Alkaline responsive self-healing nanocontainer composite reverse osmosis membrane by layer self-assembly: Enhanced permeable and chlorine resistance properties

Abstract

Low water flux and poor chlorine resistance have become barriers to the applications of polyamide reverse osmosis (RO) membranes. Here, we design and develop a novel RO membrane with high permeability and self-healing chlorine resistance capability by doping alkaline-responsive polymer nanocontainers into the polyamide layer. The nanocontainer is prepared through chemical adsorption and electrostatic self-assembly with titanium dioxide (TiO2) as the core, calcium alginate (CA) and chitosan (CS) as the repair materials, and polyaspartic acid (PASP) as the responsive shell. In addition to increasing water transport through the channels, the PASP shell of the nanocontainer reacts with alkali during conventional alkaline cleaning and thereby the CA and CS are released to precisely repair the chlorinated polyamide and restore the NaCl rejection of the RO membrane. Upon release of the nanocontainer, TiO2 is also exposed to make the membrane antibacterial. The nanocontainer doping significantly enhances surface roughness of the RO membrane, and the water permeability of the thin-film nanocomposite membrane doped with 0.005 wt% nanocontainers is increased by 43.71% to 5.03 L/m2 h bar compared with the blank membrane, while performing an excellent NaCl rejection of 98.02% and maintaining 95.95% after 8000 ppm h active chlorine treatment and alkaline cleaning process.