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Many researchers used some models based on the assumption of spherical in shape particles. Particles shape is important and should be considered in models. In this work, a new model was used for prediction of gas permeability through the Mixed Matrix Membranes (MMMs). The effects of particles shape and undesirable defects (polymer chain rigidification, partial pore blockage and void formation) were introduced to the model simultaneously. The model was employed to predict some experimental data. The results showed that the less average absolute relative error (AARE) of the model for the MMMs were about 0.73–31.53%. [ABSTRACT FROM PUBLISHER]

In this article, polyethersulfone hollow fiber membranes were prepared using dry–jet–wet spinning process via phase inversion method. Effects of polyethersulfone and polyethylene glycol concentrations and coagulation bath temperature, air–gap distance, and take-up speed on morphology of the prepared membranes were investigated. Based on L16orthogonal array of Taguchi experimental design, 32 membranes were prepared. An experimental investigation on separation of the industrial oil from oily wastewater has been done. The results showed that synthesized polyethersulfone membranes was effective and suitable for the treatment of oily wastewater to achieve up to 66.6 and 95.0% removal of total organic carbon and oil–grease content, respectively, with a flux of 72.3 L/(m2h). [ABSTRACT FROM PUBLISHER]

A self-supported ion imprinted membrane (IIM) adsorbent was synthesized via crosslinking of blended chitosan/polyvinyl alcohol (CS/PVA) with glutaraldehyde (GA) as crosslinker and copper ions as template via the solution casting method. The prepared membrane was used as adsorbent to evaluate Cu(II) ions adsorption from aqueous solutions. The metal ion equilibrium concentrations were determined and Langmuir and Freundlich isotherm models were applied to fit to the experimental data. Finally, adsorption kinetics were examined using pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. It was found out that adsorption behavior of Cu(II) ions via the IIM adsorbent match well with Freundlich isotherm and pseudo-second-order kinetic models. Reusability of the adsorptive Cu(II) imprinted membrane was confirmed via five sorption–regeneration cycles using HCl 0.5 mol L−1as desorbing agent. The SEM analysis showed that Cu(II) ions can be well adsorbed by the IIM adsorbent. [ABSTRACT FROM AUTHOR]

In this study, the morphological and separation characteristics of PVA membranes incorporated with functionalized CNTs are reported. CNTs was extensively characterized using TGA, FESEM, and TEM. The physicochemical properties of PVA-CNTs membranes were characterized using FESEM, tensile test, DSC, and XRD. DSC measurements showed an increase in melting and glass transition temperature, implying enhancement of polymer chains compacting. XRD analysis confirmed the results of DSC and showed that CNTs can promote crystallinity of the PVA membranes. In addition, tensile measurements revealed that incorporating CNTs into the PVA membranes improves their mechanical properties. The synthesized nanocomposite membranes were then evaluated in pervaporation (PV) dehydration of isopropanol (IPA). The separation results showed that incorporating CNTs into the PVA membranes significantly increases water selectivity of the PVA membranes. This can be attributed to the fact that incorporating CNTs compacts and rigidifies PVA matrix and decreases its free volume. Furthermore, permeation of water molecules through the nanocomposite membranes decrease as a result of the polymer chains rigidification. Effects of feed composition and temperature on PVA-CNTs nanocomposite membranes were investigated. Besides, effects of CNTs content on permeation properties and activation energies of PVA membranes were evaluated. [ABSTRACT FROM PUBLISHER]

In this research, continuous SAPO-34 membranes were synthesized via secondary growth method onto both α-Al2O3 and mullite supports at three levels of synthesis temperature: 185, 195, and 220°C for 24 h. The synthesized membranes were characterized using XRD and SEM analysis and single gas permeation experiments. It was found out that support material and synthesis temperature both have significant effects on the membrane performance. At higher synthesis temperature, SAPO-34 crystals grown over the mullite support become more uniform and smaller in size but those grown on the α-Al2O3 support become larger. Effect of synthesis temperature on single gas permeation properties of the synthesized SAPO-34 membranes was also studied. For the mullite supported membranes, the CH4 and CO2 permeances decrease as synthesis temperature increases; but in the case of the alumina supported membranes, by increasing synthesis temperature, CH4 and CO2 permeances first decrease up to 195°C and then increase up to 220°C. Even in equal membrane thicknesses, the mullite supported membrane shows lower gas permenaces. Increasing synthesis temperature decreases CO2/CH2 ideal selectivity for the α-Al2O3 supported membranes, while increases for the mullite supported membranes. Under optimum synthesis conditions, at room temperature and 2 bar feed pressure, the CO2 permeance through the α-Al2O3 and the mullite supported SAPO-34 membranes are 8.2 × 10-7 and 8.5 × 10-8 (mol/m2·s·Pa), respectively, and CO2/CH4 ideal selectivities are 51 and 61, respectively. [ABSTRACT FROM AUTHOR]

In this research, continuous SAPO-34 membranes were synthesized via secondary growth method onto both α-Al2O3 and mullite supports at three levels of synthesis temperature: 185, 195, and 220°C for 24 h. The synthesized membranes were characterized using XRD and SEM analysis and single gas permeation experiments. It was found out that support material and synthesis temperature both have significant effects on the membrane performance. At higher synthesis temperature, SAPO-34 crystals grown over the mullite support become more uniform and smaller in size but those grown on the α-Al2O3 support become larger. Effect of synthesis temperature on single gas permeation properties of the synthesized SAPO-34 membranes was also studied. For the mullite supported membranes, the CH4 and CO2 permeances decrease as synthesis temperature increases; but in the case of the alumina supported membranes, by increasing synthesis temperature, CH4 and CO2 permeances first decrease up to 195°C and then increase up to 220°C. Even in equal membrane thicknesses, the mullite supported membrane shows lower gas permenaces. Increasing synthesis temperature decreases CO2/CH4 ideal selectivity for the α-Al2O3 supported membranes, while increases for the mullite supported membranes. Under optimum synthesis conditions, at room temperature and 2 bar feed pressure, the CO2 permeance through the α-Al2O3 and the mullite supported SAPO-34 membranes are 8.2 × 10−7 and 8.5 × 10−8 (mol/m2 · s · Pa), respectively, and CO2/CH4 ideal selectivities are 51 and 61, respectively. [ABSTRACT FROM AUTHOR]

Novel organic–inorganic hybrid membranes were prepared by co-hydrolysis and co-condensation reactions of aminopropyltriethoxysilane (APTEOS) and tetraethylorthosilicate (TEOS) in poly(vinyl alcohol) (PVA) aqueous solution. These sol–gel reactions make a silica nanoparticles network which cross-links the structure of membranes. As a result, swelling properties of the membranes change due to these cross-linking reactions. The relative molar content of APTEOS to (APTEOS + TEOS) was changed from 0.0 to 0.75. The effect of APTEOS to (APTEOS + TEOS) on morphology as well as pervaporation performance of the membranes for dehydration of ethanol was investigated. It was found out that the hybrid membranes with a certain mass ratio of 1:1 (APTEOS + TEOS to PVA) exhibit higher permselectivity and more permeation flux for dehydration of ethanol aqueous mixtures compared with the PVA–TEOS membranes. Because hydrolysis and condensation reactions of mixed silanes make smaller silica nanoparticles, the permeability properties of the membranes improve in comparison with those of the membranes prepared using a single silane. [ABSTRACT FROM AUTHOR]

Flat sheet asymmetric polyethersulfone (PES) ultrafiltration (UF) membranes were prepared from a homogenous solution of PES via immersion precipitation in a water coagulation bath. The effect of the solvents (N-methyl-2-pyrrolidone (NMP) and N,N-dimethylformamide (DMF)) in preparation of the casting solution was studied. The effects of the molecular weight of polyethylene glycol (PEG) (400, 1500, and 6000 Da) on the morphology and the permeation properties of PES membranes were also investigated. Surface and cross-sectional morphology of the prepared membranes were studied by Scanning electron microscopy (SEM). The permeation performance of the prepared membranes was evaluated in terms of pure water flux (Jw), water content, porosity, hydraulic permeability, protein solution flux, and protein rejection. A solution of human serum albumin (HSA, Mw = 66,000 Da) was used as feed to study the permeation properties of the prepared membranes. Increasing molecular weight of PEG additives from 400 to 6000 Da enhances pure water permeation flux and HSA solution permeation flux while it reduces the protein rejection. [ABSTRACT FROM AUTHOR]

In this research, mass transport in pervaporation (PV) process of isomeric xylenes (para_xylene and ortho_xylene) was investigated by means of the resistances-in-series model. In order to obtain necessary data for the analysis, some experimental studies on separation of the xylene mixtures using a poly (vinyl alcohol) (PVA) membrane were performed. Influence of operating conditions such as para_xylene concentration in the feed and permeate pressure on the membrane performance and also the transport resistances in different layers of membrane was examined. Finally, the impact of CBr4 (Carbon tetrabromide) on the membrane performance was evaluated. The results implied that by adding CBr4 to the feed, more ortho_xylene in the permeate can be collected, because CBr4 combines with para_xylene molecules, thus ortho_xylene molecules preferably pass through the membrane rather than para-xylene molecules. The mathematical model was found to be very accurate and could be employed for prediction of PV of isomeric xylenes. [ABSTRACT FROM AUTHOR]

A theoretical model is used to predict O2, N2, CO2, CH4, N2O, and Ar gaseous penetrants’ permeabilities through zeolitic filler particles of 4A, DDR and silicalite-1 using their adsorption and diffusion data with minimum and maximum absolute relative errors (AREs) as 4.3 and 6.9% for N2and CH4permeabilities through 4A zeolite, respectively. Average AREs for 4A zeolites incorporated in mixed matrix membranes (MMMs) were found for O2permeability using modified Felske’s and Maxwell’s models as 1.2 and 55.6%, respectively. Those for DDR/MMMs and silicalite-1/MMMs CO2permeabilities were found as 0.7 and 1.8% for Bruggeman’s and Maxwell’s models and 3.1 and 22.3% for Maxwell’s and Lewis-Nielsen’s models, respectively. [ABSTRACT FROM PUBLISHER]

Carbon nanotubes were synthesized via the chemical vapor deposition method using cyclohexanol and ferrocene as carbon precursor and catalyst, respectively, and then they are functionalized with acid treatment. Chitosan/polyvinyl alcohol adsorptive membrane incorporated with carbon nanotubes (CS/PVA-CNTs membrane) was prepared via the solution casting method. The CS/PVA-CNTs membrane was employed for adsorption of lead and zinc ions from aqueous solutions. Various isotherms and kinetic models were applied to fit the experimental data. It was found out that adsorption behavior of the heavy metal ions using CS/PVA-CNTs membrane match well with the Freundlich isotherm and the pseudo-first-order kinetic models. [ABSTRACT FROM AUTHOR]

In this paper, the effects of in-line coagulation on permeation fiux (PF), fouling resistance (FR), and total organic compound (TOC) rejection (R) of synthesized mullite ceramic membranes during treatment of oily wastewater in coagulation - MF hybrid process were investigated. Four coagulant ((ferrous chloride (FeCl2.4H2O), ferrous sulphate (FeSO4.7H2O), aluminum chloride (AlCl3.6H2O) and aluminum sulphate (Al2(SO4)3.18H2O)) plus equal concentration of lime in the form of calcium hydroxide (Ca(OH)2) were evaluated in the coagulation - MF hybrid process at different concentrations (Oppm, 25ppm, 50ppm, and lOOppni). The results showed that coagulation can affect the membrane filtration by changing characteristics of the oil droplets. Coagulant agents improve the membrane performance at low dosage (25 ppm) for aluminum chloride and mean dosage (50 ppm) for ferrous chloride, ferrous sulphate, and aluminum sulphate. At the best conditions (50 ppm ferrous sulphate), PF increased from 2.22 × 10-5 to 2.76 × 10-5 (m3/m2s), FR decreased from 4.2 × 1012 to 5.55 × 1011(m-1), and R increased from 93.8% to 97.1%. [ABSTRACT FROM AUTHOR]

In this paper, the effects of in-line coagulation on permeation flux (PF), fouling resistance (FR), and total organic compound (TOC) rejection (R) of synthesized mullite ceramic membranes during treatment of oily wastewater in coagulation – MF hybrid process were investigated. Four coagulant ((ferrous chloride (FeCl2.4H2O), ferrous sulphate (FeSO4.7H2O), aluminum chloride (AlCl3.6H2O) and aluminum sulphate (Al2(SO4)3.18H2O)) plus equal concentration of lime in the form of calcium hydroxide (Ca(OH)2) were evaluated in the coagulation – MF hybrid process at different concentrations (0 ppm, 25 ppm, 50 ppm, and 100 ppm). The results showed that coagulation can affect the membrane filtration by changing characteristics of the oil droplets. Coagulant agents improve the membrane performance at low dosage (25 ppm) for aluminum chloride and mean dosage (50 ppm) for ferrous chloride, ferrous sulphate, and aluminum sulphate. At the best conditions (50 ppm ferrous sulphate), PF increased from 2.22 × 10−5 to 2.76 × 10−5 (m3/m2 s), FR decreased from 4.2 × 1012 to 5.55 × 1011 (m−1), and R increased from 93.8% to 97.1%. [ABSTRACT FROM AUTHOR]

In this paper, a new polydimethylsiloxane (PDMS) membrane was synthesized and its ability for separation of heavier gases from lighter ones was examined. Sorption, diffusion, and permeation of H2, N2, O2, CH4, CO2, and C3H8 in the synthesized membrane were investigated as a function of pressure at 35°C. PDMS was confirmed to be more permeable to more condensable gases such as C3H8. This result was attributed to very high solubility of larger gas molecules in hydrocarbon-based PDMS in spite of their low diffusion coefficients relative to small molecules. The synthesized membrane showed much better gas permeation performance than others reported in the literature. Increasing upstream pressure increased solubility, permeability and diffusion coefficients of C3H8, while these values decreased slightly or stayed constant for other gases. Local effective diffusion coefficient of C3H8 and CO2 increased with increasing penetrant concentration which indicated plasticization effect of these gases over the range of penetrant concentration studied. C3H8/gas solubility, diffusivity and overall selectivities also increased with increasing feed pressure. Ideal selectivity values of 4, 13, 18, 20, and 36 for C3H8 over CO2, CH4, H2, O2, and N2, respectively, at upstream pressure of 7 atm, confirmed the outstanding separation performance of the synthesized mebrane. [ABSTRACT FROM AUTHOR]

A mixed matrix membrane with superior performance was prepared by incorporating zeolite NaA particles in polyvinyl alcohol (PVA) for dehydration of ethylene glycol (EG)-water mixtures. The zeolite NaA, with its favorable interaction with the polymer phase, is responsible for improving the pervaporation (PV) dehydration of EG-water mixtures in terms of separation factor, permeation flux, and PV separation index (PSI). This improvement is due to hydrophilicity enhancement, and molecular sieving action and selective adsorption of zeolite. It was found out that membrane with 5 wt.% loading of particles shows the highest separation factor of 1520 with a permeation flux of 2.4 kg/m2h at 70°C for a feed mixture of 20 wt.% of water in EG. [ABSTRACT FROM AUTHOR]

NaA zeolite membranes have been used for dehydration of organic solvents in laboratory and commercial scales. There are many synthesis methods and conditions for manufacturing the membranes. The use of lactescent and clear gel solutions are two of the most important choices for high quality hydrothermal synthesis of NaA zeolite membrane in gas separation or dehydration of organic solvents. In this article, effect of hydrothermal synthesis time was investigated using the clear gel solution (Al2O3:5SiO2:50Na2O:1000H2O). Phase transformation from NaA to NaX was recognized as the most possible event when the clear gel solution was used. XRD spectra, SEM images, and GC analyses were used for evaluation of zeolite crystal phase, the membrane layer quality, and the contents of organic substances (ethanol or 2-propanol) in feed and permeate streams in pervaporation tests, respectively. From synthesis of zeolite membrane at different times, it was revealed that for achieving the pure NaA zeolite phase the synthesis time should not exceed 3 h at 100°C. [ABSTRACT FROM PUBLISHER]

Transport of phenol through a flat sheet supported liquid membrane (SLM) containing cooking oil as liquid membrane (LM) was investigated. Factors affecting permeation of phenol such as membrane phase, support material, feed phase pH, stripping phase concentration, stirring speed, and initial concentration of phenol were studied. It was found that these parameters strongly influence phenol removal efficiency; PTFE membrane as support material, grape seed oil as liquid membrane, feed pH of 2.0, initial phenol concentration of 100 mg/L, stirring speed of 350 rpm, and 0.2 M sodium hydroxide as effective stripping agent were found as the best conditions for greater phenol transport. Under these conditions, permeability was found to be 7.46 × 10−6 m/s. After 10.5 h, phenol was completely removed from the feed phase to strip phase. According to stability experiments, it was observed that the SLM is stable after 22 h. Thus, the use of cheap, nontoxic, and naturally oil as a novel and green membrane for recovery of phenol from wastewater was demonstrated. [ABSTRACT FROM AUTHOR]

In this study, effects of gel formulation parameters such as Na2O/K2O molar ratio(from 0.05 up to 3) and tetra methyl ammonium hydroxide (TMAOH) additive in the synthesis of zeolite T (Linde Type T) crystals have been investigated in different SiO2/Al2O3molar ratios from 5 to 29. Submicron and nanosize crystal of zeolite T from 100 nm up to 25 µm with distinctive crystal shapes from the needle type to cylindrical crystals have been synthesized successfully at the wide range of SiO2/Al2O3ratios with and without TMAOH. It is shown that Na2O/K2O ratio plays the most important role in gel formulation. All synthesized crystalsare characterized by XRD and SEM analysis. [ABSTRACT FROM AUTHOR]

Poly (vinyl alcohol) membranes were prepared by in-situ crosslinking of poly(vinyl alcohol) with glutaraldehyde as crosslinking agent and hydrochloric acid as catalyst and used for dehydration of IPA mixtures. Effects of feed composition, operating temperature, vacuum pressure, and Reynolds number on the permeation performance of the membranes were evaluated. Eighty-nine experimental data was applied to investigate ANN modeling. A multi layered feedforward neural network was applied to model the PV membranes. Two major training algorithms and optimum number of neurons and layers were investigated. As a result, Bayesian regularization successfully predicted experimental data. Different network structures were optimized, using multi object genetic optimization algorithm. The results concluded that the network with structure composing two hidden layers performs better than the other with one hidden layer, and also there is an excellent compatibility between the experimental data and the predicted values of optimum network structure (4:3:2:2). Furthermore, the optimum network was applied to predict extrapolation data and the results showed that this network can extrapolate data as well as interpolating. [ABSTRACT FROM PUBLISHER]

Polyimides of Matrimid 5218 and P84 as backbone and different fillers including silica aerosil, zeolite 4A, carbon nanotubes, and carbon molecular sieves were used to synthesize flat mixed matrix membranes (MMMs). Effects of different polymer types and concentrations, different filler types and contents, and fabrication procedure were investigated. Scanning Electron Microscopy (SEM) analysis showed acceptable connections between the two phases and the MMMs performed higher performance compared to the polymeric membranes. Thermal treatment of the MMMs, as a defect repairing technique, was found very effective. Performed pervaporation and gas permeation experiments showed better separation performances of the MMMs with respect to those of the neat polymeric membranes. The results showed up to seven and two times increment in separation factors of MMMs regarding to neat polymeric membranes for pervaporation and gas separation experiments, respectively, while permeation rates nearly remained constant indicating effectiveness of the proper filler incorporation within polymer matrices approach. [ABSTRACT FROM AUTHOR]