Preparation and characterization of PSF-TiO2 hybrid hollow fiber UF membrane by sol–gel method

Enhancing Water Treatment Performance of Porous Polysulfone Hollow Fiber Membranes through Atomic Layer Deposition

Polysulfone (PSF) is one of the most used polymers for water treatment membranes, but its intrinsic hydrophobicity can be detrimental to the membranes' performances. By modifying a membrane's surface, it is possible to adapt its physicochemical properties and thus tune the membrane's hydrophilicity or porosity, which can achieve improved permeability and antifouling efficiency. Atomic layer deposition (ALD) stands as a distinctive technology offering exceedingly even and uniform layers of coatings, like oxides that cover the surfaces of objects with three-dimensional (3D) shapes, porous structures, and particles. In the context of this study, the focus was on titanium dioxide (TiO2), zinc oxide (ZnO), and alumina (Al2O3), which were deposited on polysulfone hollow fiber (HF) membranes via ALD using TiCl4, diethyl zinc (DEZ), and trimethylamine (TMA), respectively, and H2O as precursors. The morphology and mechanical properties of membranes were changed without damaging their performances. The deposition was confirmed mainly by energy-dispersive X-ray spectroscopy (EDX). All depositions offered great performances with a maintained permeability and BSA retention and a 20 to 40° lower water contact angle (WCA) than the raw PSF HF membrane. The deposition of TiO2 offered the best results, showing an enhancement of 50% for the water permeability and 20% for the fouling resistance of the PSF HF membranes.

Reduced Graphene Oxide-Doped Porous Thermoplastic Polyurethane Sponges for Highly Efficient Oil/Water Separation

In this paper, a porous polyurethane sponge with excellent hydrophobicity was prepared through thermal phase separation. Preparation condition modified experiments were systematically carried out, and a sponge with a saturated oil absorption capacity (13.3 g g^-1) and a rapid absorption rate (achieving absorption equilibrium within 20 s) was achieved. The thermoplastic polyurethane (TPU) sponge as an oil absorbent is capable of selectively absorbing various oils/organic solvents from oil/water mixtures with a high recovery rate. To further enhance the hydrophobicity and mechanical properties of the porous sponge, 3% reduced graphene oxide was doped to this material. The morphological investigation indicated that the three-dimensional composite sponges have uniformly distributed micropores and nanopores, and the hydrophobicity and mechanical properties were improved. The composite as a whole exhibited remarkable superelasticity, excellent reversible compressibility, and fatigue resistance (strength up to 186 kPa at 80% strain), which allows it to re-absorb oil by simple manual extrusion. The abovementioned properties make this TPU porous material a promising candidate for practical application in water pollution treatment.

Recent Advances on the Fabrication of Antifouling Phase-Inversion Membranes by Physical Blending Modification Method

Membrane technology is an essential tool for water treatment and biomedical applications. Despite their extensive use in these fields, polymeric-based membranes still face several challenges, including instability, low mechanical strength, and propensity to fouling. The latter point has attracted the attention of numerous teams worldwide developing antifouling materials for membranes and interfaces. A convenient method to prepare antifouling membranes is via physical blending (or simply blending), which is a one-step method that consists of mixing the main matrix polymer and the antifouling material prior to casting and film formation by a phase inversion process. This review focuses on the recent development (past 10 years) of antifouling membranes via this method and uses different phase-inversion processes including liquid-induced phase separation, vapor induced phase separation, and thermally induced phase separation. Antifouling materials used in these recent studies including polymers, metals, ceramics, and carbon-based and porous nanomaterials are also surveyed. Furthermore, the assessment of antifouling properties and performances are extensively summarized. Finally, we conclude this review with a list of technical and scientific challenges that still need to be overcome to improve the functional properties and widen the range of applications of antifouling membranes prepared by blending modification.

Superhydrophobic and Corrosion Behaviour of PVDF-CeO2 Composite Coatings

Composite coatings of polyvinylidene fluoride (PVDF)/CeO₂ were developed by using the spray approach to explore the wetting and corrosion behaviour of coated materials for applications related to industry. PVDF was combined with different quantities of CeO₂ nanoparticles followed by spraying onto glass, aluminium, and steel substrates. The sessile droplet method and microscopy studies were used to assess the wetting behaviour and morphology of the coated surfaces, respectively. The corrosion resistance of uncoated substrates coated with PVDF only was compared with those coated with PVDF/CeO₂ nanoparticles through Tafel polarization techniques. In psi, the force of adhesion was measured between the coating layer and the substrates. The PVDF/CeO₂-coated steel had a significantly greater water contact angle and lower contact angle hysteresis than coated aluminium and glass substrates, reaching 157 ± 2° and 8 ± 1°, respectively. The corrosion protection efficiency of the superhydrophobic PVDF/CeO₂ coatings was considerably higher for steel and aluminium when compared with PVDF coatings. The PVDF/CeO₂ coated substrates had modest adhesion between the coating layer and the substrates, but it was still acceptable. Furthermore, the PVDF/CeO₂ coatings outperformed PVDF alone in terms of mechanical properties.

State-of-the-Art Organic- and Inorganic-Based Hollow Fiber Membranes in Liquid and Gas Applications: Looking Back and Beyond

The aggravation of environmental problems such as water scarcity and air pollution has called upon the need for a sustainable solution globally. Membrane technology, owing to its simplicity, sustainability, and cost-effectiveness, has emerged as one of the favorable technologies for water and air purification. Among all of the membrane configurations, hollow fiber membranes hold promise due to their outstanding packing density and ease of module assembly. Herein, this review systematically outlines the fundamentals of hollow fiber membranes, which comprise the structural analyses and phase inversion mechanism. Furthermore, illustrations of the latest advances in the fabrication of organic, inorganic, and composite hollow fiber membranes are presented. Key findings on the utilization of hollow fiber membranes in microfiltration (MF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), pervaporation, gas and vapor separation, membrane distillation, and membrane contactor are also reported. Moreover, the applications in nuclear waste treatment and biomedical fields such as hemodialysis and drug delivery are emphasized. Subsequently, the emerging R&D areas, precisely on green fabrication and modification techniques as well as sustainable materials for hollow fiber membranes, are highlighted. Last but not least, this review offers invigorating perspectives on the future directions for the design of next-generation hollow fiber membranes for various applications. As such, the comprehensive and critical insights gained in this review are anticipated to provide a new research doorway to stimulate the future development and optimization of hollow fiber membranes.

Performance of Sprayed PVDF-Al2O3 Composite Coating for Industrial and Civil Applications

Because of their great water repellency, Superhydrophobic coatings have a major impact on a variety of industrial applications. The current study's key originality is the development of low-cost, stable, superhydrophobic, and corrosion-resistant composite coatings. In the present work, polyvinylidene fluoride (PVDF)/Al₂O₃ composite coatings were produced using the spray technique to investigate the wettability and corrosion behavior of the coated materials for industrial and civil applications. PVDF was mixed with various concentrations of Al₂O₃ nanoparticles, and the mixture was sprayed onto steel, aluminum, and glass substrates. The wettability and morphology of the coated surfaces were investigated using the sessile droplet method and scanning electron microscopy, respectively. The corrosion resistance of bare substrates was compared to that of those coated with PVDF alone and those coated with PVDF/Al₂O₃ nanoparticles using Tafel polarization techniques. The force of adhesion between the coat and the substrates was measured in pounds per square inch. A nanoindentation test was also used to measure the hardness of the coating layer. The PVDF/Al₂O₃ coated steel showed a significantly higher water contact angle and lower contact angle hysteresis, reaching 157 ± 2° and 7 ± 1°, respectively, compared to the coated aluminum and glass substrates. Corrosion test results showed that the superhydrophobic PVDF/Al₂O₃ coatings had a much higher corrosion protection efficiency for steel and aluminum than that of the PVDF ones. The PVDF/Al₂O₃ coated substrates showed moderate but still acceptable adhesion between the coating layer and the substrates. Moreover, the PVDF/Al₂O₃ coatings had much better mechanical properties than the PVDF only coatings. Such type of coating could be a promising candidate for possible industrial and civil applications.

Stability evaluation and formula optimization of cellulose-based scaffold for the air-liquid interface cultivation of Navicula incerta

Culture scaffolds allow microalgae cultivation with minimum water requirement using the air-liquid interface approach. However, the stability of cellulose-based scaffolds in microalgae cultivation remains questionable. In this study, the stability of regenerated cellulose culture scaffolds was enhanced by adjusting TiO₂ loading and casting gap. The membrane scaffolds were synthesized using cellulose dissolved in NaOH/urea aqueous solution with various loading of TiO₂ nanoparticles. The TiO₂ nanoparticles were embedded into the porous membrane scaffolds as proven by Fourier transform infrared spectra, scanning electron microscopic images, and energy-dispersive X-ray spectra. Although surface hydrophilicity and porosity were enhanced by increasing TiO₂ and casting gap, the scaffold pore size was reduced. Cellulose membrane scaffold with 0.05 wt% of TiO₂ concentration and thickness of 100 μm attained the highest percentage of Navicula incerta growth rate, up to 37.4%. The membrane scaffolds remained stable in terms of weight, porosity and pore size even they were immersed in acidic solution, hydrogen peroxide or autoclaved at 121 °C for 15 min. The optimal cellulose membrane scaffold is with TiO₂ loading of 0.5 wt% and thickness of 100 μm, resulting in supporting the highest N. incerta growth rate and and exhibits good membrane stability.