Nanofiltration (NF) is a promising technology for brackish water desalination due to its tunable separation efficiency and effective removal of organic contaminants. However, the limited diversity of commercial NF membranes hinders optimal performance. To address this, we developed a tailored NF membrane by simultaneously increasing the piperazine (PIP) concentration and decreasing the trimesoyl chloride (TMC) concentration aiming for the treatment of a typical sulfate-type brackish water. The optimized membrane demonstrated superior performance: adequate desalination capability and improved anti-fouling properties. In particular, the NF membrane fabricated with 1.5 %( w / v ) PIP and 0.03 %(w/v) TMC exhibited a more compact polyamide structure and superior desalination performance compared to NF270. In comparison to NF90, it presented greater surface hydrophilicity (~40°) and nearly two-fold higher permeation flux. Moreover, it exhibited significantly improved anti-fouling ability, as evidenced by its 99.9 % flux recovery versus NF90's 23.5 % after brine cleaning. This enhancement is attributed to its optimized solute selectivity and surface chemistry, which reduce concentration polarization and foulant adhesion. Our work provides a practical and feasible strategy for customizing NF membrane structures to improve desalination efficiency and sustainability.
Junfeng Zheng,Meng Li,Yujian Yao,Xuan Zhang,Lianjun Wang
Zwitterionization of multiwalled carbon nanotubes (ZCNTs) is initially conducted by grafting poly(4-styrenesulfonic acid) and poly(4-vinylpyridine) copolymers via an atom transfer radical polymerization (ATRP) reaction, and the products obtained are further used as an aqueous additive to fabricate thin-film nanocomposite (TFN) nanofiltration (NF) membranes. The most optimal membrane with a ZCNT dosage of 0.01%, Z-TFN 0.01% shows nearly 31% enhancement in water permeability (14.9 ± 0.5 L m−2 h−1 bar−1), probably due to the shortened ZCNT, which could create a larger number of inorganic–organic interfaces in the barrier layers. Besides, it also exhibits MgSO4/NaCl selectivity (5.6 ± 0.8), 2.8 times higher than that of the pristine one (2.0 ± 0.2), which is attributed to the formation of ion-response channels and the stretching effect of the side chains. By using model brackish water as the feed solution and subjecting it to a two-stage NF process, the outstanding separation ability of the Z-TFN 0.01% membrane for the ions with the final Na+/Mg2+ concentration ratio in the permeate reaching as high as 589.2, as against only 111.7 for the control, is displayed. Furthermore, due to the strong bacteriostasis ability of quaternary ammonium compounds, Z-TFN 0.01% also shows excellent antibacterial properties, as evidenced by the mortality of Escherichia coli to 97% after remaining in contact with the membrane surface.
The demand for highly permeable and selective thin-film composite (TFC) nanofiltration membranes, which are essential for seawater and brackish water softening and resource recovery, is growing rapidly. However, improving and tuning membrane permeability and selectivity simultaneously remain highly challenging owing to the lack of thickness control in polyamide films. In this study, we fabricated a high-performance interlayered TFC membrane through classical interfacial polymerization on a MoS2-coated polyethersulfone substrate. Due to the enhanced confinement effect on the interface degassing and the improved adsorption of the amine monomer by the MoS2 interlayer, the MoS2-interlayered TFC membrane exhibited enhanced roughness and crosslinking. Compared to the control TFC membrane, MoS2-interlayered TFC membranes have a thinner polyamide layer, with thickness ranging from 60 to 85 nm, which can be tuned by altering the MoS2 interlayer thickness. A multilayer permeation model was developed to delineate and analyze the transport resistance and permeability of the MoS2 interlayer and polyamide film through the regression of experimental data. The optimized MoS2-interlayered TFC membrane (0.3-inter) had a 96.8% Na2SO4 rejection combined with an excellent permeability of 15.9 L m–2 h–1 bar–1 (LMH/bar), approximately 2.4 times that of the control membrane (6.6 LMH/bar). This research provides a feasible strategy for the rational design of tunable, high-performance NF membranes for environmental applications.
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