroscopy for silver quantification.
- Kinetic and thermodynamic analysis of ion release.
Main Results:
- Ion release is an oxidative process dependent on dissolved oxygen and protons, potentially forming peroxide intermediates.
- Release rates increase with temperature (0-37 °C) and decrease with higher pH or humic/fulvic acids.
- Nanosilver surfaces can adsorb silver ions, leading to Ag(0) solids, free Ag+, and adsorbed Ag+.
- Silver nanoparticles are not persistent in oxygenated environments.
Conclusions:
- Nanosilver dissolution is a complex oxidative process influenced by environmental factors.
- An empirical kinetic law was developed to model silver ion release.
- Nanosilver persistence in the environment is limited due to reactive dissolution.
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