Composite PVDF ultrafiltration membrane tailored by sandwich-like GO@UiO-66 nanoparticles for breaking the trade-off between permeability and selectivity

ZIF-67 blended PVDF membrane for improved Congo red removal and antifouling properties: A correlation establishment between morphological features and ultra-filtration parameters

Dye effluents from various sectors have constantly imperilled the environment and ecosystem. Nano-composite membrane technology incorporating metal-organic frameworks (MOFs) has shown tremendous potential for toxic pollutant remediation. This study details the impact of ZIF-67 MOF nanoparticles on the structural properties of polyvinylidene fluoride (PVDF) ultrafiltration membrane during the non-solvent induced phase separation (NIPS) process. In order to outline the properties that determine the performance parameters in a MOF-modified mixed matrix membrane, the corresponding changes in mean pore size (MPS), surface porosity, solvent viscosity, and hydrophilicity have been discussed with appropriate surface characterization analysis. The suitability of ZIF-67 as filler nanoparticles were established based on polymer compatibility, dispersibility, and water stability studies. The ZIF-67 incorporated PVDF mixed matrix membranes (MMM) showed 99.5% CR dye removal with 2.6 times DI water permeability than the neat. The flux recovery ratio (FRR) improved by 1.9 times and the membranes were found suitable for up to 5 filtration cycles. Based on the overall results, a correlation analysis between the MMM surface properties and membrane performance parameters were established to determine the key performance parameters. It was observed that in comparison to MPS, surface porosity was more correlated to J_d/J_w (r = 0.96) and FRR (r = 0.95).

Two dimensional (2D) materials and biomaterials for water desalination; structure, properties, and recent advances

BACKGROUND

An efficient solution to the global freshwater dilemma is desalination. MXene, Molybdenum Disulfide (MoS₂), Graphene Oxide, Hexagonal Boron Nitride, and Phosphorene are just a few examples of two-dimensional (2D) materials that have shown considerable promise in the development of 2D materials for water desalination. However, other promising materials for desalinating water are biomaterials. The benefits of bio-materials are their wide distribution, lack of toxicity, and superior capacity for water desalination.

METHODS

For the rational use of water and the advancement of sustainable development, it is of the utmost importance to research 2D-dimensional materials and biomaterials that are effective for water desalination. The scientific community has concentrated on wastewater remediation using bio-derived materials, such as nanocellulose, chitosan, bio-char, bark, and activated charcoal generated from plant sources, among the various endeavors to enhance access to clean water. Moreover, the 2D-materials and biomaterials may have ushered in a new age in the production of desalination materials and created a promising future.

RESULTS

The present review article focuses on and reviews the progress of 2D materials and biomaterials for water desalination. Their properties, surface, and structure, combined with water desalination applications, are highlighted. Further, the practicability and potential future directions of 2D materials and biomaterials are proposed. Thus, the current work provides information and discernments for developing novel 2D materials and biomaterials for wastewater desalination. Moreover, it aims to promote the contribution and advancement of materials for water desalination, fabrication, and industrial production.

In-situ photoreduction strategy for synthesis of silver nanoparticle-loaded PVDF ultrafiltration membrane with high antibacterial performance and stability

Ultrafiltration (UF) technology using polyvinylidene fluoride (PVDF) membrane has been widely applied to water and wastewater treatment due to its low cost and simple operation process. However, PVDF-based UF membrane always encountered the issue of membrane biofouling that greatly impacted the filtration performance. In this study, we prepare a silver nanoparticle (AgNP)-loaded PVDF (Ag/PVDF) UF membrane by an in-situ photoreduction method to mitigate the membrane biofouling. Different from the previously reported method, AgNPs were synthesized in-situ by a UV photoreduction process, in which Ag⁺ ions were reduced to zero-valent Ag nanoparticles by the photo-induced reducing radicals. Antibacterial experiments showed that the inhibition efficiency of Ag/PVDF membrane to Escherichia coli reached up to ~ 99% after antibacterial treatment for 24 h. In comparison with the pristine PVDF membrane, Ag/PVDF membrane possessed a lower water contact angle (83.7° vs. 38.1°), and its pure water flux increased by 23.7%, and a high bovine serum albumin (BSA) rejection efficiency was maintained. In addition, the high stability of the Ag/PVDF composite membrane was confirmed by the extremely low releasing amount of Ag. This study provides a novel strategy for the preparation of metal nanoparticle-incorporated Ag/PVDF ultrafiltration composite membrane showing favorable antibacterial performance and stability.

Next-generation graphene oxide additives composite membranes for emerging organic micropollutants removal: Separation, adsorption and degradation

In the past two decades, membrane technology has attracted considerable interest as a viable and promising method for water purification. Emerging organic micropollutants (EOMPs) in wastewater have trace, persistent, highly variable quantities and types, develop hazardous intermediates and are diffusible. These primary issues affect EOMPs polluted wastewater on an industrial scale differently than in a lab, challenging membranes-based EOMP removal. Graphene oxide (GO) promises state-of-the-art membrane synthesis technologies and use in EOMPs removal systems due to its superior physicochemical, mechanical, and electrical qualities and high oxygen content. This critical review highlights the recent advancements in the synthesis of next-generation GO membranes with diverse membrane substrates such as ceramic, polyethersulfone (PES), and polyvinylidene fluoride (PVDF). The EOMPs removal efficiencies of GO membranes in filtration, adsorption (incorporated with metal, nanomaterial in biodegradable polymer and biomimetic membranes), and degradation (in catalytic, photo-Fenton, photocatalytic and electrocatalytic membranes) and corresponding removal mechanisms of different EOMPs are also depicted. GO-assisted water treatment strategies were further assessed by various influencing factors, including applied water flow mode and membrane properties (e.g., permeability, hydrophily, mechanical stability, and fouling). GO additive membranes showed better permeability, hydrophilicity, high water flux, and fouling resistance than pristine membranes. Likewise, degradation combined with filtration is two times more effective than alone, while crossflow mode improves the photocatalytic degradation performance of the system. GO integration in polymer membranes enhances their stability, facilitates photocatalytic processes, and gravity-driven GO membranes enable filtration of pollutants at low pressure, making membrane filtration more inexpensive. However, simultaneous removal of multiple contaminants with contrasting characteristics and variable efficiencies in different systems demands further optimization in GO-mediated membranes. This review concludes with identifying future critical research directions to promote research for determining the GO-assisted OMPs removal membrane technology nexus and maximizing this technique for industrial application.

PVDF/MOFs mixed matrix ultrafiltration membrane for efficient water treatment

Polyvinylidene fluoride (PVDF), with excellent mechanical strength, thermal stability and chemical corrosion resistance, has become an excellent material for separation membranes fabrication. However, the high hydrophobicity of PVDF membrane surface normally leads a decreased water permeability and serious membrane pollution, which ultimately result in low operational efficiency, short lifespan of membrane, high operation cost and other problems. Metal-organic frameworks (MOFs), have been widely applied for membrane modification due to its large specific surface area, large porosity and adjustable pore size. Currently, numerous MOFs have been synthesized and used to adjust the membrane separation properties. In this study, MIL-53(Al) were blended with PVDF casting solution to prepare ultrafiltration (UF) membrane through a phase separation technique. The optimal separation performance was achieved by varying the concentration of MIL-53(Al). The surface properties and microstructures of the as-prepared membranes with different MIL-53(Al) loading revealed that the incorporation of MIL-53(Al) enhanced the membrane hydrophilicity and increased the porosity and average pore size of the membrane. The optimal membrane decorated with 5 wt% MIL-53(Al) possessed a pure water permeability up to 43.60 L m^-2 h^-1 bar^-1, while maintaining higher rejections towards BSA (82.09%). Meanwhile, the prepared MIL-53(Al)/LiCl@PVDF membranes exhibited an excellent antifouling performance.

Universitetet i Oslo-67 (UiO-67)/graphite oxide composites with high capacities of toluene: Synthesis strategy and adsorption mechanism insight

In this paper, a simple solvothermal synthesis method was proposed for the preparation of metal organic framework/graphene oxide hybrid nanocomposite (UiO-67/GO). A series of UiO-67/GO composites were prepared by varying the addition forms and amounts of GO, and the optimal synthesis conditions were screened. The composites were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission Electron Microscope (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopic (XPS), water contact angles (CA) and thermogravimetric analysis (TGA). The adsorption capacity and the adsorption process of toluene were investigated by dynamic adsorption and adsorption kinetics, respectively. The results indicated that 67/GO-0.5% reached the maximum adsorption capacity (876 mg g^-1), which far exceeded the other adsorbents. Kinetic model and the Weber-Morris model correlated satisfactorily to the experimental data. The improved adsorption performance was attributed to GO, which enhanced π-π interaction, promoted defect generation and provided more adsorption sites. Finally, the excellent regeneration performance of the adsorbent was verified by temperature programmed desorption (TPD) and cyclic adsorption-desorption experiments. Moreover, the adsorption mechanism was further revealed. Combined with the related adsorption experiments and the density functional theory (DFT) analysis, the efficient removal of toluene by UiO-67/GO was attributed to the cooperation of defects, π-π interaction and hydrogen bonding.

A poly(amidoxime)-modified MOF macroporous membrane for high-efficient uranium extraction from seawater

Although metal–organic frameworks (MOFs) own excellent uranium adsorption capacity but are still difficult to conveniently extract uranium from seawater due to the discrete powder state. In this study, a new MOF-based macroporous membrane has been explored, which can high-efficiently extract uranium through continuously filtering seawater. Through modifying the UiO-66 with poly(amidoxime) (PAO), it can disperse well in a N,N-dimethylformamide solution of graphene oxide and cotton fibers. Then, the as-prepared super-hydrophilic MOF-based macroporous membrane can be fabricated after simple suction filtration. Compared with nonmodified MOFs, this UiO-66@PAO can be dispersed uniformly in the membrane because it can stabilize well in the solution, which have largely enhanced uranium adsorbing capacity owing to the modified PAO. Last but not least, different from powder MOFs, this UiO-66@PAO membrane provides the convenient and continuously uranium adsorbing process. As a consequence, the uranium extraction capacity of this membrane can reach 579 mg·g−1 in 32 ppm U-added simulated seawater for only 24 h. Most importantly, this UiO-66@PAO membrane (100 mg) can remove 80.6% uranyl ions from 5 L seawater after 50 filtering cycles. This study provides a universal method to design and fabricate a new MOF-based adsorbent for high-efficient uranium recovery from seawater.