A study on the performance and morphology of multicomponents hollow fiber ultrafiltration membrane (original) (raw)
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Separation and Purification Technology, 2006
The objective of this study is to determine the effects of dope extrusion rate (DER) on polyethersulfone hollow fiber ultrafiltration membrane performance and morphology. The hollow fiber ultrafiltration membranes were produced by using a simple dry/wet spinning process with forced convection in the dry air gap. A newly developed dope solution consists of 20.6 wt.% polyethersulfone (PES), 63.6 wt.% 1methyl-2-pyrrolidone (NMP), 9.3 wt.% polyethylene glycol (PEG) and a mixture of potassium acetate and water (20/80 wt.%) was used as a bore fluid in this study. This newly developed dope solution was designed to be very close to its cloud point (binodal line) in order to speed up the coagulation process so that the relaxation effect on molecular orientation can be reduced. The dope extrusion rate was varied from 2.0 to 4.0 cm 3 /min with 0.5 cm 3 /min increments in order to study the effect of DER on fiber performance and morphology. The experimental results showed that the flux of the hollow fiber ultrafiltration membranes decreases while the separation performance for particular solute increases with an increase in dope extrusion rate. This suggests that the outer skin layer of the membranes becomes apparently thicker and denser with increasing dope extrusion rate. Once the separation performance reaches maximum (critical point), the rejection decreases with increasing dope extrusion rate, observed possibly due to formation of less tighten outer skin structure at high dope extrusion rate. Plane-polarized Fourier transform infrared spectroscopy revealed that membrane spun at dope extrusion rate of 3.5 cm 3 /min showed largest spectrum difference suggesting that higher molecular orientation is responsible for an enhanced separation performance. This study also indicated that ultrafiltration hollow fiber membrane produced has a high potential to be used for cyclodextrin separation.
Membranes
In this work, PPSUs with different molecular weights were synthesized for the development of highly permeable ultrafiltration hollow fiber membranes for the first time. The MW of the synthesized polymers was controlled by varying the monomers molar ratio within 1:1–1.15 under the same synthesis conditions. Based on the study of the rheological properties of polymer solutions, a high molecular weight PPSU (MW = 102,000 g/mol) was chosen for the formation of hollow fiber membranes. The addition of PEG400 to the spinning solution led to an increase in viscosity, which makes it possible to work in the region of lower PPSU concentrations (18–20 wt. %) and to form membranes with a less dense porous structure. With the addition of PEG400 to the spinning solution, the membrane permeance increased sharply by more than two orders of magnitude (from 0.2 to 96 L/m2·h bar). At the same time, the membranes had high rejection coefficients (99.9%) of Blue Dextran model filtered substance (MW = 69,0...
Malaysian Journal of Fundamental and Applied Sciences
Asymmetric, porous ultrafiltration polysulfone (PSf) hollow fiber membranes were fabricated via the dry-wet phase inversion spinning technique specifically for haemodialysis membrane. The objective was to discover the suitable spinning condition for the fabrication of ultrafiltration hollow fiber membrane with desired sponge-like structure. During haemodialysis procedure, uremic toxins such as urea and creatinine range from size 10,000-55,000 Da needs to be excreted out from the blood. While, proteins such as albumin (66,000 Da) need to be retained. The physical structure or morphology of a fabricated membrane is a major concern in determining the efficiency of a dialysis membrane. Different type of membrane morphology will give a different result in term of its permeability and clearance efficiency. The phase inversion spinning technique is suitable in producing ultrafiltation (UF) membrane where the average pore size of the fabricated membrane is in the range of 0.001 – 0.1 µm. Ho...
Desalination, 2002
Hollow-fiber membranes were prepared by the dry/wet spinning technique from polyvinylidene fluoride (PVDF) dope solutions containing the solvent N, N-dimethylacetamide and the non-solvent additive 1,2-ethanediol. Ethanol aqueous solution, 50% by volume, was used as internal and external coagulants. The effect of the non-solvent additive concentration on the morphological properties of the hollow fibers was studied in terms of atomic force microscopy (AFM) and scanning electron microscopy (SEM). The pore size, the nodule size and the roughness parameters at the inner and outer surfaces of the hollow fibers were studied by AFM. The liquid entry pressure of water (LEPw) and the porosity of the hollow fibers were evaluated. The pore size was also determined by the gas permeation test and by the solute transport using ultrafiltration of polyethylene glycol (PEG) and polyethylene oxides (PEO). A comparative study was made between the membrane characteristics parameters obtained from the different characterization techniques.
Journal of Applied Polymer Science, 2012
Poly(vinyl chloride) (PVC) hollow-fiber membranes were spun by a dry/wet phase-inversion technique from dopes containing 15 wt % PVC to achieve membranes with different pore sizes for ultrafiltration (UF) applications. The effects of the N,N-dimethylacetamide (DMAc) concentration in the internal coagulant on the structural morphology, separation performance, and mechanical properties of the produced PVC hollow fibers were investigated. The PVC membranes were characterized by scanning electron microscopy, average pore size, pore size distribution, void volume fraction measurements, and solubility parameter difference. Moreover, the UF experiments were conducted with pure water and aqueous solutions of poly(vinyl pyrrolidone) as feeds. The mechanical properties of the PVC hollow-fiber membranes were discussed in terms of the tensile strength and Young's modulus. It was found that the PVC membrane morphology changed from thin, fingerlike macrovoids at the inner edge to fully spongelike structure with DMAc concentration in the internal coagulant. The effective pores showed a wide distribution, between 0.2 and 1.1 lm, for the membranes prepared with H 2 O as the internal coagulant and a narrow distribution, between 0.114 and 0.135 lm, with 50 wt % DMAc. The results illustrate that the difference in the membrane performances was dependent on the DMAc concentration.
Journal of Membrane Science
Polyethersulfone (PES) hollow fiber ultrafiltration (UF) membranes were fabricated using methanol, ethanol, n-propanol as well as water as additives and N-methyl-2-pyrrolidone (NMP) as a solvent. Asymmetric hollow fiber UF membranes were spun by wet and dry/wet phase inversion method from 18 wt.% solids of PES/non-solvent/NMP solutions. The non-solvents were methanol, ethanol, n-propanol and water while the external coagulant was water. Effects of non-solvent and ethanol concentrations in the dope solution and air-gap distance on morphology and separation performance of PES hollow fiber UF membranes were investigated. UF membranes were characterized in terms of their solubility parameter difference, pore size and pore density measurements, scanning electron microscope (SEM) while UF experiments were conducted using polyethylene glycol (PEG 10,000 M W) and two kinds of proteins, lysozyme (14,400 M W) and chicken egg albumin (CEA 45,000 M W) as a solute. It was found that the PES UF membrane morphology changed slowly from long and wide finger-like structure through a thin finger-like structure to the sponge-like structure with some voids as ethanol concentration in the dope solution increased from 0 to 25 wt.% using 90:10 NMP/H 2 O as a bore fluid; pure water permeation fluxes (PWP) increased from 47 to 167 L/(m 2 •h•bar) while rejections of PEG 10,000 and two protein for wet-spun PES hollow fiber membranes were increased within less than 10 wt.% ethanol concentration and then decreased with an increase of ethanol concentration. Experimental results illustrated that PWP flux and solute rejection of the dry/wet-spun fibers were higher than that of the wet-spun fibers when 15 wt.% ethanol and 15 wt.% methanol were used as additives. PWP flux of PES hollow fibers using 25 wt.% n-propanol and 7.5 wt.% water (dry/wet) as additives in the dope solution were higher while their rejections were lower. In addition, the pore sizes of internal surfaces of PES hollow fiber membranes were controlled by adjusting the ethanol or methanol concentration in the dope solution. Using above method, PES hollow fiber UF membrane with high PWP could be prepared while the molecular weight cutoff of PES hollow fiber membranes is approximately 10,000.
Hollow fiber ultrafiltration membranes prepared from blends of poly (vinyl chloride) and polystyrene
Desalination, 2012
Polymeric blend ultrafiltration membranes based on poly(vinyl chloride) (PVC) and polystyrene (PSR) were prepared by phase inversion method. The PSR concentration in dope solution varied from 1 to 6 wt.%. DMAC was used as a solvent, while water was used as internal and external coagulant. Scanning electron microscope (SEM) was utilized to characterize cross-section, outer, and inner surfaces of the hollow fiber structure. Differential scanning calorimetry (DSC) was used for the determination of the glass transition temperature (Tg) of the blends. From the experimental results it was found that, the structural morphology of the polymeric blend varied with the PSR concentration. There is no significant decrease in pure water permeation flux by using 1 and 2 wt.% PSR concentration in dope solution. The PVP K-90 rejection highly improved from 76.2% to 98.53% with the addition of 1 wt.% PSR concentration. The PVC/PSR blends show incompatibility by the results of SEM and DSC. Also it was found that the mechanical properties of PVC/PSR blend membranes were improved randomly compared with that of PVC membrane.
Separation Science and Technology, 2011
Hollow fiber poly (vinyl chloride) membranes were prepared by using the dry/wet spinning method. Cross-section, internal and external surfaces of the hollow fibers structure were studied by SEM. The pore size and pore size distribution of the hollow fibers were measured by a PMI capillary flow porometer. UF experiments of pure water and aqueous solution of PVP K-90 were carried out. The effect of the PVC concentration on the hollow fibers mechanical properties was also investigated. It was found that the PVC fibers cross sectional structure was affected by the polymer concentration in the dope solution. In particular, reduction of macrovoids size was observed when increasing PVC concentration from 15 to 19 wt%. The pore size distribution of the PVC hollow fibers was controlled by adjusting the PVC concentration. Indeed, an increase of PVC concentration up to 19 wt% leads to fibers with sharp pore size distribution (the 99% of pores is about 0.15 µm).The pure water permeation flux decreased from 162 to 128 (l/m · h · bar), while the solute separation performance increased from 82 to 97.5%, when increasing the PVC concentration. The elongation at break, the tensile strength and the Young's modulus of the PVC hollow fibers were improved with PVC concentration in dope solution.
2008
Hollow fiber ultrafiltration (UF) membranes were prepared using Polyethersulfone (PES), alcohol (n-Propanol) as additive and N, N-dimethylacetamide (DMAc) as a solvent. Asymmetric hollow fiber UF membranes were spun by wet phase inversion method from 17 wt% solids of PES/additive/NMP solutions. The alcohol additive was n-Propanol while the external coagulant was water. Effects of n-Propanol concentrations in the dope solution on morphology and separation performance of PES hollow fiber UF membranes were investigated. UF membranes were characterized in terms of scanning electron microscope (SEM) while UF experiments were conducted using polyethylene glycol (PEG20,000MW) and poly (vinyl pyrrolidone) (PVP 40,000MW), as a solute. It was found that the PES UF membrane morphology changed from long two finger-like structure through a short two finger-like structure to the two void-like structure as n-propanol concentration in the dope solution increased from 5 to 20 wt % using water as a b...
Preparation, characterization, and performance of a novel hollow fiber nanofiltration membrane
Polymers for Advanced Technologies, 2015
Two generations of aliphatic hyperbranched polyester (HBPE) were synthesized from 2,2-bis(methylol)propionic acid and 1,1,1-trihydroxymethyl propane (TMP) as the core moiety by melt condensation method and were blended with cellulose acetate to prepare asymmetric membrane using a phase inversion process. Characterization of the prepared membranes for thermal behavior and morphological studies also has been made using TGA, DSC and SEM techniques. Water contact angle, pure water flux, water content, hydraulic resistance and molecular weight cutoff determinations were applied in order to study of filtration properties and surface and bulk hydrophilicity of the membranes. (FTIR/ATR) and contact angle results proved existence of (HBPE) on the surface of modified membranes and (FE-SEM) images have good correlation with flux and MWCOs. The result shows that, the surface hydrophilicity of membranes incorporating HBPE is much higher than pure CA or even (PEG-600) modified CA membranes. Furthermore, results show CA-HBPE membranes have lower flux and MWCOs, higher hydraulic resistance and better thermal and mechanical properties in comparison to the membranes modified by linear pore-forming agent.