Alumina Hollow Fiber Membranes Research Articles

Optimized Antifouling γ-Al2O3/α-Al2O3 Nanofiltration Composite Membrane for Lignin Recovery from Wastewater

This study focuses on the development of nanofiltration (NF) membranes with enhanced antifouling properties, high flux, and low molecular weight cut-off (MWCO) for the separation of lignin from paper mill wastewater. Using a sol-gel method by dip-coating, alumina hollow fiber membranes were fabricated with an interlayer to reduce surface roughness. The interlayer improved mechanical properties, effectively covering the surface irregularities and allowing for the subsequent application of a thinner functional layer. This approach significantly reduced surface roughness, from 112.6 nm to 62.9 nm, enhancing contamination resistance and lifetime. Characterization techniques, including X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM), and water contact angle measurements, confirmed the successful fabrication and enhanced properties of the membranes. The C2T6T3 membrane demonstrated the smallest roughness and the highest flux recovery rate (FRR) of 82.39% after cleaning with a 0.1 M NaOH solution. Performance evaluations showed that the developed membranes maintained high permeability (initial flux of 25.58 L·m⁻²·h⁻¹, decreasing to 14.06 L·m⁻²·h⁻¹ over time), achieved effective lignin rejection (consistently above 80%), and exhibited excellent long-term operational stability over 144 h of operation.

Dynamic Deposition of PDA on a Hollow Fiber Ceramic Membrane for Oily Water Treatment.

Ceramic membranes have been widely used in oil-water treatment; however, membrane fouling remains a challenge that must be addressed to improve the process feasibility. A thin layer of polydopamine (PDA) was dynamically deposited on the surface of the alumina hollow fiber membranes to reduce oil adhesion. The PDA-alumina membranes were characterized by using SEM-EDS, AFM, and water contact angle measurements. The performance of the modified membranes was evaluated using synthetic crude oil emulsions (100 mg·L-1) in a crossflow system. Membranes modified with PDA exhibited 97% oil rejection, and a stabilized permeate flux of 463 L·h-1·m-2 with a relative flux reduction of 60% and a flux recovery ratio of 75% was observed after cleaning, indicating lower oil adhesion and better fouling reversibility. The most predominant fouling mechanism for the modified membranes seems to be cake filtration because of the reduction in pore size due to the deposition of the PDA layer.

Four-channel catalytic micro-reactor based on alumina hollow fiber membrane for efficient catalytic oxidation of CO

The traditional automotive catalytic converter using commercial ceramic honeycomb carriers has many problems such as high back pressure, low engine efficiency, and high usage of precious metals. This study proposes a four-channel catalytic micro-reactor based on alumina hollow fiber membrane, which uses phase inversion method for structural molding and regulation. Due to the advantages of its carrier, it can achieve lower ignition temperature under low noble metal loading. With Pd/CeO2 at a loading rate of 2.3% (mass), the result showed that the reaction ignition temperature is even less than 160 °C, which is more than 90 °C lower than the data of commercial ceramic substrates under similar catalyst loading and airspeed conditions. The technology in turn significantly reduces the energy consumption of the reaction. And stability tests were conducted under constant conditions for 1000 hours, which proved that this catalytic converter has high catalytic efficiency and stability, providing prospects for the design of innovative catalytic converters in the future.

Study on design strategies and on new structure-performance relationships for CO2 capture in gas-liquid hollow fiber membrane contactors

The urgent need for carbon dioxide (CO2) capture technologies motivates this chemical engineering study, which systematically investigates the influence of macroscopic and microscopic structure on the CO2 absorption performance of hydrophobic alumina (Al2O3) hollow fiber membrane (A-HFMs) contactors. Six different A-HFMs prepared using the non-solvent-induced phase separation (NIPS) method with select solvents followed by sintering at 1300°C were then tested for chemical CO2 absorption in an A-HFM contactor using a monoethanolamine (MEA) solution. The hydrophobicity of the coatings applied on the A-HFM surfaces was confirmed by the water contact angle and thermogravimetric (TGA) analysis. Pearson's statistical analysis of a correlation matrix revealed the strength of relationships between nine variables, including outer diameter (mm), inner diameter (mm), percentage of sponge layer (%), pore size (nm), maximum pore size (nm), mechanical strength (MPa), surface porosity (m−1), overall porosity (%), and CO2 absorption flux (mol m−2 s−1). Building upon these findings, this study unveils a novel non-linear function linking three specific microscopic characteristics— pore size, surface porosity, and a geometric sponge layer factor—to CO2 absorption flux, offering valuable insights for optimizing hydrophobic A-HFM design and enhancing CO2 capture efficiency. The A-HFM, characterized by the combination of three factors (higher pore size, increased surface porosity, and a thicker sponge layer), achieved a CO2 absorption flux of 6.36 ×10−3 mol m−2 s−1 at room temperature, showcasing its exceptional performance in capturing CO2. The resulting empirical morphological factor provides a novel approach for enhancing the performance of CO2 absorption through A-HFM design optimization.

Strategies to overcome the limitations of cross-linked hydrophilic PVA membranes; carboxy methyl cellulose blending for epichlorohydrin-isopropanol-water pervaporation dehydration

Sodium carboxyl methyl cellulous (NaCMC)/Polyvinyl alcohol (PVA) coated Alumina hollow fiber (AHF) membrane was developed and applied to dehydration of ECH-IPA-water ternary feed mixture. CMC40 membrane, including 40 wt% of NaCMC showed the highest flux of 0.416 kg/m2h and a separation factor of 898 due to optimized packing density between PVA and the NaCMC polymer chain and relatively higher hydrophilic nature for PV separation to ECH-IPA-water ternary feed. After that, CMC40-coated AHF membrane was prepared according to the number of CMC40 coating and baking temperature. With an increase in baking temperature to 170 °C, the separation factor was significantly improved, while the flux decreased slightly. Moreover, NaCMC40-AHF showed robust properties with stable performance in the 50-h long-term PV test.

Two-Dimensional Conjugated Mass Transfer of Carbon Dioxide Absorption in a Hollow-Fiber Gas-Liquid Membrane Contactor.

The absorption efficiencies of CO2 in hollow-fiber membrane contactors using an ethanolamine (MEA) solvent under both concurrent- and countercurrent-flow operations were investigated theoretically and experimentally. Two-dimensional mathematical modeling was developed by Happel’s free surface model, and the resultant partial differential equations were solved analytically using the separated variables method with the use of an orthogonal expansion technique. A simplified expression of Sherwood number variations was reported by employing the relevant operations conditions and expressed in terms of the computed eigenvalues for predicting concentration distribution and absorption efficiency. It is emphasized that, in comparing various fiber packing configurations, both theoretical predictions and experimental results should be compared to find the absorption flux increment accomplished by the CO2/N2 stream passing through the fiber cells under the same mass flow rate. The value of the present mathematical treatment is evident to propose a simplified expression of the averaged Sherwood number variations, and provides the predictions of the absorption flux, absorption efficiency, average Sherwood number with the absorbent Graetz number, inlet CO2 concentration, and absorbent flow rates as parameters. The availability of such concise expressions, as developed directly from the analytical formulations, is the value of the present study. The experiments of the CO2 absorption using MEA with alumina (Al2O3) hollow fiber membranes are also set up to confirm the accuracy of the theoretical predictions. The accuracy derivations between the experimental results and theoretical predictions for concurrent- and countercurrent-flow operations are and , respectively. The operations of the hollow-fiber membrane contactor implementing N = 7 fiber cells and N = 19 fiber cells offer an inexpensive method of improving absorption efficiency by increasing fiber numbers with consideration of device performance.

Improvement in Mechanical Strength of <i>α</i>-Alumina Hollow Fiber Membrane by Introducing Nanosize <i>γ</i>-Alumina Particle as Sintering Agent

Improvement in Mechanical Strength of <i>α</i>-Alumina Hollow Fiber Membrane by Introducing Nanosize <i>γ</i>-Alumina Particle as Sintering Agent

Hydroxyl-functionalized ultra-thin graphitic-carbon-nitrite nanosheets-accommodated polyvinyl alcohol membrane for pervaporation of isopropanol/water mixture

BackgroundsThis report describes, for pervaporation dehydration of IPA/water mixtures, different types of g-C3N4 nanosheets accommodated in a polyvinyl alcohol matrix, and coating on an alumina hollow fiber membranes were fabricated. MethodsNamely, bulk g-C3N4 (BCN), from the thermal polymerization of a melamine precursor, followed by its exfoliation by acid treatment to prepare acid-treated g-C3N4 (ACN), further hydroxyl functionalization by glycidol treatment to obtain glycidol-modified g-C3N4 (GCN) were synthesized. As-synthesized BCN, ACN, and GCN sheets were characterized using FTIR, XRD, XPS, and AFM techniques. Dispersion of the BCN, ACN and GCN sheets in the PVA matrix was confirmed by FE- SEM, FT-IR, and DSC studies. Owing to the interfacial interaction between the g-C3N4 sheets and PVA, the mechanical strength of the membrane increased; it was more profound for GCN sheets accommodated membrane that attributed to hydrogen bonding interactions due to glycidol modification confirmed. Significant FindingsIn pervaporation tests, at a fixed content (2 wt.%) for evaluating the modification effect, the best performance was obtained (flux= 0.199 kg/m2h and separation factor 139.8) with the GCN type g-C3N4 sheets accommodation amidst three types of g-C3N4 nanosheet-accommodated membranes delivered at an 80/20 (w/w, (IPA)/water) feed mixture at 40 °C.

메조 세공 제올라이트 Y가 코팅 된 알루미나 중공사막을 이용한 중금속 흡착

In this study, mesoporous-zeolite-Y-coated alumina hollow fiber membranes were prepared by optimizing the synthesis conditions and using commercial zeolite Y, CTAB, as the structure-directing agent and alumina hollow fiber membranes. The removal of heavy metals was investigated using these membranes. The synthesized membranes were characterized with X-ray diffraction, field emission scanning electron microscopy, nitrogen adsorption-desorption analysis, field emission transmission electron microscopy, Fourier transform infrared spectroscopy, and the heavy metal adsorption activity of these membranes was investigated with ultraviolet-visible spectroscopy. Batch tests were conducted to investigate the capabilities of the mesoporous-zeolite-Y-coated membranes in removing Mn (II) and Fe (II)fromaqueoussolutions.Nitrogen full isotherm analyses confirmed that the synthesized mesoporous adsorbents were homogenously mesoporous. These results suggest that the mesoporous-zeolite-Y-coated membranes exhibited higher adsorption capacity than that of the alumina hollow fiber membranes. After three runs of heavy metal adsorption, there was no drop in the activity of the prepared mesoporous-zeolite-Y-coated alumina hollow fiber membranes because they were easier to separate and more durable than the conventional powdered adsorbents.

Fabrication of K-PHI Zeolite Coated Alumina Hollow Fiber Membrane and Study on Removal Characteristics of Metal Ions in Lignin Wastewater

Fabrication of K-PHI Zeolite Coated Alumina Hollow Fiber Membrane and Study on Removal Characteristics of Metal Ions in Lignin Wastewater

Dual-function ZIF-8 membrane supported on alumina hollow fiber membrane for copper(II) removal

The as-spun alumina hollow fiber membrane was used as membrane support for the development of ZIF-8 membrane. The ZIF-8 layers were successfully grown on the support by using the in-situ solvothermal method and layer-by-layer method. The morphology and physicochemical properties of the membranes were characterized using the field emission scanning electron microscope (FESEM), X-ray diffraction spectrophotometer (XRD), Fourier-Transform Infrared Spectrophotometer (FTIR). The adsorption study revealed that the removal of copper(II) ion was pH-dependent. The adsorption capacity for copper(II) adsorption is 76.5 mg/g. The adsorption mechanism of copper(II) onto the ZIF-8 membrane was best fitted to the Freundlich isotherm and pseudo-second-order model. The filtration study showed that the membranes could remove up to 90% of copper(II) ions from the aqueous solution.

Preparation and characterization of alumina hollow fiber membrane for oilfield produced water treatment

Preparation and characterization of alumina hollow fiber membrane for oilfield produced water treatment

Polyvinyl alcohol and graphene oxide blending surface coated alumina hollow fiber (AHF) membrane for pervaporation dehydration of epichlorohydrin(ECH)/ isopropanol(IPA)/water ternary feed mixture

For pervaporation dehydration of ternary azeotropes ECH/IPA/water (50/30/20, w/w,%) produced in epoxy resin manufacturing process, Graphite nanopowder was oxidized to prepare graphene oxide (GO) nanosheets, which were incorporated into a polyvinyl alcohol (PVA)-tetraethyl orthosilicate (TEOS) solution. The GO-PVA-TEOS solution was coated on the surface of a nanoporous alumina hollow fiber (AHF) membrane. The pore size and element composition on the AHF were determined using FE-SEM and energy dispersive spectroscopy. The coating thickness of the GO-PVA-TEOS membrane layer on the AHF was measured using FE-SEM analysis, and XPS, FTIR analysis of the membrane was conducted to confirm the condensation reaction between PVA and TEOS. Pervaporation dehydration of the epichlorohydrin/ isopropanol/water mixtures was conducted using the AHF membranes with and without GO in PVA-TEOS. For pervaporation output, with the addition of 0–1.5 wt% GO in the PVA-TEOS, it was quantitatively reported that the flux declined from 0.17 to 0.09 kg/m2h and the separation factor increased sharply from 1450 to 4844 with feed consisting of the ECH/IPA/water (50/30/20, w/w,%) solution at 30 °C. In terms of the long-term (240 h) pervaporation stability evaluation of 1.0 wt% GO-incorporated membrane, the excellent separation efficiency with increased of flux was obtained.

The influence of alumina particle size on the properties and performance of alumina hollow fiber as support membrane for protein separation

The advantages offered by ceramic membranes compared to the polymeric membrane have attracted more interest, especially in fluid separation application owing to its ability to withstand harsh operating conditions. In this study, five alumina hollow fiber membranes were prepared from different loading ratios of alumina particle sizes which are 1 µm, 0.5 µm, and 0.01 µm. The membranes were prepared via phase-inversion technique using water as an external and internal coagulant and sintered at 1400 °C. The effect of the alumina powder particle sizes on membrane morphology, pore size distribution, mechanical strength, surface roughness, pure water flux, and Bovine Serum Albumin (BSA) rejection was investigated in this study. By varying the overall loading and particle size of alumina, different morphologies of membranes were obtained. Higher loading of coarse particles produced more porous and low mechanical strength membranes, whereas reducing the amount of coarse particles produced a more compact membrane with the highest mechanical strength of 27 MPa. Meanwhile, BSA rejection is declining when more coarse particles were used to fabricate the membrane. Among all the membranes, the 5:3:2 ratio able to reject up to 66% of protein (BSA) with the flux of 138.7 L m−1 h−1.

Covalent Self-Assembly in Two Dimensions: Connecting Covalent Organic Framework Nanospheres into Crystalline and Porous Thin Films.

Insolubility of covalent organic frameworks (COFs) in organic solvents is one of the major obstacles for the potential application of these extended networks such as drug delivery, sensing, optoelectronics, and semiconductor device fabrication. The present work proposes a unique way to make uniform, solution-processable, crystalline, and porous COF nanospheres directly from the homogeneous solution of amine and aldehyde via spatial and temporal control of the nucleation and growth. This strategy of direct nucleation simultaneously showcases the caliber to tune the size of the COF nanospheres from 25 to 570 nm. We have also demonstrated the concept of mesoscale covalent self-assembly of those solution-processable COF nanospheres in the liquid-liquid interface (DCM-water bilayer) for the very first time, transmuting them into self-standing COF thin films with long-range ordered arrangements in two dimensions. The crystalline and porous (with TpAzo showing highest SBET of 1932 m2 g-1) free-standing COF thin films could be fabricated in a wide range of thicknesses from as low as 21 nm to as high as 630 nm. Both β-ketoenamine (TpAzo, TpDPP) and imine (TpOMeAzo, TpOMeDPP) linked COF thin films have been synthesized via mesoscale covalent self-assembly of the solution-processable COF nanospheres illustrating the generality of this eloquent methodology. Further, the solution processability has been tested and utilized to cast COF thin films uniformly in the inner and outer surface of an alumina hollow fiber membrane. The COF thin film-alumina hollow fiber membrane composites have showcased promising selective molecular separation of He and O2, He and CO2, and He and N2.

Decompression stripping of carbon dioxide from rich monoethanolamine through porous hydrophobic modified ceramic hollow fiber membrane contactor

In this study, commercial alpha alumina powder was used to fabricate hollow fiber membrane by phase inversion spinning method. The fabricated alumina hollow fiber membrane was confirmed to have high chemical and thermal stability based on thermogravimetric analysis and contact angle measurement. When CO2 stripping characteristics were examined by introducing decompression membrane contactor process in the stripping part of amine absorption process, increase in degree of vacuum resulted in increased CO2 stripping flux. In liquid to lumen operation under decompression pressure of 61.325 kPa and absorbent flow rate of 9 ml/min, CO2 stripping flux was 45.75 × 10−4 mol/m2·s. Existing articles on membrane contactor stripping were mostly N2 sweep type and reported CO2 stripping flux of 1–24 mol/m2·s, whereas the present study achieved stripping performance that was approximately 2–40 times higher. Decompression stripping of porous ceramic hollow fiber membrane contactor can be viewed as a promising process since it did not cause the phenomenon of decrease in CO2 purity due to N2 and showed similar or greater CO2 stripping flux than previously reported membrane contactor stripping processes.

Photocatalytic nanofiber-coated alumina hollow fiber membranes for highly efficient oilfield produced water treatment

Cost-effective purification technology of oilfield produced water (OPW) is becoming a global challenge for future petroleum exploration and production industry. Energy-efficient operation of membrane separation is potentially promising. However, severe fouling problem of oil droplets demands new robust and fouling-resistant membranes with high permeability and rejection efficiency. Here, we propose a photocatalytic nanofiber-coated inorganic hollow fiber membrane suitable for OPW treatment. The membrane was fabricated by coating polyacrylonitrile (PAN) nanofiber incorporated with graphitic carbon nitride (GCN) photocatalyst on an alumina (Al2O3) hollow fiber membrane. While the highly porous coating made of smooth hydrophilic nanofibers facilitated water permeation, the coating effectively captured oil droplets in its opening, resulting in a better rejection efficiency of oil contaminants. Its sparse mesh morphology prevented oil contaminants to form dense fouling film on the membrane surface and maintained high permeate flux even after 180 min filtration. The best permeate flux of 640 L·m−2·h−1 and oil rejection percentage of 99% were recorded for 180 min crossflow filtration of OPW at 2 bar along with the highest pure water flux of 816 L·m−2·h−1. The photocatalytic activity of GCN enabled the coating to degrade the captured oil contaminants under UV irradiation, demonstrating permeate flux of 577 L·m−2·h−1 and oil rejection of 97% after three cycles of 180 min filtration. The excellent fouling resistance and cleaning performances of the membrane are considerably beneficial for a long-term repeated filtration operation. This work will motivate researchers to develop nanofiber-coated hollow fiber membranes for future membrane separation technology.

High Performance of Asymmetric Alumina Hollow Fiber Membranes for the Clarification of Genipap (Genipa americana L.) Fruit Extract

Membrane filtration processes represent a suitable alternative for fruit juice treatment, but the applied membrane should present high stability and permeability. Here, we propose the development and application of ceramic asymmetric hollow fiber membranes for genipap extract clarification. Genipap is an exotic fruit from Central and South America with considerable concentration of phenolic and iridoid compounds. The dual-layer ceramic hollow fiber membrane was fabricated by a single-step co-extrusion and co-sintering process. The developed hollow fibers presented the desired asymmetric structure, with an inner finger-like region that guaranteed a suitable permeate flux (191 L h−1 m−2 at 1 bar), while the outer sponge-like layer was responsible for solid retentions and for the membrane mechanical resistance. Reductions in turbidity, total polyphenol content, and genipin concentration were of 52, 17, and 4%, respectively. Mathematical modeling of the experimental flux decay showed that pore blocking was the main fouling mechanism during filtrations of genipap extract through the asymmetric hollow fibers. The presence of microchannels with larger pore size in the inner surface of the fiber probably mitigated cake formation. The increase in the transmembrane pressure from 1 to 2 bar did not improve the permeation flux through the membrane since the fouling layer resistance was considerably higher at 2 bar than at 1 bar. Thus, asymmetric ceramic hollow fibers are suggested for juice fruit clarification with improved permeate flux and clarification degree.

Nanostructure depositions on alumina hollow fiber membranes for enhanced wetting resistance during membrane distillation

Omniphobic alumina hollow fiber membranes were developed for direct contact membrane distillation (DCMD) with a low surface tension feed in this study. Alumina hollow fiber (HF) membranes were prepared as the membrane substrates, and chemical bath deposition methods were applied to deposit ZnO nanorods and nanoparticles on the HF membranes. The SEM, EDX, and AFM analyses showed that the ZnO nanostructures were effectively deposited on the membrane surfaces and able to increase the surface roughness. After surface fluorination by FAS17, the HF membranes deposited by ZnO nanorods and nanoparticles demonstrated contact angles of 128.7° and 138.1° for a 90% v/v ethanol/water mixture, both of which were higher than 114.8° for the pristine HF membrane without ZnO nanostructures. In the DCMD experiments with the sequential addition of SDS from 0.2 to 2.0 mM, the HF membranes with ZnO nanostructures exhibited superior wetting resistances with low surface tension feeds compared to that of the pristine HF membranes. Moreover, the HF membranes with the deposited ZnO nanoparticles had the best wetting resistance, and the permeate water flux was maintained for 24 h using a 2.0 mM SDS (70 °C 1 M NaCl) solution as an initial feed. The results not only suggested that the deposition of nanostructures enhanced the wetting resistance of the alumina hollow fiber membranes to low surface tension liquids but also showed the promise of utilizing these membranes for the desalination of low surface tension wastewaters.

Preparation, characterizations and performance evaluations of alumina hollow fiber membrane incorporated with UiO-66 particles for humic acid removal

Humic acid removal requires ceramic membranes incorporated with metal organic framework (MOF) to display remarkable stability over water. Recent work has shown UiO-66, a Zr-based MOF, as an emerging material with the potential to fulfill this requirement. This work investigated the preparation, characterization and performance of UiO-66 particles deposited on alumina hollow fiber membranes. Concentrations of Zr precursors and synthesis period were varied in the preparation of UiO-66 using solvothermal synthesis. The presence of UiO-66 particles was characterized using the field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) mapping, x-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) analysis. Pure water flux and humic acid rejection tests were carried out on both pristine alumina hollow fiber membranes and alumina hollow fiber membranes deposited with UiO-66 particles. In the former, a high pure water flux value of 231.24 L m−2 h−1 was recorded, while in the latter the recorded value dropped to 9.36 L m−2 h−1. Pristine ceramic hollow fiber membranes used to separate humic acid (1 g L−1) from an aqueous solution showed a rejection rate of 98%. When UiO-66 particles were deposited on the ceramic membranes, the solute flux of the membranes increased to 68.36 L m−2 h−1. Surprisingly, it was found that 99% humic acid was rejected from a feed solution using the membranes incorporated with UiO-66 particles. Findings showed that the weight loading of the UiO-66 particles on the alumina hollow fiber membranes was very low, showing a reading of only approximately ~ 0.01 g. Based on the adsorption-desorption analysis, at high pH values (≥ 9), UiO-66 particles and humic acid displayed a similar surface charge, creating a repulsion effect during the filtration process. UiO-66 particles on alumina hollow fiber membranes showed excellent stability, making it viable for water purification applications.