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Although several sample preparation methods for analyzing microplastics (MPs) in environmental matrices have been implemented in recent years, important uncertainties and criticalities in the approaches adopted still persist. Preliminary purification of samples, based on oxidative digestion, is an important phase to isolate microplastics from the environmental matrix; it should guarantee both efficacy and minimal damage to the particles. In this context, our study aims to evaluate Fenton’s reaction digestion pre-treatment used to isolate and extract microplastics from environmental matrices. We evaluated the particle recovery efficiency and the impact of the oxidation method on the integrity of the MPs subjected to digestion considering different particles’ polymeric composition, size, and morphology. For this purpose, two laboratory experiments were set up: the first one to evaluate the efficacy of various digestion protocols in the MPs extraction from a complex matrix, and the second one to assess the possible harm of different treatments, differing in temperatures and volume reagents used, on virgin and aged MPs. Morphological, physicochemical, and dimensional changes were verified by Scanning Electron Microscope (SEM) and Fourier Transformed Infrared (FTIR) spectroscopy. The findings of the first experiment showed the greatest difference in recovery rates especially for polyvinyl chloride and polyethylene terephthalate particles, indicating the role of temperature and the kind of polymer as the major factors influencing MPs extraction. In the second experiment, the SEM analysis revealed morphological and particle size alterations of various entities, in particular for the particles treated at 75 °C and with major evident alterations of aged MPs to virgin ones. In conclusion, this study highlights how several factors, including temperature and polymer, influence the integrity of the particles altering the quality of the final data.

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In this study, a biochar obtained from poplar wood gasification at a temperature of 850 °C was used to adsorb the xenoestrogens 4-tert-octylphenol (OP) and bisphenol A (BPA) and the herbicide metribuzin from water. Scanning electron microscopy (SEM-EDX) and Fourier-transform infrared (FTIR) spectroscopy were employed to investigate the surface micromorphology and functional groups composition of biochar, respectively. The study of sorption kinetics showed that all compounds achieved the steady state in less than 2 h, according to a pseudo-second order model, which denoted the formation of strong bonds (chemisorption) between biochar and the compounds. Adsorption isotherms data were described by the Henry, Freundlich, Langmuir and Temkin equations. At temperatures of 10 and 30 °C, the equilibrium data of the compounds were generally better described by the Freundlich model, although, in some cases, high correlation coefficients (r ≥ 0.98) were obtained for more than one model. Freundlich constants, KF, for OP, BPA and metribuzin were, respectively, 218, 138 and 4 L g−1 at 10 °C and 295, 243 and 225 L g−1 at 30 °C, indicating a general increase of adsorption at higher temperature. Desorption of all compounds, especially OP and BPA, from biochar was slow and very scarce, denoting an irreversible and hysteretic process. Comparing the results of this study with those reported in the literature, we can conclude that the present biochar has a surprising ability to retain organic compounds almost permanently, thus behaving as an excellent low-cost biosorbent.