Aggregation kinetics of different surface-modified polystyrene nanoparticles in monovalent and divalent electrolytes

Area of Science:

• Environmental Science
• Materials Science
• Physical Chemistry

Background:

• Plastic debris can form nanoplastics, posing potential environmental risks.
• Limited data exists on nanoplastic environmental behavior, hindering risk assessment.
• Understanding nanoplastic aggregation is crucial for predicting their fate in aquatic systems.

Purpose of the Study:

• To investigate the aggregation kinetics of various surface-modified polystyrene nanoparticles.
• To elucidate the influence of monovalent and divalent electrolytes on nanoplastic aggregation.
• To assess the role of natural organic matter in modifying nanoplastic aggregation behavior.

Main Methods:

• Studied aggregation kinetics of unmodified (PS-Bare), carboxylated (PS-COOH), amino-modified (PS-NH2), and laser-ablated (PS-Laser) polystyrene nanoparticles.
• Utilized monovalent (NaCl) and divalent (CaCl2) electrolyte solutions.
• Incorporated Suwannee River Natural Organic Matter (SRNOM) to examine its effects.

Main Results:

• Aggregation of PS-Bare and PS-COOH followed DLVO theory in NaCl and CaCl2.
• SRNOM suppressed aggregation in monovalent electrolytes via steric hindrance.
• In divalent electrolytes, SRNOM enhanced stability at low concentrations but worsened it at high concentrations due to cation bridging.
• SRNOM adsorption altered surface charge of PS-NH2, affecting aggregation.
• PS-Laser showed cation bridging effects with high divalent electrolytes and SRNOM.

Conclusions:

• Surface charge and modification significantly dictate nanoplastic aggregation in aquatic environments.
• Electrolytes and natural organic matter play complex roles in nanoplastic fate.
• Understanding these interactions is key to assessing nanoplastic environmental risks.