Amphiphilic nanowire-assisted monomer shuttling enables ultra-selective reverse osmosis membranes for water purification
Huimin Zhou, Xingran Zhang, Zhouyan Li, Zhiwei Qiu, Zhe Yang, Ruobin Dai, Zhiwei Wang
Abstract
Reverse osmosis (RO) membrane separation is vital for the advanced removal of contaminants, playing a key role in safe water supply. However, existing RO membranes fall remarkably short in adequate removal of small neutral organic contaminants (SNOCs ≤150 Da), due to the structural heterogeneity and nanosized defects of polyamide (PA) rejection layers. To address these challenges, we propose creating a continuous solid-phase interface using amphiphilic CdII/L-cysteine nanowires that spontaneously self-assemble at the water/n-hexane interface, thereby enabling precise control of the PA structure and suppressed formation of nanosized defects. The self-assembled CdII/L-cysteine interface facilitates the shuttling of m-phenylenediamine (MPD) monomers, achieving MPD pre-enrichment in the organic phase and leading to the formation of an ultraselective PA layer for the RO membrane, with an outstanding SNOC removal rate of up to 97.9%. Furthermore, the gutter effect and enhanced surface area ratio of the PA layer, induced by the CdII/L-cysteine interface, contribute to a remarkable increase in water permeance—upgraded by a factor of 4.5, reaching 3.6 ± 0.1 L m−2 h−1 bar−1. This effectively breaks the trade-off between SNOC removal and water permeance. This work opens an appealing avenue for developing highly permeable and selective RO membranes for efficient water reuse. Enhancing rejection of small, neutral organic contaminants by reverse osmosis (RO) membrane is crucial for safe water supply. Here, authors report an amphiphilic nanowire-assisted monomer shuttling strategy that markedly improves the contaminant removal while simultaneously enhanced water permeance.