Aging behavior of biodegradable polylactic acid microplastics accelerated by UV/H₂O₂ processes.

Area of Science:

• Environmental Science
• Polymer Science
• Materials Science

Background:

• Global plastic restrictions drive increased use of biodegradable plastics.
• Microplastics (MPs) from biodegradable products are entering aquatic ecosystems.
• The environmental behavior of these plastic product-derived MPs (PPDMPs) is not well understood.

Purpose of the Study:

• To investigate the aging process and environmental behavior of polylactic acid (PLA) PPDMPs.
• To compare the aging and adsorption of PLA PPDMPs with pure PLA MPs.
• To provide insights into the environmental risks of biodegradable MPs.

Main Methods:

• Dynamic aging of PLA straws and food bags under UV/H2O2 conditions.
• Analysis using scanning electron microscopy (SEM).
• Characterization via 2D Fourier transform infrared correlation spectroscopy (2D-COS) and X-ray photoelectron spectroscopy (XPS).

Main Results:

• PLA PPDMPs aged slower than pure PLA MPs.
• Functional group response orders during aging differed between PPDMPs and pure MPs.
• Pure PLA MPs showed greater adsorption capacity increase post-aging compared to PPDMPs.

Conclusions:

• The aging mechanism of PLA PPDMPs involves initial reaction of oxygen-containing groups, followed by C-H/-C-C responses and backbone rupture.
• Pure PLA MPs undergo initial oxidation, backbone breakage, and then further oxidation.
• Differences in aging and adsorption highlight the need for specific risk assessments for biodegradable MPs.