Thin-film nanocomposite membranes incorporated with defective ZIF-8 nanoparticles for brackish water and seawater desalination

Abstract

In this work, a series of defective ZIF-8 (dZIF-8) nanoparticles with tuneable inner defects have been synthesized and successfully incorporated into the polyamide-based thin-film nanocomposite (TFN) membranes for brackish water and seawater desalination. This is the first attempt to use dZIF-8 nanoparticles as nanofillers in TFN membranes. Additional inner porosity of dZIF-8 nanoparticles endows the membranes with additional pathways for water molecules. Thus, the newly developed TFN membranes have higher separation performance for brackish water reverse osmosis (BWRO) desalination than the normal ZIF-8-incorporated TFN membranes. In addition, the influences of dZIF-8 loading on membrane properties and separation performance have been investigated. At a loading of 0.15 wt% dZIF-8 nanoparticles in the oil phase, the TFN membrane shows a water permeance of 2.61 L m-2 h-1 bar-1 (LMH bar-1) and a salt rejection of 98.6% for brackish water desalination at 20 bar. This water permeance is 52% higher than the pristine thin-film composite (TFC) membrane while the salt rejection is well maintained. Moreover, a steady water flux above 38 LMH is obtained when using seawater of 32000 ppm NaCl as the feed at 50 bar.