Recyclable Membranes through Reversible and Dynamic Crosslinking

by M. Ramirez-Martinez, S. L. Aristizabal, L. Upadhyaya, A.-H. Emwas, N. Hadjichristidis, S. P. Nunes
Journal Article Year: 2024 DOI: 10.1021/acsapm.4c02286

Extra Information

ACS Applied Polymer Materials, 6 (21), 13120-13131

Abstract

Membrane technology is one of the most sustainable methodologies in industrial separations due to its low cost, straightforward scale-up with more compact systems, simple operation, and lower energy consumption than traditional thermal separation processes. However, their linear life cycle results in a large amount of membranes being discarded every year, compromising their sustainability and long-term operational cost. While recycling membranes could enhance their sustainability, it is particularly challenging for solvent-resistant membranes. This difficulty arises from their inherent chemical stability, provided by nonreversible cross-linking with permanent covalent bonds in most cases. In this work, we propose a reversible and dynamic cross-linking with disulfide bonds by using cysteamine as a cross-linking agent to improve the chemical resistance and enable the recyclability of poly(ether imide) (Ultem) membranes. The membranes were stable in dimethylformamide (DMF) with gel contents above 90% after immersion for a week. Stable permeances of methanol, acetonitrile, and DMF with values of 1.4, 3.0, and 1.8 L m–2 h–1 bar–1, respectively, were demonstrated. The cross-linking improved the mechanical properties of the membranes without altering their microstructure and significantly enhanced the rejection of Direct Red 80 (molecular weight of 1373 g/mol) from 75% to 99% in methanol solutions. The method was applied to flat-sheet and hollow fiber membranes. The used membranes were successfully recycled by reducing the disulfide bond with 1,4-dithiothreitol, allowing them to be solubilized, purified, and cast for membrane fabrication. This study demonstrates the potential of integrating dynamic chemistry with membrane science to move toward more sustainable separation processes.

Keywords

Sustainable Membrane Recyclable Membrane Dynamic Covalent Bonds Disulfide Bonds Organic solvent nanofiltration