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

Abstract

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.