Development and Performance Characterization of a Polyimine

Nov 20, 2017 - The global demand for water is projected to increase by 55% over the next 30 years as a result of population growth, urbanization, econ...
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Development and Performance Characterization of a Polyimine Covalent Organic Framework Thin-Film Composite Nanofiltration Membrane Lauren Valentino, Michio Matsumoto, William R. Dichtel, and Benito J. Marinas Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b04056 • Publication Date (Web): 20 Nov 2017 Downloaded from http://pubs.acs.org on November 21, 2017

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Environmental Science & Technology

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Development and Performance Characterization of a Polyimine Covalent Organic Framework Thin-Film Composite Nanofiltration Membrane

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Lauren Valentino§, Michio Matsumoto†, William R. Dichtel†, Benito J. Mariñas*§

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§Safe Global Water Institute, Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801

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†Department of Chemistry, Northwestern University, Evanston, IL 60208

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*Corresponding author [phone: +1-217-333-6961; e-mail: [email protected]]

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ABSTRACT – Two-dimensional covalent organic frameworks (COFs) were used to create the

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first asymmetric, thin-film composite (TFC) nanofiltration (NF) membrane with a COF active

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layer. NF membrane active layers of polyimine COF were synthesized via the interfacial

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polymerization (IP) of terephthalaldehyde and tris(4-aminophenyl)benzene monomers on top of

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a polyethersulfone (PES) ultrafiltration membrane support. Rutherford backscattering

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spectrometry and Fourier transform infrared spectroscopy analyses confirmed the presence of an

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imine-linked film with a thickness of ~10 nm that was formed reproducibly. The rejection

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efficiencies of the COF NF membrane for a model organic compound, Rhodamine-WT, and a

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background electrolyte, NaCl, were higher than those of the PES support without the COF film.

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This enhanced solute rejection is the first successful demonstration of a TFC membrane with a

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thin COF active layer. However, this work also demonstrates the need for COF NF membranes

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with smaller active layer pores and alternative support materials. The former should result in

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greater solute rejection, and the latter is key because the PES used for support in the COF

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membranes is incompatible with the organic solvents used for the COF IP process.

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KEYWORDS: membrane, nanofiltration, covalent organic framework, COF, polyimine

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Environmental Science & Technology

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INTRODUCTION

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The global demand for water is projected to increase by 55% over the next 30 years as a

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result of population growth, urbanization, economic development, and climate change.1

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Inadequate sanitation in the developing world, combined with an increasing demand to reuse

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wastewater in developed countries, has resulted in an expanding set of contaminants that

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negatively impact water resources and public health. Both the need to provide safe drinking

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water from complex sources polluted by multiple contaminants and environmental concerns

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about conventional treatment methods have motivated the development of novel membrane

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technologies in recent decades.2-5 Nanofiltration (NF) and reverse osmosis (RO) are membrane

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processes commonly used for drinking water treatment because they offer an effective single-

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step barrier that removes both pathogens and most organic and inorganic contaminants.

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For several decades, thin-film composite (TFC) membranes with polyamide (PA) active

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layers 50-250 nm thick have dominated the pressure-driven membrane technology sector.6-8

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These PA active layers are fabricated with interfacial polymerization (IP) reaction methods,

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which are advantageous because of their scalability for commercial production and capacity to

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produce thin (