Polypropylene Hollow Fiber Membrane Research Articles

Darcy Permeability of Hollow Fiber Membrane Bundles Made from Membrana Polymethylpentene Fibers Used in Respiratory Assist Devices.

Hollow fiber membranes (HFMs) are used in blood oxygenators for cardiopulmonary bypass or in next generation artificial lungs. Flow analyses of these devices is typically done using computational fluid dynamics (CFD) modeling HFM bundles as porous media, using a Darcy permeability coefficient estimated from the Blake-Kozeny (BK) equation to account for viscous drag from fibers. We recently published how well this approach can predict Darcy permeability for fiber bundles made from polypropylene HFMs, showing the prediction can be significantly improved using an experimentally derived correlation between the BK constant (A) and bundle porosity (ε). In this study, we assessed how well our correlation for A worked for predicting the Darcy permeability of fiber bundles made from Membrana polymethylpentene (PMP) HFMs, which are increasingly being used clinically. Swatches in the porosity range of 0.4 to 0.8 were assessed in which sheets of fiber were stacked in parallel, perpendicular, and angled configurations. Our previously published correlation predicted Darcy within ±8%. A new correlation based on current and past measured permeability was determined: A = 497ε - 103; using this correlation measured Darcy permeability was within ±6%. This correlation varied from 8% to -3.5% of our prior correlation over the tested porosity range.

Thermodynamic analysis of Cr(VI) extraction using TOPO impregnated membranes

Solid/liquid extraction of Cr(VI) was accomplished using trioctylphosphine oxide impregnated polypropylene hollow fiber membranes. Extraction of 100–500mg/L Cr(VI) by the extractant impregnated membranes (EIM) was characterized by high uptake rate and capacity, and equilibrium was attained within 45min of contact. Extraction equilibrium was pH-dependent (at an optimal pH 2), whereas stripping using 0.2M sodium hydroxide yielded the highest recovery of 98% within 60min. The distribution coefficient was independent of initial Cr(VI) concentration, and the linear distribution equilibrium isotherm could be modeled using Freundlich isotherm. The mass transfer kinetics of Cr(VI) was examined using pseudo-second-order and intraparticle diffusion models and a mass transfer mechanism was deduced. The distribution coefficient increased with temperature, which indicated endothermic nature of the reaction. Enthalpy and entropy change during Cr(VI) extraction were positive and varied in the range of 37–49kJ/mol and 114–155J/mol, respectively. The free energy change was negative, confirming the feasibility and spontaneity of the mass transfer process. Results obtained suggest that EIMs are efficient and sustainable for extraction of Cr(VI) from wastewater.

Application of pseudo-emulsion-based hollow fiber strip dispersion for the extraction of p-nitrophenol from aqueous solutions

ABSTRACTThe extraction of p-nitrophenol (PNP) from aqueous solutions through a pseudo-emulsion hollow fiber strip dispersion (PEHFSD) system was conducted in a microporous hydrophobic polypropylene hollow fiber membrane contactor. For the optimization of the process variables, face-centered central composite design (FCCD) has been used. It was observed that initial feed concentration, carrier composition and stripping phase concentration were the three FCCD factors, which influenced the nitrophenol extraction. Using the optimized process conditions for the separation of PNP, experiments were also performed for the separation of other nitrophenols through PEHFSD system. By the FCCD design and analysis, almost 99% extraction of all three nitrophenols was achieved at optimum conditions. A mass transfer model was also developed and aqueous and membrane resistances were evaluated as 196.46 s cm−1 and 50.14 s cm−1, respectively.

Removal of trichloroethylene from water in the catalytic membrane reactor

This work describes a single-stage method for the removal of chlorine-containing species from water using a catalytic membrane reactor based on Pd-loaded porous polypropylene hollow fiber membranes. The kinetics of this process is characterized. The degree of water purification is shown to be not less than 98%.

Significantly reduced adsorption and activation of blood components in a membrane oxygenator system coated with crosslinkable zwitterionic copolymer

A crosslinkable zwitterionic copolymer PMBT was coated onto the surfaces of polypropylene hollow fiber membrane (PP-HFM) oxygenator and its connecting tubes. The PMBT copolymer coating on the oxygenator circuit formed a cell outer membrane mimetic surface with excellent stability. The hemocompatibility of the PMBT copolymer coated PP-HFM oxygenator circuit was evaluated by animal extracorporeal circulation. The concentrations of clotting components fibrinogen and platelet in the blood were almost unchanged during the circulation through the PMBT copolymer coated oxygenator circuits. By contrast, the concentrations of fibrinogen and platelet were significantly reduced to 52% and 56% respectively in the uncoated oxygenator group due to adsorption and thrombogenesis of the blood during 2h circulation. Moreover, concentration of activation marker beta-thromboglobulin for platelet in the blood was remarkably lower in the PMBT group than the uncoated control group (p<0.01). All the results strongly supported that the hemocompatibility of the PP-HFM oxygenator circuit could be improved significantly by coating a stable and densely assembled zwitterionic polymer film. This simple, stable and highly effective cell membrane mimetic coating strategy may be applicable in developing advanced oxygenator systems and other artificial organs. Statement of SignificanceAlthough a number of studies have reported the fabrication of zwitterionic phosphorylcholine coated oxygenators to resist the adsorption and activation of blood components and eliminate heparin-induced thrombocytopenia, none of them have fabricated stable and densely assembled film, especially with crosslinkable amphiphilic random copolymer described in our manuscript. The novel features of our work include:•The first study of fabricating crosslinked and densely assembled zwitterionic copolymer coating on surfaces of a commercial oxygenator system.•The first study on hemocompatibility of both the PMBT coated and the bare commercial PP-HFM oxygenator circuits by animal extracorporeal circulation.•Much better hemocompatibility was measured on the PMBT coated oxygenator circuit compared with the bare and other polymer coated oxygenator systems.

Exploration and optimization of two-stage vacuum membrane distillation process for the treatment of saline wastewater produced by natural gas exploitation

Membrane distillation has recently been recognized as the emerging foremost membrane separation technology for applications in industrial wastewater treatment and desalination. By employing polypropylene hollow fiber membrane, this study firstly performed the optimization of the vacuum membrane distillation (VMD) process. Subsequently, the feasibility of the VMD for the treatment of real saline wastewater produced by natural gas exploitation was investigated under optimized operation conditions. An ultrahigh water flux of 30.4kg/(m2·h) with a salt rejection rate of 99.8% was achieved. Membrane fouling was observed during experiment, which induced a sharp decrease in permeate flux and salt rejection. Thus, membrane was cleaned and the VMD performance was recovered. The membrane cleaning intervals were shortened when wastewater became concentrated. After being treated for 110h, the wastewater was filtered and then further concentrated for another 20h through the second-stage VMD. The final conductivity of wastewater feed reached 230,000μS/cm, indicating a total water recovery rate of 88.6%. This study successfully treated wastewater produced by natural gas exploitation via a newly developed two-stage VMD process, which would provide an insightful guideline for its further industrial applications and may open up alternative options of effective technologies for the treatment of high-saline wastewater.

Preparation of hydrophilic polypropylene hollow fiber membranes by UV modification

abstractA polypropylene hollow fiber membrane (PPHFM) was obtained by UV grafting polyacrylic acid (PAA) on the surface. The hydrophilicity of PPHFM was improved with water contact angle reduced from 82.3° to 73.6°. The photoinitiator and monomer concentration conditions had significant effects on the grafting rates. After modification, the pure water flux decreased, but the rejection rate was improved.

Preparation and properties of iPP hollow fiber membranes for air gap membrane distillation

Three different thickness isotactic polypropylene (iPP) hollow fiber membranes were prepared for air gap membrane distillation (AGMD) via thermally induced phase separation (TIPS) with cosolvent di-n-butyl phthalate and dioctyl phthalate. A study was carried out to investigate the effect of membrane thickness on the water flux and mechanical properties of the membranes. The ratio of membrane thickness to membrane inner diameter was constant at 0.2. Three relevant AGMD modules were fabricated. During AGMD of 6 wt% salt solution, the influence of inlet temperature of cold brine feed (T1), membrane thickness on permeate water flux (JD), gained output ratio (GOR), and thermal efficiency (TE) was experimentally investigated. The maximum JD could reach 6.62 kg/m2 h and the maximum GOR could reach 6.95, respectively. Furthermore, the maximum TE was 89.42% which was much higher than that of traditional membrane distillation modules. The results demonstrated that the prepared iPP hollow fiber membrane by TIPS method would be of great potential to be utilized in AGMD process for desalination.

Fouling of Impurities in Desulfurized Flue Gas on Hollow Fiber Membrane Absorption for CO2 Capture

Membrane-based absorption shows numerous potential applications for CO2 capture from flue gas. However, during the process, membrane fouling is not only caused by the wetting but also induced by gaseous components (SOx, NOx, and water vapor) and fine particles in the flue gas. In this work, the synergetic effects of water vapor coupling with SOx and NOx as well as the fine particles were investigated to better understand the membrane fouling and the performance of polypropylene hollow fiber membrane modules for CO2 capture in actual industrial conditions. The CO2 removal efficiency and the mass-transfer rate over time were studied under different feed gas flows of various gaseous composition schemes. The membrane performance suffered from a notable decrease after exposure to SO3 and particles, and in a wet gas stream, the effects of SO3 and particles were irreversible, whereas the influence of SO2 and NO2 can be recovered by N2 sweeping. The characterization results of membrane modules confirm that the me...

Effects of annealing stress field on the structure and properties of polypropylene hollow fiber membranes made by stretching

By adopting three types of annealing stress fields, this work focused on investigating their effects on the microstructural evolution of polypropylene (PP) hollow fiber precursors obtained by the melt spinning process.

The Removal of Dissolved Ammonia from Wastewater through a Polypropylene Hollow Fiber Membrane Contactor

This study aims to evaluate the effectiveness of a polypropylene hollow fiber membrane contactor in removing dissolved ammonia in wastewater using sulfuric acid solution as an absorbent. In the ammonia removal experiments, wastewater and absorbent solutions flowed through the shell side and the lumen side of the contactor, respectively. The pH of wastewater, rate of circulation and ammonia initial concentration were operating variables which influenced the efficiency of the removal process. The efficiency of ammonia removal increases with the wastewater pH level when it is at the same circulation rate and time. In addition, the increase in the circulation rate of the wastewater will increase the efficiency of ammonia removal and the overall mass transfer coefficient. Meanwhile, the efficiency of ammonia removal and the overall mass transfer coefficient decreased with initial ammonia concentration in the wastewater solution.

CO2 capture using a superhydrophobic ceramic membrane contactor

The wetting and fouling of a membrane contactor deteriorated performance of the membrane gas absorption system for CO2 post-combustion capture in coal-fired power plants. To solve these problems, in this study, a superhydrophobic ceramic (SC) membrane contactor was fabricated from an alumina tube with a ZrO2 layer by means of grafting with fluoroalkylsilane (FAS) in a triethoxy-1H,1H,2H,2H-tridecafluoro-n-octylsilane solution. The performances of the SC membrane contactor and polypropylene (PP) hollow fiber membrane contactor were compared through experiments conducted in a CO2 absorption experimental system using a monoethanolamine (MEA) aqueous solution. Although the membrane fabrication cost per effective membrane area (CPA) of the SC membrane is 12.5 times that of the PP hollow fiber membrane, the SC membrane fabrication cost per absorbed CO2 flux (CPC) was lower than that of the PP membrane. For the SC membrane, the detrimental effect of wetting can be alleviated by periodic drying to ensure a high CO2 removal efficiency (>90%). Drying does not work for the PP membrane because the swelling of the PP fibers is irreversible. The SC membrane contactor exhibited a better anti-fouling ability than the PP membrane contactor because the superhydrophobic surface can self-clean. To ensure a continuous, high-efficiency CO2 removal, a method was proposed in which two-hollow fiber SC membrane contactors operate alternately with the addition of periodic drying. The SC hollow fiber membrane contactor shows great potential in real industrial CO2 post-combustion capture because of its good anti-wetting and anti-fouling features.

Preparation and characterization of high-hydrophilic polyhydroxy functional PP hollow fiber membrane

High-hydrophilic PP hollow fiber membrane was prepared by grafting polyhydroxy monomer 3-hydroxy-2,2-bis(hydroxymethyl)propyl acrylate (PEA) on the surface of PP. First, PEA was synthesized by direct esterification of pentaerythritol (PE) and acrylic acid (AA). Then PEA grafted PP membrane (PP-g-PEA) was prepared by continuous UV irradiation and characterized by FTIR, XPS, SEM, dynamic water contact angle and permeation of pure water. Results showed that the water drop took only 6.3s to disappear from the surface of PP-g-PEA membrane and the pure water flux of PP-g-PEA membrane was about 4.5 times higher than the original PP. The PP-g-PEA membrane can be easily prepared and used in the fields of microfiltration and ultrafiltration process for waste water treatment, food processing and separation.

Cadmium(II) transfer using (TiOAC) ionic liquid as carrier in a smart liquid membrane technology

The transfer of cadmium(II) from acidic chloride solutions through a smart liquid membrane technology was investigated in a microporous polypropylene hollow fiber membrane contactor. The organic solution of tri-isooactylammonium chloride (TiOAC) in Exxsol D100 was used as carrier. The acidic chloride feed solution containing the metal was passed through the tube side, and the pseudo-emulsion of the organic solution and NH4OH was passed through the shell side in counter-current mode, using a unique contactor in the process. In the pseudo-emulsion based hollow fiber membrane with strip dispersion (PEHFMSD) technology, the aqueous strip solutions of ammonium hydroxide are dispersed in the organic solutions in a tank with a mixing arrangement to provide a strip dispersion. This strip dispersion circulates from the tank to the membrane module to provide constant supply of the organic solution to the membrane pores. Different hydrodynamic and chemical variables, such as variation in feed acidity, metal concentration in the feed, carrier concentration in the organic phase, variation in feed, strip and organic phase volume ratios and variation in the feed and pseudo-emulsion flows, were investigated. Mass transfer coefficients were calculated from experimental data.

Wetting of Polypropylene Membranes by Aqueous Solutions in CO2 Absorbing Devices

A polypropylene hollow fiber membrane contactor was utilized to absorb CO2 from a gas stream into an aqueous solution. Three reagents were studied: monoethanolamine, piperazine, and potassium carbonate. Attention was focused on the possible intrusion of absorbent in the membrane pores, which reduces the solute mass-transfer rate. Membrane/liquid interface was thoroughly characterized. The removal efficiency of the reagents contacted with a CO2/N2 stream was assessed. It is shown that potassium carbonate and piperazine could be considered interesting candidates for applications in membrane contactors, as they appear more successful than monoethanolamine in ensuring proper and stable conditions at the membrane/liquid/gas interface.

Glucose Monitoring Using a Polymer Brush Modified Polypropylene Hollow Fiber-based Hydraulic Flow Sensor

Tight regulation of blood glucose levels of diabetic patients requires durable and robust continuous glucose sensing schemes. This manuscript reports the fabrication of ultrathin, phenylboronic acid (PBA) functionalized polymer brushes that swell upon glucose binding and which were integrated as the sensing interface in a new polypropylene hollow fiber (PPHF)-based hydraulic flow glucose sensor prototype. The polymer brushes were prepared via surface-initiated atom transfer radical polymerization of sodium methacrylate followed by postpolymerization modification with 3-aminophenyl boronic acid. In a first series of experiments, the glucose-response of PBA-functionalized poly(methacrylic acid) (PMAA) brushes grafted from planar silicon surfaces was investigated by quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM) experiments. The QCM-D experiments revealed a more or less linear change of the frequency shift for glucose concentrations up to ∼10 mM and demonstrated that glucose binding was completely reversible for up to seven switching cycles. The AFM experiments indicated that glucose binding was accompanied by an increase in the film thickness of the PBA functionalized PMAA brushes. The PBA functionalized PMAA brushes were subsequently grafted from the surface of PPHF membranes. The hydraulic permeability of these porous fibers depends on the thickness and swelling of the PMAA brush coating. PBA functionalized brush-coated PPHFs showed a decrease in flux upon exposure to glucose, which is consistent with swelling of the brush coating. Because they avoid the use of enzymes and do not rely on an electrochemical transduction scheme, these PPHF-based hydraulic flow sensors could represent an interesting alternative class of continuous glucose sensors.

Numerical investigation of the effects of polypropylene hollow fibre membrane structure on the performance of CO2 removal from flue gas

Carbon dioxide (CO2) absorption from flue gas by hollow fibre membrane contactors is considered as a clean, highly efficient and promising decarburisation technique.

Membrane gas absorption for CO2 capture from flue gas containing fine particles and gaseous contaminants

Membrane gas absorption contactor has been an effective alternative for CO2 capture, and usually installed at the outlet of wet flue gas desulfurization (WFGD) system. However, there are also residual SO2, fine particles and water vapor in desulfurized flue gas, which possibly has significant impact on the stable operation of CO2 absorption using membrane. In order to obtain a better understanding on the influence of these components, the capture process of CO2 using polypropylene (PP) hollow fiber membrane from flue gas containing fine particles and gaseous contaminants were investigated in this work. At first, simulated flue gas was used to study the effects of SO2, water vapor and fine particles on the CO2 capture respectively. Then the separation of CO2 using PP membrane was operated under the condition of actual coal-fired desulphurized flue gas. The results revealed that the absorption performance of membrane was slightly deteriorated at the individual presence of SO2 or water vapor while the effects fine particles was significant. Following the fine particles exposure, a bulk decrease of the CO2 removal efficiency was observed due to the deposition and adsorption of fine particles on the membrane surface and pores. In addition, water vapor could accelerate the deposition of fine particles.

In situ pre-concentration and voltammetric determination of trace lead and cadmium by a novel ionic liquid mediated hollow fiber-graphite electrode and design of experiments via Taguchi method

In this research a single-use voltammetry sensor, incorporating a three electrodes configuration was developed, using ionic liquid mediated hollow fiber-graphite supported nanomagnetite working electrode. These electrodes coupled with differential pulse voltammetry (DPV) provided a screening tool for in-situ pre-concentration and determination of trace levels of Pb(II) and Cd(II). In this design, a two-centimeter piece of porous polypropylene hollow fiber membrane was impregnated with homogeneous mixture of nanomagnetic particles/ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate), and a graphite rod was located inside the fiber lumen. In this sensor, synthesized nanoparticles such as zero-valent Iron (ZVI), nanomagnetite (NM) and magnetic hollow spheres (MHS), dispersed in the ionic liquid, were used for one-step simultaneous purification, pre-concentration and trapping of pb(II) and Cd(II) ions from water samples. The Taguchi method was applied as an experimental design to determine optimum conditions for lead and cadmium ions removal. The experiments were designed, in two steps, according to Taguchi's method, OA16 L18 (21×35) and OA16 L16 (21×43) orthogonal were arrayed to the optimize experimental runs. Various affective parameters were investigated. The effect of all the input parameters on the output responses was analyzed using analysis of variance (ANOVA). The results revealed that the metal removal was influenced primarily by the amount of nanoparticle (52.18%) and agitation rate (19.71%). The extraction time (8.97%) and mercury acetate concentration in the electrolyte (7.6%) had little significant influence on metal removal efficiency. The performance characteristics of the developed method were evaluated by assessing response linearity and precision. The method was suitable for the quantitation of pb(II) and Cd(II) ions in the concentration range of 2–13000ng.mL−1 and 0.6–6500ng.mL−1 for Cd(II) and Pb(II) ions respectively. The detection limits recorded for Cd(II) and Pb(II) were 0.61 and 0.19ng.mL−1 with relative standard deviation (RSD) of 4.6%, and 2.3%, respectively. Moreover, successful applications of the sensing device to real water samples were demonstrated.

Investigation of microbial adaptation to salinity variation for treatment of reverse osmosis concentrate by membrane bioreactor

Even though reverse osmosis (RO) technologies are widely used for sustainable water reclamation, the control of concentrates containing a high concentration of dissolved matters originated from feed water should be considered. The effect of variations in salinity on biological wastewater treatment processes has to be evaluated for combined treatment with RO concentrate in sewage treatment plants. As a preliminary study, the effect of adaptation of seeding sludge on RO concentrate treatment was evaluated. The reactor inoculated by unadapted sludge had a significant inhibition on organic and ammonia removal. Especially, ammonia removal was completely inhibited and removal efficiency was maintained below 20% during 30 d of operation. However, the removal efficiencies gradually increased with operation time, and it reached a similar performance to adapted sludge in 40 d of operation. For a more quantitative study on a microbial adaptation strategy for variations on salt concentration (0–20 g/L), lab-scale membrane bioreactors (7L working volume) with polypropylene hollow fiber membrane module (pore size 0.4 μm) were used with different adaptation strategies: instant and stepwise mode. The performance of the reactor deteriorated with an increasing salt concentration, but it recovered after adaptation periods (30–70 d). Moreover, the inhibition effect of salt could be minimized by a gradual increase in salt concentration. Analysis results for polymerase chain reaction-denaturing gradient gel electrophoresis indicated that nitrifiers were still present in high salinity. These results confirmed that an appropriate adaptation strategy should be determined for RO concentrate treatment.