Performance Of Hollow Fiber Membranes Research Articles

Effect and mechanism of solution flow rate during interfacial polymerization on morphology and performance of hollow fiber membranes

Interfacial polymerization (IP) using m-phenylenediamine and trimesoyl chloride (TMC) is an essential method for producing thin-film composite (TFC) membranes. Nevertheless, IP is highly sensitive to changes in process parameters, especially the TMC solutions flow rate during inside-out TFC hollow fibers (HF) production. Research on the impact of flow conditions (i.e., laminar vs. turbulent flows) of these organic solutions on the final membrane characteristics and corresponding mechanism is still lacking. This research tested different TMC flow rates (0.1–2 mL/min) to produce inside-out TFC HF. With a TMC flow rate increase, (i) the leaf-like structures of the polyamide (PA) layer decreased in size, (ii) the thickness of the PA layer slightly increased, and (iii) the pure water permeability decreased. However, the elemental composition, chemical bonds, and NaCl rejection remained stable. Different fluid regimes are considered to affect the performance of HF membranes by affecting the heat dissipation process during IP reaction. A TMC flow rate in the laminar flow state (i.e., low flow rates) is recommended for synthesizing HFs. The current research provides new insights into the IP reaction mechanism of HF membrane, thus offering valuable guidance to optimize and produce membrane products with better performance.

Artificial intelligence and structural design of inorganic hollow fiber membranes: Materials chemistry

A key challenge is to produce the uniform morphology and regular pore design of inorganic hollow fiber membranes (HFMs) due to involvement of multiple parameters including, fabrication process and materials chemistry. Inorganic HFMs required technical innovations via novel structural design and artificial intelligence (AI) to produce the uniform structure and regular pore design. Therefore, this review aims at critical analysis on the most recent and relevant approaches to tackle the issues related to tune the morphology and pore design of inorganic HFMs. Structural design and evaluation of routes towards the dope suspension, spinning, and sintering of inorganic HFMs are critically analysed. AI, driving forces and challenges involved for harnessing of materials are revealed in this review. AI programs used for the prediction of pore design and performance of HFMs have also been explained in this review. Overall, this review will provide the understanding to build the equilibrium in spinning and sintering processes to control the design of micro-channels, and structural properties of inorganic HFMs. This review has great significance to control the new design of membranes via AI programs. This review also explain the inorganic membrane efficiency as algal-bioreactor.

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.

Removal of arsenic from water using a novel polyamide composite hollow fiber membrane by interfacial polymerization on lumen side

A novel mixed polyamide based composite membrane was prepared by interfacial polymerization (IP) of chitosan (CS) and m-phenylenediamine (MPD) mixture with trimesoyl chloride (TMC) for low pressure hollow fiber nanofiltration (NF). A uniform thin selective layer of polyamide was chemically coated on the lumen side of the polysulfone (PSF) based ultrafiltration support membrane. Permeability of the prepared hollow fiber NF membrane improved appreciably by incorporation of a small amount of CS into the MPD solution during IP process. The properties of prepared hollow fiber membranes were characterized using scanning electron microscope (SEM), contact angle, molecular weight cut off (MWCO), permeability, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and surface zeta potential. Pure water permeability of mixed polyamide composite membrane enhanced from 3.8 l/m2h bar to 32.5 l/m2h bar, which corroborated an increase in MWCO from 673 Da to 2553 Da and pore radius from 6.8 to 12.9 Å as CS was incorporated in polyamide layer. However, this drastic increase in permeate flux was not compromised with the arsenate rejection, which changed from 74.68% to 73.16% only. Thus, the prepared hollow fiber membrane performance was suitable and competent for low pressure driven hollow fiber membrane based arsenate rejection, which has many advantages over the conventional resin based filtration to remove arsenic from water. Performance of the developed hollow fiber membrane was also tested with arsenic contaminated natural groundwater prepared artificially with a rejection of 66–71% arsenate, 45–47% total dissolved solids (TDS), 47–48% hardness and 46–50% iron at 1 bar pressure with 25 l/m2h permeate flux.

Study on the effect of porosity of hollow fiber membrane on humidification performance

Hollow fiber membranes are used in industrial processes widely. Porosity is one of the important parameters affecting the humidification performance of hollow fiber membrane components. The aim of this study was to analyze the effect of porosity of hollow fiber membrane on humidification performance. In order to perform this analysis, a model based on the finite element method was used to simulate numerically the heat and mass transfer under 6 porosity conditions. Five working conditions with different air flow was considered in order to get more data. The results show that when the porosity increases from 0.35 to 0.8, the humidification performance is greatly improved. However, when it increases from 0.8 to 0.9, the humidification performance is almost unchanged. Considering the humidification performance and support strength of hollow fiber membrane, it is suggested to control the porosity of hollow fiber membrane between 0.65 and 0.8.

The Effect of Flow-Induced Vibration on Heat and Mass Transfer Performance of Hollow Fiber Membranes in the Humidification/Dehumidification Process.

Cross-flow hollow fiber membranes are commonly applied in humidification/dehumidification. Hollow fiber membranes vibrate and deform under the impinging force of incoming air and the gravity of liquid in the inner tube. In this study, fiber deformation was caused by the pulsating flow of air. With varied pulsating amplitudes and frequencies, single-fiber deformation was investigated numerically using the fluid–structure interaction technique and verified with experimental data testing with a laser vibrometer. Then, the effect of pulsating amplitude and frequency on heat and mass transfer performance of the hollow fiber membrane was analyzed. The maximum fiber deformation along the airflow direction was far larger than that perpendicular to the flow direction. Compared with the case where the fiber did not vibrate, increasing the pulsation amplitude could strengthen Nu by 14–87%. Flow-induced fiber vibration could raise the heat transfer enhancement index from 13.8% to 80%. The pulsating frequency could also enhance the heat transfer of hollow fiber membranes due to the continuously weakened thermal boundary layer. With the increase in pulsating amplitude or frequency, the Sh number or Em under vibrating conditions can reach about twice its value under non-vibrating conditions.

Fabrication of multilayer composite hollow fiber membrane comprising NH2-MIL-125 (Ti) for CO2 removal from CH4

The presence of CO2 has created significant challenges in natural gas processing in order to meet consumer’s specifications and pipeline transportation. Membrane separation is among the most effective approaches in CO2 separation from natural gas mainly to its energy efficiency. This study investigates the alternate technique for enhancing the performance of hollow fiber membrane in CO2 removal from CH4. A new type of composite hollow fiber membrane is fabricated by dip-coating of polymer solution comprising various loadings of NH2-MIL-125 (Ti) in PEBAX onto PDMS coated-polysulfone (PSf) hollow fiber. The morphology and elemental mapping analysis of the resultant membranes were characterized via scanning electron microscope (SEM) and energy dispersive X-ray (EDX), respectively. SEM images showed that no major voids or clusters were observed between the two phases of polymer and filler. Improved CO2 and CH4 gas permeance were found for composite membranes, as compared to PSf membrane coated only by PDMS and PEBAX solutions. Besides, highest improvement of CO2/CH4 ideal selectivity was obtained for composite membrane loaded with 10 wt% of filler. High porosity and high CO2 affinity of NH2-MIL- 125 (Ti) are the main reasons for the enhancement of CO2 removal from CH4. Hence, further research work is necessary to explore the performance of this membrane at various operating conditions such as temperature, flow rate, and CO2 feed concentration.

Effect of polymer molecular weight on structure and performance of PVDF hollow fiber membranes prepared via TIPS process with co-extrusion of solvent using triple orifice spinneret

The co-extrusion of solvent at the outer layer of a dope solution in a thermally induced phase separation (TIPS) process has led to significant improvements in membrane characteristics, especially pure water permeability stability. This work investigates the effects of the poly (vinylidene fluoride) (PVDF) molecular weight and concentration on the characteristics of hollow fiber membranes prepared using this method. The PVDF molecular weight had little effect on the phase diagram of the PVDF/diphenyl carbonate (DPC) system, and effectively controlled the penetration depth and quantity of the extruded solvent (propylene carbonate (PC)) inside the polymer dope solution as well as the overall performance of the hollow fiber membranes. When the PVDF concentration was low, the PVDF molecular weight was crucial in controlling the penetration of the extruded solvent. For a PVDF/DPC system that led to the mainly bicontinuous structure which resulted from L-L phase separation, the penetration of the PC inside the membrane considerably changed the surface and sublayer structure from a bicontinuous structure with spherulite to a composite spherulite embedded in the bicontinuous structure and isolated spherulite structure. To obtain an appropriate membrane with considerable water permeability stability, it is necessary to choose an appropriate polymer molecular weight and concentration.

Influence of bore fluid composition on the physiochemical properties and performance of hollow fiber membranes for ultrafiltration

Porous hollow fiber polysulfone (PSf) membranes were fabricated via a phase-inversion process and their performance during ultrafiltration (UF) was evaluated. The effects of the composition and concentration (0–50%) of different bore fluid mixtures, including N-methyl-2-pyrrolidone (NMP)/water, glycerol (G)/water, and ethylene glycol (EG)/water (in comparison with pure deionized water), on the structure, physicochemical properties, and performance of the fabricated membranes was investigated. Using these various bore fluid mixtures altered the thermodynamic and kinetic properties of the phase inversion system, and changed the morphology and structure of the fabricated membranes, especially on the lumen side. Increasing concentrations of NMP, G, and EG in the bore fluid resulted in increased pore size, porosity, and hydrophilicity. These bore fluid mixtures exhibited a strong influence on the perm-selectivity of the as-spun hollow fiber membranes. The membrane fabricated using 50% NMP/water as the bore fluid mixture exhibited the highest water flux of 166.98 LMH with a bovine serum albumin rejection rate of more than 97%. Overall, this study introduces an easy and effective way to control the structure of the membrane through bore fluid modification and shows how the inner skin layer properties can have a remarkable effect on water permeance, even in the out-in filtration test.

Preparation of a novel dual-layer polyvinylidene fluoride hollow fiber composite membrane with hydrophobic inner layer for carbon dioxide absorption in a membrane contactor

In order to improve the polyvinylidene fluoride (PVDF) hollow fiber membrane performance for carbon dioxide (CO2) absorption in membrane contactors, dual-layer PVDF composite membranes combining the advantages of high gas permeability and high hydrophobicity of the inner layer were designed and prepared. The membranes were prepared through a homocentric triple-hole spinneret via the dry-jet wet-spinning phase inversion method, and the membrane structure and properties were optimized. The outer layer of the optimized membrane exhibits a large finger-like porous structure, while the inner layer is composed of PVDF and hydrophobic modified nano-silicon dioxide (SiO2), and shows a thin but dense spherulite stacking structure. The results of membrane gas absorption experiment demonstrated that the optimized membrane exhibited excellent CO2 mass transfer flux and long-term operation stability. CO2 absorption flux of the membrane contactor obtained 2.23 × 10−3 mol·m−2·s−1 under the conditions of the inlet gas (CO2/N2 = 19/81, v/v) flowing on the shell side at a flowrate of 100 mL/min and the absorbent liquid (1 mol/L DEA) flowing counter-currently on the tube side at a flowrate of 50 mL/min. This CO2 absorption flux decreased by 18% after 160 h of operation.

Influence of flocculant polyacrylamide on concentration of titanium white waste acid by direct contact membrane distillation

Effort has been made to investigate the concentration of titanium white waste acid (TWWA) by direct contact membrane distillation (DCMD) and the focus is the influence of polyacrylamide (PAM) on membrane wetting and fouling. It was found that the presence of PAM in feed reduced membrane flux and retarded wetting development, even though its level in feed of H 2 SO 4 solution was only 0.0002 wt%. The difference between the tests using pure water and neat PAM aqueous solution, respectively, as feed also indicated the above effect registered with PAM. AFM results showed that the addition of PAM in feed solution changed the membrane shell surface morphology. However, conclusive proof of the PAM existence in membrane cross-section and inner surface was not obtained, probably due to its low concentration in feed solution. Two approaches were tried to recover membrane flux. In comparison with operation w/o any treatment, HCl solution rinsing did not lead to obvious improvement in membrane flux recovery, while rinsing combined with gas purge has clearly delayed the degradation in acid concentration factor. Nevertheless, even the latter could not ensure long term stability. High tortuosity and low hydrophobicity of the membranes used were suggested as underlying causes and should be addressed in the future. Comparison of hollow fiber membrane performance in treating pure water (left) and 0.0002% PAM aqueous solution (right) by DCMD showed that PAM reduced membrane flux and retarded wetting development.

Analysis of the Influence of On-Board Temperature and Pressure Control System on Inert Gas Generating Performance of Hollow Fiber Membrane

Based on the typical on-board membrane separation system for fuel inerting, the mathematical models of temperature and pressure control subsystem and hollow fiber membrane were built with the coupled iterative numerical solution methods. While the temperature and pressure were controlled, the design area, nitrogen production effect of hollow fiber membranes were analyzed and compared with the situation of no temperature and pressure control in the full flight envelope by numerical simulation. Moreover, the root causes for those changes were found out. It shows that the method used in temperature and pressure control can increase the bleed air pressure and enhance the stability of temperature and pressure effectively. Compared with the situation of no temperature and pressure control, the temperature and pressure control method are able to decrease the demanded area of membrane by 42.3%∼51.7%. And there is no need to adjust the membrane area for condition of low nitrogen production efficiency. But it also decreases the highest nitrogen production efficiency by 9.4% and increase the minimum oxygen concentration by 0.65%. The rate of flow has the most significant effect on nitrogen production. These phenomena are caused by the effects of the rate of flow, pressure, temperature and membrane area.

Cellulose hollow fibers for organic resistant nanofiltration

Cellulose is the most abundant biopolymer, but it is difficult to process due to its low solubility in most of the solvents. In this work, we demonstrate the preparation, of self-standing and defect-free cellulose hollow fiber membranes made by a sustainable process for filtration in organic solvent medium. The hollow fibers were made by the simple spinning technique using ionic liquids as a solvent. The spun solutions were prepared with three different ionic liquids, having imidazolium-based cations and acetate or phosphates as anions. We used X-ray diffraction to evaluate the influence of the different ionic liquids on the crystallinity of the cellulose and the membrane solvent stability. We used cryo-scanning electron microscopy to investigate the porous structure of the hydrated membranes, distinguishing it from that of the dry membranes. The hollow fiber membrane performance was studied using dyes in water and ethanol solutions. The rejection of Congo Red (696 g mol−1) was higher than 90% in ethanol and even closer to 100% in water. The best results were obtained by using 1-ethyl-3-methyimidazolium diethyl phosphate and 1,3-dimethylimidazolium dimethyl phosphate. Our results indicate that by using greener process is possible to obtain solvent resistant cellulose hollow fibers.

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...

Hydrophobization of Polysulfone Hollow Fiber Membranes

The effect of the nature of the pore-forming agent (polyethylene glycol, ethylene glycol, diethylene glycol, glycerol) on the structure and performance of hollow fiber membranes spun from polysulfone solutions in N,N-dimethylacetamide was studied. The membranes have been characterized using various methods (determination of gas permeability and water entry pressure, scanning electron microscopy, contact angle measurement). To increase the hydrophobicity of the selective layer of hollow fibers, a procedure for applying a modifying polydimethylsiloxane layer onto the inner surface of the fiber has been developed, which has made it possible to increase the contact angle from 75°–77° to 115°–151° with retaining their gas transport properties. The composite membranes designed hold promise for use in gas–liquid membrane contactors, and hydrophobized membranes with reduced gas permeability can be used for hydrophobic pervaporation.

CFD Simulation of Hydrogen Separation in Pd Hollow Fiber Membrane

Abstract In this article, hydrogen adsorption from gas mixture involve nitrogen and hydrogen by palladium hollow fiber membrane investigated and two dimensional model proposed for hydrogen adsorption in this model. This model has been evaluated based on equations (momentum and mass transfer) in all three parts (shell, membrane and tube) for existing gaseous compounds with using finite element method. The results of simulation validated by experimental data of hydrogen adsorption by palladium hollow fiber membrane. Modeling predictions shows good agreement with experimental data at different operating conditions such as different gas flows, temperature, pressure and etc. the result of simulation shows hydrogen separation efficiency increases with increasing temperature and pressure and decreases with increasing inlet rate. Also with using this model better performance of hollow fiber membranes can be obtained. In fact, hollow fiber membrane can be designed at different conditions and for different rates that it can save cost of various tests.

H2/CO mixture gas separation using composite hollow fiber membranes prepared by interfacial polymerization method

This paper describes the study on H2/CO mixture gas separation through thin film composite (TFC) membranes prepared by interfacial polymerization method. Composite membranes have been widely applied in gas separation process. Polyethersulfone (PES) hollow fiber membranes (HFMs) are fabricated using dry–wet phase inversion method as high permeability substrates. H2/CO mixture gas selectivity and permeance were studied using different concentrations of aqueous and organic phase monomers. Cross-linked structures of TFC membranes by interfacial polymerization were confirmed and discussed by using the compiled results of characterization, such as ATR-FTIR, FE-SEM, and TEM. The performance of HFM using different monomer concentrations of 1,3-cyclohexanebis methylamine (CHMA) (aqueous phase monomer) and trimesoyl chloride (TMC) (organic phase monomer) towards H2/CO mixture gas selectivity and permeance have been studied, and the effects of operating pressures, retentate flow rates and stage-cuts on separation factor and permeance were also investigated in this work. The monomers concentrations affect the selectivity and permeability in H2/CO mixture gas separation. Experimental results confirmed that increasing of operating pressure and stage-cut led to higher separation factor and showed simulation of module design to consider characteristics of membrane and behaviors for H2/CO mixture gas separation. In this paper, also represent the membrane spinning, polymerization and Membrane process design.

Enhanced hollow fiber membrane performance via semi-dynamic layer-by-layer polyelectrolyte inner surface deposition for nanofiltration and forward osmosis applications

The layer-by-layer (LBL) polyelectrolyte deposited membranes have drawn increasing attention in various applications due to the ease of selective layer formation and their stability and versatility. In this study, the LBL deposition was performed at the inner surface of the polyethersulfone (PES) hollow fiber substrate to form composite nanofiltration (NF) membrane. The semi-dynamic deposition procedure was adopted with the aid of syringes. The newly developed inner deposited (id-LBL) membranes were then tested in NF and forward osmosis (FO) applications and the performance were compared with outer surface deposition as well as some literature data. The id-LBL membranes could not only withstand higher operating pressure but also possess superior hardness rejection especially in high concentration mixed salt solutions (more than 95% rejection to Mg2+ and Ca2+ in a 5000ppm total dissolved salt (TDS) mixture under 4.8bar). As for the FO process, with only two layer deposition, the id-LBL membranes also demonstrated significant performance improvement with increased water flux (up to 70L/m2h using 0.5M MgCl2 as draw solution in active layer facing draw solution configuration) and reduced salt leakage (around 0.5g/m2h using 1M MgCl2 draw solution in active layer facing feed water configuration). This study suggests that for hollow fiber substrate, the inner surface is more suitable for the formation of the selective layer via LBL deposition than the outer surface.

Preparation of Polyvinylidene Fluoride (PVDF) Hollow Fiber Hemodialysis Membranes

In this study, the polyvinylidene fluoride (PVDF) hollow fiber hemodialysis membranes were prepared by non-solvent induced phase separation (NIPS). The influences of PVDF membrane thickness and polyethylene glycol (PEG) content on membrane morphologies, pore size, mechanical and permeable performance were investigated. It was found that membrane thickness and PEG content affected both the structure and performance of hollow fiber membranes. The tensile strength and rejection of bovine serum albumin (BSA) increased with increasing membrane thickness, while the Ultrafiltration flux (UF) flux of pure water was the opposite. The tensile strength, porosity and rejection of BSA increased with increasing PEG content within a certain range. Compared with commercial F60S membrane, the PVDF hollow fiber membrane showed higher mechanical and permeable performance. It was proven that PVDF material had better hydrophilicity and lower BSA adsorption, which was more suitable for hemodialysis. All the results indicate that PVDF hollow fiber membrane is promising as a hemodialysis membrane.

Development of Analysis Method for Forward Osmosis Hollow Fiber Membrane Performance

Development of Analysis Method for Forward Osmosis Hollow Fiber Membrane Performance