Enhanced efficiency of water desalination in nanostructured thin-film membranes with polymer grafted nanoparticles.

Polyamide composite (PA-TFC) membranes are the state-of-the-art ubiquitous platforms to desalinate water at scale. We have developed a novel, transformative platform where the performance of such membranes is significantly and controllably improved by depositing thin films of polymethylacrylate [PMA] grafted silica nanoparticles (PGNPs) through the venerable Langmuir-Blodgett method. Our key practically important finding is that these constructs can have unprecedented selectivity values ( i.e. , ∼250-3000 bar -1 , >99.0% salt rejection) at reduced feed water pressure ( i.e. , reduced cost) while maintaining acceptable water permeance A (= 2-5 L m -2 h -1 Bar -1 ) with as little as 5-7 PGNP layers. We also observe that the transport of solvent and solute are governed by different mechanisms, unlike gas transport, leading to independent control of A and selectivity. Since these membranes can be formulated using simple and low cost self-assembly methods, our work opens a new direction towards development of affordable, scalable water desalination methods.