Cellulose acetate and polyetherimide blend ultrafiltration membranes: II. Effect of additive (original) (raw)
Related papers
Journal of Membrane Science, 2003
Phase inversion polyetherimide (PEI) flat sheet membranes were surface modified using fluorinated surface modifying macromolecules (SMMs) additives. Two SMM formulations were used. Each SMM was blended into polyetherimide casting solutions containing the solvent N,N-dimethyleacetamide and the non-solvent hydroxybutyric acid γ-lactone (GBL). The effects of the SMM and the PEI base polymer concentrations on the morphological properties of the prepared membranes have been investigated. Contact angle measurements indicate that PEI membrane surface becomes more hydrophobic after adding the SMMs to the PEI casting solutions, while X-ray photoelectron spectroscopy analysis shows enrichment of fluorine on the PEI membrane surfaces. The SMM modified and unmodified PEI membranes were also characterized by means of atomic force microscopy (AFM), gas permeation tests and ultrafiltration experiments using aqueous solutions of polyethylene glycol (PEG) and polyethylene oxide (PEO) of various molecular weights. Pore sizes and nodule sizes obtained from AFM images were remarkably fitted to the log-normal probability distribution curves. Mean pore sizes, pore size distributions, nodule sizes, nodule size distributions and roughness parameters of the membranes were determined. It was found that SMM actively migrated to the air surface and changed the surface properties of the PEI membranes. The mean pore size and the molecular weight cut-off (MWCO) of the SMM modified PEI membranes were lower than those corresponding to the unmodified membranes, while the nodule sizes were larger. The surface roughness parameters were reduced when SMMs were added.
Journal of Materials Science, 2020
The study covers the fundamental relationships between the nature of aprotic polar solvents [N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF) and dimethylsulfoxide (DMSO)] used for casting solution preparation and the structure and performance of poly (amide-imide) (PAI) ultrafiltration membranes. It was found that the distinctive feature of the ternary systems PAI-poly(ethylene glycol) (PEG-400, M n = 400 g mol-1) solvent is gel formation upon the increase in PEG-400 concentration in the solution. The PEG-400 addition to the casting solution was shown to increase pure water flux of the PAI membranes prepared from the casting solutions in different solvents. However, different patterns of the change of pure water flux when gel point is exceeded in PAI-PEG-400-solvent system were revealed. The PAI membranes obtained from the ternary systems PAI-PEG-400-solvent were found to combine high pure water flux at P = 0.1 MPa (130 L m-2 h-1 for DMSO, 120 L m-2 h-1 for DMA and 70 L m-2 h-1 for NMP) and high poly(vinylpyrrolidone) (PVP) rejection coefficients: 98-99% for PVP with M n = 40000 g mol-1 and 86-95% for PVP with M n = 10000 g mol-1. SEM studies reveal the significant difference in the PAI membrane structure when different solvents are used for casting solution preparation. The structure of the membranes obtained from 20 wt% PAI solutions in NMP and DMA consists of the thin selective layer supported by substructure pierced by elongated macrovoids. Meanwhile, when DMSO and DMF are used as solvents the addition of PEG-400 yields the suppression of macrovoid formation and anisotropic sponge-like membrane structure is obtained.
Polymer Membranes for Sustainable Technologies
Membrane-based processes have found wide acceptance and are used as powerful alternatives for conventional techniques such as distillation, extraction, or energy production. Frequently, membranes prepared from commodity polymers do not have the desired properties for the various applications. For example, fouling is still an unsolved problem in membrane applications, which is closely related to surface properties of both the membrane and the foulant. To meet the requirements for the various tasks, membranes with tailor-made properties are needed. In this contribution on the one hand surface modification techniques are described, which are used to (a) obtain microfiltration membranes with low-fouling tendency and (b) to prepare membranes with required properties in pervaporation separation applications. On the other hand modification/functionalization of polymers for use as ion-exchange membranes in energy-producing systems (fuel cells) are discussed. The focus is set on surface modification with polyelectrolytes and polyelectrolyte multilayer systems. This versatile technique enables the preparation of porous membranes with adjustable surface charge and low-fouling tendency without interference of permeate quality. Dense pervaporation membranes based on polyelectrolyte multilayer systems, with high selectivities and moderately high flux were obtained. The performance of such membranes can be controlled by the polyelectrolytes used (charge density) and the preparation conditions (e.g. temperature). Finally, a short introduction of new membrane materials based on fully aromatic polymers as alternatives to perfluoroalkylsulfonic acids, such as Nafion, is given.
Journal of Membrane Science, 1983
Electron spin resonance technique was used to study the structure and transport of the asymmetric polyethersulfone (PES) membranes. 2,2,6,6-tetramethylpiperridinyloxy (TEMPO) free radical was used as a spin probe that was brought into the membrane either by ultrafiltration experiments with feed solutions involving TEMPO, or by blending TEMPO into casting solutions. Ultrafiltration experiments were further carried out with polyethylene oxide feed solutions with and without TEMPO. It was found that two types of radicals exist in studied PES membranes, one located in the membrane pore and the other, which diffused into the polymer matrix. Unlike cellulose acetate (CA) membranes, which are more hydrophilic and swollen by water, the second type of radicals in PES membranes could not be leached out even after 24 h immersion in water. It seems that both pores and the water channels through the swollen polymer matrix contribute to the transport of water in CA membranes. On the other hand, the transport of water in PES membranes is primarily through pores and the contribution of the little swollen polymer matrix is insignificant.
Methacrylamide was grafted on to poly (isophthalamide) (PIPA-g-MAA) to improve its solubility and hydrophilicity. Then, PIPA-g-MAA incorporated high performance cellulose acetate ultrafiltration (CA) membranes were prepared by phase inversion technique and physical properties of the membranes were studied by various analytical methods. The efficiency of these membranes in the removal of arsenic from aqueous stream was studied and an effort has been taken to correlate the separation efficiency with morphology. Overall results suggest that membrane hydrophilicity, structure and performance were improved significantly by the addition of PIPA-g-MAA. Thus PIPA-g-MAA can be considered as an effective modification agent for CA membranes.
A Comprehensive Review of Polymeric Wastewater Purification Membranes
Journal of Composites Science, 2021
Synthetic membranes are currently employed for multiple separation applications in various industries. They may have been prepared from organic or inorganic materials. Present research majorly focuses on polymeric (i.e., organic) membranes because they show better flexibility, pore formation mechanism, and thermal and chemical stability, and demand less area for installation. Dendritic, carbon nanotube, graphene and graphene oxide, metal and metal oxide, zwitter-ionic, and zeolite-based membranes are among the most promised water treatment membranes. This paper critically reviews the ongoing developments to utilize nanocomposite membranes to purify water. Various membranes have been reported to study their resistance and fouling properties. A special focus is given towards multiple ways in which these nanocomposite membranes can be employed. Therefore, this review provides a platform to develop the awareness of current research and motivate its readers to make further progress for u...
Journal of Membrane Science, 2005
Charged UF/NF membranes have been developed by phase inversion. The membranes were prepared with polyetherimide (PEI) and sulfonated poly(ether ether ketone) (SPEEK). SPEEK was used to improve the hydrophilic properties and permeability of the PEI membrane, as well as to provide surface charges. The membrane properties were reproducible when the proportions of SPEEK were ∼3.0% and ∼6.0% in the total blend of polymers. With the increase of SPEEK from 3% to 6% in the casting solution, water permeability increased from 24.0 ± 2.1 × 10 −11 to 36.6 ± 3.0 × 10 −11 m 3 s −1 N −1 , rejection of sodium chloride and PEG 1500 increased from 0.399 to 0.599, and 0.600 to 0.931, respectively (as measured at 100 kN m −2 ). SEM cross-sectional images showed a top layer with a sponge-type structure and a support layer with a finger-like structure. With the addition of tetrahydrofuran (THF) and 1,4-dioxane to the casting solution, water permeability decreased, rejection of PEG 1500 decreased and rejection of NaCl was generally little changed.
Chemical Engineering Journal, 2011
Polyamidehomopolymer and block copolymernanocomposites were prepared by melt processing using a co-rotating Leistritz twin screw extruder. The polymers used werepolyamide 11 (PA11) and poly (ether-block-amide), Pebax 7233. Commercially available nanoclay, Cloisite 30B was chosen as the nanofiller in this study. Particular emphasis was placed on better defining the morphological and performance characteristics of the nanocomposites prepared.Analytical techniques such as X-ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and short-term mechanical tests were employed to characterise the nanocomposite materials.XRD analysis confirmed an exfoliated structure for PA11 nanocomposite at low loading whereas for Pebax 7233, an increase in d 001 spacing suggests an intercalated structure exists. There was no significant change in melting temperature for PA11 and Pebax 7233 due to nanoclay addition; however, the crystallinity was found to decrease as measured by DSC.The performance characteristics of both nanocomposites systems were established using short-term tensile and DMA techniques.A significant increase in storage modulus was observed for both nanocomposite systems investigated.
Journal of Polymer Engineering
The transport phenomena across polymeric membrane may be enhanced by applying various strengths inside or outside the system. Recently, polymer inclusion membrane (PIM) has been considered one of the most popular methods that acts as a sink for the contaminant and immobilizes it. In the literature, there is no report about how to achieve the synthesis of multi-layer PIMs. In this paper, an improvement of a novel category of membrane without carrier for performing ion separation is reported. Different membranes were elaborated from binary mixtures of polymers, cellulose triacetate (CTA), polymethyl methacrylate (PMMA) and polyvinyl chloride (PVC) using 2-nitrophenyl octyle-ether (NPOE) as plasticizer and carrier in the same time, in order to increase specific interactions between the different polymers. The membranes (Polymer 1– NPOE – Polymer 2) were synthesized by phase inversion method modified by changing the procedure of a plasticizer/carrier addition and characterized by FTIR, ...