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Charcoal based graphene oxide-copper oxide (GO-CuO) nanohybrids were successfully synthesized via the co-precipitation method. It was then used to improve polyvinylidene fluoride (PVDF) ultrafiltration (UF) membrane properties and performance. The PVDF/GO-CuO UF nanocomposite membranes containing different contents of the synthesized GO-CuO nanohybrids were prepared via the phase inversion method. It was found that hydrophilicity of PVDF membrane containing 0.2 wt% of the synthesized GO-CuO nanohybrids increases than the neat PVDF membrane, so that its water contact angle (WCA) decreases from 80.68 ± 1.23° for the neat PVDF membrane to 60.53 ± 5.25° for the modified membrane containing 0.2 wt% of the synthesized GO-CuO nanohybrids. On the other hand, compared to the neat PVDF membrane, pure water flux (PWF) of this modified nanocomposite membrane increases by about 77% (from 101.1 ± 1.82 to 178.87 ± 1.47 LMH) and exhibits 94.28 ± 0.93% rejection of bovine serum albumin (BSA). This improvement is due to increased hydrophilicity, porosity, average membrane pore size, and decreased membrane surface roughness. The results of fouling measurements showed 42%, 60%, and 8% reduction in total fouling ratio (R t), irreversible fouling ratio (R ir), and reversible fouling ratio (R r), respectively. This indicated that antifouling properties of the modified membrane is significantly improved. It was found that the fabricated PVDF/GO-CuO nanocomposite membrane exhibits better performance than the neat PVDF membrane. Also, the results showed that this membrane also exhibits better properties and performance than the PVDF/GO and PVDF/CuO nanocomposite membranes. Therefore, it can be concluded that the fabricated PVDF/GO-CuO nanocomposite membrane has excellent potential for water and wastewater treatment applications. [Display omitted] [ABSTRACT FROM AUTHOR]

This study investigated the effects of different braid materials (polyethylene terephthalate, nylon 6, and their hybrid), weaving frequencies of the braids (7, 9, 11, 13 Hz), and concentrations of polyether sulfone solution (15% and 18 wt%) on braid angles, braid thickness, and bursting resistance. The results showed that for all types of single and hybrid braids, the braid angle decreases with increasing spinning frequency. When spinning frequency was increased from 7 to 13 Hz, the average wall thickness of polyethylene terephthalate, nylon 6, and the hybrid braids increased by approximately 50%, 65%, and 60%, respectively. The bursting pressure results were obtained in the range of 9.3 to 20.2 bars. The Fourier transform infrared spectroscopy results revealed no chemical bond between the braids and the polyether sulfone layer. Optical and electron microscope analyses revealed formation of uniform thickness of the polyether sulfone layers on the surface of the braids, as well as the penetration of polyether sulfone into the gaps between the filaments. The analyses also showed macroscopic adhesion of polyether sulfone to the braids and provided information on the amount and size of the pores in the polymer layers. The results showed that the selection of appropriate weaving frequency, braid materials, and polyether sulfone layer concentration are important as controllable parameters for producing polymeric hollow fiber composites with excellent burst pressure resistance. [ABSTRACT FROM AUTHOR]

• 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]

In emergency treatment research, the focus on chitosan-based products for wound healing has been consistent. This study specifically explores a dressing made by mixing chitosan (CS) and poly (vinyl alcohol) PVA. Using electrospinning technology, nanofiber membranes of CS and PVA are created with the assistance of non-toxic and hydrophilic polyethylene oxide (PEO). The outcome is a new nanofibrous membrane loaded with mupirocin, designed for healing burn wounds. The study delves into the influence of PVA, CS, and PEO concentrations on the structural and chemical characteristics of the mats. This comprehensive exploration involves techniques such as Scanning Electron Microscope (SEM), Atomic Force Microscopy (AFM) imaging, Fourier Transform Infrared Spectrometry (FTIR analysis), and Contact angle measurements. Additionally, the research evaluates the antibacterial performance and biomedical behavior of the developed scaffolds. PEO proves beneficial in the electrospinning process, contributing to smoother fibers. Meanwhile, the addition of CS and mupirocin leads to formation of the thinner nanofibers (251 ± 5 μm and 263 ± 4 μm, respectively) and scaffolds with higher swelling (up to ∼3.5 times at 90 min). Notably, the (MTT) assay confirms the non-cytotoxicity of the fabricated nanofibers, with proliferations exceeding ∼85% for all samples. The crosslinked samples released the drug more slowly than the non-crosslinked dressings, with 80% of the scaffolds releasing the drug within 24 h. The in-vivo investigations suggested that the drug-containing scaffolds performed reliably and showed promise as a medical dressing for treating burn wounds. • Mupirocin was incorporated into the nanofibers made from the blending of PEO, PVA, and CS. • This exploration involves techniques such as SEM, AFM imaging, FTIR analysis, and Contact angle measurements. • The developed nanofiber membranes exhibited no cytotoxicity. • The drug loaded nanofibers showed excellent antibacterial and wound healing behaviors. [ABSTRACT FROM AUTHOR]

The core of this study is utilization of the facile one-side self-polymerization of dopamine (DA) on surface of the non-recoverable polyethersulfone (PES) membrane and its antifouling ability assessment during oil-in-water (O/W) emulsion separation. The pristine PES membrane was coated by DA solution for 2 and 4 h. The membranes were characterized using FESEM, AFM, FTIR, water contact angle (WCA) and underwater oil contact angle (UOCA) analysis. The results showed that hydrophilicity and underwater oleophobicity can be achieved successfully. Antifouling properties of the modified membranes were improved so that water flux of the 4 h polydopamine (PDA) coated membrane increased about 793% in comparison to the pristine PES membrane. Also, implementation of classical models showed that PDA coating changes the membrane fouling mechanism from standard blockage model to cake filtration model. The 4 h PDA modified membrane shows antifouling property and easy recovery capability during 30 h of operation. Also, the dependences of steady-state water flux were investigated via changing initial oil concentration, feed salinity, trans -membrane pressure and self-polymerization time of DA. Self-polymerization time of DA was found as the most influential factor on water flux. Also, during O/W emulsion separation, all the membranes exhibited high removal efficiency (above 98%) introducing a promising candidate for practical applications. Image 1 • PDA was coated on PES membrane to improve its antifouling ability. • Membrane fouling mechanism was analyzed by classic fouling models. • Increasing polymerization time led to improved hydrophilicity and underwater oleophobicity. • Influences of self-polymerization time along with operating parameters on water permeability were evaluated. [ABSTRACT FROM AUTHOR]

An infected skin wound caused by external injury remains a serious challenge. Electrospun drug-loaded nanofibers with antibacterial properties based on biopolymers have been widely explored for wound healing. In this study, the double-layer CS/PVA/mupirocin (CPM) + CS/PVA/bupivacaine (CPB) mats were prepared by electrospinning method (20 % polymer weight) and then crosslinked with glutaraldehyde (GA) to optimize the water-resistant and biodegradation properties for wound dressing applications. The morphology of mats was characterized as defect-free and interconnected nanofibers by Scanning Electron Microscope (SEM) and Atomic Force Microscopy (AFM). Fourier Transform Infrared Spectrometry (FTIR) analysis also assessed the chemical structural properties. The porosity, surface wettability, and swelling degree of the dual-drug loaded mats were improved by about 20 %, 12°, and 200 % of the CS/PVA sample to provide a moist environment for efficient wound breathing and repairing. This highly porous mat facilitated the wound exudates absorption and air permeability excellently, reducing the chance of bacterial infections by inhibiting the growth of S. aureus bacterial colonies with a zone of 71.3 mm diameter. In vitro drug release results showed a high-burst release of 80 % and a continuous release profile for bupivacaine and mupirocin, respectively. MTT assay and in vivo tests indicated >90 % of cell viability and improvement in cell proliferation. It triply accelerated wound closure compared to the control group, reaching nearly full closure after 21 days as a potential clinical wound treatment. [Display omitted] • Drug release of the antibiotic/anesthetic-loaded CS/PVA bilayer nanofiber mats was tuned. • The composition, morphology, and thermal stability of each layer were characterized. • CS/PVA/bupivacaine (CPB) instantly alleviated pain with antibacterial activity. • CS/PVA/mupirocin (CPM) provided antibiotic activity in cell proliferation. • Promising results were obtained using the optimum sample for skin wound repair. [ABSTRACT FROM AUTHOR]

Polymeric membranes have been commercially used in wastewater treatment and desalination. Polymeric membranes efficiency decreases with time due to fouling, thermal and mechanical instability, chemical degradation and also swelling phenomenon occurrence. Among polymers, sulfone-based polymers have been research interest of membrane manufacturers. However, their intrinsic hydrophobic nature causes fouling under aqueous filtration. Polymer nanocomposite membranes (PNMs) with improved properties and performance than polymeric membranes have attracted much attention all over the world. Size and type of nanofillers, degree of aggregation/dispersion, nanofillers quantity incorporated into the polymeric matrices and compatibility between polymers and nanofillers are the main factors that can considerably affect the PNMs performance and properties. Carbon nanotubes (CNTs) with unique physicochemical properties could be used to improve the PNMs performances in terms of permeability and antifouling properties. Also, it has been reported that by incorporation of CNTs in the polymer matrices, hydrophilicity/hydrophobicity, pore size, porosity, mechanical and thermal stability, surface charge, solute rejection, roughness and other physicochemical properties of the PNMs could be improved, significantly. Effective CNTs functionalization could lead to the improved PNMs characteristics. This article presents an overview of current progresses in fabrication and characterization of CNTs-based PNMs used in various membrane separation processes for water treatment applications with particular emphasis on their challenges and advances. Also, effects of CNTs and their functionalization on structure, performance and properties of the CNTs-based PNMs are deeply investigated. [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]

In this study, fumed silica nanoparticles were functionalized using amine groups and used as inorganic modifiers for preparation of poly (ether-block-amide) based nanocomposite membranes. Field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and CHNO elemental analysis were used to characterize nanoparticles and nanocomposite membranes. The prepared membranes were applied for separation of carbon dioxide (CO 2 ) from methane (CH 4 ). The effects of nanoparticles loading, feed pressure and feed temperature on permeability and CO 2 /CH 4 ideal selectivity of the nanocomposite membranes were investigated. The results indicated that addition of 15 wt % of amine-functionalized fumed silica nanoparticles in the casting solution enhances the membrane CO 2 permeability and CO 2 /CH 4 ideal selectivity 10% and 14%, respectively. [ABSTRACT FROM AUTHOR]

The demand for purified hydrogen as a new green energy source has dramatically increased during last years. In this study, different -Matrimid ® - Deca-dodecasil 3R (DDR) type zeolite mixed matrix membranes were synthesized for Hydrogen purification from Methane. Results demonstrated that existence of DDR into the Matrimid ® matrix, as well as, high temperature thermal treatment enhances membrane crystallinity. Scanning electron microscope images of membranes showed uniform dispersion of zeolite in polymer matrix and well contact at polymer and zeolite interface. Gas permeation experiments exhibits that due to molecular sieving effect of DDR membrane Hydrogen permeabilities and Hydrogen/Methane selectivity enhance for 20 wt % loading of Deca-dodecasil 3R to 34.90 Barrer (100%) and 375.27 (189%), respectively. [ABSTRACT FROM AUTHOR]

The main purpose of this research is to synthesize porous ceramic membrane based on alkali-activated blast furnace slag and achieve optimal synthesis conditions for removing over 90% petroleum compounds and flux in the range of microfiltration (MF) and ultrafiltration (UF). The method applied for membrane synthesis is simple, environmentally friendly, and economical. The blast furnace slag as the main starting material was used to fabricate these free sintering and self-supported ceramic membranes. The L 9 orthogonal array of the Taguchi method was employed to determine the optimum conditions of three controlling factors, i.e. hydraulic pressing pressure, alkali-activated blast furnace slag drying time, and pressing time in three levels. Morphology and filtration performance of the synthesized membranes were characterized via SEM images using Image-j software, total porosity determination, and pore size study using bubble point method. Cross-flow filtration of 75 ppm gas oil in water emulsion was performed and COD analysis of permeate was then monitored. Distribution of synthesis parameters and their influences on the membrane fabrication process were investigated using analysis of variance (ANOVA). According to the results, drying time and hydraulic pressing pressure were known as the most effective parameters on COD and permeation flux. Two optimal membranes for COD removal and permeation flux were identified in hydraulic pressing pressure, drying time and pressing time of (400 bar, 6 h, 5 min) and (225 bar, 8 h, 30 min), respectively. COD optimal UF membrane with an average pore size of 0.07 µm and 100% removal of gas oil and permeation flux optimal MF membrane with an average pore size of 0.66 µm and pure water permeation flux of 1960 kg/m 2 h were introduced. [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]

The present paper investigates the simulation of carbon dioxide removal from natural gas stream by a mixture of three amines of diethanolamine (DEA), methyldiethanolamine (MDEA), and 2-amino-2-methyl-1-propanol (AMP) in a hollow fiber membrane contactor made from polypropylene using finite volume method (FVM). The effect of structural parameters of length and thickness of membrane and diameter of shell on the removal efficiency was studied and the optimized values were calculated. The calculations were made with the assumption of two-dimensional symmetric geometry and compared with those of three-dimensional one. The effect of number and size of the meshes on the simulation results was also studied. The simulation results were validated against the experimental values from the literature. The results imply that the increase in the length and decrease in the thickness of membrane enhances the removal efficiency. As a result, higher quantities of carbon dioxide are transferred from the shell to the membrane and amine solution inside the tube which decreases the effluent CO2 of shell and increases the average concentration of CO2 in the membrane and tube sides. The changes in effluent CO2 of shell with respect to amine solution concentration and influent CO2 indicate the insignificant influence of influent CO2 concentration on the removal efficiency. [ABSTRACT FROM AUTHOR]

Zeolitic imidazolate frameworks (ZIF-8) nanoparticles were successfully synthesized and embedded into a chitosan (CS) polymeric matrix to prepare CS/ZIF-8 mixed-matrix membranes (MMMs) in order to investigate the effect of ZIF-8 addition as novel filler on the dehydration performance of the CS polymeric membrane. MMMs were evaluated using pervaporation (PV) dehydration of isopropanol (IPA). The synthesized ZIF-8 nanoparticles and MMMs were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and a swelling study. The PV performance of the prepared MMMs with different ZIF-8 loadings for IPA dehydration was investigated. For the ZIF-8/CS MMMs, at the optimum loading the total flux increases significantly with low separation factor reduction. The good PV performance of the ZIF-8-incorporated CS membranes for dehydration of IPA is demonstrated. [ABSTRACT FROM AUTHOR]

Synthesis of nanocomposite membranes composed of polymer and inorganic nanoparticles is an efficient method to improve separation properties of polymeric membranes because they possess properties of both organic and inorganic membranes such as good permeation properties, mechanical strength, and thermal and chemical stability. In this study, three types of nano-sized inorganic fillers (TiO 2 , SiO 2 and Al 2 O 3 ) were embodied into the poly (ether-block-amide) (PEBAX-1074) matrix to synthesize nanocomposite membranes and CO 2 /CH 4 permeation properties of the membranes were investigated. The neat membranes were dense and prepared via solution casting; the solution blending technique was employed for synthesis of the nanocomposite membranes. Morphology of the membranes, formation of voids, and distribution of the nanoparticles were observed using FESEM analysis. Thermal stability of the membranes was examined using thermal gravimetric analysis (TGA). Fourier transform infrared (FTIR) spectra of the prepared membranes were analyzed to identify variations of the chemical bonds. The results obtained from the gas permeation experiments with a constant volume setup showed that the membrane incorporating Al 2 O 3 nanoparticles has more ability in passing CO 2 molecules compared to the two other fabricated membranes. [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]

Herein, hybrid adsorptive nanofiltration (NF) hollow fiber (HF) membranes with the charge-patterned structure were fabricated and characterized for enhanced boron removal application. Mg–Al layer double hydroxide (LDH) and bentonite nanoparticles (NPs) were used as adsorbents in the support layer, while pristine and novel amine modified UiO-66 metal-organic frameworks (MOFs) were used to synthesize thin-film nanocomposite polyamide (PA) selective layer. UiO-66 was modified using triethylamine (TEA) and polyethylene imine (PEI) and the modification was approved through FTIR, DLS, and FESEM analyses. Prior to the performance evaluation of the fabricated membranes, the feasibility of boron removal by PA, and pristine and modified UiO-66 was investigated using molecular dynamics (MD) simulation and the diffusion coefficients were estimated. The structure of the fabricated thin film composite (TFC) and thin film nanocomposite (TFN) membranes were characterized by AFM, zeta potential and FESEM analyses showing agglomeration of the MOFs at 0.1 wt%. Membrane performance in boron removal was evaluated through brackish water condition at 4 bar in neutral and alkaline pH. The results showed that the contribution of the adsorptive support is 8 and 4% for the supports containing LDH and bentonite, respectively. Boron removal of the UiO-66 TFN membrane was achieved up to 58%, while the charge-patterned UiO-66/PEI TFN membrane was able to remove boron up to 87 and 91% at neutral and alkaline pH conditions. [Display omitted] • Hollow fiber membranes with charge-patterned UiO-66 incorporated thin-film nanocomposite selective layer were fabricated. • Pristine and modified UiO-66 nanoparticles incorporation in selective layer was able to increase boron removal efficiency. • The fabricated membranes were able to provide 87% and 91% boron removal at neutral and alkaline pH, 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]

This study focused on removal of boron from water via hybrid nanofiltration (NF) thin film composite (TFC) hollow fiber (HF) membranes. To do so, nanocomposite polyvinyl chloride (PVC) HF membranes containing bentonite and layered double hydroxide (LDH) nanoparticles as natural and synthetic adsorbents were fabricated as the adsorptive support layers with high efficiency in boron removal. The phase inversion behavior of dope solutions and mechanical strength of the adsorptive nanocomposite PVC HF membranes were investigated and the results showed that LDH interacts better with PVC polymeric chains than bentonite. It was found that LDH with smaller pores and better adsorption capability in comparison with bentonite results in more hydrophilic membranes with better performance. On the other hand, bentonite tends to become agglomerated at above 1.5 wt%. Moreover, the fabricated membranes containing LDH have lower MWCO and more uniform pore size distribution which make them better options as support for the TFC layer formation to fabricate NF TFC membranes. The selective TFC layer was then fabricated via interfacial polymerization of m-phenylenediamine (MPD) and 1,3,5- benzenetricarbonyl trichloride (TMC) on the outer layer of the nanocomposite PVC HF membranes. Boron removal, and recovery and reusability of the fabricated NF TFC membranes were investigated by Na₂CO₃ solution. It was found that the NF TFC membranes containing LDH with boron removal of more than 83.6% and water flux of 16.1 L/m2.h at 4 bar operational pressure exhibit better performance than the NF TFC membranes containing bentonite. [Display omitted] • Nanofiltration (NF) hollow fiber membranes with adsorptive support layer were fabricated. • The fabricated NF membranes were used for boron removal from water. • Natural bentonite and LDH nanoclays were used as adsorbents in support layer. • Boron removal and adsorption recovery of the fabricated membranes were studied in five cycles. • Over 83% boron removal was achieved by the fabricated adsorptive NF membranes. [ABSTRACT FROM AUTHOR]

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]

ABSTRACT In this research, polyethersulfone (PES)/polyacrylonitrile (PAN) blend ultrafiltration hollow fiber membranes were prepared via phase inversion induced by a dry-jet wet spinning process. The membranes were characterized by water contact measurements, scanning electron microscopy analysis and permeability measurements, and fouling-resistance measurements. The results show that water contacts of the membranes are enhanced by increasing the PAN content in the spinning dope. The results of an experimental study on separation of oil from oily wastewaters are presented. The results demonstrated that the prepared PES membranes are effective in removing chemical oxygen demand (80.6%), total organic carbon (89.3%), turbidity (99.3%), total suspended solid (100%), and oil and grease content (99.7%), and final permeation flux of about 73.5 L/m2h. Also, it was found that 75/25 wt% of PES/PAN have higher mechanical strength and good separation performance. Hermia's models were used for prediction of the decline in permeation flux. Experimental data and models predictions were compared. The results showed that there is reasonable agreement between experimental data and the cake layer model followed by the intermediate blocking model. [ABSTRACT FROM AUTHOR]

In the current investigation, separation performance of poly (Ether Block Amid), PEBA (grade 1657), membrane was improved via incorporation of SiO 2 nanoparticles into the polymeric matrix. In order to attain excellent dispersion of SiO 2 nanoparticles within the polymeric matrix, a chemical surface modification was performed via esterification reaction between the nanoparticles and cis-9-octadecenoic acid (OA). To the best of our knowledge; there is no investigation on employing this type of modification for preparation of SiO 2 /polymer nanocomposite membranes. Permeation, sorption and diffusion coefficients of pure gases, CO 2 , H 2 , CH 4 and N 2 , through the prepared neat and the nanocomposite membranes were studied at temperature of (T = 25 °C) and pressure of (P = 2 bar). The results showed that, with increasing the loading content of nanoparticles from 0 wt% (the neat PEBA membrane) to 8 wt%, ideal permeation selectivity values of CO 2 /H 2 , CO 2 /CH 4 and CO 2 /N 2 improve from 9, 18 and 55 to 17, 45 and 124, respectively. [ABSTRACT FROM AUTHOR]

A new supported liquid membrane (SLM) was developed for the extraction of Europium (Eu) from nitrate medium. The idea was based on the SLM system with the sorbent interface. This membrane extraction system was a three-phase SLM consisting of an aqueous phase (feed phase), organic extractant/nano sorbent (membrane phase) and aqueous phase (Stripping phase). For this purpose, the multi-walled carbon nanotubes (MWCNTs) dispersed in the organic extractant (kerosene + Cyanex272) was held in the pores of a porous membrane by capillary forces and ultrasonic agitation. All experiments were performed using PTFE filter membranes. The results showed that loading of MWCNTs in the liquid membrane enhanced the permeation of Eu. Under the optimized extraction conditions, highest permeability coefficient value of 3.16 x 10-5 m/s was observed for 0.60 M Cyanex272 as carrier with 2 mg/ml CNTs, keeping the feed pH at 6 and 1M HNO3 as stripping solution. The stability of the SLM was satisfactory at 10 cycles of operation. [ABSTRACT FROM AUTHOR]

Carbon nanotubes–mullite composite was synthesized by direct growth of carbon nanotubes on mullite particles via chemical vapor deposition method using cyclohexanol and ferrocene as carbon precursor and catalyst, respectively. The carbon nanotubes–mullite composite was oxidized with concentrated nitric acid and functionalized with chitosan and then used as a novel adsorbent for copper ions removal from water. The results demonstrated that modification with concentrated nitric acid and chitosan improves copper ions adsorption capacity of the prepared composite, significantly. Langmuir and Freundlich isotherms and two kinetic models were applied to fit the experimental data. The carbon nanotubes growth on mullite particles to form the carbon nanotubes–mullite composite with further modification is an inherently safe approach for many promising environmental applications to avoid some concerns regarding environment, health and safety. It was found that the modified carbon nanotubes–mullite composite can be considered as an excellent adsorbent for copper ions removal from water. [ABSTRACT FROM AUTHOR]

In this work, charcoal based nanomaterial (charcoal-NM) with two-dimensional structure, high oxygen and nitrogen content (functional groups) and excellent colloidal dispersion property was synthesized and used to prepare ultrafiltration polyethersulfone (PES) mixed-matrix membranes (MMMs), via phase-inversion method. The charcoal-NM can be dispersed in water and organic solvents without sonication and its colloidal dispersion shows high stability for a long time. The influences of the charcoal-NM on morphology, antifouling behavior, pure water flux (PWF) and hydrophilicity of the fabricated MMMs were studied, and the optimum membrane was selected. Antifouling investigations were done by Bovine serum albumin (BSA) as fouling agent. It was found that incorporation of the charcoal-NM into the PES matrix causes formation of channels with vertical alignment in the membrane structure and enhancing the membrane hydrophilicity and therefore leads to improved flux recovery ratio (FRR), PWF and antifouling properties of the MMMs. The fabricated MMM with 0.6 wt% charcoal-NM was selected as the optimal membrane (with PWF of 410.16 LMH, FRR of 95.43% and BSA rejection of 95.89%). This work showed that the charcoal-NM with low cost and excellent dispersion property can be used as an effective nanofiller for MMMs preparation for environmental applications. [Display omitted] • Charcoal based nanomaterial (charcoal-NM) was synthesized and used as nanofiller. • Charcoal-NM with abundant O and N containing functional groups showed high hydrophilicity. • Charcoal-NM could be dispersed in solvent easily without sonication and modification. • Ultrafiltration polyethersulfone/charcoal-NM MMMs was fabricated, successfully. • The fabricated membranes exhibited enhanced water flux and antifouling properties. [ABSTRACT FROM AUTHOR]

In this study, chemical vapor deposition (CVD) method (with two proposed synthesis processes) was used for inducting two different morphologies of CNTs in mullite pore channels as a novel adsorptive membrane for nickel ions (Ni 2+ ) removal from water. Cyclohexanol and ferrocene were used as carbon source and catalyst, respectively. The first proposed synthesis process involves coevaporation and pyrolysis of a mixed solution composed of cyclohexanol and ferrocene in a neutral atmosphere and the second involves sublimation and decomposition of ferrocene in a reactor individually and subsequently introduction of cyclohexanol as vapor to the reactor by a carrier gas during the reaction. Effects of synthesis parameters such as reaction time, catalyst content and reactor pressure on growth process, and structure and properties of the induced CNTs in pore channels of the mullite substrate were also investigated. Finally the optimized CNTs growth conditions for achieving a uniform distribution of the CNTs in the mullite pore channels were reported. The CNTs–mullite composite membranes prepared under the optimum conditions were oxidized with nitric acid and then successfully used as adsorptive membranes for nickel ions removal from water. Moreover, Langmuir and Freundlich isotherm models were used to describe adsorption behavior of nickel ions by the prepared adsorptive membrane. [ABSTRACT FROM AUTHOR]

Fouling caused by natural organic matter like extracellular polymeric substance (EPS) is a major problem in using membranes in MBRs (MBR's) for separation of biomass from water. In this study, membrane fouling caused by a well-known protein (BSA), a humic acid and a well-known polysaccharide (dextran) as representatives of three main constituents of EPS; proteins, humic substances and polysaccharides were investigated. The objective of this study was to develop a fundamental understanding of fouling mechanisms using a combined pore blockage and cake filtration model with respect to hydrophilic nature of membranes and the pre-filtration effect of the foulant deposit layer. These two factors were inserted in a combined pore blockage and cake filtration model and this modification resulted in much better agreement between the modified model predictions and the experimental data. The experimental data were obtained over a range of foulant concentrations and transmembrane pressures. The results showed that the rate of flux decline is proportional to the hydrophilic nature of membrane, i.e. the extent of fouling in hydrophilic membranes with smaller water contact angle is smaller than that in hydrophobic membranes with larger water contact angle. Also, the fouling rate of the foulants with higher pre-filtration effect is smaller, so the foulants with higher resistance of the first deposit layer have smaller fouling rate. In this study, a modified pore blockage-cake filtration model was also developed. The predicted results were in very good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

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]

Ultrafine sub-micron Na-LTA zeolite crystals ranging from 150 to 350 nm were synthesized without template via hydrothermal method. Aluminum iso-propoxide and colloidal silica were used as Al and Si sources, respectively, to synthesize the small and uniform zeolite crystals. Zeolite Na-LTA was synthesized hydrothermally from a gel formula of 1.0 Al2O3: 2.7 SiO2: 5.85 Na2O: 150H2O in molar basis. The crystallization conditions including synthesis time, and synthesis temperature were optimized to reduce the zeolite particle size. The final crystals were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results confirmed that synthesis temperature should be lowered for better control of the crystal growth. On the other hand, at low synthesis temperatures, synthesis time should be extended to acquire the high crystallinity. Ultrafine sub-micron Na-LTA zeolite crystals were synthesized at synthesis temperature of 60 °C and synthesis time of 11 h. [ABSTRACT FROM AUTHOR]

Amino group grafted halloysite nanotubes (Hal-NH 2 s) were used to enhance adsorption/filtration performance of chitosan (CS)/poly (vinyl alcohol) (PVA) electrospun nanofibers by coating on the polymeric membrane as well as embedding them into the polymer solution. The novel cactus-like nanofibers exerted considerably higher Cd(II) and Pb(II) adsorption capacity than other functionalized materials. The compositional changes of functionalized Hals were verified by Fourier Transform Infrared Spectroscopy (FT-IR) and X-Ray Diffraction (XRD). Morphology of Hal-NH 2 loaded nanofibers was characterized as well as thermal/mechanical properties. Impacts of potentially affecting parameters including Hal-NH 2 loading, pH, temperature, contact time, and initial concentration of heavy metal ions were optimized in the adsorption process. According to the well-fitted Langmuir model, the maximum adsorption capacity of Cd(II) and Pb(II) ions at 120 min were measured to be 454.5 and 476.2 mg/g for the Hal-NH 2 entrapped nanofibers, while for the Hal-NH 2 coated nanofibers, higher values of 516.3 and 551.6 mg/g were measured, respectively. Kinetics of the adsorption process was also studied, indicating that a pseudo-second-order model was fitted on the experimental data. In contrast to the Hal-NH 2 coated nanofibers, the Hal-NH 2 entrapped nanofibers were considered stable, and their adsorption capacity remained almost intact after five adsorption/desorption cycles. These affinity membranes revealed promising Cd(II) and Pb(II) ions removal, and uniform permeation flux, indicating their ability to be the next generation of adsorptive filters. [Display omitted] • Novel electrospun chitosan/PVA-aminated Hal adsorptive membranes were fabricated. • Adding aminated Hal improved thermal and mechanical properties of chitosan/PVA. • Pb(II) and Cd(II) adsorption were enhanced about twice compared to chitosan/PVA ENMs. • Nanocomposite membrane containing 7wt% aminated Hal exhibited the best performance. • ENMs offered enhanced ion metal removal (up to 90%) with high flux performance. [ABSTRACT FROM AUTHOR]

Rational manipulation of the thin film composite (TFC) membranes properties and their surface structures are important to optimize forward osmosis (FO) performance. In this study, a facile approach is proposed for fabricating a hydrophilic and high-flux TFC membrane. Through this strategy, dopamine (DA) was mixed into m -phenylenediamine (MPD) as an aqueous solution followed by interfacial polymerization (IP) reaction with trimesoyl chloride (TMC) on a fabricated polyvinyl chloride (PVC) substrate. For the first time, the simultaneous effects of the DA concentration and the co-deposition time on the membrane morphology and FO properties were systematically investigated to explore the optimum condition. After evaluating the as-prepared membranes, the membranes with the DA concentration of 0.1 g/L and 120 min co-deposition time of PDA and MPD showed high water flux (24.40 L/m2.h) and acceptable reverse salt flux (RSF) compared with the control membrane without DA incorporation (15.95 L/m2.h) using deionized (DI) water as the feed solution (FS) and 1 M NaCl as the draw solution (DS) in the FO mode. Moreover, the optimum membranes exhibited excellent performance in the seawater desalination test. This study demonstrated that incorporation of DA during the IP reaction can be an effective and facile strategy for tailoring the membrane structure and obtaining high-performance FO membranes with outstanding performance for desalination purposes. [Display omitted] • A novel high-flux DA incorporated TFC membrane was produced. • The simultaneous effects of DA concentration and co-deposition time of PDA and MPD were investigated. • DA concentration of 0.1 g/L and 120 min co-deposition time of PDA and MPD in the IP reaction were found as the optimum condition for the membrane synthesis. • The modified membrane showed higher water flux in comparison with the control membrane. • DA incorporated TFC membrane was found as a suitable candidate for desalination application. [ABSTRACT FROM AUTHOR]

Abstract: In this study, hydroxy sodalite (HS) zeolite was synthesized via hydrothermal method. As reported in the literature, the recommended molar composition of H2O/Al2O3 for HS zeolite synthesis is about 1000. However in our work, HS zeolite was synthesized using new molar compositions of H2O/Al2O3 for different synthesis times and their effects on morphology and crystallinity of the synthesized zeolites were investigated. Also, HS zeolite membranes were synthesized on seeded supports using synthesized powders and the effect of seed size was also investigated. The products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Gas permeation through the membranes was also measured. First of all, it was found that synthesis time has a significant effect on crystallinity and crystal size of the synthesized zeolite. Also, water molar ratio can control crystal size of the synthesized zeolite. It was found out that with increasing the seed size, H2 and CH4 permeations decrease, from 3224 to 279 (Barrer) and from 611 to 45 (Barrer), respectively, while the H2/CH4 selectivity increases from 5.28 to 6.20. Finally, to obtain HS zeolite with desirable particle size, crystallinity and morphology, optimum synthesis conditions were proposed. [Copyright &y& Elsevier]

Abstract: Robust artificial neural network (ANN) was developed to forecast sorption of gases in membranes comprised of porous nanoparticles dispersed homogenously within polymer matrix. The main purpose of this study was to predict sorption of light gases (H2, CH4, CO2) within mixed matrix membranes (MMMs) as function of critical temperature, nanoparticles loading and upstream pressure. Collected data were distributed into three portions of training (70%), validation (19%), and testing (11%). The optimum network structure was determined by trial-error method (4:6:2:1) and was applied for modeling the gas sorption. The prediction results were remarkably agreed with the experimental data with MSE of 0.00005 and correlation coefficient of 0.9994. [Copyright &y& Elsevier]

In this work, metal-organic framework derived porous carbon (MOFDPC) nanoparticles (NPs) were synthesized and incorporated into cellulose acetate (CA) polymeric matrix to prepare biodegradable CA/MOFDPC adsorptive membranes via phase inversion method. Polyethylene glycol (PEG) was used as pore former agent. Performance of the prepared membranes was evaluated in methylene blue (MB) removal from aqueous solution via continuous adsorption experiments. The physicochemical properties of the fabricated membranes were characterized by contact angle measurement, SEM, FTIR, AFM, TGA and tensile strength analysis. At first, the effects of PEG concentration and MOFDPC NPs loading were investigated. It was found that the best performance is obtained for the prepared membrane containing 15 wt% PEG and 2 wt% of MOFDPC NPs as the optimal adsorptive membrane. Then, the effects of solution pH, initial MB concentration and operating pressure on the MB removal capability of the prepared optimal adsorptive membrane were investigated. Reusability of the optimal adsorptive membrane was studied via subsequent adsorption/desorption cycles. Its long-term behavior was also studied. The obtained results showed that the prepared biodegradable CA/MOFDPC adsorptive membrane with MB removal percentage of 98.2% and permeate flux of 76.03 LMH and excellent reusability and long-term behavior can be potentially utilized for wastewater treatment applications especially MB removal. [Display omitted] • CA/MOFDPC adsorptive membranes were prepared via phase inversion method. • Membrane performance was evaluated in MB removal from aqueous solution. • Membrane containing 2 wt% of MOFDPC NPs exhibited the best performance. • The MB removal percentage of 98.2% and permeate flux of 76.03 LMH were achieved. • Effects of solution pH, initial MB concentration and pressure were also investigated. [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 article, effects of synthesis parameters (synthesis temperature, synthesis time, and number of layers) on W-type zeolite membranes synthesized over flat SUS supports for O2/ SF6 gas separation were experimentally investigated. Experiments were carried out at these levels of synthesis temperature: 165°C, 185°C, and 200°C; synthesis time: 6, 12, and 18 h and number of layers: 1 and 2. Permeation measurements, XRD and SEM analysis were used for characterization of the synthesized membranes. The results showed that increasing synthesis temperature from 165°C up to 185°C increases separation factor of O2/ SF6, however, further increasing decreases the separation performance. The same trend was observed for synthesis time for the single layer synthesized zeolite W membrane, although for the double layer synthesized zeolite W membrane, separation factor increased with increasing synthesis time. Repetition of layering has a net positive effect on separation factor of O2/ SF6, and negative effect on permeation flux through the membranes. This behavior was attributed to the dual effect of synthesis temperature and synthesis time on selectivity. More zeolite crystals are deposited and larger crystals are formed at higher synthesis temperatures and longer synthesis times. Well W-type zeolite membrane was synthesized at 185°C for 18 h with two repeating layers with a high separation factor of 20.1. [ABSTRACT FROM AUTHOR]

Abstract: The current theoretical models for prediction of gas permeation through mixed matrix membranes (MMMs) were studied. The models of Maxwell, Bruggeman, Lewis–Nielsen, Chiew and Glandt and Pal were evaluated. Based on the results, average absolute relative errors (AAREs) of the models are high in prediction of MMMs permeability; for example, AAREs of permeability prediction of CO2 through MMMs composed of incorporated CMS within Matrimid is 26–34% and for O2 through two MMMs of BAPB-BPADA-zeolite 4A is 25–28% and finally for PVAc-zeolite 4A is 32–34%. These errors are due to the undesirable phenomena such as polymer chain rigidification and total or partial pore blockage in the case of porous inorganic fillers. In this study, the effects of polymer chain rigidification and partial pore blockage were considered and included in ideal models, simultaneously. The common optimized values of alpha (the partial pore blockage factor) and beta (the chain rigidification factor) were calculated for all the models and it was observed that the AARE values are less than 8% for all them. [Copyright &y& Elsevier]

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]

Carbon nanotube (CNT) sheets were synthesized via chemical vapor deposition of cyclohexanol and ferrocene in nitrogen atmosphere at 750 °C, functionalized using concentrated nitric acid and liquid ammonia and employed as adsorbents to study their nitrate adsorption characteristics. The results demonstrated that functionalization with nitrogen-containing groups improves nitrate adsorption capacity of the oxidized CNT sheets, significantly. Various isotherms and kinetic models were applied to fit the experimental data. Effects of contact time, initial nitrate concentration and adsorbent dosage were also investigated. Regeneration performance for the first time was also studied. For comparison, a similar study was performed with commercial activated carbon (AC). It was found out that the functionalized CNT sheets with higher nitrate adsorption capacity, shorter equilibrium time and better regeneration performance than AC, can be considered as potential adsorbents for nitrate removal from water in domestic applications. [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]

Abstract: Carbon nanotubes (CNTs) were synthesized by chemical vapor deposition of cyclohexanol and ferrocene in nitrogen atmosphere at 750°C, and purified by thermal oxidation and acid treatment. Desalination using purified CNTs as adsorbent was performed. Effects of purification (treatment with HNO3 (8M), HNO3/H2SO4 (1/1) and HNO3/H2SO4 (1/3)), initial salt concentration (10,000, 20,000 and 30,000mg/l), temperature (25, 35 and 45°C) and initial pH (3, 7 and 11) on adsorption uptake (mg/g) of the purified CNTs in desalination process were investigated using Taguchi experimental design (L9 orthogonal array). Optimum conditions were predicted, and confirmed by carrying out some new experiments. Relative importance of the effects of various factors was evaluated using analysis of variance (ANOVA). Langmuir and Freundlich isotherm models were applied to fit the experimental data. [Copyright &y& Elsevier]

Abstract: In this work, effect of ultrasonic waves on permeation flux of a microfiltration membrane fouled with fresh cow milk as feed was studied. Also, effects of various parameters such as feed pressure, ultrasonic irradiation power, ultrasonic source diameter, distance between the irradiation source and the fouled membrane surface and pulse irradiation were studied and permeation flux variations were recorded. In all experiments, it was found that ultrasonic irradiation increases the microfiltration flux. The highest flux enhancement factor (%FE=490%) was obtained at a pressure of 0.5bar, power of 40W and distance of 2.6cm. Continuous irradiation of ultrasonic waves uplifted the flux enhancement factor in a degree of 33% more than pulse irradiation. Also, both SEM analysis and permeation flux of pure water confirmed that ultrasonic irradiation has no destructive effects on the membrane surface. [Copyright &y& Elsevier]

Abstract: The recent development of solvent and temperature-resistant, hydrophilic zeolite NaA membranes has made it possible to overcome the limitations of hydrophilic polymeric membranes. Zeolite membranes have uniform and molecular-sized pores, and they separate molecules based on differences in the molecules'' adsorption and diffusion properties. Strong electrostatic interaction between ionic sites and water molecules makes the zeolite NaA membrane very hydrophilic. Zeolite NaA membranes are thus well suited for separating liquid-phase mixtures by pervaporation. Total flux for unsymmetrical dimethylhydrazine (UDMH)–water mixtures was found to vary from 0.329 to 0.215kg/m2·h with increasing UDMH concentration from 1 to 20wt.%. Ionic sites of the NaA zeolite matrix play a very important role in water transport through the membrane. These sites act both as water sorption and transport sites. Surface diffusion of water occurs in an activated fashion through these sites. The precise nanoporous structure of the zeolite cage helps in a partial molecular sieving of the large solvent molecules leading to high separation factors. A comparison between experimental flux and calculated flux using Stephan Maxwell (S.M.) correlation was made and a linear trend was found to exist for water flux through the membrane with UDMH concentration. [Copyright &y& Elsevier]

Abstract: Zeolite hydroxysodalite (HS) was synthesized successfully by hydrothermal method using the natural kaolin. In the first step, kaolin has been calcined at 700°C to the metakaolinite phase. As a second step, the zeolitisation experiments have been carried out under hydrothermal conditions. The metakaolinite obtained has been reacted with NaOH solutions in autoclaves at 100°C. The crystal species were characterized by X-ray diffraction (XRD) patterns and morphology of the supports subjected to crystallization was characterized by Scanning electron microscopy (SEM). Performance of the hydrophilic Nano zeolite membranes during separation of water/Ethanol mixtures was evaluated. These membranes showed very high selectivity of water for water/Ethanol mixtures. Separation factor as high as 10,000 was obtained for ethanol feed concentration of 90%. Total mass flux was also obtained 0.959kg/m2.h. [Copyright &y& Elsevier]

Abstract: Permanent hard water softening using oxidized carbon nanotube (CNT) sheets was performed. CNT sheets were synthesized by chemical vapor deposition of cyclohexanol and ferrocene in nitrogen atmosphere at 750°C, and oxidized with concentrated nitric acid at room temperature and then employed as adsorbent for permanent hard water softening. Various isotherms and kinetic models were applied to fit the experimental data. It was found out that the adsorption behavior of hard mineral ions by oxidized CNT sheets match well with the Freundlich isotherm and the pseudo-second-order kinetic model. The results demonstrated that the oxidized CNT sheets can be used as an effective adsorbent for hard water softening due to their high adsorption capacity. Also, using the oxidized CNT sheets, hard water softening without CNT leakage into water is economically feasible. [ABSTRACT FROM AUTHOR]

Abstract: Hydrothermal synthesis of zeolite T in aqueous alkaline solutions without using templates was investigated. Zeolite T crystals were prepared via hydrothermal synthesis using milk-like aluminosilicate gel with a composition of aSiO2:bAl2O3:cNa2O:dK2O:xH2O. The effects of molar compositions including silicon module (nRM =a/b) and relative alkalinity (α=OH/SiO2), and crystallization conditions including crystallization temperature (T) and time (t) on the yield of T-type crystals were investigated. This research work examines changes in the yield of crystalline zeolite phases by varying the gel composition parameters (nRM =20–25, and α=0.71–0.82) and crystallization process temperature and time (T=100°−140°C, t=120–216h), while keeping constant the parameters [OH]=2.77m, URM(Na/Na+K)=0.75, stirring time=24h , stirring temperature=30°C, and drying temperature=100°C. The crystal species of zeolite T were characterized by XRD (X-ray diffraction) and SEM (Scanning Electron Microscope). [ABSTRACT FROM AUTHOR]

Abstract: Removal of some divalent heavy metal ions (Cu2+, Zn2+, Pb2+, Cd2+, Co2+) from aqueous solutions using carbon nanotube (CNT) sheets was performed. CNT sheets were synthesized by chemical vapor deposition of cyclohexanol and ferrocene in nitrogen atmosphere at 750°C, and oxidized with concentrated nitric acid at room temperature and then employed as adsorbent for water treatment. Langmuir and Freundlich isotherms were used to describe the adsorption behavior of heavy metal ions by oxidized CNT sheets. The obtained results demonstrated that the oxidized CNT sheets can be used as an effective adsorbent for heavy metal ions removal from water. It was found out that kinetics of adsorption varies with initial concentration of heavy metal ions. Preference of adsorption onto the oxidized CNT sheets can be ordered as Pb2+ >Cd2+ >Co2+ >Zn2+ >Cu2+. Using the oxidized CNT sheets, waste water treatment without CNT leakage into water is economically feasible. Therefore, CNT sheets have good potential application in environmental protection. [ABSTRACT FROM AUTHOR]

Abstract: Dehydration of solvents using hydrophilic polyvinylalcohol pervaporation membranes is a well-established technology. However, these polymeric membranes may not be suitable for applications involving high water concentrations or applications containing harsh solvents like unsymmetrical dimethylhydrazine (UDMH) due to membrane stability problems and swelling effects. The recent development of solvent and temperature-resistant, hydrophilic zeolite Hydroxysodalite (HS) membranes has made it possible to overcome the above limitations of hydrophilic polymeric membranes. Zeolite membranes have uniform and molecular-sized pores, and they separate molecules based on differences in the molecules'' adsorption and diffusion properties. Strong electrostatic interaction between ionic sites and water molecules (due to its highly polar nature) makes the zeolite HS membrane very hydrophilic. Zeolite HS membranes are thus well suited for separating liquid-phase mixtures by pervaporation. In this study, experiments were conducted with various UDMH–water mixtures (1–20wt.%) at 25°C. Total flux for UDMH–water mixtures was found to vary from 0.323 to 0.214kg/m2 h with increasing UDMH concentration from 1 to 20wt.%. Ionic sites of the HS zeolite matrix play a very important role in water transport through the membrane. These sites act both as water sorption and transport sites. Surface diffusion of water occurs in an activated fashion through these sites. The precise nanoporous structure of the zeolite cage helps in a partial molecular sieving of the large solvent molecules leading to high separation factors. A comparison between experimental flux and calculated flux using Stephan Maxwell (S.M.) correlation was made and a linear trend was found to exist for water flux through the membrane with UDMH concentration. [Copyright &y& Elsevier]

Abstract: Mordenite membranes were prepared on the outer surface of ceramic tubular tubes via hydrothermal synthesis and evaluated for dehydration pervaporation of water unsymmetrical dimethylhydrazine UDMH mixtures. Highly water-selective mordenite membranes were prepared and the optimum reaction condition was found to be 24h crystallization time and 170°C crystallization temperature. Effect of gel composition on separation factor and water flux of the water–UDMH mixtures was investigated. X-ray diffraction (XRD) patterns showed that mordenite is the only zeolite material which presents in the membrane. Morphology of the supports subjected to crystallization was characterized by Scanning electron microscopy (SEM). In PV of the water–UDMH mixtures, the membrane exhibits a hydrophilic behavior. The best membranes had a water flux of 2.67kg/m2 h at 30°C. The best PV selectivity was obtained to be 264. [Copyright &y& Elsevier]