The application of membranes in the separation processes has been increased due to their advantages, such as: lower power consumption, easy separation, accessibility of the separated phases and less environmental problems. Research in the field of membranes and membrane separation processes is in progress. New ideas in this field consist of synthesis and characterization of nanocomposite membranes. The nanocomposite membranes have been more efficient than other membranes due to their unique structural properties. In general, nanocomposite membranes are classified into two categories: organic and inorganic. Inorganic nanocomposite membranes are polymeric membranes in which nanosize inorganic fillers are added to improve their thermal stability and permeability. These membranes enjoy high industrial capabilities. Nanocomposite inorganic membranes are in fact used to eliminate the structural and surface defects of traditional inorganic membranes, among which are the two-fiber membranes of carbon-zeolite and alumina-zeolite. In this article, a comprehensive review has been presented about the classification of nanocomposite membranes and their synthesis routes in the gas separation processes. Finally, the future and prospects of nanocomposite membranes application have been discussed.

Membrane bioreactors (MBRs) have been widely used as advanced wastewater treatment process in recent years. However, MBR system has a membrane fouling problem, which makes the system less competitive. In general, membrane fouling occurs more seriously on hydrophobic membranes than hydrophilic ones because of hydrophobic interaction between solutes, microbial cells, and membrane materials. Membrane fouling can also be attributed to the adsorption of organic species, the precipitation of less soluble inorganic species, and the adhesion of microbial cells at the membrane surface. One way for modification of membrane surface is CO2-plasma treatment. It seems that the pore size and porosity of the membranes after plasma treatment increased at first then decreased with the increase of plasma treatment time. The other way is immobilization of TiO2 nanoparticles on/in membranes. TiO2 deposited membrane shows greater fouling mitigation effect compared to that of TiO2 entrapped membrane. Regardless of polymeric material, membrane fouling is mitigated by TiO2 immobilization. It can be concluded that TiO2 immobilized membranes are simple and powerful alternative for fouling mitigation in MBR application.

The main objective of this research is to investigate the effect of surface modification of Polyvinylidene fluoride (PVDF) membrane on its filtration performance and fouling reduction. Considering Titanium dioxide (TiO2) nanoparticles properties in fouling reduction of polymeric membranes and in order to obtain ultrafine and stable nanodispersions on the membrane surface which is the main challenge in this field, composite PVDF/TiO2 ultrafiltration membranes were prepared via phase inversion and colloidal precipitation method. Among various prepared membranes, the PVDF/TiO2 composite membrane using 0.05 g/L of TiO2 in the coagulation bath was selected as the optimum membrane. Roughness reduction of about %24.34 and permeation increase of %15 for the optimum membrane were obtained. The result of the fouling analysis of nanocomposite membranes with BSA showed the improved effect of colliudal precipitation method in naoparticle dispersion on the membrane surface and fouling reduction of the prepared membranes. Indeed, the effect of TiO2 nanoparticle addition via colloidal precipitation method on membrane fouling reduction in membrane bioreactors for refinery wastewater treatment was investigated.

Oily wastewater is important environmental pollution which leads to irreparable damages to the environment. Ultrafiltration process is considered as a commonly used process is oily wastewater process. In the current study, two types of (AC/TiO2) dynamic membranes (pre-coated and self-forming dynamic membrane) was used for oily wastewater treatment to decrease fouling of ultrafiltration membrane. The pre-coated dynamic membrane decreased fouling of the of ultrafiltration membrane while the self-forming membrane intensified the membrane fouling after three cycles of filtration. The COD rejection rate obtained for self-forming dynamic membrane was 45% that is more than the pre-coated dynamic membrane and polymeric membrane, this result shows high separation efficiency for this membrane. The obtained result showed that the pre-coated (AC/TiO2) dynamic membrane can be considered as a good candidate to control the fouling effect of ultrafiltration membrane in oily wastewater treatment.

In this research, the effect of multiwall carbon nanotubes (MWCNTs) on the performance of polyvinyl chloride (PVC) membrane in the filtration of humic acid solution was investigated. The FESEM results showed that the number of surface pores in nanocomposite membranes is more than that of PVC membrane. The tensile strength and abrasion resistance of membranes increased with increasing MWCNTs up to 0.3 wt.%. It was also observed that water flux of membrane containing 0.3 wt.% MWCNTs increases up to 484.7 L/m2h. The decrease of water contact angle from 88.6° for PVC membrane to 70.2° for 0.3 wt.% MWCNTs membrane showed that the hydrophilicity of membranes increases with increasing MWCNTs. It was also found that the rejection of humic acid solution with MWCNTs membranes is more than that of PVC membrane. The analysis of fouling mechanism of membranes revealed that the cake formation model is dominant mechanism for all membranes and cake filtration-complete blockage model fits the volume-time data.

Wetting of polymeric hollow fiber membranes by chemical absorbents is one of the main challenges of gasliquid membrane contactors. This study explored an appropriate method to fabricate a superhydrophobic polypropylene (PP) hollow fiber membrane by incorporating fluorinated silica nanoparticles (fSiO2 NPs) on the PP membrane surface. The effect of the hydrophobic agent on the water repellent properties of the composite membrane was studied by varying (1H,1H,2H,2H-perfluorooctyltriethoxysilane/ tetraethylorthosilicate) (PFOTES/TEOS) molar ratio from 0 to 1. The composite membranes were characterized using field emission scanning electron microscopy (FESEM), attenuated total reflection-Fourier transform infrared (ATR-FTIR), contact angle, mechanical strength and static wettability. The obtained results showed that the surface hydrophobicity and mechanical strength of the composite membranes increased compared to pure ones. The contact angle of 156° was obtained when the (PFOTES/ TEOS) molar ratio was 0.5. Furthermore, the CO2 absorption experiment was done to evaluate the performance of the fabricated membranes in a gas-liquid membrane contactor. The obtained results showed that the PP/fSiO2 composite membrane has more potential to be used in gas-liquid membrane contactors than commonly used polymeric membranes

In this study, thin film nanofiltration membranes were modified by using Ar-Air plasma. The effect of plasma time, power and the composition of plasma gases on physico-chemical properties and separation performance of membranes were investigated. The results showed that the plasma treatment caused to increase in membrane surface hydrophilicity considerably. The surface modification of membranes by using plasma treatment led to enhancement of water flux through the membrane obviously. The separation efficiency of membranes due to surface modification was also changed broadly compared to unmodified membrane. The separation efficiency of modified membranes at 35 W and 180 s, 25 W and 120 s, and 15 W and 60 s plasma treatment measured ~30%, 76%-92%  and 77%-89% respectively. The selectivity for un-modified membrane was also measured ~90%. Among all studied membranes, the modified membrane at 50-50 (v/v) Ar-Air plasma, 25 W and 120 s treatment with considerable enhancement of water flux compared to pristine membrane was selected as the optimum sample.

In this study, graphene oxide (GO) was synthesized through the improved Hummer method and sulfonated graphene oxide nanoparticles (s-GO) were prepared by effective sulfonation reaction. To evaluate the effectiveness of nanofiltration membranes, the membranes were prepared based on the mixing of polyether sulfone with graphene oxide (GO) and sulfonated graphene oxide nanoparticles. Synthesis of GO and s-GO nanoparticles was structurally evaluated using FT-IR and Raman spectroscopy. Nanocomposite membrane containing nanoparticles were fabricated via phase inversion method and their performance was evaluated using membrane evaluation tests. Surface, cross-section morphology and membrane structure were observed by FE-SEM. The wettability of the membrane surface was determined by the test of contact angle, membrane porosity, water absorption and average membrane pore radius. Nanofiltration membrane performance was evaluated by measuring pure water flux, dye removal ability, desalination from aqueous solution, removal of heavy metals, fouling rate and flux recovery ratio. It seems, practically very hydrophilic -OSO3H groups located on GO surfaces can increase the hydrophilicity of the membrane and improve its anti-fouling properties in the final membrane. Fouling test for graphene sulfone-containing membranes showed better results.

In this work, we prepared the nafion/montmorillonite/heteropolyacid nanocomposite membranes for direct methanol fuel cells (DMFCs). The analyses such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) were conducted to characterize the filler dispersion and membrane structure in prepared nanocomposite membranes. XRD patterns of nafion-CsPW-MMT nanocomposites membranes showed the exfoliated structure of membranes by adding MMT and CsPW. SEM-EDXA results showed proper dispersion of nanoparticles in the membrane matrices. Addition of CsPW-MMT to nafion membranes increases water uptake and IEC due to increase hydrophilic groups in membranes. The proton conductivity results showed that proton conductivity increases by increasing amount of CsPW and decreasing of clay content in the membrane. Methanol crossover through polymer electrolyte membranes is a critical issue and causes an important reduction of performance in DMFCs. The developed intercalated nafion/CsPW/MMT nanocomposite membranes have successfully improved the membrane barrier properties due to the unique feature of MMT which contributed to the formation of a longer pathway towards methanol across the membrane. The lowest methanol crossover of the developed membranes in this study was 1.651×10-6 cm2 s-1 which was lower than re-cast nafion membrane (2.078×10-6 cm2 s-1). The methanol permeability was significantly reduced by the incorporation of MMT and increased by addition of CsPW in the nafion membrane. Finally, according to the selectivity results, the nafion-MMT-CsPW nanocomposite membrane with MMT mass fraction of 2.5% and CsPW mass fraction of 8% shows the best membrane selectivity and this nanocomposite membrane could be suitable for application in DMFCs.

Reactive dyes are water-soluble and causes color changes and pH. These colors create problems for humans and plants and animals living in the environment. Therefore, removal of these colors from the aquatic environment is essential. In the present study, grapen-oxide nanosheets were first synthesized using the modified Hammer method and magnetic graphene oxide was prepared using a solothermal method. The properties of nanofillers were investigated using SEM, XRD and VSM analyzes. PES membrane was studied using GO and mGO nanofilers during the phase separation process and the surface and membrane morphology of the membrane using SEM analyzes, porosity and contact angle. After measuring the flux and the properties of the membrane, the removal of RG19 and RR198 by membranes was investigated. The results showed that the hydrophilic property in all modified membranes was improved compared to pure membranes. The PES-mGO membrane has a higher pH than the PES-GO membrane; the membrane containing the PES-mGO has a contact angle of 4.24 degrees relative to the PES-GO membrane. The PES-mGO membrane porosity was higher than PES-GO and the PES-mGO membrane flux, 3.3 L / m2h, was higher than the PES-GO membrane. PES-mGO membrane flux recovery was increased to 5.7% of the PES-GO membrane. The performance of the PES-mGO membrane against RG19 and RR198 removal was 1% and 4% higher than the PES-GO membrane. Regarding the results, it can be said that magnetic nanoparticle graphon oxide has a better efficiency in membrane repair and removes dye from aqueous solutions.