Balancing NOM Removal and Polymer Stability in PVC Microplastics: A Comparative Evaluation of H2O2 Digestion Protocols.

Abstract

Hydrogen peroxide (H₂O₂) digestion is widely applied to remove natural organic matter (NOM) in microplastics (MPs) analysis. However, for sensitive polymers such as polyvinyl chloride (PVC), aggressive oxidation conditions may result in physical or chemical degradation. This study aims to evaluate nine H₂O₂ digestion protocols (25-70 °C, 6-48 h) to quantify the balance between the removal efficiency of NOM adsorbed on MP surfaces and PVC degradation. Using humic acid (HA) as a NOM proxy, we achieved 88.5% removal at 70 °C/48 h but observed significant PVC swelling (53.8% area increase). Fourier-transform infrared spectroscopy (FTIR) confirmed minimal chemical alteration (carbonyl index (CI), ≤ 0.081), though optical microscopy revealed temperature-dependent physical fragmentation. Crucially, we identify room temperature, 24 h as the optimal compromise, achieving approximately 61% NOM removal with ≤ 15% physical deformation. These findings help identify suitable conditions for PVC MP extraction in NOM-rich environments. This addresses a critical gap in MPs research.