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In this paper, the effect of Vapor-Induced Phase Separation (VIPS) time on the morphology and performance of poly (phenyl sulfone) membranes was investigated. 14 wt.% dope solutions were employed for membrane fabrication. After casting the solution, the formed polymeric film was exposed to humid air for certain times to form a porous structure. Morphology and performance of membranes were characterized by Scanning Electron Microscopy (SEM), pore size distribution, pure water flux, and Bovine Serum Albumin (BSA) retention. Pore size distribution results showed that by an increase in VIPS time, the pore size of the membrane was increased, and SEM images showed that with increasing VIPS time, the thickness of the dense skin top layer decreased, also the surface of the membranes at first became smooth and then changed to rough. Moreover, by increasing the VIPS time, the pure water flux of the prepared membranes increased from 17.12 to 37.61 L/m².h. The performance of the fabricated membranes for retention of BSA indicated that with increasing the VIPS time, the retention of BSA decreased gradually from 71.3 to 52.3% but the flux increased more sharply from 6.94 to 17.36 L/m².h. Generally, vapor induced phase separation technique is an effective method that could be applied for fabricating membranes with different characteristics for different applications from one dope solution. If a membrane with antifouling features is required, low VIPS time should be applied and if a high flux membrane is desirable, high VIPS time should be employed.

A double layer composite membrane was fabricated by matrimid 5218 as a selective layer on polyvinylidene fluoride (PVDF), a porous asymmetric membrane, as a sublayer. The effect of chemical cross-linking of Matrimid 5218 by ethylenediamine (EDA) was investigated on gas transport properties of the corresponding membrane. The permeability levels of hydrogen (H2) and nitrogen (N2) were measured through the fabricated composite membranes at 25°C under pressure range of 2-8 bar. Scanning electron microscopy (SEM) was used for morphological observations of the composite membranes. The Matrimid membranes before and after cross-linking modification were characterized by the Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and density measurement. The FTIR results showed the conversion of imide functional groups into amide through the crosslinking reaction in Matrimid. The XRD results demonstrated a reduction in d-spacing between the polymer chains through cross-linking reaction. Measuring the density of each membrane's partial selective layer and calculating the corresponding fractional free volume revealed an increase in the density and reduced free volumes in Matrimid through the cross-linking reaction. Moreover, by increasing the EDA concentration, the gas permeability in each membrane decreased significantly for nitrogen compared to hydrogen which could be related to lower gas diffusivity through chain packing due to cross-linking of the polymer. The H2/N2 selectivity at 2 bar increased through the cross-linking modification from 56.5 for the pure Matrimid to 79.4 for the composite membrane containing 12 wt% EDA. The effect of pressure on gas permeability through the composite membranes was investigated and the results found to be in agreement with the behavior of less soluble gases in the glassy polymers. Moreover, the H2/N2 selectivity decreased first at low EDA content (0-4 wt%), before reaching a constant value at 8 wt% EDA and finally increasing by 12 wt% EDA content.

A great contribution in research activities on carbon dioxide (CO2) separation, as the most important challenge in greenhouse gases control, has been made to develop new polymeric membranes. In this case, mixed matrix membranes (MMMs), comprised of rigid particles dispersed in a continuous polymeric matrix, was proposed as an effective method to improve the separation properties of polymeric membranes. In this research, ethylene vinyl acetate (EVA) copolymer and zeolite 4A powders were applied to prepare MMMs using solution casting/solvent evaporation method and CO2/N2 separation performance of the membranes was examined under different feed pressures (3-8 bar) and operating temperatures (25-50°C). Morphological and structural characterizations of the membranes were evaluated using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), density and solvent-induced swelling measurements. The gas permeability measurements through the constant-volume method showed the permeability of two gases increased in the presence of zeolite 4A nanoparticles in the polymer matrix. Calculation of diffusivity coefficients of gases revealed that improvement in the diffusivity of all gases into membrane matrix was the main reason for permeability enhancement. In addition, the increase in the CO2/N2 ideal selectivity with the presence of zeolite 4A nanoparticles in the polymer matrix was attributed to the increment in CO2/N2 diffusion selectivity. Under optimum condition, with the addition of 10 wt% zeolite 4A nanoparticles into the membrane matrix, the CO2 permeability increased from 20.81 to 35.24 Barrer and its related selectivity increased 20% compared to that of neat EVA membrane. Furthermore, the membrane performances increased upon feed pressure rise, while the selectivity decreased with the increase in temperature.

The concept of mixed matrix membranes (MMMs) comprising rigid particles dispersed in a continuous polymeric matrix was proposed to improve the separation properties of polymeric membranes. In this approach, the good advantages of both polymeric matrix and inorganic fillers combined and a good permeable membrane with high selectivity, chemical stability, mechanical strength and processability can be prepared. In this article, factors affecting the performance of MMMs where reviewed. Also, the types of MMMs by structure, preparations methods were discussed. In addition, types of common inorganic fillers, gas transport mechanism in MMMs, stress and defects in polymer/inorganic interface and the most prevalent models which can predict the performance of MMMs were stated and discussed. Finally, the future directions of researches in this context and potential usages of MMMs where shown.

Nanocomposite membranes of ethylene-propylene-diene monomer/multiwalled carbon nanotubes (EPDM/MWCNT) were prepared by solution casting، solvent evaporation and cross-link technique to be applied in CO2/N2 gas separation. Both simple and functionalized MWCNTs have been used. The effect of incorporated different amounts multiwalled carbon nanotubes (0-4 wt%)، of both simple and functionalized types، on the performance of nanocomposite membranes was studied. Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FESEM) were used to evaluate the structural/morphological observations of nanocomposite membranes. Comparing the FTIR results of pure and functionalized nanotubes confirmed the presence of carboxylic groups on the functional carbon nanotubes. The FESEM images indicated that at low concentrations، carbon nanotube particles were dispersed well in the EPDM matrix، but they formed agglomerates at concentrations beyond 1 wt%. By incorporation of MWCNTs، the mechanicalproperties of nanocomposite membranes including tensile strength، Young''s modulus and elongation-at-break considerably were improved. By increasing carbon nanotube loading up to 0. 75 wt%، the permeability of both CO2 and N2 and the CO2/N2 selectivity increased. Further loading led to higher permeability of CO2/N2، while the selectivity ofthe system decreased that could be attributed to further agglomeration of carbon nanotube particles. Furthermore، functionalization of carbon nanotubes improved their dispersion and the mechanical properties and gas separation performance of nanocomposite membranes. Through functionalizing of MWCNTs، both the CO2 permeability and CO2/N2 selectivity of the optimum membrane (0. 75 wt% MWCNTs) increased from 37. 95 and 18. 03 Barrer to 57. 57 and 23. 43 Barrer، respectively. At ambient temperature، by the increase in feed pressure a slight increase in the permeability of both CO2 and N2 gases was observed، while the CO2/N2 selectivity was not highly affected.

The present study was conduct in order to surveying the efficiency of Chitosan in performance improvement of coagulant of poly aluminum chloride in removing the turbidity, Al, and organic materials including TOC and UV254(Absorption of the organic materials by ultraviolet at 254 nm) at the slow mixing phase from drinking water. This study conducted in the labscale using jar test device in water treatment plant of Ahvaz. Optimal dosage of poly aluminum chloride together with chitosan was obtained 5 mg/L and 0.02 mg/L respectively. The efficiency of removing the turbidity, TOC, Al and UV254 in the optimal conditions of Chitosan performance were obtained for 96.59, 46.15, 80.49, and 67.86% respectively. The dominant mechanism for instable making colloidal particles and removing the natural organic materials by bridging between the particles-polymers, neutralizing the colloidal NOM charge, and common deposition mechanism by surface absorption are justified. In addition, floces formed by chitosan were coarser due to the high molecular weight and needed to the less time in order to being deposited.

One of the most important and practical methods of improving performance of polymeric membranes for gas separation is the incorporation of inorganic fillers into polymeric membrane matrix. In present study, first, the influence of different amounts of PVAc in the ABS/PVAc blend membranes in the separation of helium from methane was investigated. Then, using the best composition in case of the He permeability and He/CH4 selectivity, the effect of addition of silica nanoparticles into the membrane was studied. The results showed that addition of 3 wt% silica nanoparticles in the ABS/PVAc(20%) blend membrane, increases He permeability (from 6.3 to 59 barer), while selectivity of membrane reduces from 45 to 6.2. In order to modify selectivity, compatibilizing effect of SBR was examined adding 5-15 wt% SBR into the ABS/PVAc/SiO2(3%) membrane. It was found that the membrane with 15% SBR loading, with the He permeability of 42 barer and the He/CH4 selectivity of 52, has the best separation performance. Furthermore, He permeability decreased with increasing pressure from 1 to 4 bar, then it did not changes considerably with elevating pressures. All right reserved.

Polyacrylonitrile (PAN) micro/ultrafiltration membranes were prepared by phase inversion method. The effects of various preparation conditions including polymeric solution concentration، evaporation time، temperature، composition and residence time of the coagulation bath were investigated. Various important membrane characteristics such as pore size، bulk porosity، and mechanical and morphological properties were taken into the consideration. The characterizations were performed by measuring the bubble point، water flux، tensile strength and scanning electron microscopy (SEM) analyses. The results showed that by increasing the polymeric solution concentration from 13 to 17 wt%، the porosity and water flux were decreased. Moreover، the membrane skin layer was considerably thickened with a very significant decrease in its pore sizes which was achieved in ultrafiltration region. By increasing the evaporation time at atmospheric pressure، membrane skin layer was thickened and the pore sizes were decreased. Low coagulation bath temperatures (below 30°C) resulted in lower pore size، water flux، and an increase in membrane mechanical strength. Introduction of isopropanol (IPA) into the water coagulation bath led to lower coagulation rate and consequently، the formation of smaller pores became possible by using pure isopropanol as coagulation bath. Furthermore، by increasing the residence time in coagulation bath، a more porous structure with more uniform pore sizes were formed that showed better mechanical properties. Finally، the so-called ultrafiltration membranes were applied in concentration process of protein and milk fat. A protein rejection more than 93% was attained while a complete removal of milk fat was achieved.

In the present study, phenol removal from aqueous solutions using stabilized emulsion liquid membrane by polymer has been studied. For this purpose, the initial emulsion liquid membrane was stabilized by addition of a proper polymeric solution and then it was dispersed in an external phase containing phenol. In addition to the stability of the membrance, the effect of various parameters such as temperature, stirring speed, internal phase concentrarion, the ratio of the phases and pH of the external phase, which affects on the stability of the globules, were studied. The most stable membrane was obtained by addition of 3 wt.% of PIB to the primary emulsion at 30 °C and 210 rpm. The stability time was increased from 10 to 35 minutes that was very stuitable for this extraction. The results showed that the extraction efficiency is increased by increase in the ratio of the phases (Row), internal reagent concentration and acidity of the external phase. Under such condition, more than 94% of the initial phenol from a 100 ppm feed solution was extracted within 35 minutes.

Chitosan، is a biodegradable cationic polymer، which is derived from deacetylation of chitin. The present study was conducted to investigate the effect of chitosan as a coagulant aids in improving the performance of coagulant property of poly-aluminum chloride as a primary coagulant on the removal of turbidity from water. This study، was performed in a laboratory scale and using jar test apparatus in Ahwaz Water Treatment Plant. Experiments were performed with different concentrations of coagulants، pH and different concentrations of chitosan as a coagulant aids. First the samples mixed under rapid mixing condition (120rpm) for 1minute and then the apparatus set to slow mixing (40rpm) for 20 minute. After mixing the samples left for 30 minute in order to settle the sediments. The optimum pH was found 8 in this study. The optimum doses of poly-aluminum chloride in conjunction with chitosan، were 5mg/L and 0. 02 mg/L، respectively. The required dosage of poly-aluminum chloride as a primary coagulant be reduced upto 50% under optimum condition with chitosan. It was also found using chitosan also produced larger floc with higher settling velocity than primary coagulant alone. The results also showed that chitosan as a coagulant aid had a positive effect on turbidity removal.

CO2 separation has been more considered for its emission control in off-gas and flue gases, upgrading of natural gas, landfill gas recovery and enhanced oil recovery. In this field, here, novel membranes from the blending Acrylonitrile-Butadiene-Styrene (ABS) with Poly(Vinyl Acetate) (PVAc) were prepared. Then, the effect of various PVAc contents incorporated into polymer matrix on the permeation of CO2, CH4 and N2 were investigated. The results showed that the highest CO2 permeability arises in 10% PVAc content. The highest CO2 /CH4 selectivity in 20% PVAc content is 29 and for CO2/N2 in 30% PVAc content is 40.41. A combination of the effects of PVAc polar acetate groups, compression of membrane structure in the present of high molecular weight PVAc, acrylonitrile and flexible butadiene blocks in ABS have caused these occurrences. Furthermore, investigation of the pressure effect on permeability in the range of 2-8 bars has shown no considerable effect on the permeability data with pressure changes. Generally, the prepared membranes can be taken into account as a better membrane for CO2 /N2 separation than CO2 /CH4.

A 2D mathematical model with two approaches for unsteady CO2 permeation through a flat sheet polymeric gas separation membrane was developed. This model considered axial and radial transport in the membrane. Modeling results for CO2 transport, were compared with experimental data measured for the acrylonitrile butadiene styrene/poly vinyl acetate blend membrane. Gas permeability in various polymeric compositions and the effect of pressure on permeability are the main objectives of the comparisons. The model predictions were in excellent agreement with the experimental data.

The separation of hydrocarbon mixture using facilitated transport membrane (an immobilized liquid membrane type) was investigated. A 50:50 (vol. %) propylene-propane mixture was used as a sample of the hydrocarbon mixture. The effect of trans-membrane pressure (in the range of 50-120 kPa) and carrier concentration (in the range of 0-20 wt.% AgNO3) on separation performance was studied experimentally and mathematically. It was observed that increasing trans-membrane pressure and carrier concentration supports the separation factor and propylene permeation rate. On the other hand, increasing trans-membrane pressure and decreasing carrier concentration supports the propane permeation rate. Hence, the greater the trans-membrane pressure and carrier concentration, the more purified the product obtained. It was found that at trans-membrane pressure of 120kPa and carrier concentration of 20wt. %, the highest separation factor (270) and propylene permeation rate (7*10-7mol/s) was obtained. The average deviation between the experimental and modeling results was found to be 5.3% for propylene permeation rate and 0.03% for propane permeation rate.