Shirin Kiani

The removal of volatile organic compounds (VOCs) from aqueous streams is of considerable environmental and public-health importance. In the present work, n

In this study, polyvinylidene fluoride (PVDF) nanocomposite membranes modified with hydrophobic nano‐silica (SiO₂‐SA) were developed for desalination via membrane distillation (MD). SiO₂ nanoparticles were modified with stearic acid (SA) via a simple, cost‐effective, and environmentally friendly method to enhance their hydrophobicity before being incorporated into the PVDF matrix. The influence of SiO₂‐SA concentration on membrane properties, including morphology, porosity, surface roughness, hydrophobicity, mechanical strength and liquid entry pressure (LEP_w), was investigated. Furthermore, the impact of various feed compositions on the LEP was also evaluated to better understand membrane resistance under different operating conditions. Optimal membrane performance was achieved with the incorporation of 2 wt.% SiO₂‐SA, which led to enhanced porosity and surface roughness, a water contact angle of 94.6°, and a maximum LEP_w of 4.5 bar. In direct contact membrane distillation (DCMD) with a 3.5 wt.% NaCl feed solution, the PVDF/2% SiO₂‐SA membrane exhibited high water flux of 8.11 kg/m² h—five times that of pristine PVDF—along with excellent salt rejection (> 99.9%) and low permeate conductivity. Wetting resistance of the membranes was further assessed by introducing sodium dodecyl sulfate (SDS) into the feed solution. Additionally, fouling behavior was evaluated using a saline solution containing 3.5 wt.% NaCl and 1 g/L canola oil. The PVDF/2% SiO₂‐SA membrane exhibited stable flux under these conditions, demonstrating its superior resistance to fouling and wetting. Moreover, a 24‐h long‐term DCMD test confirmed the stability and durability of the optimized membrane, with consistent flux and high salt rejection throughout the operation. These findings highlight the potential of SiO₂‐SA modified PVDF membranes in reducing wetting, mitigating fouling, and enhancing desalination efficiency, offering a promising approach for advanced MD applications.

BACKGROUND: The control of biofouling is crucial in the membrane separation process. In the present study, graphene oxide‐silver (GO‐Ag) nanocomposite was fabricated and incorporated into polycaprolactone (PCL) membrane for the first time to increase its antibacterial properties and reduce its biofouling. Characterization of GO‐Ag nanocomposite was done by X‐ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier‐transform infrared (FTIR) spectroscopy. The PCL/GO‐Ag membranes were also characterized by XRD, attenuated total reflectance Fourier‐transform infrared (ATR‐FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), porosity determination, water contact angle measurement, and tensile test. Furthermore, pure water flux (PWF) and bovine serum albumin (BSA) rejection of the membranes were evaluated. Finally, the antibacterial activity of membranes was investigated by diffusion inhibition zone test and plate count of colony‐forming units.RESULTS: The results demonstrated that Ag nanoparticles were formed on the GO surfaces. In addition, membranes incorporated with the GO‐Ag nanocomposite were more hydrophilic, more porous, and more permeable to pure water while showing a lower protein rejection in the filtration of a BSA solution. Adding the GO‐Ag nanocomposite to the PCL membrane increased the inhibition effect against bacteria. The colony counting method confirmed that PCL/GO‐Ag membranes had higher antibacterial properties than the pure PCL membrane, and the PCL/1.8% GO‐Ag membrane represented the maximum antibacterial efficiency of 90% and 98% against P. aeruginosa and S. aureus, respectively.CONCLUSION: Overall, by the incorporation of GO‐Ag nanocomposite into the PCL membrane, PWF and antibacterial property were augmented, while protein rejection dropped. © 2023 Society of Chemical Industry.

In recent years, a well-known membrane-based process called pervaporation (PV), has attracted remarkable attention due to its advantages for selective separation of a wide variety of liquid mixtures. However, some restrictions of polymeric membranes have led to research studies on developing membranes for efficient separation in the PV process. Recent studies have focused on preparation of nanocomposite membranes as an effective method to improve both selectivity and permeability of polymeric membranes. The present study provides a review of PV nanocomposite membranes for various applications. In this review, recent developments in the field of nanocomposite membranes, including the fabrication methods, characterization, and PV performance, are summarized.

Polyphenylsulfone (PPSU) was applied for the first time in the hydrophobic PV process. Nanocomposite membranes of PPSU/graphene (Gr) nanosheets were prepared and used to separate isopropyl benzene (cumene) from water via pervaporation (PV). Analysis of the mechanical properties of the membranes showed that the tensile strength and Young's modulus had an increasing trend with the incorporation of Gr into PPSU. The water contact angle of the membranes had a rising trend with the addition of Gr, confirming the improved hydrophobicity of membranes. In the PV experiments, the membrane containing 3.5 wt% Gr provided the highest separation factor, which was 4.5‐fold as much as that of the neat PPSU membrane. Cumene separation from water by the PPSU/3.5 wt% Gr membrane was associated with the total flux of 132.73 gMH, the separation factor of 1566.36, and the PSI of 208,124.8 gMH.

In this study, novel nanocomposite membranes were fabricated for the removal of isopropyl benzene, a volatile organic compound (VOC), from water via pervaporation (PV). The membranes were made of poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) copolymer. In order to improve the hydrophobic properties of the membranes, hydrophobic silica nanoparticles that had been surface modified by hexamethyldisilazane were used as the nanofiller in the PV membranes, for the first time. Incorporating hydrophobic silica nanoparticles into PVDF‐HFP and increasing its concentration up to 9 wt% enhanced membrane hydrophobicity. Evaluation of membrane performance in VOC separation from water showed that the membrane containing 9 wt% of silica had the highest VOC separation factor, so that the values of total flux, separation factor, and PV separation index (PSI) were 3.77 g/m²/h; 42,483.81; and 158,788.50 g/m²/h for this membrane, respectively. The separation factor and PSI value of the mentioned membrane were almost 204 and 5 times higher than that of the neat PVDF‐HFP membrane.

In the present research, the low water flux of polyphenylsulfone membranes was addressed, and a novel improvement in their water permeation and fouling resistance was achieved using polyethylene glycol (PEG) as the hydrophilic additive. Scanning electron microscopy and field emission scanning electron microscopy, atomic force microscopy, attenuated total reflection Fourier‐transform infrared spectroscopy, thermogravimetric analysis, and tensile test were applied for the investigation of membrane morphology, surface topography, surface chemical structure, thermal stability, and mechanical properties, respectively. Moreover, the relative hydrophilicity/hydrophobicity of the membranes was assessed via determination of membrane water uptake capacity and water contact angle. The membrane performance was studied and compared by determination of pure water flux and filtration of canned beans production wastewater as well as bovine serum albumin solution. The filtration results indicated a remarkable pure water flux and 100% turbidity rejection provided by the polyphenylsulfone/PEG 20 000 membrane. In addition, it was confirmed that the amount of residual PEG within the membrane was increased with increasing PEG molecular weight and concentration.