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Revealing the Key Impact of Microplastic-Derived Dissolved Organic Matter Properties on Aromatic Pollutant Adsorption and the Underlying Mechanisms
Summary
Researchers examined how dissolved organic matter released from different types of microplastics affects the adsorption of aromatic pollutants like bisphenol A and naphthalene. The study found that microplastic-derived dissolved organic matter substantially suppressed the ability of treatment materials to capture these pollutants, revealing an underappreciated way that microplastic degradation products can worsen water contamination.
Microplastics (MPs)-derived dissolved organic matter (MP-DOM) is pervasive in aquatic environments, yet its mechanisms influencing organic pollutant adsorption remain insufficiently understood. Herein, MP-DOM from polyethylene (PE), polystyrene (PS), and poly(ethylene terephthalate) (PET) was examined for its effects on bisphenol A (BPA) and naphthalene (NAP) adsorption onto covalent triazine frameworks (CTF), with humic acid (HA) as a conventional DOM reference. Adsorption experiments demonstrated that MP-DOM substantially suppressed the adsorption of aromatic pollutants onto CTF compared to HA. Correlation analysis indicated that DOM aromaticity and hydrophobicity predominantly governed BPA and NAP affinity (R2 = 0.90–0.99), outweighing molecular weight effects. Three-dimensional excitation and emission matrix (3DEEM) fluorescence spectra and two-dimensional correlation spectroscopy (2D-COS) analyses revealed that low-aromaticity, protein-like constituents in MP-DOM exhibit enhanced affinity toward pollutants. MP-DOM enhanced the maximum fluorescence intensity ratio (Fmax/F0) of protein-like substances by 2.61-fold to 5.65-fold relative to DOM-free samples, exceeding that of HA and indicating a greater affinity of MP-DOM that restricts contaminant diffusion. Moreover, MP-DOM facilitated pollutant desorption via a strong hydrophobic interaction. Overall, MP-DOM inhibited the adsorption of pollutants onto CTF, through reducing diffusion and enhancing desorption. These findings provide new insights into the mechanisms by which MP-DOM regulates the environmental behavior of aromatic contaminants in aquatic systems.