Noha Salem

Water shortage poses a significant global challenge, and there is a pressing need for effective and sustainable desalination technologies that do not require brine disposal. In this study, we fabricated fiber membranes using a mixture of poly(vinylidene fluoride)-co-hexafluoropropylene (PcH) and poly(ethersulfone) (PES) polymers, incorporating black magnetic iron-nickel alloy nanoparticles at high molar ratios of Ni to Fe (90:10 and 80:20). The nanoparticles were integrated into the PcH/PES blend in two ways: (1) as a coating layer on the prepared fibers, and (2) both as a coating layer and dispersed within the PcH/PES polymer dope. The resulting fiber membranes were analyzed using various techniques, and their solar absorption capacity was assessed. This innovative approach of incorporating black magnetic iron-nickel alloy nanoparticles as photothermal agents into electrospun polymer fiber membranes was compared to our previous work on cast membranes made from the same iron-nickel/PcH/PES composite dope. This study reinforces the idea that increased thickness of the cast membranes can enable them to function as 3D blocks, enhancing solar heat concentration and, in turn, boosting the water evaporation rate. This study highlights our ongoing efforts to develop advanced materials and designs for effective solar-driven membrane distillation technology.

Water scarcity is a critical global challenge, underscoring the urgent need for efficient and sustainable desalination technologies with minimal brine disposal. This study introduces a novel solar water desalination approach using photothermal magnetic Janus membranes. The magnetic filler in the membranes serves three main functions: it maintains buoyancy at the air/water interface, captures particles to reduce contamination risks, and alters salt deposition on the membrane. A comprehensive analysis was conducted, including water contact angle measurements, light absorbance testing, and evaporation rates under natural sunlight. Additional characterization techniques, such as atomic force microscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimeter, and Fourier transform infrared spectroscopy-attenuated total reflection, were applied to both blank and photothermal membranes. Properties like mechanical strength, thickness, porosity, and surface roughness were systematically analyzed. The photothermal membranes were evaluated using a floating solar-driven desalination prototype, thermally analyzed via thermal imaging. The results showed that the iron–nickel alloy filler achieved over 90% light absorption and enhanced evaporation rates by up to 170% compared to blank membranes. Thermal imaging confirmed significant heat retention at the water surface, leading to higher evaporation rates. These findings highlight the potential of photothermal magnetic Janus membranes as a promising solution for sustainable desalination to combat global water scarcity.

In this work, a novel polymeric membrane was innovated in terms of composition and preparation techniques. A blend of poly(vinylidene fluoride-co-hexafluoropropylene) (PcH) and poly(ethersulfone) (PES) (18 wt.% total polymer concentration) was prepared using a N-methylpyrrolidone (NMP) and N, N-Dimethylformamide (DMF) solvents mixture, while Lithium chloride (0.05–0.5 wt.%) was used as an additive. The electrospinning and phase inversion techniques were used together to obtain a novel membrane structure. The prepared membranes were characterized using scanning electron microscope imaging, energy dispersive X-Ray, differential scanning calorimeter, thermogravimetric analysis, and Fourier transfer infrared spectroscopy-attenuated total reflectance analyses. Moreover, the static water contact angle, membrane thickness, porosity, surface roughness as well as water vapor permeability were determined. ImageJ software was used to estimate the average fiber diameter. Additionally, the effect of the change of PcH concentration and coagulation bath temperature on the properties of the fabricated membrane was studied. The novel developed membrane has shown a good efficiency in terms of properties and features, as a membrane suitable for membrane distillation (MD); a high porosity (84.4% ± 0.6), hydrophobic surface (136.39° ± 3.1 static water contact angle), and a water vapor permeability of around 4.37 × 10⁻⁵ g·m/m²·day·Pa were obtained. The prepared membrane can be compared to the MD membranes commercially available in terms of properties and economic value.

In this work, the efficiency of a conventional chlorination pretreatment is compared with a novel modified low-fouling polyethersulfone (PES) ultrafiltration (UF) membrane, in terms of bacteria attachment and membrane biofouling reduction. This study highlights the use of membrane modification as an effective strategy to reduce bacterial attachment, which is the initial step of biofilm formation, rather than using antimicrobial agents that can enhance bacterial regrowth. The obtained results revealed that the filtration of pretreated, inoculated seawater using the modified PES UF membrane without the pre-chlorination step maintained the highest initial flux (3.27 ± 0.13 m³·m⁻²·h⁻¹) in the membrane, as well as having one and a half times higher water productivity than the unmodified membrane. The highest removal of bacterial cells was achieved by the modified membrane without chlorination, in which about 12.07 × 10⁴ and 8.9 × 10⁴ colony-forming unit (CFU) m⁻² bacterial cells were retained on the unmodified and modified membrane surfaces, respectively, while 29.4 × 10⁶ and 0.42 × 10⁶ CFU mL⁻¹ reached the filtrate for the unmodified and modified membranes, respectively. The use of chlorine disinfectant resulted in significant bacterial regrowth.