In this study, the Surface of Polyethersulfone nanofiltration membranes was modified by a nanocomposite Layer containing POSS nanoparticles. The effect of the Surface modification, on the structure, separation, and other properties of the membranes was checked. Pristine membranes were prepared by the phase inversion method. The surface of the membrane was modified by the dip coating method. Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) analysis, and scanning electron microscopy (SEM), were applied in membrane characterization. Moreover, Pure water flux, salt rejection, membrane porosity, mean pore size of the membrane, water content, and water contact angle were applied to evaluate membranes. The FTIR results proved the creation of a nanocomposite layer with the POSS nanoparticles on the surface of the virginal membrane. SEM images confirmed that a new layer was uniformly present on the surface of the modified membranes. The amount of water content for double-layer membranes had an increasing trend compared to pristine membranes, also, the results of the contact angle showed a decrease in the surface roughness for the modified membranes then with increasing concentration of glycidyl-pass nanoparticles, that is a hydrophobic substance, went through a decreasing trend. By increasing Acrylic Acid, the porosity was enhanced but after utilizing glycidyl-pass nanoparticles, it showed a decreasing trend. Also, the pure water flux showed a decreasing trend. The rate of return had an increasing trend for the membranes. The addition of glycidyl-pass nanoparticles up to 0.1% by weight resulted in the yield of 59.74% Na2SO4 and 64% for CrSO4.

Although the membrane technology has advantages such as the high capability of separation, flexibility of operation, efficiency, etc. compared to conventional methods, fouling is the main limitation for the further use of membrane technology, mainly because of the inherent hydrophobicity of membrane materials. To overcome this drawback, nanocomposite membranes are used. Among membrane processes, nanofiltration has applications in groundwater, surface water and wastewater treatment as well as pre-desalination operations. Since NF process is performed at a lower pressure, it is a much more energy efficient process. In this review, modification of polysulfone/polyatersulfone membranes is investigated with regards to anti-fouling performance. The mechanism of fouling reduction clearly shows that surface hydrophilicity improves at the polysulfone/polyatersulfone membranes, based on different membrane modification methods. In addition, the fabrication of nanocomposite membranes resulting from the participation of nanoparticles in the polymeric matrix mixed membrane, their properties and applications using organic fillers (such as graphene and carbon nanotubes) have been thoroughly studied. Furthermore, the characterization techniques applied for modified membranes have been discussed. This comprehensive study concludes with some recommendations for future research and development of NF membranes.

Hypothesis: Nanofiltration (NF) is a very important technique in separation and purification of aqueous and non-aqueous mixtures in several applications, such as the retention of dyes from water, which is the largest application in this field. Nonetheless, it is still a key issue to enhance the rejection performance and improve the flux, the key factors for the performance of the final membrane. Accordingly, MIL-53(Al) nanoparticles were utilized in this research work because of their small pore sizes, significant hydrophilicity and outstanding water stability. Methods: In this study, the synthesis of the MIL-53(Al) nanoparticles was conducted. Then, the preparation of Polyethersulfone (PES)-MIL-53(Al) mixed matrix membranes was done through the VIPS-NIPS method, which is the vapor-induced phase inversion (VIPS) method coupled with non-solvent-induced phase inversion (NIPS) technique, in which the co-solvent of 1, 4-dioxane was employed. Finally, the prepared nanoparticles and membranes were characterized using several techniques including attenuated total reflection-Fourier transform infrared spectroscopy (ATRFTIR), X-ray diffractometry (XRD), field-emission scanning electron microscopy (FE-SEM), inductively coupled plasma optical emission spectroscopy (ICP-OES), and contact angle analyses. Findings: Different membrane compositions with various MIL-53(Al) contents were prepared so that a membrane with superior performance in dye rejection application and high flux can be achieved. The performance of the fabricated membranes was investigated for rejection of various dyes in aqueous solutions including Reactive Red (RR), Direct Yellow (DY), Methyl Green (MG), and Crystal Violet (CV), based on which a great separation performance (dye rejections of 99. 8, 99. 5, 99. 2, 98. 8 and 97. 1 for RR, MG, DY, CV and MB, respectively) and an excellent water flux (4. 8 L/m2. h. bar) were provided by the membrane containing 0. 06 wt% MIL-53(Al).

The presence of dyes in the aquatic environment can cause soil/water pollution, problems for human health, and abnormal plant growth behavior. In the present study, functionalized Polyethersulfone nanofiltration membranes were prepared by ferroxane fumarate nanoparticles. Ferroxane fumarate nanoparticles were characterized by SEM and FTIR analyzes. The effect of nanoparticles on the performance and properties of membranes was determined in terms of membrane pore size, porosity, hydrophilicity, and separation of milk powder solution by membranes. The hydrophilicity of the membranes was determined by studying the pure water flux and the contact angle of the water. Hydrophilicity increased significantly in membranes containing 0. 5% wt. of ferrooxane fumarate nanoparticles. The results of measuring the pure water flux passing through the prepared membranes showed that after functionalization of the polysulfone nanofiltration membrane by ferroxane fumarate nanoparticles, the permeability of this membrane increased more than three times. The maximum flux recovery ratio and the minimum irreversible permeability decay rate obtained by the M0. 5 membrane were 95. 20 and 4. 8%, respectively. Moreover, M0. 5 showed the highest rejection for dyes of direct red 16 (99%) and methylene blue (98%). The related results proved that an antifouling fumarate ferroxane functionalized membrane can be efficiently applied for the removal of dyes.

Polyethersulfone (PES) based hollow fiber membranes containing polydopamine-functionalized halloysite nanotubes (FHNTs) were fabricated in different concentrations employing a dry-wet approach and using phase inversion methodology. Thus, the prepared nanocomposite hollow fiber membranes were characterized using FE-SEM (Field Emission Scanning Electron Microscopy), AFM (Atomic Force Microscopy), ATR-IR, Zeta Potential, and contact angle for studying membrane surface morphology, topography, presence of functional groups, surface charge, and hydrophilicity, respectively. Filtration studies such as pure water permeability, fouling resistance, and heavy metal rejection (arsenic) were performed at a 2 bar pressure. It was found that as the concentration of FHNTs increased in the membrane, the pure water flux also increased, indicating an increase in hydrophilicity. The membrane PPD-4, with the highest percentage of FHNTs, showed the maximum heavy metal removal. It was confirmed by the values of arsenic removal by the membranes containing FHNTs at 0 wt%, 0. 2 wt%, 0. 6 wt%, and 1 wt% that were found to be 24. 80%, 33. 18%, 35. 54%, and 39. 65%, respectively.

In this study, thin film composite PVA/PES nanofiltration membranes were fabricated for the treatment of pulp and paper industrial wastewater. Phase separation induced by immersion precipitation was used to prepare the PES support membrane. PVA/PES composite nanofiltration membranes were prepared by dipping the support PES membrane in the PVA and cross-linking solutions at different conditions. Maleic acid (MA) was used as cross-linking agent. PVA and MA have concentrations of 0.5–2 and 0.05–1 wt%, respectively. Morphological studies were carried out by means of scanning electron microscopy (SEM) as well as atomic force microscopy (AFM) techniques. In addition, the hydrophilicity of membranes was examined by contact angle measurements. Permeability and ability of PVA/PES composite nanofiltration membranes to reduce COD of the wastewater were evaluated by a cross flow filtration system. SEM images indicated that the PVA layer was uniformly formed on the PES support membrane. AFM images showed that the surface roughness, porosity and pore sizes of PES support membrane were reduced after formation of PVA layer on the support surface. Moreover, the hydrophilicity of the membranes was significantly increased. Experimental results demonstrated that the PVA/PES composite nanofiltration membranes were able to reduce the COD of wastewater. Optimum conditions for preparation of PVA/PES composite membrane are consisted of PVA concentration: 1 wt%, MA concentration: 0.5 wt%, cross-linking time: 3 min and curing time: 3 min.

In this study, flat membranes containing neat Polyethersulfone and the mixed matrix membranes containing Polyethersulfone and nanoparticles such as titanium dioxide(TiO2) and functionalized multiwalled carbonnanotubes (fMWCNTs) were fabricated by wet phase inversion. And the boron ions' rejection and permeat flux behavior of these prepared membranes were evaluated and compared using the nanofiltration process. The hydrophilic properties of the prepared membranes and their structure were evaluated by measuring the contact angle and the scanning electron microscopy method, respectively. To optimize the amount of boron ion’, s rejection percentage and permeate flux on the neat Polyethersulfone membrane, the operational parameters such as the weight percentage of Polyethersulfone, pH, time, pressure, and boric acid concentration were investigated. Finally, the performance of mixed matrix membranes containing different percentages of nanoparticles was evaluated under these optimal conditions. The results showed that at optimal conditions (pressure=12 bar, Polyethersulfone=20% (W/W), concentration of boric acid=20 ppm, time= 30 minutes, and pH=12), all the prepared mixed matrix membranes have higher boron ion rejection percentage and permeate flux than the neat Polyethersulfone. The mixed matrix membrane containing fMWCNTs (0. 7%wt) has the highest boron ion rejection percentage (95/79%).