Strategies for the separation of microplastics from water via density modification

, Martínez De Pedro Zahara, Munoz Macarena, Ortiz David, Casas Jose A..

The widespread occurrence of microplastics (MPs) in the aquatic environment represents one of the most important environmental concerns nowadays. Although MPs can enter the environment through multiple pathways, wastewater treatment plants (WWTPs) have been recognized as important sources for MPs introduction into the aquatic systems. It is estimated that rivers, the main recipients of WWTPs discharges, transport up to 90% of the global MPs load into the sea (Schmidt et al., Environ. Sci. Technol. 2017, 51, 12246). Only in Europe, 520000 tons/year of MPs are released in WWTPs effluents (Alimi et al., Environ. Sci. Technol. 2018, 52, 1704). In this context, the development of innovative water treatment processes that allow the effective removal of MPs at WWTPs is crucial. This is an important challenge as the small size of MPs and their low chemical and biological reactivity significantly limit their elimination. The methods developed so far have been mainly focused on their sampling, showing important limitations for water treatment. In our research group, the development of strategies for MPs separation from water via density modification are being investigated. In this work, the removal of polystyrene (PS) and polyester fibers (PE) has been evaluated by their interaction with high-dense hematite (Fe2O3) microparticles. We have found that these mineral particles covered completely both PS and PE MPs leading to a significant increase on their density, which facilitates separation by sedimentation. On the other hand, carbon coating of MPs is being also investigated as an alternative approach to separate MPs. In this case, the removal of polyethylene terephthalate (PET) has been investigated by its coverage with a low-dense activated carbon, which allowed to increase the hydrophobic properties of the particles. These can adsorb air bubbles and float by reducing their density, favoring MPs separation via dissolved air flotation (DAF).

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