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Membrane bioreactors (MBRs) as biotechnology-based wastewater treatment processes have recently attracted lots of attentions. However, membrane fouling/biofouling as a significant obstacle has prevented MBRs from being widely used. The phase inversion method was used to fabricate a novel MIL-101(Cr) (MCPs)/polyethersulfone (PES) composite membrane. Adding MCPs up to 0.4 wt% significantly improved the membrane surface hydrophilicity and increased the membrane porosity, pore size, and fouling/biofouling formation resistance. Pure water flux of the optimal composite membrane increased by about 198.61% compared to the neat one. It also showed the lowest total fouling ratio (Rt: 48.79%) and irreversible fouling ratio (Rir: 10.43%), and the highest flux recovery ratio (FRR: 89.54%) and protein rejection (99%). Its COD removal efficiency for acetate as synthesis wastewater was about 75%. Performance of the optimal composite membrane was also evaluated at varied mixed liquor suspended solids (MLSS) concentrations of 8000, 10,000, and 12,000 mg/L. Increasing MLSS concentration decreased permeation flux due to rising sludge viscosity and fouling/biofouling formation. The results gave useful insights into preparation of hydrophilic composite membranes through blending of MCPs and PES to treat organic wastewaters using the MBR applications. [ABSTRACT FROM AUTHOR]

Cake formation is the most important phenomenon to reduce cross-membrane flux in cross-flow microfiltration although pore blocking and concentration polarization (CP) phenomena affect it. Electric field may be used to enhance process efficiency and decreased fouling phenomena in the process. An empirical model is developed here taking into consideration the cake formation effects on permeate flux reduction in the presence of AC electric field. A semi-empirical model is also developed in the presence and absence of electric field at two cases; with and without considering membrane structure in the modeling. It is the first time that electric field effects on microfiltration performance are modeled macroscopically and used with pore blocking phenomenon simultaneously. The predicted permeate fluxes by the models are compared against experimental permeate fluxes in absence and presence of electric field. Comparison of the model based predictions against experimental results indicate semi-empirical model precision with a maximum error of 8.9% for the case without and 3.6% for the case with pore blocking consideration and a maximum error for empirical model of 11.9%. Effects of different electric potentials and distances between the electrodes on CP layer thickness and oil concentration on membrane surface are also studied. The predicted results showed that the CP layer thickness is decreased by 60.9% through applying an electric potential of 500 V and also decreased by 65.2% through decreasing the distance between the electrodes from 2.3 to 1.3 mm at 200 V. The oil concentration on the membrane surface is also decreased by 72.3% as a result of applying the electric field while it is decreased by 19.2% when the electrodes distance is decreased from 2.3 to 1.3 mm at 200 V. Image 1 • The environmental problem of oily waste water emulsions was studied. • Cross-flow microfiltration assisted by electric field was used to separate oil from the emulsion. • An empirical and a semi-empirical models were developed for microfiltration in the presence and absence of electric field. • In order to consider pore blocking phenomenon, membrane structure was added in the model geometry. • CP thickness and oil concentration on membrane surface were investigated under various conditions. [ABSTRACT FROM AUTHOR]

This article has been retracted: please see Elsevier Policy on Article Withdrawal ( http://www.elsevier.com/locate/withdrawalpolicy ). This article has been retracted at the request of the Editor-in-Chief. The article duplicates significant parts of an article that had already appeared in Desalination, 262/1-3 (2010) 273-279 http://dx.doi.org/10.1016/j.desal.2010.06.004 . The authors have also plagiarized significant parts of an article that had appeared in the Journal of Membrane Science 179 (2000) 185-205 http://dx.doi.org/10.1016/S0376-7388(00)00515-9 . One of the conditions of submission of a paper for publication is that authors declare explicitly that their work is original and has not appeared in a publication elsewhere. Re-use of any data should be appropriately cited. As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process. [ABSTRACT FROM AUTHOR]

Abstract Mordenite (MOR) and faujasite (FAU) were formed as a membrane layer on tubular mullite and disk-shaped α-alumina supports for pervaporation (PV) dehydration of ethanol (EtOH). Structural analyses were carried out using XRD, SEM and EDAX. EtOH/water PV process was utilized to assess the membranes performances. The experiments show the fairly high separation factor representing the defect-free membrane layer and legible nonzeolitic pores on the top-layer. The effects of synthesis parameters including ceramic support, repetition of coating, seeding method, crystallization time (14 and 18 h) and temperature (160, 170 and 180 °C), and Si/Al ratio of the precursor gel formulation (12 and 16) on the membranes structures and their PV performances were investigated. Furthermore, the effective operational conditions (feed concentration (50, 70 and 90 wt% EtOH) and temperature (25 and 45 °C), and vacuum on permeate side (80 and 130 mmHg)) on PV performance of the membranes were studied. According to a combined performance parameter, pervaporation separation index (PSI), the MOR layer on α-alumina (MOR_D-II) can be reported as the best membrane for EtOH/water PV process. Permeation flux (43.43%), separation factor (30.39%) and PSI (62.35%) decrease with increasing EtOH concentration in feed (50–90 wt%). However, increasing feed temperature increases permeation flux and decreases separation factor, whereas applying higher vacuum in the permeate side leads to the opposite trend. Highlights • Secondary growth was used for seed deposition on mullite and α-alumina supports. • PV EtOH dehydration of the synthesized MOR and FAU membranes was determined. • Defect-free zeolite layer with negligible nonzeolitic pore was successfully formed. • Repetition of coating improved the selectivity of the final membranes. • Structural and operational analyses were done considering several parameters. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A 2D CFD-based model was developed for estimating FO water flux. • Using sorption coefficient led to improved accuracy in estimating FO water flux. • Tradeoffs between membrane structural parameter and selectivity, ECP and ICP are found. • FO water fluxes were similar in counter-current and co-current flows. • ICP was the most significant resistance to flow, reducing FO water flux up to 75%. Abstract A 2D computational fluid dynamic-based finite element model was developed to describe water flux and concentration polarization in forward osmosis (FO) under steady-state conditions. The extended UNIQAC equation in the feed and the Flory Huggins equation on the membrane side were solved simultaneously to calculate the activity coefficients of the diffusion components. The ratio of the feed component activity coefficient to that on the membrane surface was defined as the sorption coefficient. Employing the sorption coefficient led to a significantly improved accuracy of the developed model in estimating water flux. The membrane structural parameter determining internal concentration polarization (ICP) should be maintained at reasonable values. Otherwise, it may significantly increase the reverse salt flux and external concentration polarization (ECP) on the active layer. This suggests the tradeoffs between the membrane structural parameter and membrane selectivity, between ECP and ICP. Water fluxes were similar in counter-current and co-current flow modes. ICP had the most significant resistance to flow, reducing the water flux up to 75%. ECP on the feed side had a limited effect on FO water flux, particularly at high flow velocity. ECP on the draw side and reverse salt flux had negligible effects on FO water flux in our modeling. Our study provides important insights into developing high-performance FO membranes with reasonably low structural parameters and improving FO water flux by reducing the key limiting factor (e.g. ICP). [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]

Selective and simultaneous separation of H2S and CO2 from CH4 was accomplished in a hollow‐fiber membrane contactor (HFMC). The absorption of both H2S and CO2 using an aqueous solution of methyldiethanolamine (MDEA) was almost complete and acid gases were totally removed. Despite the large difference between H2S and CO2 concentrations, the rate of H2S absorption was not significantly influenced by CO2 absorption. The independent effect and interactions of several process variables on the separation performance of H2S and CO2 were investigated. The results indicated that the membrane contactor could be a highly efficient choice for removal of almost all H2S in the presence of a large CO2 content even at high gas/liquid flow ratio. The selectivity of H2S was about three times higher compared to the conventional absorption packed towers. Selective and simultaneous removal of H2S and CO2 from CH4 by hollow‐fiber hydrophobic membrane contactors is introduced. The removal performances of H2S and CO2 using an aqueous methyldiethanolamine solution were much higher than those reported for conventional packed towers. The membrane contactor is a highly efficient tool for removal of almost all H2S in the presence of a large CO2 content. [ABSTRACT FROM AUTHOR]

Mixed matrix membranes (MMMs) with superior structural and functional properties provide an interesting approach to enhance the separation properties of polymer membranes. As a matter of fact, MMMs combine the advantages of both components; polymeric continuous phase and nanoparticle dispersed phase. Generally, the separation performance of polymeric membranes suffers from an upper-performance limit. Hence, the incorporation of nanoparticles helps to overcome such limitations. Block copolymers such as poly(ether-block-amide) (PEBA) composed of immiscible soft ether segments as well as hard amide segments have been shown as excellent materials for the synthesis of membranes. Consequently, PEBA membranes have been extensively used in scientific research and industrial processes. It is thus aimed to provide an overview of PEBA MMMs. This review is especially devoted to summarizing the effects of nanoparticle loading on PEBA performance and properties such as selectivity, permeability, thermal and mechanical properties, and others. In addition, the preparation techniques of PEBA MMMs and solvent selection are discussed. This article also discusses the many types of nanoparticles incorporated into PEBA membranes. Furthermore, the future direction in PEBA MMMs research for separation processes is briefly predicted. [ABSTRACT FROM AUTHOR]

In membrane bioreactor (MBR) application, there are considerably influencing factors on membrane performance over time making serious problems, including reduced permeation flux and rejection percentage as well as formed thick fouling/biofouling layer. This study provided a new preparation strategy to fabricate extraordinary superhydrophilic CuO/PVDF nanocomposite membranes with micro/nano hierarchical structure, using a wet micro-pattern casting knife with simultaneous bombardment of hydrophilic CuO nanoparticles/non-solvent solution via cold spray coating (s-NIPs method). When compared to the neat membrane, the main characteristics of the superhydrophilic membrane enhanced such as surface area (70%) and pure water flux (PWF) (400%). Protein rejection (PR) and chemical oxygen demand (COD) removal were also obtained as about 96.7% and 97.8% at constant mixed liquor suspended solids (MLSS = 6000 mg/l) in a submerged aerobic MBR, fed by the synthesized sodium acetate wastewater (compared to the neat case: 78% and 91%), respectively. Furthermore, its excellent antifouling/biofouling properties were proved via significantly less formation of biofilm and adherence of extracellular polymeric substances (EPSs) and soluble microbial products (SMPs) on the membrane surface. Low variation of sludge flux and COD removal by increasing MLSS from 6000 (348 LMH and 96.7%) to 12000 mg/L (200 LMH and 94.2%) proved the significant impact of the preparation method on the membrane performance. Stability of the F–CuO coated layer caused superhydrophilicity and antibacterial properties to be maintained under long-period. The obtained results demonstrated potential of the fast, facile, simple, and one-step preparation method without compromising the membrane separation ability, while simultaneously providing superhydrophilicity, antibacterial activity, and ultra-low fouling/biofouling formation. [Display omitted] • Superhydrophilic membrane was prepared with micro/nano hierarchical structure. • Stable layer of antibacterial CuO NPs was coated on membrane surface by cold spray deposition. • Implementation of hierarchical structure increased active surface area up to 70%. • Optimal membrane exhibited highest PWF with ultra-low fouling/biofouling formation. • FRR, COD removal, and protein rejection were increased up to 94, 98 and 97%. [ABSTRACT FROM AUTHOR]

Submerged ceramic membrane bioreactors (SCMBRs) are more efficient combinations of traditional activated hazardous sludge and new membrane separation processes in wastewater treatment. Suspended solids are separated from hazardous effluent using microfilter ceramic membranes in SCMBRs. A high loaded wastewater was treated using an SCMBR employing a homemade tubular ceramic membrane in laboratory scale. Hydraulic Retention Time (HRT) was 32 h and COD range was varied from 2000 to 5000 mg/l. COD removal was evaluated to be more than 90% after a week and the lab scale SCMBR showed desired performance for the wastewater treatment. Mixed Liquor Suspended Solid (MLSS) was increased from 2000 to 4000 mg/L during the SCMBR operation time. [ABSTRACT FROM AUTHOR]

The main goal of the present study is synthesis, characterization and performance evaluation of an optimized photocatalytic ceramic membrane for wastewater treatment. It consists of three layers including alumina (Al 2 O 3 ) macroporous support, colloidal titania (TiO 2 ) mesoporous intermediate layer and polymeric TiO 2 mesoporous top layer in order to obtain a pore gradient from the support through the top layer of membrane. The colloidal and polymeric TiO 2 layers were prepared via the sol-gel method and coated using sol dip-coating approach. In order to optimize the membrane, physical separation and photocatalytic degradation capabilities of each colloidal and polymeric layer as a function of time were evaluated using Rhodamine B (RhB) aqueous solution. Thus, optimum coating number of intermediate layer and top layer were determined. Also, the performance of the optimized membrane was investigated via oily wastewater treatment using crude oil and water emulsion. Based on the performance results, two consequence colloidal layers and one polymeric layer were considered as the optimum layer number. Also, RhB photocatalytic degradation was 24.7% and RhB physical separation and permeation flux were 40.4% and 25.7 kg m −2 h −1 , respectively. Furthermore, based on the oily wastewater treatment experiments, permeation flux and chemical oxygen demand (COD) rejection at the best-operating conditions (pressure of 5 bar, the temperature of 30 °C and cross flow of 600 l h −1 ) were 29.1 kg m −2 h −1 and 78.4%, respectively. The prepared membrane was found efficient and exhibited high industrial potential due to its multifunctional capability and thus can be employed as an advanced material for wastewater treatment applications. [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]

Beside several methods of membrane fouling reduction, induction of electric field in system of dielectric materials can also postpone fouling. For the first time, CFD technique is used to develop a model to predict behavior of a sample oil droplet located on the membrane surface affected by dielectrophoresis force in a good agreement with experimental data. Then experimental design is used to study the effects of electric field induction within defined ranges of system variables. In order to quantify droplet behavior, critical voltage is defined as minimum required electric potential to detach droplet from the membrane surface. Contact angle, droplet diameter, interfacial tension, membrane thickness, shear rate, pore diameter and trans-membrane pressure are system variables. Initially, screening experiments with 2-level factorial approach identify first four variables as effective factors. Subsequently, response surface methodology and central composite design were employed for critical voltage modeling and optimization. A quadratic model (R 2 = 0.997) is suggested for square root of critical voltage between 1800 and 22,000 V. Optimum or minimum critical voltage is observed at 0.01 N/m interfacial tension, 110° contact angle, 2 µm droplet diameter and 100 µm membrane thickness. The predicted value for optimum critical voltage by a second-order polynomial correlation is 1734 V which deviates about 4% from 1800 V as critical voltage calculated from the CFD model. [ABSTRACT FROM AUTHOR]

Supported carbon membranes were prepared using phenolic resin as the carbon precursor and porous graphite as the support. The support was impregnated with the resin solution, dried, cured and carbonized to obtain a membrane layer. One-time coating cannot effectively reduce the number of defects in the membrane. Repeated impregnation cycles to add more carbon layers, using a slow cooling rate during carbonization, performing carbonization at a low temperature and short time (500°C and 10min), and coating the supported membranes with permeable polymers were used simultaneously to reduce the population of defects to a certain extent. As a result, gas separation selectivity of the membranes was significantly increased. [ABSTRACT FROM AUTHOR]

The effect of carbonization temperature and treatment with ozone on the porosity and gas separation behavior of carbons produced from phenolic resin was investigated. Results showed that with increasing carbonization temperature from 500 to 800°C, the average pore diameter decreased, while the pore volume and the adsorption capacity of the carbons first increased and then decreased. A molecular sieve separation mechanism was also observed for the sample carbonized at 800°C. The pore size increased and the adsorption capacity and the kinetic adsorption selectivity for oxygen/nitrogen were decreased by the ozone treatment. [New Carbon Materials 2013, 28(1): 39–46] [Copyright &y& Elsevier]

In this work, the response surface methodology (RSM) based on the central composite design (CCD) was used to examine effects of different gamma alumina (γ-AlO) loadings (0 to 8 wt.%) and various polyethylene glycol 1000 (PEG1000) contents (0 to 40 wt.%) as parameters on membrane preparation. Accordingly, pure carbon dioxide (CO) and methane (CH) gasses permeability and ideal CO/CH selectivity values were considered as responses. Poly (ether block amide) 1657 (Pebax1657) was used as the base polymer matrix for the membranes fabrication. The neat Pebax1657 membrane was prepared via solution casting-solvent evaporation method and the other membranes were prepared via solution blending technique. Analysis of variance (ANOVA) was used to analyze the experiments statistically and the results indicated that the optimized amounts of γ-AlO nanoparticles and PEG1000 in order to enhance both CO permeability and ideal CO/CH selectivity were 8 wt.% and 10 wt.%, respectively. Additionally, a comparison between the separation performance of the neat membrane, the nanocomposite membrane with the optimum amount of γ-AlO nanoparticles, the blended membrane with optimum amounts of PEG1000, and the blended nanocomposite membrane with optimum amounts of γ-AlO nanoparticles and PEG1000 was presented. The obtained gas permeation results showed that the blended nanocomposite membrane exhibits the highest CO/CH separation performance compared to the neat Pebax membrane. [ABSTRACT FROM AUTHOR]

Polymeric gas separation membranes have found widespread application particularly for CO2 capture and natural gas sweetening. Permeability through these membranes depends on solubility (S) and diffusion (D) coefficients of the gas penetrants, for which estimation of the molar heat of sorption (ΔHS), is of high importance to attain the S value. A well-known linear empirical correlation to predict ΔHS in rubbery polymers, has been already proposed by van Amerongen [Rubber Chem. Technol. 1964, 37, 1065]. In this paper, a correlation based on the physical properties of the gas penetrants and polymers has been provided as a basis for the extensively applied ΔHS correlation for the glassy polymers in the literature developed according to van Amerongen's empirical method. The proposed correlation, takes into account the contribution of the polymer nature, which is more distinct for small molecule, highly supercritical gas solutes, that is, much above their critical temperatures, such as H2 and He. It was found that the physical properties of the penetrants play a significant role in the ΔHS calculation. The developed correlation was satisfactorily validated for various gases including CO2, CH4, C2H4, C2H6, C3H6, C3H8, C4H10, SO2, O2, He, H2, and N2, and glassy polymers consisting of poly(vinyl acetate) (PVAC), poly(ethylene terephthalate) (PETP), poly(vinyl chloride) (PVC), and polycarbonate (PC). [ABSTRACT FROM AUTHOR]

The permeation behavior of thin films of fumed silica loaded polyvinyl alcohol (PVA) coated over tubular porous ceramic supports were investigated. Mullite based support enhances mechanical strength of PVA membranes. Effects of temperature, fumed silica loading and active layer thickness on the permeation behavior of the prepared membranes were studied in terms of permeation flux and water selectivity. Experimental data were obtained by dehydration of 90 wt.% ethanol using pervaporation (PV). The privileges of the synthesized membrane to its rivals, superior permeation flux (0.05–2.92 kg/m 2 h), water selectivity (3–180) and pervaporation separation index (PSI) (5.84–82.81) along with its low manufacturing costs, let it have a potential to be used for dehydrated ethanol production in industrial scale. A solution diffusion based mathematical model, including surface exchange and bulk diffusion resistances, was developed to predict permeation flux of both components as functions of temperature, fumed silica loading, active layer thickness and feed composition. Results showed that permeation flux enhances with temperature, fumed silica loading and diminishes with membrane thickness. Besides, increasing temperature and fumed silica loading reduces selectivity while increasing membrane thickness increases selectivity. [ABSTRACT FROM AUTHOR]

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]

The present research investigates deeply the effect of 1-ethyl-3 methylimidazolium tetrafluoroborate ([Emim][BF 4 ]) ionic liquid on separation performance and transport properties of poly(ether-b-amide6) (Pebax1657) at different operating pressures from 2 to 20 bar and temperatures from 25 to 65 °C. [Emim][BF 4 ] showed interesting separation factor for CO 2 /light gases as a solvent and it was expected that its addition to Pebax1657 leads to more amorphous structure, thereby increasing diffusion and permeability of gases. [Emim][BF 4 ] was added to the polymer solution up to 100 wt% of Pebax1657 weight and permeation coefficients of CO 2 , H 2 , CH 4 and N 2 through the prepared membranes were measured. The results showed remarkable increment in permeation of all the tested gases, particularly CO 2 and ideal selectivity of CO 2 /H 2 enhanced significantly due to high solubility selectivity of the added compound. Effect of operating conditions on solubility coefficients was also investigated; thus sorption isotherms and activation energies of permeability, solubility and diffusion were calculated. In addition, the membranes were characterized by SEM, DSC, FT-IR spectroscopy and Tensile analysis to inspect changes in their physical and thermal properties, precisely. [ABSTRACT FROM AUTHOR]

Abstract: Different Sigma-1 zeolite loaded Matrimid®5218 mixed matrix membranes (MMMs) were prepared by solution casting and CO2/CH4 gas separation experiments were performed. Also, the Maxwell model was employed to predict through the CO2/CH4 permeability prediction Sigma-1–Matrimid®5218 MMMs. Without considering the polymer chain rigidification and the partial pore blockage effects on the Maxwell model, the AARE (average absolute relative error) values were high, i.e. for CO2 permeability as 14.2%, for CH4 permeability as 65.9% and for selectivity prediction as 30.5%. However, the AARE values were reduced after including the polymer chain rigidification and the partial pore blockage effects into the Maxwell model by introducing two parameters, and , into the model so that the AARE value for CO2 permeability prediction was 1.6%, for CH4 permeability prediction was 14.5% and for selectivity prediction was 15.7%. [Copyright &y& Elsevier]

Poly(sodium4-styrenesulfonate)- (PSS-) wrapped multiwalled carbonnanotubes (MWNTs) were incorporated into poly(vinyl alcohol) (PVA)solution for the preparation of PVA/MWNTs-PSS nanocomposite membranes.According to field-emission scanning electron microscopy (FESEM) observations,wrapping MWNTs with PSS leads to better dispersion of the MWNTs inthe polymer matrix. The membrane performances were tested in the pervaporation(PV) process for the dehydration of isopropanol (IPA). Upon additionof 0–3 wt % MWNTs-PSS to the PVA matrix, the permeance decreased,whereas the selectivity increased. For example, the water permeancedecreased from 4200.8 to 3243.9 GPU, and the selectivity increasedfrom 39.8 to 249.4 when the MWNTs-PSS content was increased from 0to 3 wt %. The estimated permeation and diffusion parameters showthat the prepared membranes provide high separation performance forwater–IPA mixtures. [ABSTRACT FROM AUTHOR]

Abstract: This study deeply investigates gas separation performance of neat and alloyed poly(Ether Block Amide) [PEBA] (grade 1657) membranes. Poly(ethylene glycol 600 diacrylate), [PEGDA], was used as alloying agent with different weight fractions, 20%, 40% and 60%, based on weight of the neat PEBA membrane. The main aim of this work is removing CO2 from syngas stream. Therefore, permeability, selectivity and activation energy of permeation for pure gases, CO2, H2, CH4 and N2, were studied within wide ranges of temperature, 25–75°C, and pressure, 8–40bar. The prepared PEBA and alloyed PEBA/PEGDA membranes were characterized by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), and X-ray diffraction (XRD) and dynamic mechanical thermal analysis (DMTA). Obtained results in this investigation showed that the alloyed membranes exhibit better separation performance compared with the neat PEBA membranes. [Copyright &y& Elsevier]

Abstract: Hybrid membrane bioreactors have emerged to alleviate membrane fouling, the drawback of conventional membrane. In this study immobilized acclimatized activated sludge on either polypropylene or polyurethane carriers were exploited to run two types of hybrid bioreactors and compare their performances with one conventional MBR in treatment of a synthesized phenolic wastewater at 1000mg/L and a hydraulic retention time of 13h. Immobilization on polyurethane foam resulted in phenol removal of 99% as compared to 72.5% for polypropylene and 70.6% for the conventional MBR. Complete membrane fouling occurring at trans-membrane pressure of 0.6bar was observed after 5, 9 and 21days for conventional MBR, polypropylene and polyurethane hybrid bioreactors, respectively. Additionally, analyses of soluble microbial products showed that proteins positively affect membrane fouling. The performance of hybrid bioreactor containing polyurethane foams under phenol loading shocks was also examined by sudden variations from 1000 to 1250 and 1500mg/L in influent phenol concentration where it was found that although persistent shocks had adverse effect on phenol removal, complete retrieval of phenol removal could be achieved after elimination of shocks. Among bioreactors examined, a hybrid bioreactor using polyurethane foam is therefore proposed as a superior bioreactor considering both performance efficiency and membrane fouling for wastewater treatment. [Copyright &y& Elsevier]

Abstract: The effect of silica addition on the photocatalytic and separation properties of mesoporous titania–silica membranes was investigated. Macroporous α-alumina support was used as substrate, and intermediate layer was obtained by deposition and calcination of the colloidal titania sol on the substrate. Then, titania and titania-5% silica polymeric sols were prepared for deposition on the interlayer as membrane top layer. The samples were characterized by DLS, TG-DTA, XRD, FTIR, BET, FESEM, TEM and AFM. The photocatalytic capability of the membranes was evaluated using methyl orange photo-degradation. The mesoporous composite membrane was prepared with the average pore size of 3.94nm. The dye removal efficiency of the titania–silica membrane has been determined to be 63% after 60min UV-irradiation. By coupling separation process with photocatalytic technique, the removal efficiency was improved up to 94%. The synthesized titania–silica membrane showed a great potential due to its multifunctional capability for water treatment. [Copyright &y& Elsevier]

A template-free seeded short-time in situ hydrothermal treatment was carried out in a brass autoclave to synthesize crystalline mordenite (MOR) membranes on alumina-silicate disk supports with micro-scale pores. According to XRD analysis, MOR was the only zeolitic material present in the membrane layers on the supports. SEM examination of the membranes showed three different layers of the membrane thickness: (i) support sub-layer, (ii) mix penetrated mid-layer, the MOR crystals filling the pores among the support (about 4-5 μm), and (iii) MOR top-layer (about 4-5 μm). The crystalline bonds between MOR crystals of the membrane top-layer and the crystals of the support were clearly observed within the mid-layer. The continuous top-layer of zeolitic membrane was formed by many large and well-shaped crystals. The seeding treatment significantly enhanced the formation of MOR crystals onto the surface of the supports. EDAX analysis showed a Si/Al ratio of 6.8 for the MOR layer of the membrane. Due to their hydrophilic natures, the polycrystalline MOR membranes were found to be selective for continuous dehydration of different EtOH-water mixtures through an adsorption-diffusion-desorption mechanism. Both total permeation flux and separation factor of the membrane were found to increase by increasing temperature and water concentration of feed. The continuity and high crystallinity of the membrane top-layer led to the fairly high dehydration of EtOH. It was found that there was no pinhole within the layer and the morphology of the membrane was almost defect-free. [ABSTRACT FROM AUTHOR]

The core of this study was fabrication of novel cellulose acetate/pluronic F-127 (CA/PF-127) composite membranes for forward osmosis (FO) applications. Performance and structure of the FO membranes under the influence of different applicator clearance gaps (ACGs) along with PF-127 wt.% contents were examined during the non-solvent phase separation (NIPS) method. Scanning electron microscopy, water contact angle, atomic force microscopy and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) analysis were used to characterize the membrane properties. The best performance was attributed to the lower thickness and the higher porosity. The lower structural parameter, which reduces the internal concentration polarization (ICP), led to the highest water flux. The values of 10.58 (L/m2.h) and 0.39 (g/L) were obtained as water flux and specific reverse salt flux (SRSF) of the optimal FO membrane, which was synthesized by 20 wt.% of CA, 79.00 wt.% of N-methyl-2-pyrrolidone (NMP), 1.0 wt.% of PF-127 and 100 µm of ACG, respectively. [ABSTRACT FROM AUTHOR]

Different SAPO-34 zeolite loaded Matrimid® 5218 mixed matrix membranes (MMMs) were prepared by solution casting method and characterized using XRD and SEM analysis. Findings showed that semi crystalline neat polymer becomes more crystalline after thermal treatment at higher temperatures close to Matrimid® 5218 glass transition temperature. Furthermore, incorporation of crystalline filler particles of SAPO-34 zeolite resulted in more and more crystallinity of the MMMs. SEM images also exhibited acceptable contacts between the filler particles and the polymer chains. Permeation measurement showed that CO2 permeabilities and CO2/CH4 selectivities of the MMM with 20 wt% loading of SAPO-34 zeolite particles up to 6.9 (Barrer) and 67, respectively. This can be attributed to size discrimination of SAPO-34 pores that falls between CO2 and CH4 kinetic diameters. [ABSTRACT FROM AUTHOR]

In this work, the nanostructured anatase mesoporous membranes were prepared for water ultrafiltration (UF) process with photocatalytic and physical separation capabilities. A macroporous substrate was synthesized from α-Al2O3, then a colloidal titania sol was used for the preparation of the intermediate layer. Also, the membrane top layer was synthesized by deposition and calcination of titania polymeric sol on the intermediate layer. The characterization was performed by DLS, TG-DTA, XRD, BET, FESEM, TEM, and AFM techniques. Also, the filtration experiments were carried out based on separation of methyl orange fromaqueous solution by a membrane setup with a dead-end filtration cell. Photocatalytic activity of themembranes was evaluated by methyl orange photodegradation using UV-visible spectrophotometer. The mean particle size of the colloidal and polymeric sols was 14 and 1.5 nm, respectively. The anatase membranes exhibited homogeneity, with the surface area of 32.8m2/g, the mean pore size of 8.17 nm, and the crystallite size of 9.6 nm. The methyl orange removal efficiency by the mesoporous membrane based on physical separation was determined to be 52% that was improved up to 83% by a coupling photocatalytic technique. Thus, the UF membrane showed a high potential due to its multifunctional capability for water purification applications. [ABSTRACT FROM AUTHOR]

Abstract: The present study explores the fundamental science of estimating sorption of gases in membranes comprised of inorganic porous fillers within a polymer matrix with a novel semi-empirical correlation. The sorption properties of H2, C3H8, CO2 and CH4 were determined in polydimethylsiloxane (PDMS)/zeolite 4A mixed matrix membranes (MMMs) to assess the viability of these membranes for hydrogen purification and natural gas sweetening. Zeolite filling in MMMs results an increase in solubility over neat PDMS membrane. In addition, incorporation of zeolite 4A to PDMS membrane improved H2 permeation and H2/CH4 selectivity. The results confirmed that zeolite 4A can significantly improve the separation properties of poorly H2-selective PDMS membrane from 0.7 up to 11 and this overcomes the Robeson upper-bound limitation. This improvement was explained referring the Flory–Huggins interaction parameter within MMMs. [Copyright &y& Elsevier]

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]

Abstract: The transport properties of gases in polydimethylsiloxane (PDMS)/zeolite A mixed matrix membranes (MMMs) were determined based on pure gas permeation experiments. MMMs were prepared by incorporating zeolite 4A nanoparticles into a PDMS matrix using a new procedure. The permeation rates of C3H8, CH4, CO2, and H2 were evaluated through a dense homogeneous pure PDMS membrane and PDMS/4A MMMs to assess the viability of these membranes for natural gas sweetening and hydrogen purification. SEM investigations showed good adhesion of the polymer to the zeolite in MMMs. Permeation performance of the membranes was also investigated using a laboratory-scale gas separation apparatus and effects of feed pressure, zeolite loading and pore size of zeolite on the gas separation performance of the MMMs were evaluated. The MMMs exhibited both higher selectivity of H2/CH4 and H2 permeability as compared with the neat PDMS membrane, suggesting that these membranes are very promising for gas separations such as H2/CH4 separation. [Copyright &y& Elsevier]

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]

Abstract: Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) perovskite powder was synthesized via EDTA/citrate complexation method. BSCF membranes were formed by pressing powder at 400MPa and sintering at 1100°C for 10h. XRD patterns showed that a high pure powder with cubic structure was obtained. SEM micrographs revealed that the membranes are dense with large grains. Effects of temperature, feed and permeate side oxygen partial pressures, flow rates and membrane thickness on oxygen permeation flux were studied experimentally. A Nernst–Planck based mathematical model, including surface exchange kinetics and bulk diffusion, was developed to predict oxygen permeation flux. Considering non-elementary surface reactions and introducing system hydrodynamics into the model resulted in an excellent agreement (RMSD=0.0617, AAD=0.0487 and R 2 =0.985) between predicted and measured fluxes. The results showed that oxygen permeation flux increases with temperature, feed side oxygen partial pressure and flow rates, however decreases with permeate side oxygen partial pressure and membrane thickness. Contribution of feed side surface exchange reactions, bulk diffusion and permeate side surface exchange reactions resistances in the total resistance are in the range of 8–32%, 10–81% and 11–59%, respectively. Permeation rate-limiting step was determined using the membrane dimensionless characteristic thickness. [Copyright &y& Elsevier]

In this work, separation of toluene/n-heptane mixtures via pervaporation using a composite membrane was investigated. Effects of operating conditions such as feed temperature, feed composition and downstream pressure on the membrane performance were studied. Experimental results were obtained at different feed compositions (10-40 wt.%), operating temperatures (25-85°C) and downstream pressures (2-32 mbar g). The membrane selectivity for toluene was found to be greater than that for n-heptane. According to the results, it was observed that increasing toluene concentration in the feed and operating temperature enhance the membrane swelling and increase the polymeric chain mobility. Therefore, feed concentration and temperature have the same effects on toluene selectivity and permeation flux of the membrane. Permeation flux increases and toluene selectivity decreases with increasing feed concentration and temperature. In contrary, the membrane performance enhances with decreasing downstream pressure. It was found out that for a feed with 10wt.% of toluene, at a temperature of 85°C and a downstream pressure of 2 mbar g, the highest PSI value of 18.371 kg/m² h (in which permeation flux = 4.610 kg/m² h and toluene selectivity = 4.985) is achieved. [ABSTRACT FROM AUTHOR]

Abstract: Robust artificial neural network (ANN) was developed based on experimental data to predict dehydration of isopropanol by means of novel PVA–APTEOS/TEOS nanocomposite membranes in pervaporation (PV) process. The input properties were water concentration, feed temperature and nanoparticles content, while pervaporation separation index (PSI) was output. The Bayesian Regularization (BR) training method with full sampling was employed to train the network. Then, optimal ANN architecture was determined as 3:3:3:1 with log-sigmoid transfer function for hidden and output layers. The model finding revealed that nanoparticles content has significant effect on membrane performance (about 70%). The results demonstrated that the ANN model prediction and experimental data are quite match and the model can be employed with confidence for prediction of each nanocomposite membrane performance. Simulated annealing (SA) was also employed to determine controllable conditions to find the biggest PSI. [Copyright &y& Elsevier]

Abstract: Carbon nanotubes (CNTs) were synthesized by CVD method using cyclohexanol and ferrocene as carbon precursor and catalyst, respectively. Nitric acid was used for purification and functionalization of CNTs. TEM image of CNTs before and after purification revealed that acid treatment could remove encapsulated catalyst particles. Afterward, highly pure and functionalized CNTs were incorporated in poly (vinyl alcohol) (PVA) to synthesize PVA–CNTs nanocomposite membranes. FESEM characterization was carried out to investigate dispersion of different CNTs loading in PVA matrix. The results showed that 2wt.% CNTs loading is better dispersed in the polymer and increasing CNTs loading more than 2wt.% agglomerates CNTs. Degree of swelling results for nanocomposite membranes showed that present of CNTs in the PVA membranes reduce the degree of swelling. Furthermore, pervaporation (PV) results revealed that incorporating of CNTs in PVA matrix increases significantly water selectivity due to rigidification of the polymer chains. The water selectivities for the pristine PVA and 2wt.% CNTs loading nanocomposite membranes were evaluated as 119 and 1794, respectively. [Copyright &y& Elsevier]

Abstract: Cyclohexanol and xylene were used as carbon precursors, for synthesis of multiwall carbon nanotubes (MWCNTs) arrays in a CVD system at temperature of 750°C, using nitrogen as carrier gas and ferrocene as catalyst. Different characterization methods were employed to compare the MWCNTs structure synthesized by these two precursors. All scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA) and Raman spectroscopy results illustrated that using cyclohexanol could significantly reduce formation of amorphous carbon and catalyst particles in the as-grown CNTs. The less amorphous carbon can be attributed to in situ oxidation in presence of oxygen atom of cyclohexanol. Characterizations showed that MWCNTs with high purity could be obtained using cyclohexanol as carbon precursor. The as-grown MWCNTs were purified by oxidation and acid treatment. Characterization of the purified MWCNTs using HNO3/H2SO4 (1/3 or 1/1), 8M HCl or 8M HNO3 was carried out. The results showed that 8M HNO3 could be considered as the best chemical to obtain more pure MWCNTs, less amorphous and metal particles and less damaged MWCNTs. The Raman spectroscopy results demonstrated that HNO3/H2SO4 (1/3) treatment could more disorder the MWCNTs structure and this was attributed to the bigger destroying effect of this acid treatment. Furthermore, the TEM analysis of MWCNTs before and after acid treatment revealed that acid treatment could remove encapsulated catalyst particles. The FTIR analysis illustrated that purification of the MWCNTs with nitric acid could connect the functional groups onto the outer surface of MWCNTs and this resulted in more dispersion of the MWCNTs in water. [Copyright &y& Elsevier]

Abstract: Carbon nanotube (CNT) film was synthesized directly on macroporous surface of α-alumina support by chemical vapor deposition (CVD) of cyclohexanol and ferrocene in nitrogen atmosphere at 650°C, and oxidized using HNO3 and H2SO4 and then employed as membrane in desalination process (sodium chloride removal from water). In order to enhance the performance of the oxidized CNTs membrane, effects of operating parameters on the yield of desalinated water (separation percent and permeate flux) were studied. Four parameters at three levels were selected: feed concentration (10,000, 20,000 and 30,000ppm), temperature (25, 35 and 45°C), pressure (4, 7 and 10bar) and flow rate (200, 350 and 500l/h). Taguchi method was used to plan a minimum number of experiments and to find the optimal conditions. The results showed that increasing feed concentration, temperature and flow rate as well as decreasing pressure optimize the performance of the oxidized CNTs membrane (separation percent and permeate flux). Analysis of variance (ANOVA) was applied and it was found that temperature is the most influential factor on the oxidized CNTs membrane performance (its contribution percentage was calculated to be about 60%). [Copyright &y& Elsevier]

Abstract: In a comparative research, five polymeric membranes were employed to treat the oily wastewater of Tehran refinery using cross-flow membrane filtration. To do these experiments, the outlet wastewater of the API (American Petroleum Institute) unit of Tehran refinery was used as the feed. Five different membranes were used including two microfiltration (MF) PS (0.1μm) and PS (0.2μm) membranes and three ultra-filtration (UF) PAN (20kDa), PS (30kDa) and PAN (100kDa) membranes. The performances of these membranes for treatment of the oily wastewater were evaluated and compared. The final permeation flux of oily wastewater was determined for each membrane (76.0, 73.1, 53.7, 32.1 and 96.2L/m2 h, respectively). The PAN (20kDa), PS (30kDa) and PAN (100kDa) membranes showed higher rejection, lower permeation flux and higher permeation flux, respectively. The PAN (100kDa) UF membrane was effective and suitable for treatment of the oily wastewater to achieve up to 94.1%, 31.6%, 96.4%, and 97.2% removal of TSS, TDS, turbidity and oil-grease content, respectively with a permeation flux of 96.2L/(m2 h). In this work, Hermia''s models were used to investigate the fouling mechanisms of polymeric membranes. The results show that cake filtration model can well predict the initial and final permeation flux of MF and UF membranes. After cake filtration model, the best permeation flux predicted to the experimental data was intermediate pore blocking model and worst predicted permeation flux was for complete pore blocking model. Chemical cleaning of polymeric membranes fouled with oily wastewater was investigated with metal chelating agent (EDTA), surfactant (SDS), and their combination. The results showed that combination of SDS and EDTA are able to clean the fouled polymeric membranes effectively. Mechanisms of the membrane fouling and chemical cleaning of them were also investigated. [Copyright &y& Elsevier]

Abstract: In this study, asymmetric cellulose acetate (CA) membranes were prepared from polymeric blend of CA–PEG/1-methyl-2-pyrrolidone (NMP) system via phase inversion induced by immersion precipitation in water coagulation bath. Effects of PEG concentration (0wt.%, 5wt.% and 10wt.%) and coagulation bath temperature (CBT=0°C and 25°C) on morphology, pure water permeation flux (PWF) and thermal/chemical stability of the prepared membranes were studied and discussed. Rejection of the developed CA membranes was quantified using human serum albumin (HSA) solution. Increasing PEG concentration in the cast solution film along with higher CBT results in increasing the membrane thickness, pure water flux (PWF) and HSA transmission, also these changes facilitate macrovoids formation (even with the size of more than 50µm) in the membrane sublayer. On the other hand, increasing PEG concentration along with reduction of CBT results in increasing the thermal/chemical stability of the prepared membranes. Presence of low molecular weight PEG additive in the cast solution film increases porosity/permeability and simultaneously thermal/chemical stability of the prepared membranes. On the other hand, using cold coagulation bath despite of increasing the thermal/chemical stability of the prepared membranes results in reduction of membranes porosity/permeability. [Copyright &y& Elsevier]

Abstract: Implementation of try and error method for membrane preparation procedures is a time and cost consuming technique. This study tries to present a novel idea to make membrane preparation procedure heuristic. Applying this method, helps researchers to predict performance of a membrane prior to its preparation. At first, a number of membranes are prepared and characterized. Then, their measured separation properties are used for prediction of performance of a membrane before its preparation. Furthermore, after preparation of each new membrane, its relevant data can be added to the data bank of the model to improve its capability for the next predictions. Therefore, this model will be improved step by step, after each new preparation. Fuzzy logic-based (FL) model and Principal Component Analysis (PCA) were employed to predict permeability of C3H8, CH4 and H2 in ternary gas mixtures using a membrane gas separation module. Based on Placket–Burman (P–B) design, eight different polydimethylsiloxane (PDMS) membranes were synthesized using different preparation conditions, solvent concentration, crosslinker concentration, catalyst concentration, type (or boiling point) of solvent, stirring time and synthesis times in ambient temperature and in an oven at 80°C, and their gas permeation properties were investigated. In an innovating procedure, effects of operating conditions, including feed temperature, pressure, flow rate, C3H8 and H2 concentration, as well as preparation conditions on the permeability of gasses through the synthesized membranes were investigated. Basically, in order to develop a FL model to predict permeability of gasses through all the synthesized membranes, synthesis and operating conditions should be considered, simultaneously, and this extends dimensionality of the problem. In all engineering problems, as the number of variables increases, the corresponding data matrix extends. To overcome the problem, PCA method was randomly used for seven of the prepared membranes from P–B design, and it was shown that the first four principal components could describe almost all of the variation in the data matrix. This means that the dimensionality of the problem reduced from 12 to 4. Using the first four principal components, a Sugeno type FL inference system was trained and applied to predict permeability of gasses. FL modeling results showed that there is an excellent agreement between the experimental data and the predicted values, with mean squared relative error (MSRE) of less than 0.0095. The developed model was used for the 8th membrane and its ability to predict separation parameters of this membrane was confirmed. [Copyright &y& Elsevier]

Phase inversion method was used to prepare polyethersulfone (PES) ultrafiltration (UF) membranes. Polyethylene glycol (PEG); N, N-dimethyl formamide (DMF) and water were utilized as pore-forming additive, solvent and non-solvent, respectively. Effects of PES and PEG concentrations in the casting solution, PEG molecular weight (MW) and coagulation bath temperature (CBT) on morphology of the prepared membranes were investigated. Taguchi experimental design was applied to run a minimum number of experiments. 18 membranes were synthesized and their permeation and rejection properties to pure water and human serum albumin (HSA) solution were studied. It was found out that increasing PEG concentration, PEG MW and CBT, accelerates diffusional exchange rate of solvent (DMF) and non-solvent (water) and consequently facilitates formation of macrovoids in the membrane structure. The results showed that, increasing PES concentration, however, slows down the demixing process. This prevents instantaneous growth of nucleuses in the membrane structure. Hence, a large number of small nucleuses are created and distributed throughout the polymer film and denser membranes are synthesized. A trade-off between water permeation and HSA rejection was involved, with membranes having higher water permeation exhibited lower HSA rejection, and vice versa. Hence, optimizing preparation variables to achieve high pure water permeation flux along with reasonable HSA rejection was inevitable. Analysis of variance (ANOVA) showed that all parameters have significant effects on the response (water flux and HSA rejection). However, CBT and PES concentration were more influential factors than PEG concentration and MW on the responses. [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]

Abstract: Oily wastewaters in Tehran refinery has become a big issue of water and environment pollution to be solved urgently. The results of an experimental study on separation of oil from oily wastewaters are presented. A polyacrylonitrile (PAN, 20kDa) membrane as the ultrafiltration (UF) membrane and an outlet wastewater of API unit of Tehran refinery were employed and the interaction effects of different operating parameters such as transmembrane pressure (TMP), cross-flow velocity (CFV), temperature and pH on permeate flux and fouling resistance were investigated. In this research, Taguchi method (L9 orthogonal array (OA)) was used initially to plan a minimum number of experiments. In this work, Hermia''s models were used to investigate the fouling mechanisms involved in UF of oily wastewaters. The results showed that the best fit to experimental data corresponds to the cake layer formation model followed by the intermediate blocking model for all the experimental conditions tested. A more detailed analysis of the fouling mechanisms was studied via dividing the filtration curves into different regions corresponding to the different fouling mechanisms. Intermediate blocking and cake layer formation or combinations of them were found to occur during the UF experiments depending on the operating conditions. [Copyright &y& Elsevier]

Abstract: A polydimethylsiloxane (PDMS) membrane was synthesized and permeation behavior of ternary gas mixtures including C3H8, CH4 and H2 through it was studied as a function of operating parameters. Mixed gas permeability values were also compared with pure gas data as well as literature to validate experimental results. The aim was to predict separation factor (SF) of C3H8 as a function of feed temperature, pressure, flow rate and C3H8 concentration with the aid of artificial neural network (ANN) technique. Multilayer perceptron (MLP), which is the most common type of feedforward neural network (FFNN), was used for prediction. The Levenberg–Marquardt training method was initially employed to train the net. Then, optimum numbers of hidden layers and nodes in each layer were determined. The selected structure (4:4:5:1) was finally used to predict SF of C3H8 for different inputs in the domain of training data. The modeling results showed that there is an excellent agreement between the experimental data and the predicted values, with mean absolute errors of less than 1%. Both modeling and experimental results confirmed that increasing feed temperature, feed pressure and C3H8 concentration in feed debilitates separation performance; however, SF increases with increasing feed flow rate. As a result, ANN can be recommended for the modeling of mixed gas transport through dense membranes such as PDMS. [Copyright &y& Elsevier]

Abstract: In this study, effects of Tween 80 (polyoxyethylene sorbitan monooleate) as a variable hydrophilic surfactant additive on morphology and permeability of flat sheet polyethersulfone (PES) membranes prepared from PES/polyethylene glycol (PEG)/n-methyl-2-pyrrolidone (NMP) system via phase inversion induced by immersion precipitation in water coagulation bath were investigated. Cross-sectional morphology of the prepared membranes was studied by scanning electron microscopy (SEM). Permeation performance of the prepared membranes was evaluated in terms of pure water permeability (L P), water content, porosity, hydraulic permeability and thickness of the prepared membranes. It was found out that little addition of Tween 80 to the casting solution increases water content and porosity of the membrane support layer and enhances pure water permeability through the membranes. [Copyright &y& Elsevier]

Abstract: A composite polydimethylsiloxane (PDMS)/polyamide (PA) membrane was synthesized and sorption, diffusion and permeation of C3H8, CH4 and H2 were studied both in pure and mixed gas experiments. Pure gas experiments showed that, increasing transmembrane pressure increases solubility, permeability and diffusivity coefficients of heavier gases, C3H8, while does not affect or slightly decreases those of lighter ones, CH4 and H2. Exactly opposite behavior was observed in mixed gas experiments (with the exception of C3H8 and CH4 solubility) due to the competitive sorption and diffusion in the plasticized polymer matrix. Temperature was realized to induce similar effects on permeation properties of pure and mixed gases. As expected, in rubbery membranes such as PDMS, permeability values of more condensable gases decrease with increasing temperature, whereas those of permanent gases increase. Parameters indicating linear pressure dependence (slopes m, n and q) and Van’t Hoff–Arrhenius type temperature dependence (activation energies E p , ΔH s and E d ) of permeability, solubility and diffusivity coefficients in both pure and mixed gas experiments were estimated and discussed thoroughly. In the case of mixed gas experiments, increasing C3H8 concentration in the feed led to increasing solubilities, permeabilities and diffusivities of all the components due to the C3H8-induced swelling of the PDMS film. Experimental results demonstrated ability of the synthesized PDMS/PA membrane for separation of organic vapors from permanent gases. [Copyright &y& Elsevier]

Abstract: This paper presents experimental data, a fuzzy logic (FL) model, a mathematical model (MM) and a coupled MM–FL model for a laboratory scale electrodialysis (ED) cell. The aim was to predict separation percent (SP) of zinc ions as a function of concentration, temperature, flow rate and voltage. At first, a Sugeno type FL inference system was applied to model zinc ions separation from wastewater using ED. FL modeling results showed that there is an excellent agreement between the experimental data and the predicted values, with mean squared relative error (MSRE) of less than 0.01. Then, the results of a previously developed MM were presented. The MM related SP to hydrodynamic dimension of the ED cell and operation conditions via two distinct parameters. This ability favored the MM for scale-up applications. However, based on MSRE of the MM (about 24), it could not obviously predict the experimental data as well as FL. Hence, as a final step, the MM was coupled with FL to achieve benefits of both. It was found out that the developed coupled model (MM–FL) is able to predict SP of zinc ions at all operating condition and almost every dimension to a high degree of accuracy (MSRE=0.05). [Copyright &y& Elsevier]

Abstract: In this study, cellulose acetate (CA) ultrafiltration (UF) membranes were prepared using the phase inversion method. Effects of CA and polyethylene glycol (PEG) concentrations in the casting solution and coagulation bath temperature (CBT) on morphology of the synthesized membranes were investigated. Based on L 9 orthogonal array of Taguchi experimental design 18 membranes were synthesized (with two replications) and pure water permeation flux through them were measured. It was found out that increasing PEG concentration in the casting solution and CBT, accelerate diffusional exchange rate of solvent 1-methyl-2-pyrrolidone (NMP) and nonsolvent (water) and consequently facilitate formation of macrovoids in the membrane structure. Increasing CA concentration, however, slows down the demixing process. This prevents instantaneous growth of nucleuses in the membrane structure. Hence, a large number of small nucleuses are created and distributed throughout the polymer film and denser membranes are synthesized. Rate of water flux through the synthesized membranes is directly dependent on the size and number of macrovoids in the membrane structure. Thus, maximum value of flux is obtained at the highest levels of PEG concentration and CBT (10wt.% and 23°C, respectively) and the lowest level of CA concentration (13.5wt.%). Analysis of variance (ANOVA) showed that all parameters have significant effects on the response. However, CBT is the less influential factor than CA and PEG concentrations on the response (flux). [Copyright &y& Elsevier]