Critical comparison of rapid methods for the extraction of microplastics from wastewater and investigation of a facile alternative

Microplastics (MPs) are a pervasive contaminant detected across environmental matrices, including wastewater. Their effective removal remains challenging because established protocols are optimized using parameters incongruous with environmental samples or lacking a comprehensive comparison of MPs. In this study, six common digestion protocols were evaluated on four common plastics that are representative of the actual size range of MPs generally found in wastewater (12 μm-3 mm). Methods were evaluated using gravimetric analysis, scanning electron microscopy (SEM), Raman spectroscopy, analysis of variance (ANOVA), and latent class analysis (LCA). Additionally, there is a demand for MP recovery methods that incur minimal damage to particle morphology. Few studies have investigated MP recovery from wastewater with an oil extraction protocol (OEP), and none have tested OEP using pure compounds. For the first time to the authors' knowledge, this study proposes an OEP combined with Fenton's reagent for the extraction of MPs from wastewater. The results of this study demonstrate that MP recovery increases with size; nylon and low-density polyethylene are more sensitive to removal methods than polypropylene and polystyrene; oleic acid is more effective at recovering MPs than canola oil, although Raman spectroscopy is less sensitive to canola oil.