Polyamide-based membranes with structural homogeneity for ultrafast molecular sieving

Abstract

Thin-film composite membranes formed by conventional interfacial polymerization generally suffer from the depth heterogeneity of the polyamide layer, i.e., nonuniformly distributed free volume pores, leading to the inefficient permselectivity. Here, we demonstrate a facile and versatile approach to tune the nanoscale homogeneity of polyamide-based thin-film composite membranes via inorganic salt-mediated interfacial polymerization process. Molecular dynamics simulations and various characterization techniques elucidate in detail the underlying molecular mechanism by which the salt addition confines and regulates the diffusion of amine monomers to the water-oil interface and thus tunes the nanoscale homogeneity of the polyamide layer. The resulting thin-film composite membranes with thin, smooth, dense, and structurally homogeneous polyamide layers demonstrate a permeance increment of ~20–435% and/or solute rejection enhancement of ~10–170% as well as improved antifouling property for efficient reverse/forward osmosis and nanofiltration separations. This work sheds light on the tunability of the polyamide layer homogeneity via salt-regulated interfacial polymerization process.

Nanofiltration Membranes with Crumpled Polyamide Films: A Critical Review on Mechanisms, Performances, and Environmental Applications

“…An increase in the reaction rate can well match these goals, for example, by adding acid acceptors, , increasing reaction temperature, , and adding other comonomers . One can also control the diffusion of PIP (activator) and change the interfacial tension by adding chemicals such as PVA, salts, , and surfactants , to the PIP solution and coating a hydrophilic gel layer on the substrate …”

Polyamide Covalent Organic Framework Membranes for Molecular Sieving

“…The development of effective separation technology is one of the ways to relieve environmental pressure. Membrane separation has attracted widespread attention in the field of separation technology due to its simplicity, high efficiency, energy saving, and environmental protection. − In this context, a variety of polymer materials have been developed for separation membranes. , Among them, polyamide is one of the most widely used membrane materials due to their high chemical stability, strong mechanical strength, and innately hydrophilic feature, which has exhibited pressure compaction resistance, wide pH operating range, and superior water flux during nanofiltration or reverse osmosis operation. , However, traditional polyamide membranes are amorphous and possess a large amount of nonuniformly distributed free volume pores, which limit the further improvement of inefficient permselectivity . To overcome this disadvantage, developing polyamide materials with well-ordered porous structures is highly desired for the fabrication of high-performance membranes …”

“…6,7 However, traditional polyamide membranes are amorphous and possess a large amount of nonuniformly distributed free volume pores, which limit the further improvement of inefficient permselectivity. 8 To overcome this disadvantage, developing polyamide materials with well-ordered porous structures is highly desired for the fabrication of high-performance membranes. 9 To reach this goal, covalent organic frameworks (COFs) may offer an effective platform.…”

Enhancing the Antifouling Ability of a Polyamide Nanofiltration Membrane by Narrowing the Pore Size Distribution via One-Step Multiple Interfacial Polymerization

“…Although it is well known that narrowing the pore size distribution can greatly improve the separation selectivity of nanofiltration membranes, − the effect of the pore size distribution on their antifouling performance is still mysterious. Li et al have found that the nanofiltration membranes with different pore size distributions (i.e., NF270 and NF10) showed different fouling behaviors for polycyclic aromatic hydrocarbon micropollutants, that is, the nanofiltration membrane with a wider pore size distribution showed more serious fouling potential, and the larger pores were more easily fouled due to a higher local permeation flux.…”