Slow hydrophobic hydration induced polymer ultrafiltration membranes with high water flux

Tailoring Morphology and Properties of Tight Utrafiltration Membranes by Two-Dimensional Molybdenum Disulfide for Performance Improvement

To enhance the permeation and separation performance of the polyethersulfone (PES) tight ultrafiltration (TUF) membrane, two-dimensional molybdenum disulfide (MoS2) was applied as a modifier in low concentrations. The influence of different concentrations of MoS2 (0, 0.25, 0.50, 1.00, and 1.50 wt%) on TUF membranes was investigated in terms of morphology, mechanical strength properties, permeation, and separation. The results indicate that the blending of MoS2 tailored the microstructure of the membrane and enhanced the mechanical strength property. Moreover, by embedding an appropriate amount of MoS2 into the membrane, the PES/MoS2 membranes showed improvement in permeation and without the sacrifice of the rejection of bovine serum protein (BSA) and humic acid (HA). Compared with the pristine membrane, the modified membrane embedded with 0.5 wt% MoS2 showed a 36.08% increase in the pure water flux, and >99.6% rejections of BSA and HA. This study reveals that two-dimensional MoS2 can be used as an effective additive to improve the performance and properties of TUF membranes for water treatment.

Biofouling-Resistant Ultrafiltration Membranes via Codeposition of Dopamine and Cetyltrimethylammonium Bromide with Retained Size Selectivity and Water Flux

Biofouling is a serious problem in ultrafiltration (UF) membrane applications. Modifying the surface of membranes with low molecular weight, commercially available antibacterial chemistries is an excellent strategy to mitigate biofouling. Herein, we report a new strategy to impart antibacterial and anti-biofouling behavior without changing the support membrane's size selectivity and pure water permeance (PWP). To this end, a strong antibacterial agent, cetyltrimethylammonium bromide (CTAB), was codeposited with dopamine onto commercial polyethersulfone (PES) UF membranes in the presence of nitrogen (N₂) gas backflow. The PWP and pore size of the support membrane did not change with codeposition, confirming the benefit of N₂ backflow in mitigating the solution intrusion phenomenon. X-ray photoelectron spectroscopy (XPS), surface ζ potentials, and contact angle measurements confirmed the successful codeposition of polydopamine (PDA) and CTAB onto the membrane. Among three different CTAB concentrations systematically investigated, the membrane functionalized with CTAB at the critical micelle concentration (CMC) provided the best anti-biofouling activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and retained its surface ζ potential after being stored in 1 M NaCl (pH = 6.8) for 3 months. Our results demonstrate the potential of using a facile, one-step approach to modify commercial UF membranes without compromising their pore size or flux, while simultaneously endowing antibacterial activity.

Synchronous Engineering for Biomimetic Murray Porous Membranes Using Isocyanate

Highly permselective and durable membranes are desirable for massive separation applications. However, currently most membranes prepared using nonsolvent-induced phase separation (NIPS) suffer from low permeability and a high fouling tendency due to the great challenges in a rational design and also practical approach for membrane optimization. Inspired by the natural Murray network from vascular plants, we developed a hierarchical membrane via a straightforward yet robust strategy, using isocyanate as a multifunctional additive. Thanks to the integrated functions of a phase separation regulator, blowing agent, cross-linker, and functionalization anchor of isocyanate, our strategy is featured as a perfect combination of a phase separation and chemical reaction, and it enables synchronous engineering of the membrane hierarchy on porosity and components. The representative membrane exhibits superior water permeance (334 L/m²·h·bar), protein retention (>98%), and antifouling ability (flux recover ratio ∼ 98%). This work highlights a versatile path for pursuing a highly enhanced performance of NIPS-made membranes, from the fancy perspective of Murray bionics.

Bimetallic polyphenol networks structure modified polyethersulfone membrane with hydrophilic and anti-fouling properties based on reverse thermally induced phase separation method

In order to improve the hydrophobicity of traditional polyethersulfone (PES) membranes, this study combined the reverse thermally induced phase separation (RTIPS) method with the constructed bimetallic polyphenol networks (BMPNs) to prepare hydrophilic anti-fouling membranes. As for BMPNs, tannic acid (TA) was served as an intermediate to construct both the inner and surface hydrophilic layers of the PES membranes. On the one hand, etching Zeolitic imidazolate framework-8 (EZIF-8) with synergistic etching and surface functionalization via TA not only retained the high pore structure of MOFs, but also had good hydrophilicity. On the other hand, the MPN hydrophilic layer was formed on the membrane surface by the combination of TA from the surface of EZIF-8 and iron ions in the coagulation bath. Therefore, BMPNs structure penetrated the interior and surface of PES membrane, which greatly improved the hydrophilic properties. In addition, the membrane with porous surfaces and spongy cross sections by RTIPS method improved the permeability and mechanical properties of the membrane by several times compared with the membrane via NIPS method. The obtained membranes in this experiment showed excellent permeability, just like pure water flux reached 1662.16 L/m² h, while BSA rejection rate remained at 92.78%. Compared with pure membrane, it showed a better flux recovery rate (FRR = 83.33%) after cleaning, and the reduction of irreversible (R_ir = 16.67%) fouling indexes indicated that the adsorption of protein was inhibited. These results suggested that the hydrophilic anti-fouling PES membranes prepared by this method possessed great application potential in membrane separation technology.

Improved anti-organic fouling and antibacterial properties of PVDF ultrafiltration membrane by one-step grafting imidazole-functionalized graphene oxide

At present, membrane fouling is a thorny issue that limits the development of polyvinylidene fluoride (PVDF) composite membrane, which seriously affects its separation performance and service lifespan. Herein, an imidazole-functionalized graphene oxide (Im-GO) with hydrophilicity and antibacterial performance was synthesized, and it was used as a modifier to improve the anti-organic fouling and antibacterial properties of PVDF membrane. The anti-organic fouling test showed that the maximum flux recovery ratios against bovine serum albumin and humic acid were 88.9% and 94.5%, respectively. Conspicuously, the grafted imidazole groups could effectively prevent the bacteria from growing on the membrane surface. It was gratifying that the antibacterial modifier Im-GO was almost not lost from the hybrid membranes even by the ultrasonic treatment, which was different from the conventional release-killing antibacterial agents. Owing to the long-term anti-organic fouling and antibacterial properties, Im-GO/PVDF hybrid membranes exhibit a great application potential in the fields of rough separation and concentration of biomedical products.

Polydopamine-Assisted Two-Dimensional Molybdenum Disulfide (MoS2)-Modified PES Tight Ultrafiltration Mixed-Matrix Membranes: Enhanced Dye Separation Performance

Tight ultrafiltration (TUF) membranes with high performance have attracted more and more attention in the separation of organic molecules. To improve membrane performance, some methods such as interface polymerization have been applied. However, these approaches have complex operation procedures. In this study, a polydopamine (PDA) modified MoS₂ (MoS₂@PDA) blending polyethersulfone (PES) membrane with smaller pore size and excellent selectivity was fabricated by a simple phase inversion method. The molecular weight cut-off (MWCO) of as-prepared MoS₂@PDA mixed matrix membranes (MMMs) changes, and the effective separation of dye molecules in MoS₂@PDA MMMs with different concentrations were obtained. The addition amount of MoS₂@PDA increased from 0 to 4.5 wt %, resulting in a series of membranes with the MWCO values of 7402.29, 7007.89, 5803.58, 5589.50, 6632.77, and 6664.55 Da. The MWCO of the membrane M3 (3.0 wt %) was the lowest, the pore size was defined as 2.62 nm, and the pure water flux was 42.0 L m⁻² h⁻¹ bar⁻¹. The rejection of Chromotrope 2B (C2B), Reactive Blue 4 (RB4), and Janus Green B (JGB) in aqueous solution with different concentrations of dyes was better than that of unmodified membrane. The separation effect of M3 and M0 on JGB at different pH values was also investigated. The rejection rate of M3 to JGB was higher than M0 at different pH ranges from 3 to 11. The rejection of M3 was 98.17–99.88%. When pH was 11, the rejection of membranes decreased with the extension of separation time. Specifically, at 180 min, the rejection of M0 and M3 dropped to 77.59% and 88.61%, respectively. In addition, the membrane had a very low retention of salt ions, Nacl 1.58%, Na₂SO₄ 10.52%, MgSO₄ 4.64%, and MgCl₂ 1.55%, reflecting the potential for separating salts and dyes of MoS₂@PDA/PES MMMs.

Amphiphilic Block Copolymer of Poly(dimethylsiloxane) and Methoxypolyethylene Glycols for High-Permeable Polysulfone Membrane Preparation

Poly(dimethylsiloxane)-block-methoxypolyethylene glycols (PDMS-b-mPEG) were synthesized by Steglich esterification. The high-permeable membrane (PSf/PDMS-b-mPEG) was prepared by using PDMS-b-mPEG as additives. The successful synthesis of PDMS-b-mPEG was confirmed by nuclear magnetic resonance. Field emission scanning electron microscopy images show that the distribution of finger-like macroporous and sponge-like macroporous can be modulated by controlling the ratio of the hydrophilic/hydrophobic components of additives. The distribution of additives and membrane wettability are validated with X-ray photoelectron spectroscopy and water contact angle test. The permeability of the blended membrane, especially for the membrane PSf/PDMS-b-mPEG1900 (M3), was remarkably improved. The water permeability of M3 (239.4 L/m²·h·bar) was 6.6 times that of the unblended membrane M0 (42.5 L/m²·h·bar). The findings of protein BSA filtration show that the flux recovery ratio of M3 is 89.2% at a BSA retention rate of about 80%, which demonstrates that the polysulfone membranes blended with PDMS-b-mPEG have excellent antifouling performance and extraordinary permeability.

Improved filtration performance and antifouling properties of polyethersulfone ultrafiltration membranes by blending with carboxylic acid functionalized polysulfone

Ultrafiltration membranes with improved filtration performance and antifouling properties have been synthesized through blending polyethersulfone with carboxylic acid functionalized polysulfone.