Articles
Separation and Purification Technology (13835866)354
Janus membranes have asymmetric wettability on each side. This contrasting structure gives them an internal driving force for spontaneous fluid transport (caused by Laplace pressure). The objective of this research is to attain the maximum Laplace pressure for electrospun PVDF/PAN Janus membranes by adjusting the fiber diameter and, consequently, the pore size and contact angle in each layer of the membrane. To achieve this goal, the Taguchi method was employed, and the parameters of the electrospinning process were modified to determine the optimal conditions for obtaining the smallest and largest fiber diameters for PAN and PVDF polymers. Accordingly, four distinct types of Janus membranes with different morphologies in each layer were synthesized. SEM analysis was employed to characterize the structural and morphological properties of the fibers in each layer. Additionally, the contact angle (CA) was measured to assess the hydrophilicity of each layer and determine the droplet penetration rate across the membrane. According to the results, the maximum Laplace pressure (205.60 kPa calculated by the analysis of SEM images and 197.4 kPa calculated by the bubble point test) and highest droplet penetration rate (0.83 µL/s) were attributed to the Janus membrane with the lowest pore size in the hydrophilic layer (0.65 µm) and the highest pore size in the hydrophobic layer (3.44 µm). The performance of the optimized membrane was evaluated with respect to unidirectional water transport and water–oil mixture separation. The results showed a rectification ratio of 3.92, a permeate flux of 7.9 × 104 L·m−2·h−1·bar−1, and a separation efficiency of 96.8 %. Finally, it was demonstrated that the Laplace pressure of the optimal Janus membrane in this study is 2.66 times superior to that of the best similar one in previous studies. The appropriate and allowable range for pore size and contact angle, necessary to attain a satisfactory Laplace pressure (exceeding 100 kPa), has been explored, determined, and recommended for future researchers to foster inspiration in the field of Janus membranes. © 2024 Elsevier B.V.
Desalination and Water Treatment (19443994)286pp. 16-28
An interpenetrating polymer network (IPN) membrane and its modified form with NaA zeolite were prepared using polyvinyl alcohol/polyacrylic acid and were used in desalination of saline solutions by pervaporation and reverse osmosis. The prepared membranes were characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, tensile and swelling test. The effective parameters in the membrane preparation were investigated and optimized through experimental design. Then, Salt rejection and solution flux were selected as the criteria for the membrane performances. The pervaporation results showed that the flux increases with the feed temperature going up and the membrane thickness decrease. However, better rejection was achieved at less feed temperature and more membrane thickness. At the optimized conditions, flux 7.1 kg/h·m2 and rejection 99% were obtained by net IPN membrane while, these parameters were changed to 11.2 kg/h·m2 and up to 95% by IPN/NaA membrane. Reverse osmosis experiments revealed that as the pressure on the membrane increases, the amount of flux goes up, while it requires less pressure and more cross-linked membrane for having higher rejection (flux 16.2 kg/h·m2 and rejection 90%). According to the obtained results, it was found that this composite membrane has a high ability in desalination with appropriate rejection and fluxes. © 2023 Desalination Publications. All rights reserved.
Desalination and Water Treatment (19443994)307pp. 18-29
Composite membranes consisting of PVA/PAA as interpenetrating polymer networks (IPN), along with various MOFs (MIL-101-Cr, Cu-BTC, UiO-66-NH2) or graphene oxide (GO), were synthesized using a sequential method. These membranes were designed for use in the pervaporation desali-nation of NaCl and MgCl2 salts. The membranes were characterized using swelling, contact angle, FTIR, tensile, and SEM tests, and the optimal preparation parameters were determined using an experiment design method. Subsequently, the optimal membranes were employed in the pervapo-ration desalination process, with salt rejection and fluxes serving as the pervaporation responses. The results showed that as the temperature of the feed increased, the water flux also increased. However, as the feed solution temperature and concentration increased, the salt rejection decreased. Under optimal conditions, the IPN/MIL-101-Cr membrane provided 15.19 and 14.59 kg/m2·h flux and 99.24% and 99.37% rejection for sodium and magnesium ions, respectively, while the GO/IPN membrane provided 13.65 and 12.98 kg/m2·h flux and 98.97% and 99.10% rejection for sodium and magnesium ions, respectively. These composite membranes also exhibited excellent performance in salt mixtures. Based on the experimental design results, preliminary evaluation tests, and comparison with other membranes, it can be concluded that the IPN/MIL-101-Cr composite membrane is highly effective for pervaporation desalination and has potential for industrial-scale applications. © 2023 Elsevier Inc.
