Accelerated Hydrolysis Method for Producing Partially Degraded Polyester Microplastic Fiber Reference Materials

Antonio Sarno,Fuad Karimov,Kjell Olafsen,Andy M Booth,Shannen T L Sait,Lisbet Sørensen,Stephan Kubowicz

doi:10.1021/acs.estlett.0c01002

Abstract

Microplastic fibers (MPFs) from textiles significantly contribute to the microplastic (MP) load in many environmental matrices and have been shown to negatively impact the organisms therein. Most fate and effect studies to date rely on pristine reference MP materials that have limited relevance compared with the partially degraded MP particles and fibers typically present in the natural environment. The current study aimed to develop and validate a rapid method to generate environmentally relevant polyester (PET) MPF reference material with controllable levels of degradation. Importantly, the method produced the same degradation products (terephthalic acid (TA) and ethylene glycol (EG)) as those generated during natural UV (sunlight) exposure of PET. Alkaline hydrolysis provided linearly increasing degrees of degraded PET MPFs over just a few hours, with full decomposition into molecular fragments occurring after 3 h. The extent of physical degradation was determined by scanning electron microscopy, whereas chemical degradation was quantified by measuring the production of TA and EG degradation products. The proposed accelerated hydrolysis degradation method is relevant for producing partially degraded PET MPF reference materials for use in fate and effect studies.

Highlights

PET degradation by alkaline hydrolysis leads to the formation of its constitutive components terephthalic acid (TA) and ethylene glycol (EG).[24]
Microplastic fibers (MPFs) (24 h), the PET fibers were subjected to alkaline hydrolysis over time to determine whether they were suitable for use as partially degraded MPF reference materials
We suggest that by 6 h, the fibers are largely degraded into a mixture of monomers (i.e., EG and TA) and short watersoluble polymers, some heavily degraded PET fibers remain detectable by Scanning electron microscopy (SEM) at this point

Summary

Introduction

Microplastic fibers (MPFs) derived from synthetic textiles and other sources represent a significant proportion of the microplastic (MP) load in many environmental matrices[1−3] and have been shown to have negative impacts on aquatic organisms.[4,5] the majority of studies investigating the fate and effects of MP particles have employed commercially available pristine spherical reference materials, limiting the relevance of the data produced.[6,7] As a result, some recent studies have explored ways to produce more environmentally relevant MP reference materials.[1−3,8] For example, marine litter can be cryomilled to produce irregular shaped fragments with complex surface morphologies and chemistries.[8]. The environmental relevance of the accelerated hydrolysis method was verified by comparing the hydrolyzed PET and degradation products to PET MPFs exposed to UV irradiation in seawater.

Results

Conclusion