Construction of a gelatin scaffold with water channels for preparing a high performance nanofiltration membrane

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.

Recent advances in thin film nanocomposite membranes containing an interlayer (TFNi): fabrication, applications, characterization and perspectives

Polyamide (PA) reverse osmosis and nanofiltration membranes have been applied widely for desalination and wastewater reuse in the last 5-10 years. A novel thin-film nanocomposite (TFN) membrane featuring a nanomaterial interlayer (TFNi) has emerged in recent years and attracted the attention of researchers. The novel TFNi membranes are prepared from different nanomaterials and with different loading methods. The choices of intercalated nanomaterials, substrate layers and loading methods are based on the object to be treated. The introduction of nanostructured interlayers improves the formation of the PA separation layer and provides ultrafast water molecule transport channels. In this manner, the TFNi membrane mitigates the trade-off between permeability and selectivity reported for polyamide composite membranes. In addition, TFNi membranes enhance the removal of metal ions and organics and the recovery of organic solvents during nanofiltration and reverse osmosis, which is critical for environmental ecology and industrial applications. This review provides statistics and analyzes the developments in TFNi membranes over the last 5-10 years. The latest research results are reviewed, including the selection of the substrate and interlayer materials, preparation methods, specific application areas and more advanced characterization methods. Mechanistic aspects are analyzed to encourage future research, and potential mechanisms for industrialization are discussed.

A super-hydrophilic partially reduced graphene oxide membrane with improved stability and antibacterial properties

In order to improve stability and antibacterial property, a novel super-hydrophilic partially reduced graphene oxide membrane was prepared by interfacial polymerization of piperazine and partially reduced graphene oxide as aqueous solution and trimesoyl chloride as organic solution. Fourier transform infrared spectroscopy, scanning electron microscope, and contact angle measurement were conducted to probe the morphology and properties of the membranes. The modified membrane possessed super-hydrophilicity, improved durability and swelling resistance. The optimized membrane had a molecular weight cut off of about 674 Da and possessed a pure water permeability of 49.86 L·m^-2·h^-1·MPa^-1. The retention order of salts was Na₂SO₄ > MgSO₄ > MgCl₂ > Na₂CO₃ > CaCl₂ > NaCl, while the rejection for four kinds of pharmaceuticals followed the order of ibuprofen (92%) > carbamazepine (87%) > amlodipine (80%) > atenolol (76%), indicating that the negatively charged membrane could improve the retention performance by the electrostatic repulsive effect. Moreover, the enhanced antibacterial performance of membrane attributed to the dual effects of the super-hydrophilicity and the tea polyphenols antibacterial material loading, which may alter the charge distribution on and within the membrane, leading to loss of cell viability.

Lyophilized Gelatin@non-Woven Scaffold to Promote Spheroids Formation and Enrich Cancer Stem Cell Incidence

A gelatin@non-woven fabric (gelatin@NWF) hybrid scaffold with tailored micropore structures was fabricated by lyophilizing, using gelatin to support cells and the NWF matrix as a frame to enforce the mechanical stability of gelatin. By freezing the gelatin and NWF hybrid in liquid nitrogen and subsequently lyophilizing and crosslinking the process, the gelatin@NWF scaffold was prepared to support cell growth and promote cell aggregation and spheroids’ formation. The results indicated that by tuning the lyophilizing temperature, the micropore size on the gelatin could be tailored. Consequently, tumor spheroids can be formed on gelatin@NWF scaffolds with honeycomb-like pores around 10 µm. The cell spheroids formed on the tailored gelatin@NWF scaffold were characterized in cancer stem cell (CSC)-associated gene expression, chemotherapy drug sensitivity, and motility. It was found that the expression of the CSC-associated biomarkers SOX2, OCT4, and ALDH1A1 in gene and protein levels in DU 145 cell spheres formed on gelatin@NWF scaffolds were significantly higher than in those cells grown as monolayers. Moreover, cells isolated from spheroids grown on gelatin@NWF scaffold showed higher drug resistance and motility. Tumor spheroids can be formed on a long-term storage scaffold, highlighting the potential of gelatin@NWF as a ready-to-use scaffold for tumor cell sphere generation and culturing.

Enhancing H2O2 Tolerance and Separation Performance through the Modification of the Polyamide Layer of a Thin-Film Composite Nanofiltration Membrane by Using Graphene Oxide

Through interfacial polymerization (IP), a polyamide (PA) layer was synthesized on the top of a commercialized polysulfone substrate to form a thin-film composite (TFC) nanofiltration membrane. Graphene oxide (GO) was dosed during the IP process to modify the NF membrane, termed TFC-GO, to enhance oxidant resistance and membrane performance. TFC-GO exhibited increased surface hydrophilicity, water permeability, salt rejection, removal efficiency of pharmaceutical and personal care products (PPCPs), and H₂O₂ resistance compared with TFC. When H₂O₂ exposure was 0–96,000 ppm-h, the surfaces of the TFC and TFC-GO membranes were damaged, and swelling was observed using scanning electron microscopy. However, the permeate flux of TFC-GO remained stable, with significantly higher NaCl, MgSO₄, and PPCP rejection with increasing H₂O₂ exposure intensity than TFC, which exhibited a 3.5-fold flux increase with an approximate 50% decrease in salt and PPCP rejection. GO incorporated into a PA layer could react with oxidants to mitigate membrane surface damage and increase the negative charge on the membrane surface, resulting in the enhancement of the electrostatic repulsion of negatively charged PPCPs. This hypothesis was confirmed by the significant decrease in PPCP adsorption onto the surface of TFC-GO compared with TFC. Therefore, TFC-GO membranes exhibited superior water permeability, salt rejection, and PPCP rejection and satisfactory resistance to H₂O₂, indicating its great potential for practical applications.

Alginate Hydrogel Assisted Controllable Interfacial Polymerization for High-Performance Nanofiltration Membranes

The deepening crisis of freshwater resources has been driving the further development of new types of membrane-based desalination technologies represented by nanofiltration membranes. Solving the existing trade-off limitation on enhancing the water permeance and the rejection of salts is currently one of the most concerned research interests. Here, a facile and scalable approach is proposed to tune the interfacial polymerization by constructing a calcium alginate hydrogel layer on the porous substrates. The evenly coated thin hydrogel layer can not only store amine monomers like the aqueous phase but also suppress the diffusion of amine monomers inside, as well as provide a flat and stable interface to implement the interfacial polymerization. The resultant polyamide nanofilms have a relatively smooth morphology, negatively charged surface, and reduced thickness which facilitate a fast water permeation while maintaining rejection efficiency. As a result, the as-prepared composite membranes show improved water permeance (~30 Lm⁻²h⁻¹bar⁻¹) and comparable rejection of Na₂SO₄ (>97%) in practical applications. It is proved to be a feasible approach to manufacturing high-performance nanofiltration membranes with the assist of alginate hydrogel regulating interfacial polymerization.