Single Hollow Fiber Research Articles

From single tube to multi-channel configuration: Constructing nanofiltration membranes with superior adhesion strength on the ceramic support by interfacial polymerization

Ceramic membranes with multi-channel configurations exhibit superior mechanical strength, high packing density, and high separation efficiency, making them more suitable for industrial applications than single tube and hollow fiber membranes. However, the preparation of thin-film composite (TFC) membranes on multi-channel ceramic supports remains a challenge because of the poor compatibility between organic and inorganic materials and their special configuration. In this study, nanofiltration membranes with a stabilized structure supported by 19-channel ceramic membranes were successfully prepared with improved adhesion strength and dynamic interfacial polymerization. TFC membranes with different channels exhibited uniform microstructure and stable performance. Specifically, polyethyleneimine, which served as a polymerization reactant, can be tightly wound on the surface of ceramic membranes via hydrogen bonding and van der Waals forces during interfacial polymerization. Owing to the enhanced cross-linked network interactions between the support and separation layers, the adhesion strength was significantly improved. Consequently, the optimized membranes maintained excellent rejection to MgCl2 of ∼94 % after the back-flush test under the pressure of 4 bar. Additionally, the multi-channel TFC membranes exhibited stable performance, with a pure water permeance of ∼14.9 LMH/bar and a molecular weight cut-off of 450 Da. When filtering sunset yellow for 10 h, the prepared membranes exhibited stable permeance and excellent rejection performance.

CFD simulation and design of ceramic hollow fiber membrane stack for oxygen separation

Hollow fiber ceramic membrane technology demonstrates a great potential for high performance oxygen separation from air. Upscaling of single hollow fiber membrane for membrane stacks and modules is necessary toward practical applications. However, experimental methods are very time-consuming and highly cost. Mathematical modeling is a cost-effective technique and very flexible to evaluate different upscaling strategies. In this research, built upon the experimental results of a proof-of-concept hollow fiber membrane stack, a computational fluid dynamics-based Multiphysics stack model is developed and validated. Comprehensive simulations are conducted to understand the behaviors of stacks under different operating conditions. Different designs strategies are also evaluated toward optimizations of stack performance.

Effect of flux and shear rate on E. coli recovery in tangential flow filtration through a single hollow fiber.

Pathogenic bacteria which enter a viable but non-culturable (VBNC) state impede efforts to reach detectable concentrations required for PCR methods. This motivated a strategy for tangential flow filtration to concentrate bacteria in aqueous samples while maintaining the bacteria in a viable state, maximizing their recovery and achieving high fluxes through a single hollow fiber membrane. Filtrations were carried out for green fluorescent protein (GFP) E. coli at high shear rates (up to 27,000 sec-1) through 0.2 μm cut-off polyethersulfone (PES) microfilter membranes or 50 kDa polysulfone (PS) ultrafilter membranes. High shear minimized bacterial attachment on membrane surfaces, which would otherwise occur due to forced convection of the particles to the membrane surface at high flux conditions. Single fiber filter modules were constructed to facilitate concentration of Escherichia coli at fluxes ranging from 55 to 4500 L m-2 h-1. The effect of high shear rates on bacterial viability was found to be minimal with bacterial losses during filtration caused principally by their accumulation on the membrane surface. Recoveries of 90% were achievable at high shear rates when the average flux was ≤300 L m-2 h-1. This corresponded to a 3-h filtration time for a 225 mL sample through a single hollow fiber. Detectable bacteria concentrations of 1800 colony-forming unit (CFU)/mL were achieved for starting concentrations of 140 CFU/mL.

Iron Control in Liquid Effluents: Pseudo-Emulsion Based Hollow Fiber Membrane with Strip Dispersion Technology with Pseudo-Protic Ionic Liquid (RNH3+HSO4-) as Mobile Carrier.

The transport of iron(III) from aqueous solutions through pseudo-emulsion-based hollow fiber with strip dispersion (PEHFSD) was investigated using a microporous hydrophobic hollow fiber membrane module. The pseudo-protic ionic liquid RNH3HSO4- dissolved in Solvesso 100 was used as the carrier phase. This pseudo-protic ionic liquid was generated by the reaction of the primary amine Primene JMT (RNH2) with sulphuric acid. The aqueous feed phase (3000 cm3) containing iron(III) was passed through the tube side of the fiber, and the pseudo-emulsion phase of the carrier phase (400 cm3) and sulphuric acid (400 cm3) were circulated through the shell side in counter-current operational mode, using a single hollow fiber module for non-dispersive extraction and stripping. In the operation, the stripping solution (sulphuric acid) was dispersed into the organic membrane phase in a tank with a mixing arrangement (a four-blade impeller stirrer) designed to provide strip dispersion. This dispersed phase was continuously circulated from the tank to the membrane module in order to provide a constant supply of the organic solution to the fiber pores. Different hydrodynamic and chemical parameters, such as feed (75-400 cm3/min) and pseudo-emulsion phases (50-100 cm3/min) flows, sulphuric acid concentration in the feed and stripping phases (0.01-0.5 M and 0.5-3 M, respectively), metal concentration (0.01-1 g/L) in the feed phase, and PPILL concentration (0.027-0.81 M) in the carrier phase, were investigated. From the experimental data, different diffusional parameters were estimated, concluding that the resistance due to the feed phase was not the rate-controlling step of the overall iron(III) transport process. It was possible to concentrate iron(III) in the strip phase using this smart PEHFSD technology.

Upscaling of asymmetric hollow fiber‐supported thin film membranes for oxygen separation from air: Proof of concept

AbstractHollow fiber membranes demonstrate various advantages for high performance oxygen separation. However, the small diameters of hollow fibers and the brittleness of ceramics limit their mechanical strength, imposing great difficulties on stack and module development. Gas‐tight sealing is another challenge for upscaling of hollow fiber membrane technology. Low temperature sealant materials of epoxy resin or silicon are typically used for hollow fiber stacks, requiring that the sealing portions be located out of hot zone. Consequently, only partial length of hollow fibers participates in oxygen permeation. In this study, upscaling of our recently developed asymmetric hollow fiber‐supported thin film membranes is conducted, where individual hollow fibers are assembled in parallel to form a stack. A reliable gas‐tight sealing is obtained by combining ceramic paste with conductive adhesive ink cohesively. Comprehensive oxygen permeation test is conducted with the sealing portions being in hot zone and compared with a single hollow fiber membrane. Fundamental mechanism is discussed to understand the performances and their differences. An accelerated long‐term test (∼320 h, 16 thermal cycles) demonstrates excellent stability and robustness of the stack and sealing. The characterization of post‐test samples further confirms excellent stability and robustness of the phases and microstructures of the stack.

Vibration Characteristic Analysis of Hollow Fiber Membrane for Air Dehumidification Using Fluid-Structure Interaction.

Hollow fiber membrane dehumidification is an effective and economical method of air dehumidification. The hollow fiber membrane module is the critical component of the dehumidification system, which is formed by an arrangement of several hollow fiber membranes. The air stream crosses over the fiber bundles when air dehumidification is performed. The fibers vibrate with the airflow. To investigate the characteristics of the fluid-induced vibration of the hollow fiber membrane, the two-way fluid-structure interaction model under the air-induced condition was established and verified by experiments. The effect of length and air velocity on the vibration and modal of a single hollow fiber membrane was studied, as well as the flow characteristics using the numerical simulation method. The results indicated that the hollow fiber membrane was mainly vibrated by fluid impact in the direction of the airflow. When the air velocity was 1.5 m/s~6 m/s and the membrane length was 100~400 mm, the natural frequency of the membrane was negatively correlated with length and positively correlated with air velocity. Natural frequencies were more sensitive to changes in length than changes in air velocity. The maximum equivalent stress and total deformation increased with air velocity and length. The maximum equivalent stress was concentrated at both ends, and the maximum deformation occurred in the middle. The research results provided a basis for the structural design of hollow fiber membranes under flow-induced vibration conditions.

Dual-layer hollow fibre haemodialysis membrane for effective uremic toxins removal with minimal blood-bacteria contamination

Bacterial endotoxin contamination in dialysate may pass through haemodialysis membrane and cause a silent chronic microinflammation to kidney patients. Dual-layer hollow fibre (DLHF) membranes with dual function, biocompatible adsorptive and antibacterial effects were developed to solve the problem of incompatible membrane and endotoxin contamination. All membranes were fabricated via the co-extrusion dry-wet phase inversion technique. In this study, silica/α-mangostin nanoparticle was incorporated into the inner layer of membrane to enhance the biocompatibility of the membrane while maintaining its adsorption capacity. Activated carbon (AC) was incorporated in the outer layer of membrane for improved antibacterial property. The DLHF membranes were characterised based on its morphology and surface hydrophilicity. The performance of the DLHF membranes was evaluated in terms of permeability, urea, and creatinine removal capabilities, bovine serum albumin (BSA) rejection and antibacterial properties. The dense and small pore size on the outer layer of AC created a smoother surface for the DLHF membrane. The BSA rejection of the DLHF membranes was enhanced by 6–8% compared to that of unmodified single layer hollow fibre membrane. Silica/α-mangostin nanoparticle in the inner layer of membrane enhanced the removal of urea and creatinine by chemisorption. Result also showed that the incorporation of AC in the outer layer of DLHF membrane successfully filtered bacteria by bacteria entrapment. DLHF membrane with the combination of silica/α-mangostin nanoparticle in the inner layer and AC in the outer layer possessed the higher bacteria inhibition into blood compartment against Escherichia coli and Staphylococcus aureus, with removal rate of 68% and 75%, respectively, and better urea and creatinine removal by 60.57% and 75.18%, respectively, compared to single-layer PSf based membrane. The development of co-adsorptive biocompatible DLHF membrane can play an important role in improvement of kidney patient life.

Novel ceramic hollow fibre membranes contactor derived from kaolin and zirconia for ammonia removal and recovery from synthetic ammonia

The adverse effects of ammonia found in wastewater streams lead to the development of advanced water treatment technology, i.e. membrane contactor (MC). In this study, single layer hollow fibre membrane (SLZK) and dual layer hollow fibre membrane (DLZK) were prepared from zirconia and kaolin and modified into hydrophobic membrane through simple grafting process via fluoroalkylsilane (FAS) agent. The properties of membranes such as morphology, surface roughness, mechanical strength, wettability and liquid entry pressure were analysed through scanning electron microscopy (SEM), atomic force microscopy (AFM), 3-point bending strength, contact angle and LEPw setup. Finally, the performance of the membranes was also investigated towards ammonia removal via membrane contactor system. Our findings showed that hydrophobicity properties significantly improved for both SLZK and DLZK membranes after grafting modification process as indicated by the increase of contact angle value from 5° and 1° to 132.7° and ~180.0° respectively. Based on the morphological analysis, the surface of DLZK showed more porous structure as compared to the SLZK. In addition, DLZK also displayed the highest mechanical strength and contact angle reading of 125 MPa and ~180° respectively. This suggests that the DLZK showed an excellent membrane contactor performance with highest value of mass transfer coefficient (3.77 x 10-5 ms-1) and almost complete removal of ammonia removal (91%). Overall, these results implied that dual layer ceramic membrane developed from kaolin and zirconia could provide the basis for the development of alternative ceramic membrane with excellent properties for membrane contactor system.

Numerical Simulation of the Water Vapor Separation of a Moisture-Selective Hollow-Fiber Membrane for the Application in Wood Drying Processes.

In this study, a simplified two-dimensional axisymmetric finite element analysis (FEA) model was developed, using COMSOL Multiphysics® software, to simulate the water vapor separation in a moisture-selective hollow-fiber membrane for the application of air dehumidification in wood drying processes. The membrane material was dense polydimethylsiloxane (PDMS). A single hollow fiber membrane was modelled. The mass and momentum transfer equations were simultaneously solved to compute the water vapor concentration profile in the single hollow fiber membrane. A water vapor removal experiment was conducted by using a lab-scale PDMS hollow fiber membrane module operated at constant temperature of 35 °C. Three operation parameters of air flow rate, vacuum pressure, and initial relative humidity (RH) were set at different levels. The final RH of dehydrated air was collected and converted to water vapor concentration to validate simulated results. The simulated results were fairly consistent with the experimental data. Both experimental and simulated results revealed that the water vapor removal efficiency of the membrane system was affected by air velocity and vacuum pressure. A high water vapor removal performance was achieved at a slow air velocity and high vacuum pressure. Subsequently, the correlation of Sherwood (Sh)–Reynolds (Re)–Schmidt (Sc) numbers of the PDMS membrane was established using the validated model, which is applicable at a constant temperature of 35 °C and vacuum pressure of 77.9 kPa. This study delivers an insight into the mass transport in the moisture-selective dense PDMS hollow fiber membrane-based air dehumidification process, with the aims of providing a useful reference to the scale-up design, process optimization and module development using hollow fiber membrane materials.

Development of a hollow fibre-based renal module for active transport studies

Understanding the active transport of substrates by the kidney in the renal proximal convoluted tubule is crucial for drug development and for studying kidney diseases. Currently, cell-based assays are applied for this this purpose, however, differences between assays and the body are common, indicating the importance of in vitro–in vivo discrepancies. Several studies have suggested that 3D cell cultures expose cells to a more physiological environments, thus, providing more accurate cell function results. To mimic the renal proximal tubule, we have developed a custom-made renal module (RM), containing a single polypropylene hollow fibre (Plasmaphan P1LX, 3M) that serves as a porous scaffold and compared to conventional Transwell cell-based bidirectional transport studies. In addition, a constant flow of media, exposed cells to a physiological shear stress of 0.2 dyne/cm2. MDCK-Mdr1a cells, overexpressing the rat Mdr1a (P-gp) transporter, were seeded onto the HF membrane surface coated with the basement membrane matrix Geltrex which facilitated cell adhesion and tight junction formation. Cells were then seeded into the HF lumen where attachment and tight junction formation were evaluated by fluorescence microscopy while epithelial barrier integrity under shear stress was shown to be achieved by day 7. qPCR results have shown significant changes in gene expression compared to cells grown on Transwells. Kidney injury marker such as KIM-1 and the hypoxia marker CA9 have been downregulated, while the CD133 (Prominin-1) microvilli marker has shown a fivefold upregulation. Furthermore, the renal transporter P-gp expression has been downregulated by 50%. Finally, bidirectional assays have shown that cells grown in the RM were able to reabsorb albumin with a higher efficiency compared to Transwell cell cultures while efflux of the P-gp-specific substrates Hoechst and Rhodamine 123 was decreased. These results further support the effect of the microenvironment and fluidic shear stress on cell function and gene expression. This can serve as the basis for the development of a microphysiological renal model for drug transport studies.

Designing scalable dual-layer composite hollow fiber nanofiltration membranes with fully cross-linked ultrathin functional layer

The treatment of industrial wastewater containing complex foulants demands high efficiency yet cost-effective separation process. The composite hollow fiber nanofiltration membranes suffer from tedious fabrication procedures, impeding the large volume fabrication and application. Herein, we reveal a very simplified designing strategy by polyelectrolyte modification of the co-extruded polyimide/polyethersulphone dual-layer hollow fibers with hierarchical structure and chemistry. The active layer's thickness of the dual-layer hollow fiber substrate is only 800 nm, the thinnest in literature. Compared to integral active single layer hollow fiber, the ultrathin active layer not only leads to over 4 times increase in mechanical flexibility and tenfold reduction in material cost but also enables fully chemical transition from imide to cross-linked polyamide, minimizing the intrinsic hydrolysis tendency of active material. The optimized membranes with a well-defined pore radius of 0.23 nm have 93–95% rejection to Mg2+ and Ca2+ and PWP of 9.1 LMH/bar. Moreover, the composite membranes exhibit backwash ability and stability in the heated feed solutions, which meets the demand for direct treatment of industrial effluents. This work paves the way for the large volume fabrication and application of hollow fiber nanofiltration membranes for treating municipal water, industrial wastewater, and other applications.

Direct visualization of virus removal process in hollow fiber membrane using an optical microscope

Virus removal filters developed for the decontamination of small viruses from biotherapeutic products are widely used in basic research and critical step for drug production due to their long-established quality and robust performance. A variety of imaging techniques have been employed to elucidate the mechanism(s) by which viruses are effectively captured by filter membranes, but they are limited to ‘static’ imaging. Here, we propose a novel method for detailed monitoring of ‘dynamic process’ of virus capture; specifically, direct examination of biomolecules during filtration under an ultra-stable optical microscope. Samples were fluorescently labeled and infused into a single hollow fiber membrane comprising cuprammonium regenerated-cellulose (Planova 20N). While proteins were able to pass through the membrane, virus-like particles (VLP) accumulated stably in a defined region of the membrane. After injecting the small amount of sample into the fiber membrane, the real-time process of trapping VLP in the membrane was quantified beyond the diffraction limit. The method presented here serves as a preliminary basis for determining optimum filtration conditions, and provides new insights into the structure of novel fiber membranes.

Delamination of single layer hollow fiber membranes induced by bi-directional phase separation

Structural delamination across the hollow fiber wall is a major challenge for the fabrication of dual-layer hollow fiber membranes. Delamination may also exist in single-layer hollow fiber membranes because the dope solution undergoes phase separation at both inner and outer surfaces. Different phase inversion mechanisms and rates at the inner and outer surfaces result in hollow fibers with different morphologies across the wall and may lead to delamination between the layers. In this work, the origins of delamination for single-layer hollow fiber membranes are investigated. The effects of dope composition, bore fluid chemistry as well as spinning conditions on delamination are disclosed. Among these parameters, bore fluid composition has the most profound impact on fiber delamination. With carefully designed spinning conditions (e.g. high air gap and take-up speed), the occurrence of fiber delamination can be mitigated. A membrane with a delaminated inner layer often possesses a highly porous inner surface with an improved permeance for water filtration. This work offers feasible solutions to resolve structural delamination of hollow fiber membranes during spinning. It may also provide a new method to fabricate high-flux hollow fiber membranes by producing fiber delamination intentionally.

Preparation and characterization of different geometrical shapes of multi-bore hollow fiber membranes and application in vacuum membrane distillation

Multi-bore hollow fiber membranes were prepared through phase inversion spinning process using new locally designed spinnerets of various geometrical shapes. The spun cylindrical-like, rectangular or ribbon-like, and triangular-like are prepared, dried, and characterized by scanning electronic microscope. Fibers of circular (seven, five, and four bores) shape, rectangular of five bores, and triangular of three bores were chosen to study the effect of both geometrical configuration and the number of bores on the amorphous structure and the mechanical properties of the membranes. Membrane geometry, surface amorphous, and bore arrangements are very sensitive to the operating conditions, especially the extrusion and drawing rates. Three polymeric blends of different compositions are used to prepare multi-bore hollow fiber membranes. This study revealed that the blend composition of PES 16%, PVP 2%, PEG 2%, diethylene glycol 2%, and NMP 78% gives excellent mechanical properties. Optimization of the preparation conditions also developed, where the dope flow rate, the bore flow rate, and the air gap were 1.14 cm3 s−1, 1.1 cm3 s−1, and 0 cm, respectively. Furthermore, this study proved that the circular arrangement has high mechanical strength. The prepared seven-MBHF membranes were applied in the membrane distillation process, a solution of 35 g/l NaCl was used to test the membrane performance, and the achieved flux and rejection were 28.32 L/m2 h and 98.9%, respectively. This performance demonstrated that the prepared membrane in this way is suitable to compete with conventional reverse osmosis technology that uses single track hollow fibers.

Analysis of pressure-driven water vapor separation in hollow fiber composite membrane for air dehumidification

A two-dimensional axisymmetric mathematical model was established to describe the pressure-driven water vapor separation in the hollow fiber composite membrane for air dehumidification. The developed transport model considered the permeation in the dense layer and the diffusion in the porous membrane substrate, in which the mass and momentum balance equations were coupled. The predicted results by the simulation model was consistent well with the experimental data. The velocity, pressure and concentration profiles and the mass transfer process in a single hollow fiber membrane were then solved and analyzed in detail, including the effects of feed velocity, feed humidity and transmembrane pressure on the dehumidification performance. The results show that the amount of water vapor separation (outlet humidity) is more sensitive to the medium feed velocity with the separation amount about twice than that of high and low velocities. The separated amount of water vapor by the membrane is less dependent on the feed inlet humidity. And the air dehumidification performance of the membrane could be realized effectively until the transmembrane pressure over a critical value, which is 1.0 bar in this model. The findings deliver an insight into the mass transport in the membrane-based dehumidification process, with the aims to provide a useful reference to the design, process optimization and module development using hollow fiber membrane.

Nitric oxide reduction by hydrogen peroxide absorption through a ceramic hollow fiber membrane contactor

Nitric oxide reduction by hydrogen peroxide absorption through a ceramic hollow fiber membrane contactor was studied experimentally. A membrane contactor with a single ceramic hollow fiber was characterized by multiple techniques, including contact angle measurement, gas permeation, water permeation and spectroscopy. The superhydrophobic ceramic was first used to achieve nonwetting conditions, and overatmospheric operating conditions were applied to enhance mass transfer. The effects of the process parameters on NO reduction were tested and discussed. It was found that NO reduction increases linearly with diffusion length. The gas flow rate and absorbent flow rate are suggested to be low to achieve high-efficiency gas absorption. NO reduction increases linearly with the enhancement factor or the square root of hydrogen peroxide concentration. Elevated pressure increases NO absorption flux and helps NO reduction within the breakthrough pressure.

Ex vivo evaluation of the blood compatibility of mixed matrix haemodialysis membranes

The patients with end stage kidney disease need haemodialysis therapies, using an artificial kidney. Nevertheless, the current therapies cannot remove a broad range of uremic toxins compared to the natural kidney. Adsorption therapies, using sorbent-based columns, can improve the clearance of uremic toxins, but the sorbent particles often require polymeric coatings to improve their haemocompatibility leading to mass transfer limitations and to lowering of their performance.Earlier, we have developed a dual layer Mixed Matrix fiber Membrane (MMM) based on polyethersulfone/polyvinylpyrrolidone (PES/PVP) polymer blends. There, the sorbent activated carbon particles are embedded in the outer membrane layer for achieving higher removal whereas the inner blood contacting selective membrane layer should achieve optimal blood compatibility. In this work, we evaluate in detail the haemocompatibility of the MMM following the norm ISO 10993–4. We study two generations of MMM having different dimensions and transport characteristics; one with low flux and no albumin leakage and another with high flux but some albumin leakage. The results are compared to those of home-made PES/PVP single layer hollow fiber and to various control fibers already applied in the clinic. Our results show that the low flux MMM successfully avoids contact of blood with the activated carbon and has good haemocompatibility, comparable to membranes currently used in the clinic. Statement of SignificanceHaemodialysis is a life-sustaining extracorporeal treatment for renal disease, however a broad range of uremic toxins cannot still be removed. In our previous works we showed that a double layer Mixed Matrix Membrane (MMM) composed of polyethersulfone/polyvinylpyrrolidone and activated carbon can achieve higher removal of uremic toxics compared to commercial haemodialysers. In this work we evaluate the haemocompatibility profile of the MMM in order to facilitate its clinical implementation. The lumen particle-free layer of the MMM successfully avoids the contact of blood with the poorly blood-compatible activated carbon. Moreover, thanks to the high amount of polyvinylpyrrolidone and to the smoothness of the lumen layer, the MMM has very good haemocompatibility, comparable to membranes currently used in the clinic.

Tracing the Dynamic Changes of Element Profiles by Novel Soil Porewater Samplers with Ultralow Disturbance to Soil-Water Interface.

In flooded soils, soil–water interface (SWI) is the key zone controlling biogeochemical dynamics. Chemical species and concentrations vary greatly at micro- to cm-scales. Techniques able to track these changing element profiles both in space and over time with appropriate resolution are rare. Here, we report a patent-pending technique, the Integrated Porewater Injection (IPI) sampler, which is designed for soil porewater sampling with minimum disturbance to saturated soil environment. IPI sampler employs a single hollow fiber membrane tube to passively sample porewater surrounding the tube. When working, it can be integrated into the sample introduction system, thus the sample preparation procedure is dramatically simplified. In this study, IPI samplers were coupled to ICP-MS at data-only mode. The limits of detection of IPI-ICP-MS for Ni, As, Cd, Sb, and Pb were 0.12, 0.67, 0.027, 0.029, and 0.074 μg·L–1, respectively. Furthermore, 25 IPI samplers were assembled into an SWI profiler using 3D printing in a one-dimensional array. The SWI profiler is able to analyze element profiles at high spatial resolution (∼2 mm) every ≥24 h. When deployed in arsenic-contaminated paddy soils, it depicted the distributions and dynamics of multiple elements at anoxic–oxic transition. The results show that the SWI profiler is a powerful and robust technique in monitoring dynamics of element profile in soil porewater at high spatial resolution. The method will greatly facilitate studies of elements behaviors in sediments of wetland, rivers, lakes, and oceans.

Theoretical demonstration of single polarization single mode hollow core anti-resonance fiber using surface plasmon resonance

We designed a hollow core anti-resonance fiber based on surface plasmon resonance (SPR) and optimized its characteristics by using the finite element method with perfectly matched layer boundary condition. A single mode single polarization bandwidth, up to 200 nm, is obtained by employing SPR which is produced by two embedded gold wires. Only the x-polarized fundamental mode of the fiber suffers a high loss because of the SPR. In addition, single mode guidance is obtained by adjusting the size of cladding tubes. Simulation results show that the designed fiber has an effective single polarization single mode guidance in the wavelength range from 1.3 to 1.5 μm. In this range, both the higher order mode extinction ratio and the polarization mode extinction ratio are more than 100. The structure is shown to have a good fabrication tolerance with respect to variations in the position and size of the gold wires. The proposed fiber has many potential applications in polarization splitters, fiber-optic gyroscopes and polarization-dependent fiber systems.

The Effect of Ca and Mg Ions on the Filtration Profile of Sodium Alginate Solution in a Polyethersulfone-2-(methacryloyloxy) Ethyl Phosphorylchloline Membrane

The efforts to improve the stability of membrane filtration in applications for wastewater treatment or the purification of drinking water still dominate the research in the field of membrane technology. Various factors that cause membrane fouling have been explored to find the solution for improving the stability of the filtration and prolong membrane lifetime. The present work explains the filtration performance of a hollow fiber membrane that is fabricated from polyethersulfone-2-(methacryloyloxy) ethyl phosphorylchloline while using a sodium alginate (SA) feed solution. The filtration process is designed in a pressure driven cross-flow module using a single piece hollow fiber membrane in a flow of outside-inside We investigate the effect of Ca and Mg ions in SA solution on the relative permeability, membrane resistance, cake resistance, and cake formation on the membrane surface. Furthermore, the performance of membrane filtration is predicted while using mathematical models that were developed based on Darcy’s law. Results show that the presence of Ca ions in SA solution has the most prominent effect on the formation of a cake layer. The formed cake layer has a significant effect in lowering relative permeability. The developed models have a good fit with the experimental data for pure water filtration with R2 values between 0.9200 and 0.9999. When treating SA solutions, the developed models fit well with experimental with the best model (Model I) shows R2 of 0.9998, 0.9999, and 0.9994 for SA, SA + Ca, and SA + Mg feeds, respectively.