Cellulose Acetate Hollow Fiber 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 Hollow Fiber Membranes for Forward Osmosis Using the Green Solvent Agnique AMD 3 L

A set of cellulose acetate (CA) hollow fiber membranes is manufactured by using a variation of CA (20–25 wt %) and different weight ratios of acetone and the green solvent Agnique AMD 3 L (3:2, 1:1, 2:3) in dope solutions (DS). The DSs are spun combining an evaporation and non-solvent-induced phase separation (EIPS–NIPS) process. The obtained hollow fibers (HF) annealed in either water (95 °C) or humid air (95 °C, 98% relative humidity) reveal an asymmetric membrane structure with a dense layer on the shell side and a molecular weight cutoff down to 100 g mol–1. Regarding the use of forward osmosis (FO), the hollow fibers are tested with aqueous NaCl (1 M) as draw solution in the lumen of the fibers and ultra-pure water as feed at the shell side. With a decreasing amount of acetone in the DSs, an increase in water flux from 2.0 L m–2 h–1 (LMH) to 6.2 LMH and a reverse salt flux from 0.5 g m–2 h–1 (GMH) to 13.3 GMH of the HF annealed in water are found. When annealing in humid air, the water flux of the HF increases from 2.0 to 4.5 LMH and a reverse salt flux from 0.5 to 4.1 GMH occurs, compared to annealing in water. Decreasing the NaCl concentration to 0.5 M, an increase in the performance ratio up to 17.9% is given, which is in the same range of commercially available cellulose ester-based HFs for FO.

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.

Comparison of Post-Treatment Methods on the Performance of Hollow Fiber Membranes Containing Metal Organic Framework in Gases Separation

In the current work, thermal treatment, PDMS coating, and combined thermal treatment with PDMS coating methods were applied over NH2-MIL-53(Al)/cellulose acetate (CA) hollow fiber mixed matrix membranes (HFMMM) for CO2/CH4 and CO2/N2 separation. The results showed that upon thermal treatment at 170 °C, CO2/CH4 and CO2/N2 gas pair selectivities of HFMMM were improved from 9.1 to 9.9 and 7.7 to 8.4, respectively. On the other hand, CO2/CH4 and CO2/N2 gas pair selectivities of HFMMMs were improved from 9.1 to 14.1 and 7.7 to 12.0, respectively, after thermal treatment at 220 °C. Substantial increment in gas pair selectivities of the thermally treated fibers was mainly due to polymer densification, which condensed the voids between polymer and particles. Subsequently, PDMS-coated HFMMMs exhibited gas pair selectivities of 17.0 and 16.2, respectively, which were higher compared to the untreated and thermally treated HFMMM. Highest improvement of CO2/CH4 and CO2/N2 gas pair selectivities were found for combined...

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.

Optimization of Deacetylation Process for Regenerated Cellulose Hollow Fiber Membranes

Cellulose acetate (CA) hollow fibers were spun from a CA+ Polyvinylpyrrolidone (PVP)/N-methyl-2-pyrrolidone (NMP)/H2O dope solution and regenerated by deacetylation. The complete deacetylation time of 0.5 h was found at a high concentration (0.2 M) NaOH ethanol (96%) solution. The reaction rate of deacetylation with 0.5 M NaOH was faster in a 50% ethanol compared to a 96 vol.% ethanol. The hydrogen bond between CA and tertiary amide group of PVP was confirmed. The deacetylation parameters of NaOH concentration, reaction time, swelling time, and solution were investigated by orthogonal experimental design (OED) method. The degree of cross-linking, the residual acetyl content, and the PVP content in the deacetylated membranes were determined by FTIR analysis. The conjoint analysis in the Statistical Product and Service Solutions (SPSS) software was used to analyze the OED results, and the importance of the deacetylation parameters was sorted as Solution > Swelling time > Reaction time > Concentration. The optimal deacetylation condition of 96 vol.% ethanol solution, swelling time 24 h, the concentration of NaOH (0.075 M), and the reaction time (2 h) were identified. The regenerated cellulose hollow fibers under the optimal deacetylation condition can be further used as precursors for preparation of hollow fiber carbon membranes.

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...

Preparation of Cellulose Acetate Hollow-Fiber Membranes for CO2/CH4Separation

Abstract The effect of ethanol (EtOH) concentration and air-gap distance on the gas separation performance of cellulose acetate (CA) membrane was studied. CA asymmetric hollow-fiber membranes were prepared through a dry/wet spinning process using nonsolvent-induced phase separation from dope solutions containing N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), and EtOH, which were then coated with polydimethylsiloxane. CA hollow-fiber membranes made from C2 dope composition (62 wt% NMP, 23 wt% CA, 10 wt% THF, and 5 wt% EtOH) and air-gap distance of 15 cm exhibited excellent separation properties for CO2 and CH4: 12.9 GPU CO2 permeance and 43.8 CO2/CH4 selectivity. Results indicated that the air-gap distance and ratio of THF/EtOH in the dope solution play an important role in the spinning process and production of a well-organized skin for CA asymmetric hollow-fiber membranes, which are known to affect the CO2/CH4 separation performance. To verify the separation performance of the prepared membranes, a...

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.

Fabrication of cellulose acetate ultrafiltration membrane with diphenyl ketone via thermally induced phase separation

ABSTRACTWith diphenyl ketone as diluent, cellulose acetate (CA) ultrafiltration (UF) membrane with a bicontinuous structure was prepared via thermally induced phase separation (TIPS) method. The liquid–liquid phase separation region of CA/diphenyl ketone system was measured and the maximum corresponding polymer concentration was approximately 53 wt %. The effects of polymer concentration, coarsening time and coarsening temperature on the morphologies, and mechanical properties of CA membranes were investigated systematically. As the polymer concentration increased from 15 to 30 wt %, the bicontinuous structure could be obtained and the tensile strength of CA membranes increased from 3.92 to 30.17 MPa. With the increase of coarsening time, the thickness of dense skin layer and the asymmetry of cross‐section reduced. However, excess coarsening rendered the membrane morphology evolved from a bicontinuous structure to a cellular structure. When the coarsening time was 5 min, the bicontinuous structure in cross‐section showed good interconnectivity and the dense skin layer exhibited a thin thickness of 2 μm. The fabricated CA hollow fiber UF membrane exhibited a high tensile strength of 31.00 MPa and rejection of 96.10% for dextran 20 kDa. It is indicated that diphenyl ketone is a competitive diluent to prepare CA membranes with excellent performance via TIPS. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42669.

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.

Cellulose acetate core–shell structured electrospun fiber: fabrication and characterization

This study explored the effect of type of core fluids on the fabrication of hollow and core–sheath cellulose acetate (CA) fiber. Tailoring the CA fiber with desirable features such as reinforced core, porous and hollow structure provides unique features for use in various applications. Fibers with such characteristics can be used for better controlled release drug delivery system or to promote cell adhesion in tissue engineering. Type of core material, tensile strength, and rheological properties were evaluated. DSC and FTIR analysis were performed to confirm the presence of core and sheath components. CA hollow structures were successfully obtained after selectively extracting the mineral oil. CA hollow fibers were twice the size of solid fiber despite similar solution and process conditions. Fiber morphologies indicated incomplete encapsulation by the CA when 80 kDa PCL molecular weight was used. This problem was not observed with 43 and 10 kDa PCL. DSC and FTIR analyses showed presence of both PCL and CA components. The rheology results suggest that the fibers could be formed when the viscosity of the core is less than that of sheath. Hydrated CA–43 kDa PCL fibers showed nearly ten-fold improvement in break point and stiffness. Human umbilical vein endothelial cells showed increased attachment and viability in both hollow CA and CA–PCL fibers relative to tissue culture plastic.

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.

Dual-layer hollow fiber of polyaniline–cellulose acetate prepared with simple wet technique of chemical polymerization of aniline

Polyaniline–cellulose acetate hollow fibers prepared from cellulose acetate (CA) solution of aniline (ANI) were founded to show dual layers structure, when wet technique was applied for using syringe injection of the solution to acidic water for ANI polymerization. In this technique, the polymerization of ANI occurred simultaneously by the monomer injection in coagulated CA fibers. Then, the PANI–CA composite fibers were obtained. The formation of the PANI–CA composite fiber was dependent upon HCl concentration and initiator of ammonium persulfate. Especially, when the coagulation time was 1 min, the obtained PANI–CA fibers showed hollowed dual-layer structure having outer layer of PANI and inner layer of CA. Evidence was presented that the dual structure fiber had 40 μm outer layer and 60 μm inner porous layer in their thicknesses. Cyclic voltammograms of the PANI–CA fiber were indicated that the outer layer was composed of PANI layer showing electrochemical properties with electrical capacity of about 0.003 C.