Interactions between methyl octabromo ether flame retardant and expanded polystyrene microplastics in the photoaging...

Area of Science:

• Environmental Science
• Polymer Science
• Materials Chemistry

Background:

• Expanded polystyrene (EPS) is a common plastic pollutant due to its buoyancy and light absorption.
• Flame retardants are added to EPS, potentially altering its environmental degradation pathways.
• The impact of flame retardants on EPS microplastic (MP) photoaging remains underexplored.

Purpose of the Study:

• To investigate the effect of methyl octabromoether flame retardant (MOBE) on the photodegradation of EPS microplastics.
• To compare the photoaging behavior of flame retardant-added EPS (FR-EPS) and original EPS (OR-EPS).
• To understand the role of additive-plastic interactions in MP environmental fate.

Main Methods:

• Laboratory simulation of photoaging for FR-EPS and OR-EPS particles.
• Analysis of particle size reduction, surface morphology changes (hole formation), and weight loss.
• Monitoring of chemical changes using carbonyl index and O/C ratio.
• Application of a diffusion model (Fick's second law) to track MOBE concentration.

Main Results:

• MOBE accelerated EPS MP size reduction and surface hole formation.
• FR-EPS showed significantly higher weight loss (40.85 ± 3.72%) compared to OR-EPS after 36 days of irradiation.
• MOBE initially inhibited photoaging by competing for photons but later promoted degradation by generating hydroxyl radicals (•OH).
• EPS's light absorption capacity also accelerated MOBE degradation.

Conclusions:

• Additive-plastic interactions, specifically MOBE in EPS, significantly alter MP photoaging behavior.
• Commercial EPS products with flame retardants degrade differently than pure EPS.
• These interactions have crucial implications for assessing the environmental fate and risks of microplastics.