Abstract
A hydrophilic, hydrostable porous metal organic framework (MOF) material-MIL-101 (Cr) was successfully doped into the dense selective polyamide (PA) layer on the polysulfone (PS) ultrafiltration (UF) support to prepare a new thin film nanocomposite (TFN) membrane for water desalination. The TFN-MIL-101 (Cr) membranes were characterized by SEM, AFM, XPS, wettability measurement and reverse osmosis (RO) test. The porous structures of MIL-101 (Cr) can establish direct water channels in the dense selective PA layer for water molecules to transport through quickly, leading to the increasing water permeance of membranes. With good compatibility between MIL-101 (Cr) nanoparticles and the PA layer, the lab made TFN-MIL-101 (Cr) membranes integrated tightly and showed a high NaCl salt rejection. MIL-101 (Cr) nanoparticles increased water permeance to 2.2 L/m2·h·bar at 0.05 w/v % concentration, 44% higher than the undoped PA membranes; meanwhile, the NaCl rejection remained higher than 99%. This study experimentally verified the potential use of MIL-101 (Cr) in advanced TFN RO membranes, which can be used in the diversified water purification field.
Highlights
Reverse osmosis (RO) is a pressure-driven membrane separation technology, which has been rapidly developing and widely applied in seawater, brackish water and the sewage desalination process [1,2,3]
The X-ray photoelectron spectroscopy (XPS) measurement was performed on ESCALAB 250 spectrophotometer (Thermo Fisher, Waltham, MA, USA) to determine the elemental compositions of the membranes
MIL-101 (Cr) was by nm XRDdiameter (Figure 3a), and(Figure the diffraction agree withof the reported result [46]
Summary
Reverse osmosis (RO) is a pressure-driven membrane separation technology, which has been rapidly developing and widely applied in seawater, brackish water and the sewage desalination process [1,2,3]. Compared with the conventional thermal-based desalination technologies, RO is more energy-efficient and can produce fresh water at a lower cost. The high cross-linked PA selective layer prepared by the interfacial polymerization process has good hydrophilicity, mechanical strength, thermal/chemical stability, selectivity, and cost advantages. The water permeance of PA composite membranes are slightly low due to the high extent of cross-linking [4]. Given this situation, there is still an opportunity to improve TFC RO membranes by enhancing their water permeability.
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