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Magnetic Extraction of Microplastics from Environmental Samples Jelena Grbic, Brian Nguyen, Edie Guo, Jae Bem You, David Sinton, and Chelsea M. Rochman Environ. Sci. Technol. Lett., Just Accepted Manuscript • DOI: 10.1021/acs.estlett.8b00671 • Publication Date (Web): 25 Jan 2019 Downloaded from http://pubs.acs.org on January 26, 2019
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Environmental Science & Technology Letters
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Magnetic Extraction of Microplastics from Environmental Samples
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Jelena Grbic†®, Brian Nguyen‡®*, Edie Guo†, Jae Bem You‡, David Sinton‡, Chelsea M. Rochman†
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† Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario M5S 3B2, Canada
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‡ Department of Mechanical and Industrial Engineering and Institute for Sustainable Energy, University of Toronto, 5 King’s College Road, Toronto, Ontario M5S 3G8, Canada
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® these authors contributed equally to this work
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*Corresponding Author:
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Brian Nguyen, Email:
[email protected] 11 12
Keywords: microplastics, extraction, environmental monitoring, method development, magnet
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Abstract
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Separating microplastics (MPs) from environmental samples is challenging, but necessary to determine their environmental prevalence. Current methods are not standardized across environmental sample type and it is unclear how well they recover smaller sized MPs. In response, we developed a method that extracts plastics magnetically, taking advantage of their hydrophobic surface to magnetize the plastics. We created hydrophobic Fe nanoparticles that bind to plastic, allowing magnetic recovery. With this principle applied to a simple method, we recovered 92% of 10 – 20 µm polyethylene and polystyrene beads and 93% of > 1 mm MPs (polyethylene, polyethylene terephthalate, polystyrene, polyurethane, polyvinyl chloride, and polypropylene) from seawater. We also recovered 84% and 78% of MPs (polyethylene, polystyrene, polyurethane, polyvinyl chloride, and polypropylene) ranging from 200 µm to 1 mm from freshwater and sediments, respectively. Overall, the procedure is efficient for various sizes, polymer types, and sample matrices, and can be considered by researchers to be included as a step of the extraction procedure for MPs (i.e. post density separation) or stand-alone for cleaner samples (i.e. drinking water).
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Table of Contents Graphic
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Introduction
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Microplastics (MPs) have been found in seemingly all environmental matrices around the world,
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including surface waters1, sediments2, air3, the water column4, soil5,6, and in organisms7–9. Consequently,
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governments are considering regularly monitoring environmental MPs. For example, California has called
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for a “standard methodology to be used in the testing of drinking water for microplastics”10. Therefore,
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efficient sampling, extraction, and analysis techniques are needed.
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Common extraction methods for MPs in environmental samples include flotation (separation by
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density), chemical digestion (separation by biogenic material removal), sieving or filtration (separation by
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size), and visual identification (separation by manual sorting)11. Presently, there is no standardized
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method for extraction. For example, density separation methods use solutions widely ranging in density
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including, but not limited to, sodium chloride (NaCl, 1.2 g/cm3), zinc chloride (ZnCl2, 1.5-1.7 g/cm3) and
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sodium iodide (NaI, 1.6-1.8 g/cm3)2. Chemical digestions also vary by type of chemical used and
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accompanying temperature, some of which can degrade MPs12. Additionally, new methods, such as
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electrostatic separation13 and elutriation column optimization14, are being continually developed.
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Reliable collection of small (
