Film Composite Hollow Fiber Membranes Research Articles

Microfluidic preparation of thin film composite hollow fiber membrane modules for water nanofiltration: Up-scaling, reproducibility and MOF based layers

BackgroundThe commercialization of thin film composite (TFC) hollow fiber (HF) membranes remains challenging owing to issues associated with membrane manufacturing. MethodsTFC membranes were synthesized by microfluidic interfacial polymerization of polyamide (PA) on polysulfone hollow fiber (HF) membrane modules. A total of 33 HF membrane modules were prepared with different number of HFs (from 1 to 25) and different lengths (from 10 to 50 cm). They were evaluated in a nanofiltration operation in terms of water permeance and rose Bengal (RB) and MgSO4 rejections. Significant findingsAmong the 33 modules, 73% showed RB rejections higher than 95%, while 36% of the modules reached rejections above 99%. During the membrane synthesis, different parameters, such as PA monomer concentration, residence time and reaction time, were studied. As a result, the amount of monomer was reduced by ca. 80%. The versatility of microfluidics allowed incorporating hydrophilic metal-organic framework (MOF) ZIF-93 to produce HF modules with PA/MOF bilayered membranes (a continuous layer of MOF between the support and the PA film) which led to an important enhancement of the water permeance from 1.3 (bare PA membrane) to 5.3 L·m−2·h−1·bar−1 (PA/ZIF-93 HF membrane), maintaining RB rejection above 95%.

Hollow fiber composite membranes of poly(paraterphenyl-3-bromo-1,1,1-trifluoroacetone) and PVA/glycine for ethanol dehydration

Thin film composite hollow fiber membranes (TFC-HFMs) usually have permeate flux of less than 2 kg m−2 h−1 for pervaporation (PV) dehydration of ethanol, as well as complicated and pragmatic preparation process, limiting their application in the PV. In this study, the TFC-HFMs with excellent PV performance are fabricated on newly-developed poly(paraterphenyl-3-bromo-1,1,1-trifluoroacetone) (PTB) hollow fiber supports. The PTB hollow fiber supports exhibit low mass transfer resistance as a result of high pure water permeance of 1.6 × 103 L m−2 h−1 bar−1, high porosity of 63.8% and mean pore size of 2.53 μm. Furthermore, self-assembly sandwich structure dense-selective layers are formed on the lumen side of PTB hollow fiber supports via heterostructured evolution that derives from a mixture of polyvinyl alcohol (PVA) and glycine (Gly). The resulting TFC-HFMs display the excellent separation performance. Especially, the TFC4.1-HFMs show a high permeate flux of 3.49 kg m−2 h−1, 91.1 wt% water in the permeate and excellent stability for dehydrating 85 wt% ethanol aqueous solution at 50 °C. The newly developed TFC-HFMs should have a wide application in the PV dehydration of ethanol due to simple preparation progress and efficient separation.

On Performance and fouling of thin film composite hollow Fiber membranes using polycarbonate/polyvinylchloride as porous substrates for forward osmosis applications

In this study, thin-film composite (TFC) hollow fibers (HFs) were fabricated by an in-situ coating of polyamide layer on the lumen side of PVC/PC blend substrates for desalination by forward osmosis (FO). Particularly, the substrate HFs were spun at two air gap distances of 2 and 6 cm, to investigate the effect of the air-gap distance on the FO performance. The substrate HFs were characterized by pure water flux measurement, FESEM, and gas permeability test. The Interfacial polymerization (IP) method was then utilized for coating polyamide (PA) layer on the lumen surface of the substrate to fabricate TFC HFs. The TFC HFs so fabricated were also characterized by FESEM, before their FO performance was tested. Furthermore, the effect of HF length on the FO flux was investigated. The results showed that the novel TFC HFs exhibited good FO performance. The longer the air gap distance, the better becomes the FO performance in terms of simultaneous water flux and alginate fouling resistance, while the effect of the HF length remains a controversial issue.

Low-cost silica based ceramic supported thin film composite hollow fiber membrane from guinea corn husk ash for efficient removal of microplastic from aqueous solution

In this study, an economic silica based ceramic hollow fiber (HF) microporous membrane was fabricated from guinea cornhusk ash (GCHA). A silica interlayer was coated to form a defect free silica membrane which serves as a support for the formation of thin film composite (TFC) ceramic hollow fiber (HF) membrane for the removal of microplastics (MPs) from aqueous solutions. Polyacrylonitrile (PAN), polyvinyl-chloride (PVC), polyvinylpyrrolidone (PVP) and polymethyl methacrylate (PMMA) are the selected MPs The effects of amine monomer concentration (0.5 wt% and 1 wt%) on the formation of poly (piperazine-amide) layer via interfacial polymerization over the GCHA ceramic support were also investigated. The morphology analysis of TFC GCHA HF membranes revealed the formation of a poly (piperazine-amide) layer with narrow pore arrangement. The pore size of TFC GCHA membrane declined with the formation of poly (piperazine-amide) layer, as evidenced from porosimetry analysis. The increase of amine concentration reduced the porosity and water flux of TFC GCHA HF membranes. During MPs filtration, 1 wt% (piperazine) based TFC GCHA membrane showed a lower transmission percentage of PVP (2.7%) and other suspended MPs also displayed lower transmission. The impact of humic acid and sodium alginate on MPs filtration and seawater pretreatment were also analyzed.

High loading and high-selectivity H2 purification using SBC@ZIF based thin film composite hollow fiber membranes

Membrane-based separation systems have been widely explored for hydrogen production and purification in the development of next-generation fuels. In this work, we propose a thin film composite hollow fiber membrane (TFCHFM) for H2 purification, incorporating poly(styrene-co-butadiene) copolymers (SBC, 4% butadiene, for flexibility and ease of processing) and ZIF-8 nanoparticles. The TFC was supported on a PEI-based hollow fiber substrate. SBC containing a flexible butadiene segment showed enhanced compatibility through π-π interactions. The morphology of ZIF-8 was altered from a cubic shape to a smaller spherical shape by altering the molar ratio of NH4+/Zn2+. The gas separation mechanism of the ZIF-8 based TFC membrane was predicted by the Maxwell model. In the binary gas permeation test (5 vol% H2), the H2 permeance and H2/CH4 selectivity of TFCHFMs were 6.85 GPU and 152.20, respectively, with 50 wt% ZIF-8 loading. We believe that the high loading weight (50 wt% ZIF-8) and H2/CH4 selectivity presented here are unprecedented for ZIF-8 based TFC membranes reported in the literature.

Performance, fouling and cleaning of a thin film composite hollow fiber membrane during fertiliser-drawn forward osmosis process for micro-polluted water

Analysis of occurrence and cleaning regeneration of organic/inorganic fouled FO membranes in the FDFO process and related mechanisms.

Highly permeable thin film composite hollow fiber membranes for brackish water desalination by incorporating amino functionalized carbon quantum dots and hypochlorite treatment

A novel strategy has been demonstrated to synergistically improve the separation performance of thin film composite (TFC) hollow fiber membranes for brackish water reverse osmosis (BWRO) desalination. It consists of two steps. Firstly, a series of amino functionalized carbon quantum dots (CQDs) were synthesized and incorporated into the polyamide layer of TFC membranes. The modified TFC membrane with the optimal amino functionalized CQDs has a pure water permeability (PWP) of 5.50 LMH/bar and a NaCl rejection of 98.0% against a 2000 ppm NaCl feed solution at 15 bar. Comparing with the unmodified TFC membrane, the modified TFC membrane has a 42.1% higher PWP without compromising the salt rejection. Then the modified TFC membrane was treated by a sodium hypochlorite solution at different concentrations. Chlorine was bonded to the polyamide layers, enhancing their repulsion against charged solutes and making the polyamide network less cross-linked. As a result, both PWP and NaCl rejection of the TFC membranes could be improved. After being treated with a sodium hypochlorite aqueous solution at 4000 ppm for 3h, the aforementioned modified TFC membrane displays a PWP of 10.13 LMH/bar and a NaCl rejection of 98.9% against a 2000 ppm NaCl solution at 15 bar, which demonstrates a great potential for brackish water desalination. This study may mark a milestone for the development of future BWRO membranes based on the use of amino functionalized CQDs and hypochlorite treatment.

Polyamide/MOF bilayered thin film composite hollow fiber membranes with tuned MOF thickness for water nanofiltration

A bilayered polyamide-MOF membrane was synthesized on the inner surface of a hollow fiber support (200/350 mm ID/OD). The continuous MOF layer was prepared by liquid phase crystallization, and after that a polyamide layer was formed by interfacial polymerization on the top of the MOF. Firstly, the influence of time in the crystal growth of the MOF layer (from 15 to 120 min) was studied. The main characteristics of such MOF layer were tested (gas permeance and selectivity, and layer thickness measurements by SEM) to decide which of them were the optimum to support the polyamide thin film. The final bilayered membranes were characterized by SEM imaging and XPS and their performance was established in the nanofiltration of a solution of sunset yellow (450 Da) in water. Both permeance and selectivity were improved compared to a conventional TFC membrane (without the MOF layer): water permeance from 0.06 ± 0.01 to 0.24 ± 0.09 L·m−2·h−1·bar−1, and dye rejection from 88 ± 2 to 98 ± 1%).

Nafion/TiO2 nanoparticle decorated thin film composite hollow fiber membrane for efficient removal of SO2 gas

In this work, thin film nanocomposite (TFN) membranes for SO2 gas removal have been fabricated by incorporation of PEBAX and Nafion/TiO2 (hereafter referred as Nf/TiO2) nanoparticles on a polyethersulfone hollow fiber membrane substrate. Membrane structure, inner coating, and thickness were confirmed by SEM cross-sectional images. In addition, morphological and structural analyses of the membranes were performed using FTIR, SEM, EDX, TEM, and AFM. To investigate the effects of Nf/TiO2 nanoparticles on the gas permeation performance, four membrane modules with different mass concentrations of Nf/TiO2 – 0.025, 0.050, 0.075, and 0.1 g – were fabricated. The gas permeation experiments were performed with pure SO2, N2, and CO2 gases and a mixed gas (SO2/CO2/N2) within a pressure range of 1–3 bar and feed gas flow rate of 0.03–0.15 L/min. The obtained experimental results suggest that the addition of Nf/TiO2 nanoparticles improved the membrane performance by introducing sulfonate and hydroxyl functional groups to the membrane, and thus increased SO2 permeation and selectivity. The SO2 permeation was found to be 411–1671 GPU in the range of the studied parameters. The ideal selectivities achieved for SO2/N2 and SO2/CO2 were 2928 and 72, respectively. Overall, an SO2 removal efficiency of 93% was achieved by using the Nf/TiO2 incorporated TFN membrane.

A new commercial biomimetic hollow fiber membrane for forward osmosis

Hollow fiber membranes have shown great promise as a platform for osmotic processes such as forward osmosis (FO) and pressure retarded osmosis (PRO). Numerous hollow fiber FO membranes have been designed by academic researchers around the world. However, few of these designs have made it to full scale production. In this study, we report on the newly launched Aquaporin Inside™ hollow fiber FO membrane from Aquaporin A/S, Denmark. These membranes were tested in miniature modules under various osmotic testing conditions. With incorporating biomimetic aquaporin proteins as “water channel” in the selective layer, these membranes exhibited excellent FO performance with water flux of 21 LMH, reverse salt flux of 3.6 gMH and specific reverse salt flux of 0.18 g/L in PRO mode with 1 M NaCl and deionized water as draw and feed solutions, respectively. The structure parameter was determined to be 210.5 ± 55.5 μm, which is one of the lowest S values reported for thin film composite hollow fiber membranes.

Gelled Graphene Oxide-Ionic Liquid Composite Membranes with Enriched Ionic Liquid Surfaces for Improved CO2 Separation.

Blends containing ionic liquid (IL) 1-ethyl-3-methyimidazolium tetrafluoroborate [emim][BF4] gelled with Pebax 1657 block copolymers were modified by adding graphene oxide (GO) and fabricated in the form of thin film composite hollow fiber membranes. Their carbon dioxide (CO2) separation performance was evaluated using CO2 and N2 gas permeation and low-pressure adsorption measurements, and the morphology of films was characterized using scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. Upon small addition of GO into the IL-dominated environment, the interaction between IL and GO facilitated the migration of IL to the surface while suppressing the interaction between IL and Pebax, which was confirmed using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Amplified migration of IL to the surface and better dispersion of GO stacks were further achieved under alkaline conditions. With the enriched IL on the surface, the gas permeation through the films at 0.5 wt % GO and approximately 80 wt % IL loading reached 1000 GPU for CO2 with their CO2/N2 selectivity (up to 44) approaching that of pure IL.

Novel thin film composite hollow fiber membranes incorporated with carbon quantum dots for osmotic power generation

By means of carbon quantum dots incorporation, we have developed novel thin film composite (TFC) membranes for osmotic power generation. The newly developed TFC membrane exhibits a peak power density as high as 34.20W/m2 at 23bar using 1.0M NaCl and deionized water as the feed pair. To our best knowledge, this is the highest ever power density reported in the literature. The carbon quantum dots (CQDs) are a new class of carbon nanomaterials with advantages of excellent hydrophilicity, low toxicity, environmental friendliness, easy synthesis and low cost. The CQDs are incorporated into the polyamide selective layers via the conventional interfacial polymerization reaction. The effects of incorporating different CQDs and their loadings on membrane morphology, properties and PRO performance have been examined. It is found that the addition of Na+–functionalized CQDs not only increases the existence of hydrophilic oxygen-containing groups and surface area of the polyamide layer, but also changes the morphology with a looser and thinner polyamide network. The TFC membrane comprising 1wt% Na–CQD-9 has the optimal performance. Compared with the control, the water flux and power density at 23bar increase from 44.52 to 53.54 LMH and 28.44 to 34.20W/m2 respectively, while the reverse salt flux remains unchanged.

Fabrication of a pilot scale module of thin film composite hollow fiber membrane for osmotic pressure‐driven processes

ABSTRACTPolyamide thin film composite hollow fiber membranes have advantages in their unique structure compared to flat sheet membranes. This study examined interfacial polymerization methods for fabricating pilot scale hollow fiber membranes (membrane area: 1.2 m2, number of hollow fiber strands: 1200). For use in osmotic pressure‐driven processes, a one‐pot hydrophilic interfacial polymerization procedure was developed simultaneously to modify the surface property and synthesize polyamide thin film. With the procedure, a pilot scale module has a water flux of 13 LMH using a draw solution of 0.6M NaCl and a feed solution of distilled water through the design of the module configuration. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46110.

Module scale-up and performance evaluation of thin film composite hollow fiber membranes for pressure retarded osmosis

Pressure retarded osmosis (PRO) demonstrates great potential in energy harvesting when combining with seawater reverse osmosis. However, the lack of suitable membrane modules and the issue caused by the membrane fouling greatly impede the practical application of PRO to a larger scale. In this study, two-inch thin film composite hollow fiber modules were fabricated by using in-house developed PRO membranes. The produced PRO modules have a maximum effective area of 0.5m2. By assessing the PRO performances of the modules with different sizes, external concentration polarization (ECP) was found to have significant impact on the flux reduction during module scale-up. Different module designs, including fiber bundles, distribution baffles and distribution tubes, were thus adopted as an attempt to boost the membrane performance. A power density of 8.9W/m2 at 15bar was obtained using tap water as feed and 1M NaCl solution as draw solution. PRO performance tests were also carried out using the developed two-inch modules on a pilot-scale setup with actual wastewater retentate as feed solution. Low pressure nanofiltration was selected as the pretreatment of the wastewater retentate to mitigate fouling. A power density of larger than 8W/m2 was obtained when pretreated wastewater retentate was used as the feed solution, implying high potential of PRO in the pilot scale. Nevertheless, full potential of PRO can only be realized by mitigating ECP, which could be achieved by improving the module design in the further endeavor.

Modification of thin film composite hollow fiber membranes for osmotic energy generation with low organic fouling tendency

The emerging technology of pressure retarded osmosis (PRO) has been intensely studied over the past decades due to its potential in harvesting salinity gradient energy, but membrane fouling can deteriorate the PRO performance. To mitigate membrane fouling, the outer surface of the inner-selective thin-film composite (TFC) polyetherimide (PEI) hollow fiber membrane was modified by depositing poly-(allylamine hydrochloride) (PAH) and poly acrylic acid (PAA) polyelectrolytes. The results show that the outer surface of the modified membrane had less pores exposed and was more negatively charged, which was beneficial for preventing the entrance and adsorption of the negatively charged foulants into the membrane substrate. It was further proved that the modified membrane was effective in reducing PRO fouling by organic macromolecules such as alginate and bovine serum albumin, while maintaining the mechanical properties and intrinsic separation properties well. Interestingly, after 200ppm alginate was introduced to the feed water, the power density of the modified membrane could be maintained constant at 16.2W·m−2 at 15bar while that of the non-modified membrane reduced around 17% at the end of a 300-min testing period. The results suggest that the polyelectrolytes deposition is a feasible strategy for adding anti-fouling property to PRO membranes.

An automated lab-scale flue gas permeation membrane testing system at the National Carbon Capture Center

A constant pressure, mixed gas permeation testing skid was deployed at the National Carbon Capture Center to test membrane performance when continuously exposed to slipstream post-combustion flue gas. Small, laboratory scale membranes can be loaded for testing and the degree of automation allowed the skid to be run unattended for several weeks at a time. In this report, we share our experience in commissioning the skid and quantifying CO2, N2 and O2 permeances of several membranes during the first round of testing. Dense films of polydimethylsiloxane and poly(bistrifluoroethoxyphosphazene) were tested with flue gas for approximately 20h each. In addition, we successfully tested four thin film composite hollow fiber membranes made by a dip coating process, consisting of porous Torlon hollow fibers coated with a selective layer of poly(bistrifluoroethoxyphosphazene) or its mixed matrix with a metal organic framework SIFSIX-Cu-2i filler particles. Initial results suggest the polydimethylsiloxane showed comparable results to the literature data, but the coated hollow fiber membranes have lower CO2 permeances relative to N2 or O2 permeances compared to their performance under idealized, dry, contaminant-free mixed gas conditions. While quantification of H2O permeance was performed, we found it was affected by concentration polarization even with small membrane area and a low stage cut.

CO2/CH4 separation using inside coated thin film composite hollow fiber membranes prepared by interfacial polymerization

Carbon dioxide (CO2) is greenhouse gas which originates primarily as a main combustion product of biogas and landfill gas. To separate this gas, an inside coated thin film composite (TFC) hollow fiber membrane was developed by interfacial polymerization between 1,3–cyclohexanebis–methylamine (CHMA) and trimesoyl chloride (TMC). ATR-FTIR, SEM and AFM were used to characterize the active thin layer formed inside the PSf hollow fiber. The separation behavior of the CHMA-TMC/PSf membrane was scrutinized by studying various effects like feed gas pressure and temperature. Furthermore, the influence of CHMA concentration and TMC concentration on membrane morphology and performance were investigated. As a result, it was found that mutually the CHMA concentration and TMC concentration play key roles in determining membrane morphology and performance. Moreover, the CHMA-TMC/PSf composite membrane showed good CO2/CH4 separation performance. For CO2/CH4 mixture gas (30/70 by volume) test, the membrane (PD1 prepared by CHMA 1.0% and TMC 0.5%) showed a CO2 permeance of 25 GPU and the best CO2/CH4 selectivity of 28 at stage cut of 0.1. The high CO2/CH4 separation performance of CHMA-TMC/PSf thin film composite membrane was mostly accredited to the thin film thickness and the properties of binary amino groups.

Evolution of micro-deformation in inner-selective thin film composite hollow fiber membranes and its implications for osmotic power generation

Since thin film composite (TFC) hollow fiber (HF) membranes may experience micro-deformation under high hydraulic pressures in the pressure retarded osmosis (PRO) process due to their polymeric nature and self-supported configuration, this paper aims to elucidate (1) the micro-deformation of polyethersulfone (PES) TFC HF membranes within the pressure range from 0 to 20bar and (2) its effects on water and salt permeability of the polyamide layer, and structure parameter and tortuosity of the substrate layer for osmotic power generation. It is found that pre-stabilization of the TFC HF membranes at a high pressure close to their burst pressures for a certain period of time is a powerful way to maximize their PRO performance. After stabilization at 20bar for 30min, the power density of the PES TFC HF membranes increase from 15.37 to 22.05W/m2 due to the increased membrane surface area, stretched polyamide selective layer (i.e., decreased water transport length and resistance) and decreased membrane structure parameter (i.e., lower tortuosity and internal concentration polarization (ICP)). The intermittent cycle tests have confirmed the sustainability of the enhanced water flux and power density after stabilization of the TFC HF membranes at 20bar without compromising their selectivity.

Preparation, characterization and performance evaluations of thin film composite hollow fiber membrane for energy generation

This article analyzes the different types of thin film composite hollow fiber (TFC-HF) membranes and their performance of pressure retarded osmosis (PRO) for power generation. Pressure retarded osmosis (PRO) is an osmotically-driven membrane process that can be used to harvest salinity-gradient power. For the first time, the potential of using different types of TFC-HF membranes for PRO has been explored. Several types of TFC-HF membranes with well-designed substrate structures were prepared. This study systematically investigates the effects of operating conditions and effect of membrane preparation/fabrication conditions such as concentration of monomers like m-phenylenediamine (MPD) and trimesoyl chloride (TMC), effect of reaction times, effect of pressures on the membrane performance using KIER manufactured polyethersulfone (PES) HF membranes as a substrate. The TFC-HF membranes show reasonably high water fluxes under the PRO mode using 0.6M NaCl as the draw solution and deionized water as the feed solution. Moreover, the surface and skin morphology of the substrate may play an essential role in the formation of the polyamide layer as well as in its perfectness and PRO performance. The implications of the results for power generation by PRO are evaluated and discussed. Our results provide significant implications for PRO scaling control.