Ultrathin sulfonated mesoporous interlayer facilitates to prepare highly-permeable polyamide nanofiltration membranes

Micelles regulated thin film nanocomposite membrane with enhanced nanofiltration performance

The desalination performance of thin film nanocomposite (TFN) membranes is significantly influenced by the nature of nanofillers and the structure of the polyamide (PA) layer. Herein, a micelles regulated interfacial polymerization (MRIP) strategy is reported for the preparation of TFN membranes with enhanced nanofiltration (NF) performance. Specially, stable and ultrafine micelles, synthesized from the poly(ethylene oxide)-b-poly(4-vinyl pyridine)-b-polystyrene (PEO-PVP-PS) triblock copolymers, were utilized as regulators in the aqueous phase during the interfacial polymerization (IP) process. TFN membranes were fabricated with varying concentrations of micelles to improve their properties and performances. The structure of the PA layer was further regulated by modulating the content of trimesoyl chloride (TMC), which significantly enhances the performance of the TFN membrane with micelles. Attributable to the homogeneously dispersed micelles and the modified PA layer, the optimized membrane denoted as TFN-2-0.3 exhibits an improved separation performance of 20.7 L m-2h-1 bar-1 and 99.3 % Na2SO4 rejection, demonstrating nearly twice the permeance and 2.7 % higher rejection than that of the original control membrane, respectively. The mechanism of this MRIP strategy was investigated through the diffusion experiments of piperazine (PIP) and interfacial tension tests. The incorporated micelles effectively lower the interfacial tension, promote the diffusion of PIP and accelerate the IP reaction, resulting in a denser and thinner PA layer. Collectively, these findings demonstrate that TFN membranes with micelles exhibit increased roughness, enhanced hydrophilicity, superior rejection to divalent salts, and better acid-base resistance, highlighting their potential applications in the design of TFN membranes.

Fabrication of polyamide nanofiltration membrane with tannic acid/poly(sodium 4-styrenesulfonate) network-like interlayer for enhanced desalination performance

The traditional polyamide composite nanofiltration membranes have high selectivity and low water permeance, so it is necessary to find strategies to raise the permeance. Herein, a novel polyamide nanofiltration membranes with high permeance were fabricated by coating a loose hydrophilic network-like interlayer, where tannic acid (TA) with pentapophenol arm structure binds to poly(4-styrenesulfonate) (PSS) polymer through hydrogen and ionic interactions. The effects of the network-like TA/PSS interlayer on surface morphology, surface hydrophobicity, and the interfacial polymerization mechanism were investigated. The outcomes demonstrated that the TA/PSS interlayer can offer a favorable environment for interfacial polymerization, enhance the hydrophilicity of the substrate membrane, and delay the release of piperazine (PIP). The optimized TFC-2 presents pure water flux of 22.7 ± 2.8 L m-2 h-1 bar-1, Na2SO4 rejection of 97.1 ± 0.5 %, and PA layer thickness of about 38.9 ± 2.5 nm. This provides new strategies for seeking to prepare simple interlayers to obtain high-performance nanofiltration membranes.

Effect of Interlayer Construction on TFC Nanofiltration Membrane Performance: A Review from Materials Perspective

Polyamide (PA) thin-film composite (TFC) nanofiltration (NF) membranes, which are extensively utilized in seawater desalination and water purification, are limited by the upper bounds of permeability-selectivity. Recently, constructing an interlayer between the porous substrate and the PA layer has been considered a promising approach, as it may resolve the trade-off between permeability and selectivity, which is ubiquitous in NF membranes. The progress in interlayer technology has enabled the precise control of the interfacial polymerization (IP) process, which regulates the structure and performance of TFC NF membranes, resulting in a thin, dense, and defect-free PA selective layer. This review presents a summary of the latest developments in TFC NF membranes based on various interlayer materials. By drawing from existing literature, the structure and performance of new TFC NF membranes using different interlayer materials, such as organic interlayers (polyphenols, ion polymers, polymer organic acids, and other organic materials) and nanomaterial interlayers (nanoparticles, one-dimensional nanomaterials, and two-dimensional nanomaterials), are systematically reviewed and compared. Additionally, this paper proposes the perspectives of interlayer-based TFC NF membranes and the efforts required in the future. This review provides a comprehensive understanding and valuable guidance for the rational design of advanced NF membranes mediated by interlayers for seawater desalination and water purification.