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• Real industrial mixtures of 12 components were separated by PV using MSE membranes. • Aromatics were recovered from their mixture with alicyclics/aliphatics/alcohols. • Methanol contamination negatively affects aromatic recovery via coupling effect. • Membrane plasticization by aromatics is intensified by methanol contamination. • Benzene has stronger coupling effects on n-hexane/cyclohexane compared to toluene. The pervaporation separation of aromatics from real industrial multicomponent mixtures containing 12 aromatic/alicyclic/aliphatic/alcoholic compounds was investigated using MSE polymer membranes. The effects of operating parameters including temperature, flow rate, permeate pressure, total aromatic content, and methanol contamination on PV performance were investigated. The behavior of the membrane in terms of swelling, plasticization and coupling effect in contact with real industrial multicomponent feed was evaluated and the work was completed by finding how the operating parameters influence the mass transfer mechanisms, component activity, dominant and limiting transfer phenomena, and coupling effect. The results showed that methanol contamination weakened the positive influences of increasing temperature and reducing permeate pressure. The coupling effects between benzene/toluene as fast-permeating components on n-hexane/cyclohexane as slow-permeating components in the presence of methanol were investigated. The results revealed that benzene has a stronger kinetic coupling effect on n-hexane and cyclohexane than toluene has. Furthermore, the coupling effect is more effective on n-hexane than cyclohexane. The results also showed that the presence of a second fast-permeating component (methanol) typically enhances the permeation of slow-permeating species. In general, the coupling effect had a negative effect on the PV performance in this work which favors the aromatic recovery. [ABSTRACT FROM AUTHOR]

Positively charged hybrid nanofiltration membrane were prepared by the incorporation of Triethylenetetramine (TETA) functionalized multiwall carbon nanotube (MWCNT) into Polyethersulfone (PES) matrix. In the best nanoparticles loading ratio of 0.4 wt%, the fabricated membrane exhibits a pore diameter of 0.73 nm, a molecular weight cut off (MWCO) of 570 Da and a pure water flux (PWF) of 84.35 L/m 2  h which shows 130% improvement compared to the neat PES. Regarding salts rejection, it follows the order R (MgCl 2 ) > R (MgSO 4 ) > R (Na 2 SO 4 ) > R (NaCl) which confirms positively charge nature of the membranes. Furthermore, the prepared membrane demonstrates effective rejection for two cationic dyes i.e. Rhodamine B (99.23%) and Crystal violet (98.43%) and acceptable rejection for two anionic dyes i.e. Indigo carmine (87.12%) and Orange G (82.13%). In addition of improvements in their mechanical and thermal stabilities, antifouling nature of the hybrid membranes enhances as well due to lower surface roughness and higher hydrophilicity. [ABSTRACT FROM AUTHOR]

The novel polyurethane (PU)/polyethylene glycol (PEG) self-support blend membranes were prepared via solution casting method to investigate their gasoline desulfurization performance. Pervaporation (PV) method was employed to separate thiophene from model gasoline consisting of a binary mixture of thiophene and n -heptane. The membrane sorption (S) and diffusion (D) coefficients were obtained from the sorption test. Characteristics and morphological attributes of the membrane were studied using FTIR and SEM analysis. SEM images exhibited a fine heterogeneous blended phase with a defect-free surface. Blending intensified the properties of individual PU and PEG membranes bringing about satisfactory permeability and desulfurization performance. A normalized flux of 25.5 kg µm/m 2 h and an enrichment factor of 7.1 were obtained at 65 °C. The membranes were constructed and evaluated in self-support form, which indicates their mechanical and chemical strength when operated up to 120 h. Both the blending method and the selection of the proper PU with appropriate blending ratio resulted in the fabrication of apposite membranes for separation of thiophene from n -heptane and also the development of a membrane material to be utilized in desulfurization industry. [ABSTRACT FROM AUTHOR]

This study tries to develop an explicit and phenomenological model to describe transport properties of penetrants through nanocomposite membranes. The model development procedure was conducted regarding experimental observations. Poly(Ether Block Amid), PEBAX (grade 1657), and SiO 2 nanoparticles were applied to fabricate the neat and the nanocomposite membranes. Permeability, solubility and diffusivity of four permanent gases (CO 2 , H 2 , N 2 and CH 4 ) were measured through the fabricated membranes at temperature range of (298–338 K), and a fixed transmembrane pressure (TMP) of 2 bar. The proposed model was developed based on the solution-diffusion theory, to calculate solubility, diffusivity and permeability of the penetrants through the nanocomposite membranes. The Van Amerongen and Van Krevelen relations were applied to estimate solution and diffusion coefficients of the penetrants through the neat membrane regarding the physical properties of penetrants and glass transition temperature of the polymer. Then, solution and diffusion coefficients through the nanocomposite membranes were correlated to those of the neat membrane and structural properties of the nanocomposite membranes. The results showed that the presented model in this study can efficiently calculate solubility, diffusivity and then permeability of the penetrants through the fabricated nanocomposite membranes (e.g. the calculated values and the experimental data have a correlation coefficient, R 2 , higher than 0.95, 0.97, and 0.96 for solubility, diffusivity and permeability, respectively). [ABSTRACT FROM AUTHOR]

[Display omitted] • Antifouling hollow fiber membranes with inner-selective layer were synthesized via facile fabrication method. • High water flux and low reverse salt flux were obtained through OMBR application where wastewater was used as feed flow. • Hollow fiber membranes consisted of antimicrobial outer skin layer and porous medium for enhance wastewater treatment. • Specific performance index (SPI), as a new concept was introduced which is believed to have the potential to be used as a unique FO membrane characteristic. Forward osmosis (FO) hollow-fiber membranes were prepared by in situ thin layer assembly of polyethyleneimine (PEI) on antifouling PES-based porous nanocomposite membranes during membrane formation by spinning and phase inversion, via incorporation of surface-modified silver nanoparticles (NPs) in the dope solution and addition of PEI in the bore liquid; after cross-linking with glutaraldehyde the FO selective layer was obtained at the lumen surface while the shell surface had ultrafilter (UF) properties. This design enabled the utilization of the FO membranes in active layer facing draw solution (DS) orientation to employ maximum effective osmotic pressure, while the UF layer in combination with the antibacterial NPs was supposed to reduce fouling by the wastewater used as feed solution (FS). The quality of the active layer assembly was characterized using atomic force microscopy and scanning electron microscopy analyses, as well as salt rejection, structural parameter (S), and molecular weight cut-off (MWCO) measurements. The separation performance of these membranes was evaluated in an osmotic membrane bioreactor (OMBR) system, showing for the best FO nanocomposite membranes less than 10% fouling and flux reduction over 5 cycles of operation over a total period of 5 days. The best-suited membrane showed promising separation performance in the OMBR system by providing 43.4 LMH water flux and only around 0.2 g/l specific reverse salt flux (SRSF) with 1 M NaCl and DI water serving as DS and feed, respectively. This study focused also on distinctive performance criteria in combined FO and OMBR systems, such as the membrane's potential in a pretreatment step of brine streams (used as DS) to provide proper feed composition for RO units and introduced a new specific performance index (SPI) for better characterization of FO membranes which summarizes all essential characteristics of the membrane application, instead of using existing structural parameter equations for membrane characterization. The best-suited FO membrane offered an SPI of 778.2 gl−1 m−2 h−1, meaning 778.2 g/l reduction of TDS in DS per unit membrane surface area per hour. [ABSTRACT FROM AUTHOR]

Abstract: Water/unsymmetrical dimethylhydrazine (UDMH) mixtures were separated at ambient temperature and atmospheric pressure by pervaporation (PV) using NaA zeolite membranes. Effects of crystallization time and temperature on the membrane performance were studied. These membranes showed very high selectivity of water for water/UDMH mixtures. Separation factor as high as 52000 was obtained for UDMH feed concentration of 5%. Total mass flux was also obtained up to 3.95kg/m2 h. The results confirm the superior performance of the zeolite membranes for dehydration of water/UDMH mixtures due to their uniform nanopores. [Copyright &y& Elsevier]

In this paper, electrodialysis (ED) process was modeled based on basic electrochemistry rules and copper ion separation experimental data. Experiments were conducted by Taguchi method as an experimental design. Then the same experiments were performed for zinc, lead and chromium ions. It was found that performance of an ED cell is almost independent on the type of ions and only depends on the operating conditions and the cell structure. With the aid of this valuable result, a model was used for total definite concentration of ion mixtures. The model starts from a differential equation of steady state mass balance. Neglecting resistances of ion exchange membranes compared with resistances of bulk solutions in dilute and concentrate compartments and deriving a relation for solution resistance as a function of concentration and temperature, the final one-parameter model was obtained. The model parameter was determined by experimental data. The approached model gives separation percent for various temperatures, concentrations, flow rates and voltages. In order to assess the reliability of the model, the calculated results were compared with measured experimental data. It was found that there is an acceptable agreement between the calculated results and experimental data. [Copyright &y& Elsevier]

Ceramic membranes specially zeolite membranes are usually used for dewatering of organics by pervaporation. In the previous work, it was observed that kaolin calcined at 1050 °C has a separation factor 19.25 while kaolin calcined at 800 °C does not show any separation activity and its separation factor is equal to 1. In this research, effect of calcination temperature on flux and separation factor of kaolin modules that prepared by electrophoresis as a support of zeolite membranes was investigated. By increasing the kaolin calcination temperature, the flux of membrane increases due to many pores created in the module. This was confirmed by SEM micrographs. The highest flux was about 18 kg/m2 h for modules calcined at 1200 °C with ethanol 95%. Their separation factors were almost the same for each module. It was very low but comparable with some porous and non-porous polymeric membranes. Increasing calcination temperature causes module strength to enhance. It was found that the module calcined at 1200 °C may be suitable as a support for zeolite A membranes. [Copyright &y& Elsevier]

• Treatment of ZIF-8 nanoparticles resulted in better dispersion within the PEBAX matrix and preparation of defect-free MMMs. • PEBAX/EDD-ZIF-8 membranes showed higher plasticization resistance for the mixed gas feed. • CO 2 sorption capacity of PZ20T was found 15% higher than that of PZ20U. • PZ20T showed 78% increment in CO 2 permeability compared with PZ20U. • ED treated ZIF-8 nanoparticles (PZ20T) enhanced CO 2 /CH 4 selectivity 37% compared with PZ20U. In this work, as synthesized and modified ZIF-8 nanoparticles were used as the filler particles for mixed matrix membranes (MMMs) preparation for natural gas CO 2 removal. Characterization of the prepared MMMs using SEM, XRD and FTIR were performed provided essential insights to the MMMs structure and revealed no defect in the MMMs due to incorporation of the ZIF-8 nanoparticles within the polymer matrix. The nanoparticles were also loaded by ethylenediamine (ED) amine loaded and incorporated within the PEBAX1074 matrix up to 20 wt% without agglomeration. After modification of the nanoparticles with ED, the ZIF-8 nanoparticles loading in the MMMs were extended up to 30 wt% without any agglomeration. The MMMs CO 2 and CH 4 adsorption and permeation rate were evaluated at the room temperature and different transmembrane pressures. The unmodified ZIF-8 nanoparticles loaded MMMs adsorption capacities for CH 4 and CO 2 were found as 6.28, 27.07 cm3 STP/cm3, respectively, compared with those of the modified ZIF-8 nanoparticles loaded MMMs were found as 6.88 and 30.46 cm3 STP/cm3, respectively. CH 4 and CO 2 permeabilities through the unmodified ZIF-8 nanoparticles loaded MMMs were found as ~9.39 and 134 Barrer, respectively, while for the modified MMMs, CH 4 and CO 2 permeation were measured as ~14.2 and 344 Barrer, respectively. The results showed significant improvement in ideal and real CO 2 /CH 4 selectivity (71% and 40%) at 30 wt% of the ZIF-8 loading. [ABSTRACT FROM AUTHOR]

• Silica incorporated PDMS mixed matrix membranes were prepared via spraying technique. • BBD design was applied to optimize effects of preparation factors on membrane performance. • The membrane with inappropriate density did not exhibit good performance. • The membrane with high weight ratio of silica to PDMS exhibited the best performance. • The spray technique for fabrication of MMMs can be recommended to industrial applications. Ethanol pervaporation during its fermentative production alleviates product inhibition and hence enhances bioethanol production as a source of renewable energy. In this work, a novel microporous silicalite-1/PDMS mixed matrix membrane was fabricated by spraying as a facile, fast and low-cost method on a flat ceramic membrane. The effect of PDMS (0.05–0.15 g/ml), silica (0–0.06 g/ml) and curing temperature (80–150 °C) on the separation factor and permeation flux of the membranes was investigated using Box-Behnken design for separation 5 wt% ethanol/water solution at 30 °C which circulated at 400 (ml/min). Membranes were characterized by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and contact angle (CA). PDMS concentration acted as an influential factor. Higher curing temperatures led to separation factors less than one due to the higher density of the PDMS matrix. While lower temperatures caused low density, which decreased separation factors. Consequently, pervaporation performance improvement according to the hydrophobicity is possible as far as negative effects on the density of the polymer matrix can be controlled. Additionally, effects of temperature (30–70 °C), concentration (5–10 wt%), and flow rate (400–1000 ml/min) of the feed stream on the optimal membrane performances were examined. The best performances of permeation flux of 3.64 (kg/m2·h) and separation factor of 17.24 corresponded to the membrane (0.08 (g/ml) of PDMS, 0.06 (g/ml) of silica and curing temperature of 109.5 °C) with CA of 142° for separating 5 wt% solution at 60 °C and 400 ml/min. Eventually, this novel membrane can enhance bioethanol production and make it more affordable. [ABSTRACT FROM AUTHOR]

[Display omitted] • The PAN/FCS-NaY TNAM was fabricated with a sandwich-like composite structure. • The PAN/FCS-NaY TNAM was studied for Cu(II) and Pb(II) dynamic adsorption. • The loaded zeolite increased the adsorption capacity of the nanofibrous membrane. • High ions removal (94%<) was achieved at the optimum feed concentration, pH, and time. • Dynamic metal ions adsorption was modeled using dynamic filtration prediction models. In this study, an innovative PAN/FCS-NaY TNAM was fabricated using an electrospinning technique for Cu(II) and Pb(II) removal from contaminated water. Top and bottom fibrous layers (M1) were fabricated using a combination of FCS and PAN blends. Middle layer (M2) was electrospun from pure PAN solution and loaded with NaY zeolite particles. The physicochemical properties of the material and fibrous samples were investigated through SEM, FTIR-ATR, DSC, AFM, DMTA analysis, and contact angle measurement. The effective parameters, including initial ions concentration, time, reusability, and pH on the dynamic adsorption performance of the prepared membrane and its stability in the aqueous medium for Cu(II) and Pb(II) ions removal were investigated at a pressure of 0.006 bar. Dynamic metal ions adsorption was modeled using dynamic filtration prediction models such as Thomas and Yoon-Nelson. The fabricated nanostructure fibrous membranes with the removal percentage of Cu(II) and Pb(II) ions (94.6% and 98.7%, respectively) under the optimal operating conditions (initial concentration: 50 ppm, time: 10 min, and pH: 4.6), high compatibility in modeling dynamic filtration (R2 > 0.99), high pure water flux (298 LMH), suitable reusability (four-cycle without significant reduction in adsorption) as well as long-term stability, can be as potential filters in water treatment applications. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Goethite nanoparticles were synthesized successfully. • Nanocomposite membranes were synthesized successfully via phase inversion. • Polymer, pore former and nanoparticles were recognized as main effective factors. • BD was used based on RSM. Water permeability and heavy metal ions removal became maximized. • The membrane was reusable after regeneration with 0.1 M HCl soaking. Abstract In this study, novel ultrafiltration (UF) polyacrylonitrile (PAN) based nanocomposite membranes, containing goethite nanoparticles (NPs), were fabricated for copper ions (Cu(II)) adsorptive removal from aqueous solutions. First, goethite NPs, with diameter up to 50 nm, were synthesized. The next step was fabrication and evaluation of the nanocomposite membranes with the embedded NPs in it. The optimum compositions for the fabrication of the membranes were determined using response surface methodology (RSM) based on Box-Behnken design (BBD), at which the effect of membrane composition, on the metal ion removal and water permeability was studied under constant operating conditions. The evaluated variables were PAN concentration (15–18%), polyvinylpyrrolidone (PVP) concentration as an additive (1.3–1.5%), and loading percent of the NPs (0.0–0.5 wt%). The optimum conditions, at which the maximum ion removal and the maximum water permeability were achieved, were 15%, 1.3% and 1.0% for PAN, PVP, and NPs loading, respectively; at this point, the highest Cu(II) ions removal was 49.1% and the maximum water permeability was 285 LMH/bar. These values confirmed the experiments and the predicted values by the model which were 47.6% and 268 LMH/bar, for removal and water permeability, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Negatively charged CPES/PES blend HF UF membranes were fabricated. • The UF flux increased 250% using CPES/PES blend, losing 8% rejection. • The UF membrane WCA reduced from 76° to 42°, using CPES/PES blend. • The UF membrane FRR improved from 59% to 86% using CPES/PES blend. • The best membrane was used as substrate for HPEI thin-film layer assembly to achieve NF membrane. • The NF rejection increased up to 95% from 81% for the NF membrane prepared with the neat PES substrate. In this work, carboxylic polyethersulfone (CPES) was synthesized through acetylation and oxidation of polyethersulfone (PES). The success rate of the reaction and the formation of CPES were analyzed by fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. Negatively charged CPES/PES blend hollow fiber ultrafiltration (UF) membranes were fabricated via the wet-spinning method. Surface and structural properties of the membranes were characterized by scanning electron microscopy (SEM), water contact angle (WCA), and atomic force microscopy (AFM). significant improvement of the membranes' hydrophilicity due to the presence of the CPES was approved through the decrease of WCA from 76°(neat PES) to 42°. The permeability was increased up to about three times of the neat PES membrane, while the rejection was not affected that much and just decreased from 94% to 86%. Membrane's antifouling properties were significantly improved according to the flux recovery ratio (FRR) of more than 90%. The best-suited hollow fiber membrane was used as a substrate for hyperbranched polyethyleneimine (HPEI) thin-film layer assembly to achieve nanofiltration (NF) membrane. It was shown that the presence of the CPES improved the layer assembly of the HPEI and thus the M g C l 2 rejection in NF membranes. In this case, the salt rejection increased up to 95% for the best-suited membrane from 81% for the membrane with a neat PES substrate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Asymmetric nanofiltration PVC hollow fiber membranes were fabricated via dry-wet spinning technique. • Delayed demixing was achieved by addition of high molecular weigh PVP. • Volatile solvent evaporation resulted in dense selective layer. • The effect of fabrication parameters were investigated in order to introduce best-suited membrane. • The effect of DS concentration and temperature were studied by means of Flux and SRSF. PVC hollow fiber (HF) membrane for forward osmosis (FO) application as a potential candidate for water desalination was fabricated by altering the spinning conditions. High molecular weight polyvinylpyrrolidone (PVP) was used as a blending additive to control the phase inversion process by increasing viscosity leading to delayed demixing as observed on the ternary phase diagram and confirmed by the simulation results, and forming dense barrier layer structure by providing chain entanglements with the PVC matrix. PVP/PVC ratio of 5/100 was proved to offer suited membrane morphology and selective layer. Different air gap distances and bore fluid flow rates were investigated to achieve proper fabrication parameters. The prepared membranes presented high flux and salt rejection in nanofiltration (NF) and FO tests. The best-suited membrane demonstrated the structural parameter of 389 µm with a narrow pore size distribution and a molecular weight cut-off of 490 Da. In different draw solution (DS) concentrations, it was observed that the membranes perform well in all conditions. Considering the PVC-PVP chain entanglements and mobility and the possibility of PVP being washed away, the membranes' performance at different temperatures indicated that 25–45 °C would be the safe operating range for the fabricated membranes with stable values of 31.0–33.4 LMH and 0.17–0.18 (FO mode) and 33.0–33.4 LMH and 0.23–0.24 (PRO mode) for water flux and specific reverse salt flux. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, effect of influential factors on separation of monovalent (Na+), divalent (Cu2+, Zn2+, Pb2+) and trivalent (Cr3+) ions from wastewater was investigated. Two types of different membranes (AMV and CMV made by Asahi Glass and AR204SXR412 and CR67MK111 made by Ionics) with different ion exchange capacities (IEC) were used. Taguchi experimental design was used to plan a minimum number of experiments. A L9 orthogonal array (OA, four factors in three levels) was employed to evaluate effect of concentration (100, 500, and 1000ppm), temperature (25, 40, and 60°C), flow rate (0.07, 0.7, and 1.2mL/s) and voltage (10, 20, and 30V) on separation percent (SP) of the individual ions in the solution. A L16 OA (five factors in four levels) was applied to enquire the effect of ion valence in a mixture of ions on the response (SP). Statistical analysis, ANOVA, was also employed to determine the relationship between experimental conditions and yield levels. The results show that increasing concentration, voltage and temperature improves cell performance; however, SP decreases with increasing flow rate. At concentrations of more than 500ppm, dependency of SP on concentration diminishes. The optimum levels of influential factors, determined for all ions are: concentration 1000ppm, temperature 60°C, flow rate 0.07mL/s and voltage 30V. According to the results, using a membrane pair with higher IEC improves SP. It was found that performance of an electrodialysis (ED) cell is almost independent on the type of ions and only depends on the operating conditions and the cell structure. This result was confirmed by the experiments conducted on a mixture of ions. It was also found that SP of monovalent ions is larger than divalent and trivalent ions (S Cr < S Cu, S Zn, S Pb < S Na). For ions of similar valence, SP was found to be restricted by molecular weight and electrochemical activation energy of the ions (S Pb < S Cu < S Zn). [Copyright &y& Elsevier]

• PVDF/Mg-Al LDH ultrafiltration membrane was fabricated via phase inversion method. • Polymer, pore former and nanoparticles concentrations were optimized. • Membrane's hydrophilicity and porosity were maximized at 0.5 wt% LDH content. • Structure, performance and antifouling properties of the membranes were enhanced. • BSA rejection simulation of the fabricated optimum membrane was performed. In this work, Mg-Al layer double hydroxide (Mg-Al LDH) nanoparticles were synthesized through co-precipitation technique. Then, a novel polyvinylidene fluoride (PVDF) mixed-matrix ultrafiltration (UF) membrane containing the synthesized Mg-Al LDH nanoparticles was fabricated via the phase inversion technique. The nanoparticle and membrane were characterized by Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FESEM), X-Ray diffraction (XRD), Water contact angle (WCA), and Atomic force microscopy (AFM). The effects of polymer, pore-former, and nanofiller contents were studied to find the optimum membrane by the stepwise procedure. The obtained results showed that with increasing the content of Mg-Al LDH nanoparticles up to an optimum value (0.5 wt%), surface hydrophilicity, average pore size, porosity, roughness, and antifouling properties of the fabricated mixed-matrix membranes considerably improve. The pure water flux, BSA rejection, and the flux recovery ratio of 213 L/m2 h, 98.8%, and 94.8%, were achieved, respectively. Finally, the simulation of concentration, velocity, and pressure profiles on the optimum membrane was performed, which covered the experimental results with 0.2% discrepancy. [ABSTRACT FROM AUTHOR]

High performance nanofiltration hollow fiber membrane with over 95% flux recovery with backwashing was successfully prepared and characterized thoroughly. • Hollow fiber PES/PI negatively charged membranes were successfully fabricated with optimum PI composition as UF substrate. • In order to achieve green chemistry in PEI crosslinking, HCl formation was eliminated by using GA instead of TMC. • Nanofiltration layer assembly was improved due to uniform PSD, charged surface and higher roughness. • The influence of PEI nanofiltration layer assembly conditions such as pH, PEI/GA concentration and reaction time were studied on the hollow fiber substrate membranes. • Different salts were used to evaluate the properties of the NF hollow fiber membranes. In this study, high performance positively charged hyper-branched polyethyleneimine (PEI) nanofiltration (NF) layer was assembled successfully on negatively charged polyethersulfone/polyimide (PES/PI) hollow fiber ultrafiltration (UF) membranes under different conditions. In accordance with principles of green chemistry, glutaraldehyde (GA) as cross-linker and purely aqueous solutions were used as a less hazardous alternative compared to, e.g. trimesoyl chloride in an organic solvent. The effects of the surface roughness and charge of the substrate UF membranes, due to the presence of PI, and various fabrication conditions, such as pH of PEI aqueous solution, GA/PEI ratio and crosslinking reaction time, were investigated and discussed. Electron microscopy images revealed the successful assembly of the PEI NF layer at uniform coverage of the PES/PI UF membranes. It was found that the varied preparation conditions drastically affect the membrane surface hydrophilicity, surface zeta potential, permeation flux, and salt rejection. The membrane fabricated at optimum conditions had a molecular weight cut-off of ≤ 400 Da; steric hindrance and Donnan exclusion resulted to achieve salt rejections of 94.2% and 87.4% for MgCl 2 and MgSO 4 , respectively. Moreover, fabricated membranes were tested through three cycles of six-hour filtrations and over 95% flux recovery after the filtration of salts via the backwashing process was recorded. [ABSTRACT FROM AUTHOR]

Abstract: A method for simulation of gas separation with nano-composite membranes was presented using artificial neural network (ANN). In this investigation, a number of nano-composite silica/PDMS (polydimethylsiloxane) membranes were synthesized with different amounts of silica nano-composite loaded into the polymer matrixes. The permeation behavior of pure gases including C3H8, CH4, and H2 has then been studied as functions of pressure and nano-composite loading. Experimental results were used to develop a black box model to predict gas permeability for the synthesized membranes as a function of operating pressure, nano-composite loading and one of the physical properties of the gases used. A comparison was made between three different groups of data including pressure as the first effective parameter, nano-composite loading as the second, and one out of the four variables, molecular diameter, molecular weight, boiling point, and critical temperature, as the third. It was concluded that feed pressure, nano-composite loading, and boiling point temperature in the feed neurons provides the best combination and leads to the least error in prediction of the gas permeation flux values. The results showed that, increasing pressure increases permeability of the condensable gas, C3H8, whereas permeabilities of the lighter gases, H2 and CH4, decrease with increasing pressure. In addition, nano-composite loading decreases permeability of the non-condensable gases, H2 and CH4, while that of C3H8 increases up to 2% of nano-composite loading. Ultimately, it was concluded that ANN method can be successfully used for prediction of gas separation properties of nano-composite membranes after proper network training in this case resulting in predictions of less than 4.0842 RMSE. [Copyright &y& Elsevier]

Abstract: This work presents a comprehensive two-dimensional mathematical model for unsteady state permeation of pure gas and ternary gas mixture through a synthesized single layer PDMS membrane. A numerical model was established for predicting permeation behavior of pure and mixed gases, at different operating conditions of upstream temperatures, pressures and feed compositions. The time lag method was also employed to calculate the diffusion coefficient of each component in a concentration dependant system. The results achieved show that permeability of heavier gas (C3H8) decreases with increasing feed pressure and temperature, whereas those of lighter gases (H2 and CH4) in contrary would increase. Increasing C3H8 concentration in the feed improves permeation of all components, while increasing H2 concentration, significantly increases permeability of H2, in comparison with those of other components. Furthermore, both the comparison between mixed and single gases permeation performances and the effect of cross-link density on PDMS membranes performances were highlighted in this study. The simulation results proved this fact that diffusivity is the dominant parameter on permeability of the lighter gases (H2 and CH4), while solubility has the prevailing affect on permeability of the heavier gases such as C3H8. The simulated results were finally validated with independent pure gas and ternary gas mixture experiments. The results confirmed that there is a reasonable conformity between the predicted values for permeability, solubility, diffusivity and mole fraction in the permeate side of aforementioned components and experimental available data. [Copyright &y& Elsevier]

• HPEI was assembled onto PAN support layer and then cross-linked by GA. • Effect of f-MWNTs or GO incorporation in the PAN support layer was investigated. • Incorporation of f-MWNTs and GO enhanced permeability 38% and 64%, respectively. • The prepared TFN membranes were used for desalination application, successfully. • Rejection order of R (MgCl 2) > R (MgSO 4) > R (NaCl) > R (Na 2 SO 4) was obtained. In this work, new types of positively charged thin-film nanocomposite (TFN) membranes were prepared by assembling hyperbranched polyethyleneimine (HPEI) followed by chemical cross-linking using glutaraldehyde (GA) onto hydrolyzed polyacrylonitrile (PAN) support layer containing functionalized multi-walled carbon nanotubes (f-MWNTs) or graphene oxide (GO). The effects of HPEI concentration, deposition time and HPEI solution pH on the thin-film composite (TFC) membrane performance were evaluated in details. TFN membranes were synthesized using the optimized conditions in terms of HPEI deposition parameters. The effect of f-MWNTs or GO incorporation in the support layer of the prepared TFN membranes on membrane water permeability and salt rejection was also investigated. The obtained results demonstrated that pure water permeability of the prepared TFN-CNT and TFN-GO membranes enhanced by 38% and 64%, respectively, compared to the TFC membrane. Moreover, the TFN membranes overcame the trade-off between rejection and permeability. The rejections of the TFC and both TFN membranes for salts decreased in an order of R (MgCl 2) > R (MgSO 4) > R (NaCl) > R (Na 2 SO 4) confirming positively charge of the membrane surface. This indicated that the rejection mechanism of the salts is mainly the Donnan exclusion. [ABSTRACT FROM AUTHOR]