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Rational design and synthesis of molecular sieving, photocatalytic, hollow fiber membranes for advanced water treatment applications

Rational design and synthesis of molecular sieving, photocatalytic, hollow fiber membranes for advanced water treatment applications

The photocatalytic activity of the composite hollow fibers was evaluated using four UV-A lamps (SYLVANIA Blacklite F8W/BL350, 330 – 370 nm emission; 8 Watt each) as the UV source. Acid Orange 7 (AO7) was used as a model colour dye due to its excellent stability under UV irradiation [34]. 25 ml of AO7 (20 ppm; pH 6.5) in a quartz reactor vessel was placed concentrically at 15 cm away from the UV lamps in the UV chamber to minimize the heating effect of the UV lamps. The sintered hollow fiber membranes weighing about 50 mg (membrane surface area: approximately 1.5 × 10 -4 m 2 ) were immersed in the AO7 solution in the reactor. 30 min dark sorption experiment was performed prior to switching on the UV lamps. The measured intensity of the UV via an intensity meter (Model 308, OAI) received on the membrane is approximately 0.17 mW cm ‒2 in the presence of AO7 solution. During the photocatalysis under UV exposure, the temperature of the reactor gradually increased from room temperature (22 °C under air condition) to about 40 ± 1 °C, of which the impact on the photo-degradation of the AO7 dye is considered insignificant based on our observations and the literature [30, 35-37]. Hence, the temperature effect is
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A Comparative Study on the Application of Porous PES and PEI Hollow Fiber Membranes in Gas Humidifcation Process

A Comparative Study on the Application of Porous PES and PEI Hollow Fiber Membranes in Gas Humidifcation Process

The objective of this study is to apply two different polyetherimide (PEI) and polyethersulfone (PES) hollow fiber membranes in gas humidification process and comparing their performance at various operating conditions and study the effect of operating parameters on the water vapor flux. PEI and PES membranes have good thermal and chemical resistance and have been applied in membrane gas absorption process [25, 26] which showed reasonable results; therefore it is expected that PEI and PES membranes present suitable performance in humidification process. Furthermore, comparing the characteristics of membranes provides the criteria to find the ones that govern the performance of the membrane in the humidification process.
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Clarification of factors that affect the 
		flux performance of Hollow Fiber membranes during Ultra filtration using 
		Design of Experiments

Clarification of factors that affect the flux performance of Hollow Fiber membranes during Ultra filtration using Design of Experiments

In this paper, the separation of humic substances from oily wastewater was investigated using Hollow Fiber membranes. Consideration was given to the increse of membrane permeability or flux of the Ultrafiltration process. Specifically, several factors which were temperature, pressure, time, pH and surface area of membrane, were studied. The Design of Experiments (DOE) methodology was used to investigate the effect of the factors. From the analysis of variance (ANOVA), it was determined that the pH and temperature of feed solution, time of separation process and transmembrane pressure are significant. The results of this study help to increase the permeability of membranes, thus contributing to a more sustainable filtration system.
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Fabrication of Crosslinkable Hollow Fiber Membranes for Pervaporation Dehydration

Fabrication of Crosslinkable Hollow Fiber Membranes for Pervaporation Dehydration

Integrally-skinned asymmetric Polyetherimide/Poly (vinyl alcohol) (PEI/PVA) hollow fiber membranes for pervaporation dehydration were fabricated by non-solvent induced phase inversion. PVA inside the PEI matrix could be crosslinked to provide membrane performance stability during long term operation. The effects of different PEI/PVA blend ratio, external coagulant type and flow rate, and crosslinking conditions on the membrane structure and the separation performance were investigated. Generally, hollow fibers using PEI/PVA blend are less selective than those of neat PEI, probably due to the defects evolved between PEI and PVA. The influence of coagulant type on membrane pervaporation performance was specific to dope formulation; when using n-butanol as external coagulant, the higher the coagulant flow rate, the better the membrane separation performance. PVA crosslinking by maleic acid (MA) enhanced the membrane performance, obviously. PEI/PVA Hollow fibers formed using n-butanol as external coagulant obtained a separation factor of 28 after crosslinking, much better than 4.4 with the original one. The crosslinked membrane exhibited higher stability than the neat PEI membrane. The separation factor of the latter degraded by more than half after around 200 h operation. Finally, this work has provided a new approach for fabricating crosslinkable asymmetric membrane suitable for pervaporation dehydration.
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An Experimental Study on the Oily Wastewaters Treatment by Polyethersulfone (PES) Nanostructure Hollow Fiber Membranes

An Experimental Study on the Oily Wastewaters Treatment by Polyethersulfone (PES) Nanostructure Hollow Fiber Membranes

Oily wastewaters from oil refineries and oil distribution centers are one of the most important environmental concerns in recent decades; therefore, it is critical to treat these types of wastewaters. In this study, the performance of different polyethersulfone hollow fiber membranes in oily wastewaters treatment was investigated and the effects of operating conditions such as transmembrane pressure, oil concentration in the feed and feed cross flow velocity (CFV) on the membrane performance were studied. Increasing the pressure makes more membrane compactness and higher membrane fouling; as a result, higher pressure reduces the membrane performance. The optimum operating conditions for oily wastewaters separation are P = 1 bar, low feed concentration (300 ppm) and high feed cross flow velocity (0.18 m s -1 ). In this
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Quality of Kiwifruit Juice Clarifed by Modifed Poly(Ether Ether Ketone) Hollow Fiber Membranes

Quality of Kiwifruit Juice Clarifed by Modifed Poly(Ether Ether Ketone) Hollow Fiber Membranes

In this study, however, PEEK-WC HF membranes were used to clarify kiwifruit juice after a preliminary depectinization step. A special attention was paid at evaluating the potential of the prepared membranes in the recovery of bioactive compounds characterising the functional and health- benefit properties of kiwifruit juice. At this purpose, permeate and retentate streams were characterized regarding total antioxidant activity (TAA), total polyphenols, Vitamin C and organic acids content, as well as suspended solids and total soluble solids. An analysis of membrane fouling and cleaning efficiency was also performed through the evaluation of the hydraulic permeability of the membrane measured before and after the treatment with juice and cleaning procedures.
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Latest development of carbon hollow fiber membranes for gas separation

Latest development of carbon hollow fiber membranes for gas separation

especially carlnn membrane has emerged as anothei :itemative membrane in the separation t€chnology. Generallv- inorganic membmnesian be dividcd into two diilerent categoriesi pot[r]

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Membrane module design and dynamic shear-induced techniques to enhance liquid separation by hollow fiber modules: a review

Membrane module design and dynamic shear-induced techniques to enhance liquid separation by hollow fiber modules: a review

To correlate the bubble size/characteristics (effects of air flow rate, orifice size, fluid properties, submergence. etc) and bubble induced fiber movement into the module performance, it is essential to characterize the uniqueness of the bubbling system and distinguish the contribution from bubbles of different sizes. Many researchers [11, 75-78] have investigated the effect of bubble size on module performance in the submerged MBR systems. For example, to observe the relationship between bubbling and module performance via critical flux, trans- membrane pressure (TMP) and membrane fouling formation, Wicaksana et al [11] studied the interaction between bubbling and fiber movement in submerged hollow fiber membranes. It was found that a lower fouling rate could be achieved by more fiber movement under certain conditions such as fiber looseness, smaller bubbles, higher air flow rate, lower feed viscosity and lower solid concentration. The authors also stated that the fiber movement was enhanced by using thinner and longer fibers, but it was insensitive to nozzle sizes (bubble sizes) used in the system. To study the fouling mechanism in submerged hollow fiber membrane modules with bubbling, Yeo et al [76, 79] used particle image velocimetry (PIV) to examine the bubble- induced phenomena by varying and correlating different operating parameters, they also stated that many small bubbles are better than few large bubbles.
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Surface modified hollow fiber membrane contactor for carbon dioxide absorption and desorption

Surface modified hollow fiber membrane contactor for carbon dioxide absorption and desorption

liquid into membrane pores should be prevented as pore wetting reduces the mass transfer in contactor significantly and makes it less competitive compared to the conventional column. One cause of pore wetting is capillary condensation (Mavroudi et al. 2006), but more importantly the pressure of the feed liquid should surpass a critical value for the liquid to enter into push the liquid pores. This critical value, called liquid entry pressure of water, depends on some properties of membrane such as pore size, hydrophobicity, surface roughness and chemical resistance to solvent (Dindore et al. 2004) and also, on the surface tension of solvent and operating conditions of absorption process. Thus, it is possible to reduce the wettability of membranes by decreasing pore size and using membranes of high hydrophobic surface. In hollow fiber membrane contactor furthermore hydrophobicity, pore size is important as well. Hollow fiber membranes with very small pore size show low mass transfer flux due to lower interfacial surface of gas and liquid. Therefore, in order to decreasing wettability of membrane and increasing mass transfer flux, this is essential to fabricate hollow fiber membrane with high hydrophobic surface and large pore size.
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Thin Film Composite and/or Thin Film Nanocomposite Hollow Fiber Membrane for Water Treatment, Pervaporation and Gas/Vapor Separation

Thin Film Composite and/or Thin Film Nanocomposite Hollow Fiber Membrane for Water Treatment, Pervaporation and Gas/Vapor Separation

PRO can be viewed as an intermediate process between FO and RO, where hydraulic pressure is applied in the opposite direction of the osmotic pressure gradient (similar to RO). Loeb and Norman [36] proposed pressure-retarded osmosis (PRO) process. In a PRO process, water flows naturally from a low salinity stream (feed water) at an ambient pressure across a semi-permeable membrane to a pressurized high salinity stream (draw solution) driven by the osmotic pressure difference across the membrane. Chou et al. [37] first time reported the fabrication of thin-film composite hollow fiber membranes which could be used in PRO process. Composite hollow fiber membrane was prepared by depositing a thin layer of PA on PES hollow fiber via IP. The main reagents used were m-phenylenediamine (MPD), trimesoyl chloride (TMC) and cyclohexane. From the performance test, it was revealed that The TFC PRO hollow fiber membranes have a water permeability (A) of 9.22 × 10 −12 m/(s Pa), salt permeability (B) of 3.86 × 10 −8 m/s and structural
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Preparation and characterization of novel PSf/PVP/PANI-nanofiber nanocomposite hollow fiber ultrafiltration membranes and their possible applications for hazardous dye rejection

Preparation and characterization of novel PSf/PVP/PANI-nanofiber nanocomposite hollow fiber ultrafiltration membranes and their possible applications for hazardous dye rejection

Hollow fiber membranes show increased water flux when compared to flat sheet membranes since they have a higher surface area per unit of membrane module volume. The membrane cross-flow filtration tests indicate that, flux increases with increasing PANI- nanofiber concentration for constant pressure of 2 bar as shown in Fig.9. The higher water flux for new membranes can be attributed to increased hydrophilicity and increased porosity due to PVP and PANI-nanofiber additives. The nanocomposite membrane showed increased flux and rejection due to the additives. The PANI-nanofibers are hydrophilic in nature and during the membrane formation process, they migrate towards the surface of the membrane [30]. This migration through the polymer matrix, forms finger like interconnected pores in the membrane cross section. This increases flux and reduces resistance to flow of water through the membrane Also, due to the hydrophilic PANI-nanofibers moving to the surface, the membrane surface becomes more hydrophilic and this in turn increases wetting of the surface contributing to the increase in flux. PVP has been used as a pore forming agent and is reported to increase the formation of pores on the membrane surface [31] thus increasing flux of water through the membrane. Also, since PVP is a water-soluble polymer, it may be leached out from the polymer matrix when the membrane is immersed in water, causing the formation of micro voids and thereby increasing the porosity of the membrane [36].
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Fabrication and Modification of Thin-Film Composite Hollow Fiber NF Membranes

Fabrication and Modification of Thin-Film Composite Hollow Fiber NF Membranes

Thin-film composite hollow fiber membranes were prepared by interfacial polymerization of Piperazine in aqueous phase with TMC in organic phase (i.e. n-hexane). The concentration of additives in the aqueous phase are given in Table 2. The PSF hollow fiber support membrane was submerged into the aqueous phase for 90 s. Subsequently, the membrane was taken out to drain off the excess monomers for 1 min. The amine saturated membrane was again immersed into the organic phase containing 0.5% (w/v) TMC in n-hexane where the conventional IP reaction took place. Afterward, the membrane was taken out and air-dried at 70 °C for 4 min. The dipping process had been carried out such a way that only the external surface has come in contact with reactants to form polyamide skin layer.
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Ionic liquid loaded hollow fiber membrane as a solid phase microextraction fiber; application in determination of aromatic
hydrocarbons in water samples

Ionic liquid loaded hollow fiber membrane as a solid phase microextraction fiber; application in determination of aromatic hydrocarbons in water samples

Use of hollow fiber membranes as fiber coating was reported previously[22]. Results showed good extraction ability of hollow fiber membrane due to its porous structure but weak ability of it in retaining BTEX is a major disadvantage. It isn’t able to retain the analytes more than 2 minutes. In order to solve this problem, incorporating IL as a green separation medium in porous structure of hollow fiber using sol-gel formulation was considered. Comparative results between these two fibers (hollow fiber and IL-loaded hollow fiber) shows that extraction time was increased from 2 min to 40 min and the analytes weren’t leave the fiber at room temperature. Morphological studies on fiber surface were performed using scanning electron microscopy (SEM) and were presented in Figure. 2. SPME fibers are exposed to the hot injection port of the GC. So, thermal stability of them must be studied. The backbone of the proposed fiber is polypropylene (melting point 160-170 ºC). According to the results of thermogravimetric studies (Figure 3-a, b and c) at 150 ºC amount of converted hollow fiber was 7.80%. In the case of IL loaded hollow fiber and sol-gel based IL loaded hollow fiber amount of conversion were 1.99% and 1.28%, respectively. Results indicate significant increase in thermal stability of the proposed fiber.
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Application of Salt Additives and Response Surface Methodology for Optimization of PVDF Hollow Fiber Membrane in DCMD and AGMD Processes

Application of Salt Additives and Response Surface Methodology for Optimization of PVDF Hollow Fiber Membrane in DCMD and AGMD Processes

In this study, the influence of the salts as an additive on the performance of the membrane was investigated and an extensive work was performed to optimize PVDF hollow fiber membranes through a response surface methodology (RSM). The prepared membranes were characterized by SEM, contact angle and LEP measurement. Then, the RSM was used for the optimization of surface pore size, porosity and hydrophobicity of the synthesized hollow fiber at different conditions (polymer concentration, salt concentrations, and air gap). Under MD conditions (feed concentration, 100 mg/l; feed temperature 80 °C, and cooling temperature 15 °C), the optimum membrane was compared with the virgin one in the same condition. In addition, the influence of distillate flux at different feed concentrations and temperatures was evaluated. The results show that the optimum hollow fiber membrane was fabricated in the polymer concentration of 22 %w/w, BaCl 2 concentration of 2.9 %w/w and an air gap of 34.5 cm. Consequently, the optimum fiber was examined for the desalination
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CO2 biofixation by Dunaliella Salina in batch and semi-continuous cultivations, using hydrophobic and hydrophilic poly ethylene (PE) hollow fiber membrane photobioreactors

CO2 biofixation by Dunaliella Salina in batch and semi-continuous cultivations, using hydrophobic and hydrophilic poly ethylene (PE) hollow fiber membrane photobioreactors

A schematic of HFMPB is shown in Fig. 1. An aeration gas was supplied to the lumen of the hollow fiber membranes. The reactor was constructed of tubular plexi-glass sealed with epoxy-resin. Overall length of reactor was 42 cm and the total volume was 157 mL. Fabricated membranes, described above, were used to prepare hollow fiber membrane modules. Modules were called PE-HFMPB and HPE-HMPB, when neat and hydrophilized PE hollow fiber membranes were used, respectively. Each module contained 35 fibers with an active length of 38 cm, outer diameter of 790 µm, and inner diameter of 420 µm. The membranes occupied 4% of the photo bioreactor total volume and total surface area for transfer was 318 cm 2 . A water jacket was installed around the modules in order to keep the temperature constant. Liquid re-circulation was provided using a peristaltic pump and a reservoir tank. In each run, fresh culture medium was added to the tank by a 100 mL Burette and circulated in HFMPB by peristaltic pump. On the contrary with conventional airlift and bubble column photobioreactors, there is no direct contact between gas and liquid phases and CO 2 bubble penetrate into the liquid
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Hollow Piezoelectric Ceramic Fibers for Energy Harvesting Fabrics

Hollow Piezoelectric Ceramic Fibers for Energy Harvesting Fabrics

This dilemma is resolved in a novel kind of commercially available sensors. These Piezoelectric Fiber Composite (PFC) sensors, manufactured (among other companies) by Advanced Cerametrics Inc., and shown in Figure 2, incorporate solid-core PZT fibers inside a passive polymer matrix with interdigitated electrodes. The main advantage of the PFC sensors is that they combine the mechanical flexibility of polymers with the large transduction capabilities of ceramics, and constitute in fact the state-of-the-art technology for flexible energy harvesting sensors. Their principle is illustrated in Figure 3.
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Study Of Staircase Effect On Seismic Performance Of Multistoried Frame Structure

Study Of Staircase Effect On Seismic Performance Of Multistoried Frame Structure

Hollow bricks are widely used as building structural elements. Their acoustic properties are greatly influenced by the pattern of the blocks.[15] Multilayer materials have been widely used as an effective sound attenuation material feasible prediction via a so-called transfer matrix method is often used. This method is based on a theory, which says that the relation between the pressure and bulk flow of two ends of a sound propagating route can be expressed by a matrix.In solid blocks sound insulation is very high as the sound waves cannot pass through it properly.In case of both concrete and clay hollow blocks there are two surfaces for reflection of sound wave so the may can be better insulator but with same they have higher echo effect[23].Fiberous material such as cellulose fiber or glass fiber or any other fiber can act as good acoustic insulator as they are good in absorbing the sound wave.So composite hollow blocks have better sound insulation[24].
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Investigating the Effects of Different Repellent Agents on the Performance of Novel Polyester/Wool Blended Fabrics

Investigating the Effects of Different Repellent Agents on the Performance of Novel Polyester/Wool Blended Fabrics

The effects of fluorocarbon finishing of hollow and solid polyester/wool were studied in order to establish the processing behavior and performance characteristics of the treated fabrics. Polyester/wool blended fabrics before and after dyeing were treated with different fluorochemicals; their liquid repellency after washing and dry cleaning was evaluated. Fabric mechanical properties were compared by measuring tensile strength and low stress mechanical properties. The results indicate that the finishing agent formulation has a great effect on the fabrics repellent properties. Studying the fluorocarbon chain re- orientation during laundering and dry cleaning revealed that each fluorocarbon has different ability to retrieve its original configuration via air drying with subsequent necessity of hot pressing to reach acceptable repellency. Also, the effect of hollow fibers on fabric mechanical properties is practically insignificant. The low stress mechanical properties indicate only relatively small differences among the samples. However, finishing with all chemicals and methods resulted in higher friction between the fibers and yarns, and in increased bending and shear rigidity, and shear hysteresis.
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CO2 Capture by Dual Hollow Fiber Membrane Systems

CO2 Capture by Dual Hollow Fiber Membrane Systems

Membrane based gas separation systems have been used in industries varying from petroleum to municipal water treatment. In addition, membrane systems offer the advantage of a high surface area to volume ratio, and therefore a relatively small equipment footprint. This combined with ease of operation make them particularly attractive for gas separations in remote and lightly manned or unmanned locations such as offshore oil and gas platforms. The ability to treat the produced gas to injection/fuel standards is limited due to the space restrictions on the platform. Most traditional gas treatment systems such as absorption contactors require a significant amount of space for equipment and chemical storage and use, and can be susceptible to the platform motion. Hollow fiber membrane contactors (HFMC) are used in gas treating due to high surface area per unit contactor volume, independent control of gas and liquid flow rates without any flooding, loading, weeping, foaming, or entrainment problems encountered in traditional absorber columns. HFMCs usually have smaller equipment footprints and require lower energy consumption than conventional absorption columns, which makes them particularly favored for offshore gas processing where space is limited. HFMCs can be operated under either cross flow mode or parallel flow mode, depending on the relative flow directions of both fluids. In general, cross flow membrane modules are favored because they can offer higher mass transfer coefficient, better shell side flow distribution and lower pressure drop compared to that of parallel flow modules. When the solvent is passed through shell side, the continuous splitting, and remixing of the liquid phase enhances the mass transfer coefficient,
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Minimizing morphological defects of PEI hollow fibre membrane by 
		optimizing the dope viscosity

Minimizing morphological defects of PEI hollow fibre membrane by optimizing the dope viscosity

structure of membranes to achieve optimum separation performance (Ismail and Lai, 2003). Figure-2 displays the SEM images of PEI hollow fibre membranes using various polymer concentrations. Figure-2a shows the morphological structure of 10 wt. % PEI in NMP. The lower concentration of PEI in dope solution leds to loosely packed structure, thereby the non-solvent water penetrated through the inner surface of hollow fibre membrane and created pores on the membrane surface. Prior to entering the water coagulation bath, the inner water diffused rapidly through the membrane structure and created pores on the surface largely due to the loosely packed polymer chains. The phase separation process was so instantaneous that it created finger-like pores that extended all the way to the outer surface. This morphology will lead to poor separation performance and low mechanical strength (Benjamin and Li. 2009). Similar morphology was found for 15 wt.% PEI/NMP dope solution (Figure-2b). This indicated that 10 and 15 wt. % PEI concentration in NMP solvent is too low to form mechanically strong membranes which may achieve good separation performance. For 20 wt. % PEI concentration, finger-like pores existed but the length and width of the pores have been greatly enhanced forming macrovoids. Also, thin-skinned layer was observed and finger-like pore structure dominated the outer skin layer. The presence of outer skinned layer ensures its ability to perform in separatioin applications but the presence of macrovoids in the surface morphology suggested a membrane with higher permeance but lower selectivity.
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