Cellulose Acetate Hollow Fiber Membranes Research Articles

Facile method to fabricate robust homogeneous braid-reinforced cellulose acetate hollow fiber membranes with enhanced physiochemical properties

Facile method to fabricate robust homogeneous braid-reinforced cellulose acetate hollow fiber membranes with enhanced physiochemical properties

Cellulose acetate/nanoclay composite membranes with enhanced mechanical properties and improved permeance in gas separation

AbstractDiethyl ether is a valuable chemical product in petrochemical industry used in different applications. In diethyl ether (DEE) production by the dehydration of ethanol (EtOH), the products from DEE production are commonly mixed with EtOH and the % yield of DEE generally has not exceeded 60%. This contribution describes the preparation and performance of hollow fiber membranes for the separation of gaseous product (DEE) and reactant (EtOH). Cellulose acetate (CA)/nanoclay (NC)‐based hollow fiber composite membranes were prepared using a wet spinning process of CA solution and the addition of hydrophilic NC particles to improve the mechanical properties and permeability. According to the findings, the 20 wt% CA/0.5 wt% NC hollow fiber showed the higher mechanical strength than the 20 wt% CA hollow fiber without NC. Moreover, the 20 wt% CA hollow fiber without NC provided EtOH and DEE permeances of 8.44 × 10−11 and 4.25 × 10−10 mol m−2 s−1 Pa−1, respectively, while the 20 wt% CA/0.5 wt% NC hollow fiber showed higher EtOH and DEE permeances of 6.50 × 10−10 and 8.49 × 10−9 mol m−2 s−1 Pa−1 plausibly because of the higher porosity based on the SEM images. Furthermore, both CA hollow fiber membranes were selective for DEE over EtOH and were more selective with the addition of NC.

Cellulose Acetate Hollow Fiber Membranes from Banana Stem Fibers Coated by TiO2 for Degradation of Waste Textile Dye

Cellulose acetate hollow fiber membrane from banana stem fibers coated by TiO2 (CAHFMT) was prepared and characterized as an alternative material for degradation of waste textile dye. Its applicability was demonstrated by mechanical properties, FTIR, SEM, thermal resistance, performance, and degradation efficiency. Cellulose acetate (CA) was synthesized from banana stem fibers by swelling stage, acetylation reaction, and hydrolysis reaction. CA was modified using TiO2 of various concentrations. CAHFMT with 22 % w/v dope concentration has the optimum mechanical properties (stress, strain and Young’s modulus), as well as hydrophilic properties. The performances of CAHFMT with Congo red were determined. The SEM results showed that the membrane had rigid pores. Moreover, this research stated that CAHFMT could be a solution to overcome economical and effective problems.

A cell retention system composed of cellulose acetate hollow fiber membranes for cultivation of Dunaliella salina in a helical photobioreactor

AbstractBackgroundOne of the challenges in commercial‐scale cultivation of Dunaliella salina is low biomass productivity and concentration. In addition, cultivations in wastewaters may encounter some nutrient limitations. Hence, there is a need for a cultivation system which is capable of continuous provision of nutrients while the cells are retained in the system. In this study, the feasibility of using a cell retention system (CRS) for increasing biomass productivity and concentration of D. salina was investigated. The CRS was composed of cellulose acetate hollow fiber membranes (HFMs) coupled with a helical photobioreactor.ResultsUsing the produced HFMs with mean pore size of 124 nm and overall porosity of 78.9%, the rejection of D. salina microalgae was as high as 93.2%. Continuous cultivation of D. salina in the helical photobioreactor at a dilution rate of 0.48 day−1 resulted in a biomass productivity (concentration) of 4.9 × 107 cells L−1 h−1 (2.7 × 106 cells mL−1). Interestingly, cultivation at the same initial dilution rate (0.48 day−1) in the helical photobioreactor coupled with the CRS resulted in a biomass productivity (concentration) of 9.3 × 107 cells L−1 h−1 (6.7 × 106 cells mL−1).ConclusionsThe results revealed the potential of the proposed system for enhancing biomass productivity by 90% and biomass concentration by more than twofold. The cultivation system is also proposed as a potential tool for cultivations in wastewaters. © 2019 Society of Chemical Industry

Effect of spinning conditions on the fabrication of cellulose acetate hollow fiber membrane for CO2 separation from N2 and CH4

In the current work, effect of spinning conditions including, take-up speed and air-gap distance and post-treatment methods on the fabrication of cellulose acetate hollow fiber membranes (CA-HFMs) for CO2/N2 and CO2/CH4 separations have been reported. The gas permeation results obtained in this work revealed that permeances of gases were decreased with increase in take-up speed from free fall to 12.2 m/min. Meanwhile, gas pair selectivities increased with increasing take-up speed. Subsequently, increment in air-gap distance produced the “V” pattern for gases permeances and “A” pattern of gas pair selectivities for all CA-HFMs spun at different take-up speeds. Therefore, optimum take-up speed and air gap distance of CA-HFMs of 12.2 m/min and 5.0 cm were obtained, respectively. CA-HFM spun at optimum spinning conditions showed the highest CO2/CH4 and CO2/N2 ideal selectivities of 7.9 and 6.0, respectively. On the other hand, permeation results also demonstrated that the CO2/CH4 and CO2/N2 ideal selectivities of PDMS coated CA-HFMs were higher about 70.9% and 84.1%, respectively, compared to those values obtained from thermally treated CA-HFMs. Therefore, PDMS coating is considered as an effective approach to seal the macro-voids of HFMs compared to the thermal treatment in order to achieve higher permeation performance for CO2 separations. In addition, permeation results also manifested that the CA-HFM fabricated at optimum conditions has incredible worth from the prospective of industrial separations of CO2 from flue and natural gas.

Separation of biogas using newly prepared cellulose acetate hollow fiber membranes

The highly selective cellulose acetate (CA) asymmetric hollow fiber membranes were prepared via a dry/wet spinning process with NIPS from dope solutions containing NMP as a solvent and THF and EtOH as a non-solvent and coated with PDMS. The prepared CA hollow fiber membranes showed excellent selectivity about 37.0 for CO2 and CH4 at optimized condition (23 wt% CA, 62 wt% NMP, 10 wt% THF, 5 wt% EtOH, and 15 cm air-gap) and 5 wt% PDMS coating. The newly prepared CA hollow fiber membranes were applied to CO2/CH4 separation. The newly prepared CA hollow fiber membranes showed much better performance than the existing commercial membranes.

Fabrication of Defect-Free Cellulose Acetate Hollow Fibers by Optimization of Spinning Parameters.

Spinning of cellulose acetate (CA) with the additive polyvinylpyrrolidone (PVP) in N-methyl-2-pyrrolidone (NMP) solvent under different conditions was investigated. The spinning parameters of air gap, bore fluid composition, flow rate of bore fluid, and quench bath temperature were optimized based on the orthogonal experiment design (OED) method and multivariate analysis. FTIR and scanning electron microscopy were used to characterize the membrane structure and morphology. Based on the conjoint analysis in Statistical Product and Service Solutions (SPSS) software, the importance of these parameters was identified as: air gap > bore fluid composition > flow rate of bore fluid > quench bath temperature. The optimal spinning condition with the bore fluid (water + NMP (85%)), air gap (25 mm), flow rate of bore fluid (40% of dope rate), and temperature of quench bath (50 °C) was identified to make high PVP content, symmetric cross-section and highly cross-linked CA hollow fibers. The results can be used to guide the spinning of defect-free CA hollow fiber membranes with desired structures and properties as carbon membrane precursors.

Modification of braid-reinforced cellulose acetate hollow fiber membrane by doping graphene oxide

Modification of braid-reinforced cellulose acetate hollow fiber membrane by doping graphene oxide

The Effect of Membrane Material and Surface Pore Size on the Fouling Properties of Submerged Membranes

We aimed to investigate the relationship between membrane material and the development of membrane fouling in a membrane bioreactor (MBR) using membranes with different pore sizes and hydrophilicities. Batch filtration tests were performed using submerged single hollow fiber membrane ultrafiltration (UF) modules with different polymeric membrane materials including cellulose acetate (CA), polyethersulfone (PES), and polyvinylidene fluoride (PVDF) with activated sludge taken from a municipal wastewater treatment plant. The three UF hollow fiber membranes were prepared by a non-solvent-induced phase separation method and had similar water permeabilities and pore sizes. The results revealed that transmembrane pressure (TMP) increased more sharply for the hydrophobic PVDF membrane than for the hydrophilic CA membrane in batch filtration tests, even when membranes with similar permeabilities and pore sizes were used. PVDF hollow fiber membranes with smaller pores had greater fouling propensity than those with larger pores. In contrast, CA hollow fiber membranes showed good mitigation of membrane fouling regardless of pore size. The results obtained in this study suggest that the surface hydrophilicity and pore size of UF membranes clearly affect the fouling properties in MBR operation when using activated sludge.

Effects of Different Ionic Liquids as Green Solvents on the Formation and Ultrafiltration Performance of CA Hollow Fiber Membranes

In this work, we have examined and compared the interactions between cellulose acetate and different ionic liquids at a molecular level and explored their effects on dope rheology, hollow fiber morphology, and performance. Ionic liquid, 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc), was found to interact with cellulose acetate (CA) more closely with intensive hydrogen bonds than 1-ethyl-3-methylimidazolium thiocyanate ([EMIM]SCN). Thus, the CA/[EMIM]OAc solution exhibits a more pronounced charge-ordered network than the CA/[EMIM]SCN solution. In addition, the former does not obey the Cox–Merz rule, whereas the latter obeys the rule with its shear viscosity η identical to its complex viscosity |η*| at the equivalent shear rate and angular frequency. These dissimilar factors have contributed to an instantaneous liquid–liquid demixing and resulted in a dense outer skin surface and a porous cross-sectional structure comprising macrovoids for the CA/OAc membrane. In contrast, the CA/SCN membrane has a looser...

Direct osmosis process for power generation using salinity gradient: FO/PRO pilot plant investigation using hollow fiber modules

The phenomenon of osmosis is known for more than 150 years and involves the contact of a semi-permeable membrane with solutions of different salinity. The osmotic flux that permeates through the membrane can be used for electric power generation as a renewable source of energy. This process can be accomplished by means of the pressure retarded osmosis (PRO). This work consisted of the construction of a demonstrative FO/PRO power pilot plant. Assymetric polymeric cellulose acetate hollow fiber membranes were produced and conditioned in permeation modules. The pilot plant consists of three countercurrent flow hollow fiber modules connected in parallel. According to the modules and fibers dimensions, the membrane area per module can reach 1.5m2 that means a packing density of 1500m2m−3. The pilot scale enables the activation of a hydroturbine/generator device coupled to a 9-LEDs panel which can establish the technological and scientific bases for further industrial upscaling. A forward osmosis (FO) test using a MgSO4 solution (0.8M, π: 22bar) and an intermittent PRO test using a NaCl solution (0.8M, π: 37bar) were performed, where the maximum osmotic flux values were 33 and 8Lm−2h−1, corresponding to an energy performance of 5 and 2Wm−2, respectively. These values are comparable with most of the latest bench-scale FO membrane investigations.

Structure design and performance study on braid-reinforced cellulose acetate hollow fiber membranes

A novel braid-reinforced (BR) cellulose acetate (CA) hollow fiber membrane consisting of separation layer and ‘hybrid’ braid was reported in this study. The ‘hybrid’ braid containing CA and polyacrylonitrile (PAN) fiber not only provided the membrane well interfacial bonding state but also overcame the negative effect of CA fiber׳s swelling on membrane permeability. The influences of braid composition and CA concentration on the structure and performance of BR CA membranes were investigated. There were two kinds of interfaces between the braid and the separation layer, which were named homogeneous-reinforced (HMR) interface and heterogeneous-reinforced (HTR) interface. Taking into account both interfacial bonding state and membrane permeability, the best ratio of the fibers in the braid was 2/1(CA/PAN). Increased CA concentration brought about reduced permeate flux and increased protein rejection. The BR CA membranes exhibited excellent anti-fouling property with flux recovery rates higher than 80%. The tensile strength of BR CA hollow fiber membranes varied from 16.0MPa to 62.9MPa by adjusting the braid composition. The BR CA membrane showed similar performance with the commercial hydrophilic polyvinylidene fluoride (PVDF) hollow fiber membrane during the filtration of milk solution, and the flux could be recovered by chemical cleaning.

Preparation and performance of homogeneous braid reinforced cellulose acetate hollow fiber membranes

Homogeneous braid reinforced (HBR) cellulose acetate (CA) hollow fiber membranes were fabricated through dry–wet spinning process which consisted of CA separation layer and CA hollow tubular braids. The performance of various CA concentration membranes were characterized in terms of pore size distribution, pure water flux (PWF), protein solution flux (PSF), mechanical strength, and membrane morphologies were observed by a scanning electron microscope. The results showed that the HBR CA hollow fiber membranes, especially with high CA concentration in the dope solutions, possessed dense and smooth outer surface. The tensile strength of HBR CA hollow fiber membranes which exceeded 11 MPa mainly depended on the tubular braids. With the increase of CA concentration, the tensile strength and bursting strength of the membranes increased. In addition, there was effective interfacial bonding state between the separation layer and the tubular braid when the CA concentration was higher than 10 wt%. The increase of CA concentration brought about the decrease of membrane pore size and the increase of protein rejection. Considering the PWF, rejection and stable PSF, the best CA concentration in the dope solutions was 10 wt%. Then the membrane fouling and cleaning processes for the activated sludge solution were studied by comparing with reinforced polyvinylidene fluoride (PVDF) hollow fiber membrane. The lower flux decline in the filtration of activated sludge solution and higher recovery in the flux indicated that the HBR CA hollow fiber membrane had better anti-fouling properties than the PVDF membrane.

Enhanced double-skinned FO membranes with inner dense layer for wastewater treatment and macromolecule recycle using Sucrose as draw solute

Internal concentration polarization (ICP) that occurs in the membrane sublayer is considered a serious problem restricting the performance of forward osmosis (FO) processes. Aiming at reducing ICP and fouling propensity, novel nanofiltration (NF) hollow fiber membranes with two apparently dense skins have been designed from cellulose acetate (CA) for FO applications by manipulating different phase inversion rates and degrees of annealing at the inner and outer layers. For the CA hollow fibers precipitated rapidly and then annealed at the lumen side, the surface pores within the inner skin layer show a very narrow size distribution with a mean radius of 0.34nm. Being also relatively dense, the outer skin layer may keep the feed solutes from entering the sublayer and avoid their accumulation within the sublayer if the feed solutes are macromolecules or multi-valence ions with relatively larger sizes. Thus, the double-skinned FO membrane would have improved performance by suppressing ICP at a cost of additional external concentration polarization (ECP) at the outer surface. In the FO process, the CA hollow fiber membrane with inner selective layer generates a water flux of 17.1LMH (Lm−2h−1) with 2.0M MgCl2 draw solution running at the lumen side of the fibers and DI water feed at the shell side. When using 1.0M Sucrose (26.7bar osmotic pressure) as the draw solution at the shell side and DI water feed at the lumen side, a water flux of 12.9LMH is obtained with a negligible reverse Sucrose flux. This FO performance is comparable to that created by 1.0M MgCl2 draw solution although 1.0M MgCl2 has a much higher osmotic pressure of 93.7bar. With wastewater feed containing 200–2000mgL−1 mixed metal ions at the lumen side and 0.5M Sucrose draw solution at the shell side, water fluxes in the range of 9.9–6.5LMH with minimal reverse Sucrose fluxes are observed. These results have revealed great potential of the newly developed double-skinned CA hollow fiber membranes as well as using Sucrose as the draw solute for wastewater reclamation and macromolecule recycle.

Investigation of unique interactions between cellulose acetate and ionic liquid [EMIM]SCN, and their influences on hollow fiber ultrafiltration membranes

This study investigates the molecular interactions between ionic liquid, 1-ethyl-3-methylimidazolium thiocyanate ([EMIM]SCN) and cellulose acetate (CA), employing not only experimental characterizations including FTIR and rheological tests, but also molecular dynamics simulations. Due to the electrostatic nature of ionic liquids, [EMIM]SCN interacts intensely with CA molecules through pronounced hydrogen bonding, Coulombic forces and van der Waals interactions, which play an important role in dissolving CA and also greatly contribute to the unique rheological characteristics of CA/[EMIM]SCN solutions. The competition between the charge-ordered structure and polymer chain entanglement in the CA/[EMIM]SCN solutions leads to a three-region flow curve under shear stress. The charge-ordered network in CA/[EMIM]SCN solutions as well as the affinity and unique solvent exchange characteristics between non-solvents and [EMIM]SCN are found to greatly influence the phase inversion paths of membranes. In addition, the effects of dope flow rate, dope temperature and air-gap distance on hollow fiber formation have been elucidated and correlated to the interactions between CA and [EMIM]SCN and the phase inversion mechanisms. By tuning the spinning conditions, CA hollow fiber membranes are successfully fabricated for ultrafiltration with a PWP value of 90.10 (L/m 2 bar h) and a mean effective pore diameter of 16.68 nm.

High functional hollow fiber membrane modified with phospholipid polymers for a liver assist bioreactor

For practical application of a liver assist system with a tissue-conjugated hollow fiber membrane (HFM) bioreactor used in an extracorporeal therapy, it would require a highly sophisticated HFM which has both hemocompatibility on one side and cytocompatibility on the other side. In this study, we present a cellulose acetate (CA) HFM modified with 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymers (PMB30 (MPC-co- n-butyl methacrylate) and PMA30 (MPC-co-methacrylic acid) for preparing a novel liver assist HFM bioreactor. A CA/PMB–PMA30 HFM modified asymmetrically on the inner and outer surface with the PMB30 and PMA30 was prepared successfully. Analysis with an X-ray photoelectron spectroscope showed that the intensity of the phosphorus atom attributed to the MPC units on the outer surface of the modified HFM was stronger than that of the inner surface. The PMA30 was immobilized on the outer surface of the CA/PMB30 blend HFM by a chemical condensation reaction. The CA/PMB–PMA30 HFM showed good water and solute permeability in comparison with the CA HFM. The morphologies of the adherent hepatocytes were round in shape in comparison with the cells that adhered on CA HFM. Furthermore, hepatocytes cultured on the inner surface of the CA/PMB–PMA30 HFM showed higher functional expression in terms of urea synthesis and albumin synthesis than that of the CA HFM.

The preparation and characterization of silver‐loading cellulose acetate hollow fiber membrane for water treatment

AbstractSilver‐loading asymmetric cellulose acetate (CA) hollow fiber membrane was spun via the dry jet‐wet spinning technique. The spinning solution was prepared by dissolving AgNO3 and CA in N,N‐dimethylformamide (DMF). The silver ions were reduced in the spinning dope into silver nano‐particles. The morphology of the resulting hollow fibers was examined using a scanning electron microscope and the silver content in the fiber was measured using an inductively coupled plasma atomic emission spectrometer. The antibacterial activities were evaluated. These hollow fibers had a sponge‐like structure and dense inner and outer surfaces. At a 50 k magnification, the pore on the skin layer was not observable, while the nodule size was smaller than 10 nm. The residual silver content of as‐spun hollow fiber was about 60% of the original silver added in the polymer solution. After immersing in water bath for 180 days, the silver content in the bulk of the hollow fibers decreased to 60% and the silver content on the surface reduced to 10%, yet still showed antibacterial activity against Escherichia coli and Staphylococcus aureus. After permeating with water for 5 days, the silver content in the hollow fibers decreased, and did not show antibacterial activity against E. coli and S. aureus. Thus, silver content must be periodically replenished after permeation. The proper range of AgNO3 in the spinning solution for CA hollow fiber should be about 100–1000 ppm. Copyright © 2005 John Wiley & Sons, Ltd.

Effect of coagulant temperature and composition on surface morphology and mass transfer properties of cellulose acetate hollow fiber membranes

AbstractCellulose acetate (CA) hollow fibers were spun via the dry‐jet wet spinning technique under various external coagulant compositions and temperatures. The surface morphology of the resulting hollow fiber was examined using field emission scanning electron microscopy (FESEM) and tapping mode atomic force microscopy (TMAFM). The pure water permeability (PWP) and the retention of dextran of the hollow fiber were also measured. The results showed that both the temperature and composition can affect greatly the surface morphology and hence the permeation performance of hollow fiber membranes when the temperature was over 55°C and the dimethyl formamide (DMF) content was higher than 15%. The on‐line draw ratio increased with the coagulant temperature and DMF content (in the range of 0 to 10%) in the external coagulant. The ultimate tensile strength also increased when the fibers were coagulated in 5–10% DMF and at 70°C. The PWP increased with the DMF content in the coagulant and the coagulant temperature. The retention of dextran decreased with the increase of the DMF content in the coagulant and the coagulant temperature. Copyright © 2005 John Wiley & Sons, Ltd.

Design of functional hollow fiber membranes modified with phospholipid polymers for application in total hemopurification system

In this study, we prepared cellulose acetate (CA) hollow fiber membranes (HFMs) modified with poly (2-methacryloyloxyethyl phosphorylcholine (MPC)-co- n-butyl methacrylate)(PMB30 and PMB80) by the dry-jet wet spinning process. The physical and chemical structures of the HFMs were controlled in order to design highly functional HFMs that had suitable performance to each targeting HFM device used in a total hemopurification system. The CA HFMs modified with the MPC polymer, such as CA/PMB30, CA/PMB80, and CA/PMB30-80 HFMs, were successfully prepared by controlling the spinning conditions. The modified HFMs showed an improved performance in solute and water permeability, due to the modification by the hydrophilic MPC polymers. The CA/PMB30 and CA/PMB80 showed a high potential in an application for a high performance hemocompatible plasmapheresis and hemofilter device. Furthermore, CA/PMB30-80 HFM, modified asymmetrically with PMB30 and PMB80, showed a potential for application in an advanced total hemopurification system as a highly functional scaffold for a biohybrid renal tubule, or a liver assist bioreactor device, because of their enhanced permeability, hemocompatibility, and cytocompatibility.

In situ modification on cellulose acetate hollow fiber membrane modified with phospholipid polymer for biomedical application

The hollow fiber membrane (HFM) made from synthetic polymers need improvement in terms of hemocompatibility or biocompatibihty, for use in the medical field. In this study, cellulose acetate (CA) HFM modified with the water-soluble amphiphilic 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymer (poly (MPC-co- n-butyl methacrylate) (PMB80, MPC:BMA = 80:20 (mol%)) was prepared by a dry-jet wet spinning process. The PMB80 was coated on the CA HFM surface in situ during the phase inversion of the dope solution by using a PMB80 solution as an inner coagulant. The CA/PMB80 coating HFM showed no physical structure changes in comparison with the CA HFM prepared using the same preparative conditions. The structure and permeability of the CA/PMB80 coating HFM was controllable by changing the preparative conditions. From the results of the X-ray photoelectron spectroscopic (XPS) observations, the amount of modification was changed with the concentration of PMB80 in the coagulant. The XPS signal attributed to the phosphorus atom of the PMB80 remained even after 1 month of rinsing with distilled water. Also, the CA/PMB80 coated HFM showed good permeability and a low membrane fouling property in comparison with the non-modified CA HFM, due to the low protein adsorption property of the PMB80.