Papers by Keyword: Composite Membrane

Abstract: Modification of polymer solution with various additive is generally conducted to improve the membrane performance. In this study, we investigate the modification of Polyvinylidene fluoride (PVDF) membranes by addition of cellulose nanocrystals (CNC) into polymer solution. The effect of the addition of 0.5 wt% of CNC was studied in detail on the membrane structure, water content, and its filtration performance. The water content of the modified PVDF membrane with CMCs was higher than that of the pristine PVDF membrane. Pure water flux shows a similar trend with the addition of 0.5wt% CNC, which correlates with the results of porosity and membrane swelling tests. The increase in water content, permeability, porosity, and swelling indicates an improvement in the antifouling properties of the membrane. This research provides insight that the addition of CNC enhances the performance of PVDF polymer membranes for use in water treatment.

Abstract: The paper presents a comparison of the techniques for polydecylmethylsiloxane selective layer coating to the inner and outer sides of a polysulfone hollow fiber support. It has been shown that coating to the outer side allows one to obtain a composite membrane with a higher selectivity for CO₂/N₂ vapor. A decrease in the number of defects in the selective layer is achieved by increasing the viscosity of the polydecylmethylsiloxane solution. The resulting membrane was characterized in the separation of a model mixture of hydrocarbons, and a high separation selectivity was shown - 12.4 with respect to the n-butane / methane gas pair.

Abstract: Membrane technologies are currently among the most demanded. This is evidenced by their variety and a wide range of membrane applications in the most topical areas of human life. This work proposes a simple and inexpensive method for producing composite membranes for ultrafiltration and nanofiltration with a surface layer of cellulose acetate for water purification and water treatment processes. A nylon microfiltration membrane was used as a membrane base. The surface layer was obtained by immersion in a solution of cellulose acetate in acetone. Composite membranes with different retention properties were obtained depending on the number of deposited layers. The resulting membranes were examined for total porosity, water absorption, cellulose acetate content, contact angle, and IR absorption spectra. The specific productivity of the obtained membranes with respect to distilled water was also established.

Abstract: The operating efficiency of asymmetric porous and composite membranes with a thin non-porous selective layer was compared in the processes of CO₂ absorption and desorption in gas-liquid membrane contactors using aqueous solutions of monoethanolamine (MEA) with low concentration (<14 %). Composite membranes were prepared by direct deposition of poly (1-trimethylsilyl-1-propyne) (PTMSP) in a hollow fiber membrane module. The effects of gas flow rate and MEA solvent linear velocity on the CO₂ mass transfer were evaluated. Porous membranes were shown to be more effective in the process of CO₂ absorption, because they allow to remove more than 90 % of CO₂ from the gas mixture during one pass of the solvent through the contactor. Composite membranes were more promising for CO₂ desorption, since they provide half as much of the solvent vapor losses with comparable desorbed CO₂ fluxes (0.12-(STP)/(m²·h)). The contributions of membrane and liquid phase to the overall mass transfer resistance during the CO₂ absorption process were estimated. It was demonstrated that deposition of a thin selective layer from a highly permeable PTMSP with a thickness of only 3 μm increases the membrane contribution to the total mass transfer resistance from 10-20 % to 60-80 %.

Abstract: A method of composite membrane obtaining effects on its transport properties. In the present work, for the first time, the influence of the method of applying a selective layer of polyheptylmethylsiloxane on the composite membrane pervaporation properties in the process of alcohol separation from water was studied. The comparison of two casting methods (kiss-coating and spin-coating) was conducted. Morphology of the obtained membranes and their separation properties during the pervaporation of the mixture of C₂-C₄ alcohols and water. It was shown that kiss-coating allows completely prevent leakage of the selective layer into the substrate pores. And, such a way, it allows to improve permeability of composite membrane (BuOH - 3.5 mol/(kPa·h·m2)). Besides, spin-coating method leads to higher selectivity (BuOH/H₂O - 2.3). It is caused by blocking the swelling of that part of the selective layer that is locked in the pores of the substrate. Thus, the choice of the casting method can determine the compatibility of the composite membrane with a specific separation task.

Abstract: In recent years, membrane separation technology has emerged as efficient and promising separation process from laboratory scale applications to wide range of technical industrial applications. The development of composite asymmetric membrane is a major breakthrough in membrane research field, as this membrane offers significantly high selectivity without affecting the mechanical durability of the membranes. In this chapter, structural characteristics and different fabrication techniques of composite membranes are reviewed. Moreover the mass transfer mechanism through the composite asymmetric membrane is described in details following solution-diffusion theory, Knudsen diffusion, and series resistance model. Composite membranes are preferred over others because of the high flux and enhanced selectivity without disturbing the mechanical stability of the membranes. These membranes are now widely employed in the applications of reverse osmosis (RO), nanofiltration (NF), pervaporation, gas separation, hydrocarbon fractionations, etc. As composite asymmetric membranes are “tailor-made” in nature, membrane characteristics can be tuned accordingly depending on their end use. Therefore plentiful research opportunities still exist to elevate their performance ability in terms of stability, selectivity and fouling resistance, which will in turn augment its application domain.

Abstract: In this paper, the effect of adding modified graphene nanoplatelets (MGNPs) as a filler on the characteristics and performance of Polyvinylidene fluoride (PVDF) membrane in a direct contact membrane distillation (DCMD) configuration was investigated. Both pure PVDF and PVDF/MGNPs composite (2%) membranes were fabricated by using electrospinning technique. The fabricated membranes were characterized using different analyses techniques such as SEM imaging, XRD analysis, static water contact angle as well as membrane porosity and liquid enter pressure measurements. Also, the average fiber diameter and the average membrane pore diameter were estimated using ImageJ software. The prepared PVDF/MGNPs composite membrane exhibited lower fiber diameter by about 5.7%, whereas the contact angle increased by 10 and liquid entry pressure increased by 11.7%. The membrane also showed an enhanced flux that reached about 19.8 kg/m²∙h at feed inlet temperature of 65°C, feed flow rate of 30 l/h. and feed inlet concentration of 10000 ppm. This represents about 13.46% improvement over the pure PVDF membrane at the same conditions. The produced membrane presents a viable alternative to commercial MD membranes.

Abstract: This study was conducted to characterize the industrial wastewater containing Copper (II) ion and to evaluate the effect of different thickness of polysulfone as the support membrane in the fabrication of thin film composite membrane (TFC), on the removal of Copper (II) ion. From the wastewater analysis, it showed that the concentration of copper (II) ion are out of the acceptable range of Environmental Quality (Industrial Effluent) Regulations 2009. For the TFC, the polysulfone support membrane was prepared at two thicknesses, 60μm and 90μm. For each thickness, two formulations of thin layer were coated on it; i) A polymer blend of Polyvinyl Alcohol and Chitosan, and ii) Hybrid membrane as thin layer. Before undergo the treatment process, the pH of the wastewater sample was altered to 7 as the pre-treatment. The final result shows that composite membrane with hybrid membrane as thin layer with 90μm thickness of polysulfone membrane was the best membrane because it could remove 99.67% of copper (II) ion. Finally, the treated water can be discharged to the groundwater because the concentration of copper ion is less than 1 ppm, which it has fulfilled the Environmental Quality regulations. Keywords— Chitosan, Copper ion, composite membrane, hybrid membrane, industrial wastewater

Abstract: In order to enhance the surface anti-fouling property of separation membrane, TiO2/polysulfone (PSF) membrane was prepared by the phase inversion method, and the surface was treated by oxygen plasma to obtain a composite membrane with photo catalysis activity. To evaluate the effect of oxygen plasma on the surface modification, positron annihilation γ-ray spectroscopy coupled with a positron beam was utilized to probe the surface feature, while the catalysis evaluation system was employed to study the anti-fouling activity of the membrane. The results indicate that with increasing plasma treatment time, the membrane exhibits higher S parameter in the lower energies, while the photo catalysis activity is strengthened. It can be concluded that plasma technique can improve the photo catalysis activity of the composite membrane.

Abstract: The use of inorganic composite membranes in chemical industries has received a lot of attention more recently due to a number of exceptional advantages including thermal stability and robustness. Inorganic membranes can selectively remove water from the reaction mixture during esterification reactions in order to enhance product formation. The characterisation of inorganic composite membranes used in this work including the determination of the pore diameter and specific surface area was performed using Liquid Nitrogen adsorption at 77 K. The membrane was modified once. The permeation test for the single gases including carbon dioxide (CO₂), helium (He), nitrogen (N₂) and argon (Ar) through the inorganic composite ceramic membrane was carried out at the gauge pressure range of 0.10 – 1.00 bar and at the temperature of 393 K. The order of the gas molecular weight was He < N₂ < CO₂ < Ar. The BET surface area of the dip-coated silica membrane showed a type IV isotherm characteristic of mesoporous structure with hysteresis. The BJH curve of the silica-membrane was in accordance with mesoporous classification.