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Heteroaggregation of different surface-modified polystyrene nanoparticles with model natural colloids
Su-Juan Yu1, Qing-Cun Li2, Wan-Yu Shan2
1State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P. O. Box 2871, Beijing 100085, China.
The Science of the Total Environment
|April 25, 2021
Summary
Surface modifications on polystyrene nanoparticles (PSNPs) significantly influence their aggregation with natural colloids like hematite and kaolin. Electrostatic interactions and environmental factors like organic matter and electrolytes play key roles in nanoparticle fate and transport.
Area of Science:
- Environmental Science
- Nanotechnology
- Colloid Science
Background:
- Understanding nanoparticle (NP) interactions with natural colloids is crucial for predicting their environmental fate.
- Surface properties of NPs, such as charge and functionalization, dictate their aggregation behavior.
- Natural organic matter and electrolytes significantly influence NP-colloid interactions in aquatic systems.
Purpose of the Study:
- To investigate the heteroaggregation of surface-functionalized polystyrene nanoparticles (PSNPs) with model natural colloids (hematite and kaolin).
- To elucidate the mechanisms governing heteroaggregation under varying NP/colloid ratios and environmental conditions.
- To assess the impact of natural organic matter and electrolytes on NP-colloid heteroaggregation.
Main Methods:
- Synthesized and characterized three types of PSNPs: unfunctionalized (Bare-PS), carboxylated (COOH-PS), and amino-functionalized (NH2-PS).
- Conducted heteroaggregation experiments with positively charged hematite and negatively charged kaolin at controlled concentrations.
- Varied NP/colloid concentration ratios and introduced electrolytes and Suwannee River natural organic matter (SRNOM) to simulate environmental conditions.
Main Results:
- Electrostatic interactions were the primary drivers of heteroaggregation, with charge neutralization and charge reversal mechanisms observed.
- Heteroaggregation stability varied with NP surface charge, colloid type, and NP/colloid ratio; large aggregates formed at charge neutralization points for hematite systems.
- NH2-PS showed minimal aggregation with kaolin due to rapid surface charge reversal, while same-charge interactions were unfavorable.
- Electrolytes promoted both homoaggregation and heteroaggregation, with hematite homoaggregation being significant at low NP concentrations.
- SRNOM modified NP surface charges, influencing heteroaggregation, with stability depending on concentration, electrolyte type, and ionic strength.
Conclusions:
- Surface functionalization of NPs critically impacts their heteroaggregation with natural colloids.
- Electrostatic forces, charge neutralization, and charge reversal are key mechanisms in NP-colloid interactions.
- Environmental factors like electrolytes and natural organic matter significantly alter NP aggregation, influencing their environmental fate and transport.
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