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Abstract: Molecularly imprinted nanofiber membranes were fabricated from chitin and print molecule of phenylalanine derivative by simultaneously applying an alternative molecular imprinting and an electrospinning. The D-enantiomer imprinted nanofiber membrane preferentially incorporated the D-enantiomer and selectively transported D-enantiomer and vice versa. The permselectivity was exponentially increased with the increase in the membrane thickness, implying that multi-stage cascade membrane separation was carried out within the nanofiber membrane. The present study led to the conclusion that a molecularly imprinted nanofiber membrane is one of suitable membrane forms for the separation membrane with relatively high flux and permselectivity. Keywords: Cascade separation, Chitin, Chiral separation, Molecularly imprinted membrane, Molecular imprinting, Multi-stage cascade membrane separation, Nanofiber, Optical resolution.Download Full Article |
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Abstract: Graphene (GE) based poly(vinyl alcohol) (PVA) nanocomposite membranes were prepared by solution blending method. The influence of GE on morphological, structural, and thermal properties of GE/PVA membranes was studied. Then, malic acid (MA) was used as a crosslinker of the nanocomposite membranes. The effect of MA content on the degree of crosslinking, thermal, mechanical properties, and pervaporation (PV) performance of nanocomposite membranes was investigated. The characterizations of GE/PVA and MA crosslinked GE/PVA nanocomposite membranes were performed by X-ray diffraction spectrum, transmission electron microscope, Fourier-transform infrared spectroscopy, and differential scanning calorimetry, and tensile testing. The characterization results indicated that the good compatibility between GE and PVA was obtained with 0.5wt% filler content. Thermal stability and mechanical properties of MA crosslinked GE/PVA membranes were enhanced by adding 20wt% MA with respect to PVA. The best PV performance for dehydration of 50wt% ethanol solution was obtained by using the 20wt% MA crosslinked GE/PVA membrane. This membrane showed that the total permeation flux and selectivity are 0.690kg/m2h and 23.89, respectively. Keywords: Graphene, PVA, malic acid, pervaporation, dehydration, ethanol.Download Full Article |
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Abstract: A nanofiltration hollow fiber membrane made from sulfonated polysulfone was proposed in this work to meet the demands of having tolerance against chemicals. The sulfonate group in the molecule is a source of highly hydrophilic properties and may increase the inter-molecular force acting between molecules on which it is attached. It also contributes to forming a tight structure in the membrane. The membrane may produce higher water flux than those of commercially available nanofiltration membranes made from polyamides. The state of water in the wet membrane was examined with a nuclear magnetic resonance spectrometer. The bonding force to confine water molecules in the membrane may be considered to control the water flux and salt rejection of membranes. It is revealed that there were two kinds of water in the membrane and the salt rejection was raised when the interaction to the water molecules from sulfonate groups in the sulfonated polysulfone molecule was increased. The salt rejection and water flux is highly correlated with the chemical shift of constrained water. Keywords: Nanofiltration, Hollow fiber membrane, sulfonated polysulfone, salt rejection, nuclear magnetic resonance spectroscopy. Download Full Article |
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Abstract: The need for advancement in filtration technology has spurred attention to advanced materials, such as electrospun nanofiber membranes, for providing clean water at a low cost with minimum initial investment. Polymer nanofibers can be fabricated by using different techniques, such as template synthesis, self-assembly, drawing, phase separation, and electrospinning. Due to its distinctive properties, electrospinning has become a method of choice for fabricating nanofiber membranes quickly with minimal investment. In this study, polyacrylonitrile (PAN) was dissolved in dimethylformamide (DMF), and different weight percentages of polyvinylpyrrolidone (PVP) and gentamicin sulfate powder were added to the solution to fabricate nanomembranes via the electrospinning process. Gentamicin was added to remove bacteria and viruses and prevent fouling, while PVP was added to make the surface of the membrane hydrophilic for enhancing the filtration rate and efficiency. Two water samples were chosen for the filtration processes: dam water and city wastewater. For the dam water sample, PH, turbidity, TDS, Ca++, Mg++, sulfates, nitrates, fluoride, chloride, alkalinity and silica were reduced to +3.64%, 89.6%, 6.52%, 10.5%, 9.96%, 5.16%, 17%, 19.5%, 6.63%, 1.43% and 63.5% respectively. The total coliforms and E. coli content were reduced to 4.1 MPN/100ml and 0 MPN/100ml, respectively with PAN containing 10 wt. % PVP and 5 wt. % Gentamicin. For wastewater sample, PH, turbidity, TDS, TSS, BODs, phosphate, ammonia, oil-greases and DO were reduced to + 3.62%, 79%, 6.33%, 84%, 68%, 1.70%, 15.8%, 0% and 6% respectively. The total coliforms and E. coli content were also lowered to 980 MPN/100ml and 1119.9 MPN/100ml, respectively with PAN containing 10 wt. % PVP and 5 wt. % Gentamicin. The morphology and dimensions of the nanofibers were observed using a scanning electron microscope (SEM). Both SEM and microscopic images of the nanomembrane before and after filtration proved that electrospun PAN nanofibers have superior water filtration performance. Keywords: Nanotechnology, Electrospinning, Water Treatment, Total Coliform, E. coli, Turbidity, Total Suspended Solids (TSS). Download Full Article |
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Abstract: An air sweep pervaporation process with thin anion-exchange hollow fibers was investigated for various water-organic solvent mixtures at different operating conditions. It was found that flux and separation factor increased with a decrease of the dielectric constant of the organic solvent. When the temperature of the process was increased, the flux increased. At feed temperatures of 65–70°C it was possible to reduce the water concentration in a 3–10% isopropyl alcohol (IPA) solution to 0.5%. The energy requirement for decreasing the water concentration in IPA from 3–10% to 0.5% was 100–225 kWh ton-1. Keywords: Solvent dehydration, pervaporation, anion exchange hollow fibers, dielectric constant. Download Full Article |