Fabrication of synthetic channel-based reverse osmosis membrane for water desalination

Abstract

The inherent permeability-selectivity (permselectivity) tradeoff is one of the issues thin-film composite reverse osmosis (TFC-RO) membranes have been facing since their inception in the 1980s. Membrane researchers have tirelessly studied methods to overcome the permselectivity tradeoff. Biomimetic RO membranes are subsequently studied as they present the potential to overcome the mentioned limitations of TFC membranes. Such membranes have aquaporin (AQP) proteins embedded into the polyamide (PA) layer due to the protein’s intrinsic exceptional water transport capabilities whilst maintaining salt rejection levels. However, as good as it may sound, the AQP-based biomimetic membrane has its limitations with regard to the cost and workability of the biological channels. To address the limitations of the AQP-based biomimetic membranes, synthetic nanochannels that possess similar water permeability and salt rejection capabilities have been proposed as alternatives to AQPs. In this work, we attempted to directly incorporate the peptide-attached (pR)-pillar(5)arenes (pRPH) synthetic nanochannels into the PA layer to investigate the effects on water permeability and salt rejection. From the experimental results, a ~32% increase in the water flux was observed (64.5 L m-2 h -1 (LMH) to 85.1 LMH). At the same time, the selectivity of the optimized membrane remains relatively the same. Hence, the results show the feasibility of incorporating pRPH nanochannels, to fabricate a thin-film nanocomposite membrane (TFN), as a practical method to overcome the permselectivity tradeoff to a greater extent.