Simultaneous Increase of Solvent Flux and Rejection of Thin-Film Composite Membranes by Incorporation of Dopamine-Modified Mesoporous Silica

Abstract

Thin-film nanocomposite membranes have shown great promise in organic solvent nanofiltration. However, it is challenging to acquire high permeation flux without severe swelling, which might do harm to rejection and long-term stability. In this study, we introduced dopamine-modified mesoporous silica nanoparticles into the polyamide (PA) matrix via interfacial polymerization to fabricate a series of thin-film nanocomposite membranes. By using polyethyleneimine (PEI) as the aqueous monomer, the modified nanoparticles are designed to be cross-linked within the PA network, which allows the penetration of PEI into the mesopores, and therefore, the membranes show better resistance to solvent-induced swelling and pressure-induced densification. More importantly, the mesopores of nanoparticles provide additional fast channels for solvents, resulting in an unusual enhancement of solvent flux under reduced membrane swelling. Along with the permeation flux, the rejection performance of the nanocomposite membranes is simultaneously improved, thanks to the controlled swelling arising from the strong interfacial adhesion. Thin-film nanocomposite membranes with optimal filler concentration exhibit a high isopropanol permeance of 8.47 L m −2 h −1 bar −1 as well as a quite low-molecular-weight cutoff of 281 Da.

Nonlinear Flux–Pressure Behavior of Solvent Permeation through a Hydrophobic Nanofiltration Membrane

“…Swelling of the membrane occurs upon exposure to solvent, generally leading to higher permeance. 19 However, when the applied pressure attains a critical value, the membrane suffers compaction, affecting the permeance. The conceptualization of membrane swelling followed by pressureinduced membrane compaction is illustrated in Figure 1.…”

“…The present authors explain this nonlinear behavior as follows. Swelling of the membrane occurs upon exposure to solvent, generally leading to higher permeance . However, when the applied pressure attains a critical value, the membrane suffers compaction, affecting the permeance.…”