Search Results (9)

Omniphobic membranes have gained extensive attention for mitigating membrane wetting in robust membrane separation owing to the super-repulsion toward water and oil. In this study, a Teflon/PAI composite membrane with omniphobic characteristics was prepared by a vacuum-assisted dip-coating strategy on the PAI hollow fiber membrane. A series of characterizations on morphological structure, surface chemical composition, wettability, permeability, mechanical properties, and stability were systematically investigated for pristine PAI and Teflon/PAI composite membranes. Subsequently, the experiment was conducted to explore the oil–gas separation performance of membranes, with standard transformer oil containing dissolved gas as the feed. The results showed that the Teflon AF2400 functional layer was modified, and C-F covalent bonds were introduced on the composite membrane surface. The Teflon/PAI composite membrane exhibited excellent contact angles of 156.3 ± 1.8° and 123.0 ± 2.5° toward DI water and mineral insulating oil, respectively, indicating omniphobicity. After modification, the membrane tensile stress at break increased by 23.0% and the mechanical performance of the composite membrane was significantly improved. In addition, the Teflon/PAI composite membrane presented satisfactory thermal and ultrasonic stability. Compared to the previous membranes, the Teflon/PAI composite membrane presented a thinner Teflon AF2400 separation layer. Furthermore, the omniphobic membrane demonstrated anti-wetting performance by reaching the dynamic equilibrium within 2 h for the dissolved gases separated from the insulating oil. This suggests an omniphobic membrane as a promising alternative for oil–gas separation in monitoring the operating condition of oil-filled electrical equipment online. Full article

Membrane distillation demonstrates ideal separation performance towards saline water; however, it fails to accomplish the classification and recovery of multiple components from complex saline solutions (i.e., heavy metal ion-laden saline water in process industries). Herein, an adsorption–membrane distillation (MD) coupling process was proposed, as an example of a Pb(II)/NaCl mixed solution, in which the prepared adsorption membrane was firstly employed to adsorb heavy metal ions in the mixed solution and then the brine was concentrated by the MD process to realize water source recovery and utilization. Firstly, an FeOOH@PVDF adsorptive membrane was fabricated to adsorb Pb(II) ions. It was demonstrated that chemical adsorption was identified as the dominant mechanism, and the composite membrane showed excellent selective adsorption for Pb(II). Following this, the omniphobic membrane was then employed to concentrate the Pb(II)-removed saline solution, maintaining a water flux of 16.12 kg·m⁻²·h⁻¹ at a concentration factor of 7.7, demonstrating excellent MD concentration performance. Through this coupled process, the saline wastewater containing heavy metal ions was successfully separated into purified water and concentrated brine without heavy metal ions, providing a novel approach for the treatment and recycling of complex saline wastewater. Full article

Commercial hydrophobic membranes encounter severe problems such as membrane wetting and membrane fouling under extreme conditions, which affect membrane separation performance. To enhance the anti-fouling abilities of hydrophobic membranes, a composite membrane with omniphobic characteristics was fabricated successfully in this paper. Titanium dioxide (TiO₂) nanoparticles were in-situ grown via the hydrothermal synthesis method, and then fluorosilane with low surface energy was grafted on polyvinylidene fluoride (PVDF) membranes. Subsequently, the morphologies, chemical compositions, wetting properties and structural parameters of composite membranes were characterized systematically. Various contaminants were added to the feed to investigate the anti-fouling and anti-wetting performances of the composite membrane in membrane distillation tests. The results showed that butyl titanate was first hydrolyzed to form titanium hydroxide (Ti(OH)₄) and then it was dehydrated to form TiO₂ in the hydrothermal environment. TiO₂ crystals continued to grow and formed rough morphology with micro-nano synergistic distribution, which is similar to a “sunflower” disk composed of cubic clusters and nanopillars. Meanwhile, fluorosilane successfully was grafted onto TiO₂. The contact angles of deionized water, 0.4 mM sodium dodecyl sulfate (SDS) solution and 0.2% v/v mineral oil emulsion on the composite membrane surface were 167.3°, 162.0° and 158.5°, respectively, endowing the composite membrane with excellent omniphobic features. In direct contact membrane distillation (DCMD) tests, the composite membrane exhibited a relatively stable membrane permeate flux, and the salt rejection rate almost reached 100%. The mixture, consisting of inorganic salts, organic substances, surfactants and oil emulsions, was used as feed. In contrast, the commercial PVDF membrane flux decreased drastically and even dropped to 0 due to the membrane fouling and wetting. As for the pristine PVDF membrane, the membrane surface was covered with pollutants and membrane pores were blocked. Therefore, it was proved that the omniphobic composite membrane possesses outstanding anti-fouling and anti-wetting performance. Full article

Extracorporeal membrane oxygenation (ECMO) is a crucial life support therapy for patients with severe cardiac and respiratory failure. However, the complications associated with venoarterial ECMO (VA-ECMO), including thrombus formation, bleeding, and hemolysis, remain significant challenges that impact patient outcomes and healthcare costs. These complications primarily arise from blood–material interactions within the ECMO circuit, necessitating the development of biocompatible materials to optimize hemocompatibility. This review provides an updated overview of the latest advancements in VA-ECMO materials, focusing on cannula, oxygenators, and centrifugal pumps. Various surface modifications, such as heparin coatings, nitric oxide-releasing polymers, phosphorylcholine (PC)-based coatings, and emerging omniphobic surfaces, have been explored to mitigate thrombosis and bleeding risks. Additionally, novel oxygenator membrane technologies, including zwitterionic polymers and endothelial-mimicking coatings, offer promising strategies to enhance biocompatibility and reduce inflammatory responses. In centrifugal pumps, magnetic levitation systems and hybrid polymer-composite impellers have been introduced to minimize shear stress and thrombogenicity. Despite these advancements, no single material has fully addressed all complications, and further research is needed to refine surface engineering strategies. This review highlights the current progress in ECMO biomaterials and discusses future directions in developing more effective and durable solutions to improve patient safety and clinical outcomes. Full article

In this numerical study, the performance of ceramic-based mullite hollow fiber (HF) membranes in a direct contact membrane distillation (DCMD) process was evaluated. Three types of membranes were tested: (i) hydrophobic membrane C8-HFM, (ii) rod-like omniphobic membrane (C8-RL/TiO₂), and (iii) flower-like omniphobic membrane (C8-FL/TiO₂). The CFD model was developed and validated with experimental results, which were performed over a 500 min period. The initial mass flux of C8-HFM was 30% and 9% higher than that of C8-FL/TiO₂ and C8-RL/TiO₂, respectively. However, the flower-like omniphobic membrane C8-FL/TiO₂ had the lowest drop in flux, around 11%, while the rod-like omniphobic membrane C8-RL/TiO₂ had a 15% reduction, both better than the 23% reduction in the hydrophobic membrane C8-HFM over the 500 min. The study also analyzed the impact of fouling by examining the variation in mass transfer coefficient (MTC) over time. The results indicated that the ceramic-based mullite HF membranes with TiO₂ flowers and rods demonstrated a high resistance to fouling compared to C8-HFM. The modified membranes could find applications in the desalination and handling of seawater samples containing organic contaminants. The CFD model’s versatility can be utilized beyond the current investigation’s scope, offering a valuable tool for efficient membrane development solutions, particularly for challenges such as the presence of organic contaminants in seawater. Full article

Nanofibrous membranes for membrane distillation (MD) have demonstrated promising results in treating various water and wastewater streams. Significant progress has been made in recent decades because of the development of sophisticated membrane materials, such as superhydrophobic, omniphobic and Janus membranes. However, fouling and wetting remain crucial issues for long-term operation. This mini-review summarizes ideas as well as their limitations in understanding the fouling in membrane distillation, comprising organic, inorganic and biofouling. This review also provides progress in developing antifouling nanofibrous membranes for membrane distillation and ongoing modifications on nanofiber membranes for improved membrane distillation performance. Lastly, challenges and future ways to develop antifouling nanofiber membranes for MD application have been systematically elaborated. The present mini-review will interest scientists and engineers searching for the progress in MD development and its solutions to the MD fouling issues. Full article

Membrane distillation (MD) is an emerging technology for water recovery from hypersaline wastewater. Membrane scaling and wetting are the drawbacks that prevent the widespread implementation of the MD process. In this study, coaxially electrospun polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP) nanofibrous membranes were fabricated with re-entrant architecture and enhanced hydrophobicity/omniphobicity. The multiscale roughness was constructed by incorporating Al₂O₃ nanoparticles and 1H, 1H, 2H, 2H Perfluorodecyltriethoxysilane in the sheath solution. High resolution transmission electron microscopy (HR-TEM) could confirm the formation of the core-sheath nanofibrous membranes, which exhibited a water contact angle of ~142.5° and enhanced surface roughness. The membrane displayed a stable vapor flux of 12 L.m⁻².h⁻¹ (LMH) for a 7.0 wt.% NaCl feed solution and no loss in permeate quality or quantity. Long-term water recovery from 10.5 wt.% NaCl feed solution was determined to be 8–10 LMH with >99.9% NaCl rejection for up to 5 cycles of operation (60 h). The membranes exhibited excellent resistance to wetting even above the critical micelle concentration (CMC) for surfactants in the order sodium dodecyl sulphate (SDS) (16 mM) > cetyltrimethylammonium bromide (CTAB) (1.5 mM) > Tween 80 (0.10 mM). The presence of salts further deteriorated membrane performance for SDS (12 mM) and Tween-80 (0.05 mM). These coaxial electrospun nanofibrous membranes are robust and can be explored for long-term applications. Full article

Membrane distillation (MD) has unique advantages in the treatment of high-salt wastewater because it can make full use of low-grade heat sources. The high salinity mine water in western mining areas of China is rich in Ca²⁺, Mg²⁺, SO₄²⁻ and HCO₃⁻. In the MD process, the inorganic substances in the feed will cause membrane fouling. At the same time, low surface tension organic substances which could be introduced in the mining process will cause irreversible membrane wetting. To improve the anti-fouling and anti-wetting properties of the membrane, the PVDF omniphobic membrane in this paper was prepared by electrospinning. The water contact angle (WCA) can reach 153°. Direct contact membrane distillation (DCMD) was then used for treating high-salinity mine water. The results show that, compared with the unmodified membranes, the flux reduction rate of the omniphobic membrane was reduced by 34% in 20 h, showing good anti-fouling property. More importantly, the omniphobic membrane cannot be wetted easily by the feed containing 0.3 mmol/L SDS. The extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory was used to analyze the free energy of the interface interaction between the membrane and pollutants, aiming to show that the omniphobic membrane was more difficult to pollute. The result was consistent with the flux variation in the DCMD process, providing an effective basis for explaining the mechanism of membrane fouling and membrane wetting. Full article

Simultaneous fouling and pore wetting of the membrane during membrane distillation (MD) is a major concern. In this work, an electrospun bilayer membrane for enhancing fouling and wetting resistance has been developed for treating hydraulic fracture-produced water (PW) by MD. These PWs can contain over 200,000 ppm total dissolved solids, organic compounds and surfactants. The membrane consists of an omniphobic surface that faces the permeate stream and a hydrophilic surface that faces the feed stream. The omniphobic surface was decorated by growing nanoparticles, followed by silanization to lower the surface energy. An epoxied zwitterionic polymer was grafted onto the membrane surface that faces the feed stream to form a tight antifouling hydration layer. The membrane was challenged with an aqueous NaCl solution containing sodium dodecyl sulfate (SDS), an ampholyte and crude oil. In the presence of SDS and crude oil, the membrane was stable and displayed salt rejection (>99.9%). Further, the decrease was much less than the base polyvinylidene difluoride (PVDF) electrospun membrane. The membranes were also challenged with actual PW. Our results highlight the importance of tuning the properties of the membrane surface that faces the feed and permeate streams in order to maximize membrane stability, flux and salt rejection. Full article