Polypropylene Hollow Fiber Membrane Research Articles

A nano-Al2O3 modified polypropylene hollow fiber membrane with enhanced biofilm formation in membrane aerated biofilm reactor application

Membrane Aerated Biofilm Reactor (MABR) stands out as an innovative technology for wastewater treatment. However, biofilm formation poses a significant challenge in its implementation. Surface modification emerges as a viable strategy to enhance biofilm development. In this study, biofilm formation was effectively promoted by coating polydopamine (PDA) and loading aluminum oxide nanoparticles (Al2O3 NPs) onto a polypropylene (PP) hollow fiber membrane, aiming to improve wettability and potential. Results from the bacterial attachment assay demonstrated a significantly higher bacterial attachment rate on the membrane loaded with Al2O3 NPs compared to PDA/PP and PP membranes. A comprehensive investigation into the MABR process was conducted, assessing both short-term and long-term (72 days) performance. In the short-term process, the Al2O3 NPs-PDA modified membrane exhibited superior removal efficiency for chemical oxygen demand (COD), ammonium nitrogen (NH4+-N), and total nitrogen (TN) compared to other membranes. Transitioning to the long-term process, the start-up period for the Al2O3 NPs(10)-PDA/PP membrane was notably shortened to 27 days, surpassing the start-up times of PP and PDA/PP membranes by 13 and 5 days, respectively. Throughout the long-term operation, when the influent COD, NH4+-N, and TN concentrations increased, the Al2O3 NPs-PDA/PP membrane consistently maintained removal efficiency above 95%, 98%, and 85% for COD, NH4+-N, and TN, respectively, demonstrating excellent resistance to shock loading.

Preparation of PDMS and PDMS-UiO-66 oxygen-rich membranes and modules for membrane-aerated biofilm reactors.

A membrane-aerated biofilm reactor (MABR) combines membrane technology with biofilm processes and has unique advantages in the treatment of organic wastewater and volatile wastewater. The common membranes for MABR systems usually have relatively uneven pore structures and low bubble point pressure, resulting in unsatisfactory O2 utilization and wastewater treatment efficiency. In this work, polydimethylsiloxane (PDMS) and UiO-66 (a Zr-based metal organic framework) were coated on the surface of a commercial polypropylene (PP) hollow fiber membrane to prepare oxygen-rich MABR membranes and modules, which showed an attractive O2 utilization rate and wastewater treatment efficiency. The bubble points of the PDMS and PDMS-UiO-66 membranes were significantly higher than those of the PP membranes, and the PDMS-UiO-66 membranes had better oxygen enrichment capacity and biological affinity. The optimal PDMS-UiO-66 membrane modules had an O2 permeance of 31.65 GPU (1 GPU = 3.35 × 10-10 mol m-2 s-1 Pa-1), with O2/N2 selectivity of 2.21. The membrane hanging effect and processing capacity for domestic sewage were greatly improved. This study may provide insights and guidelines to fabricate porous mixed matrix membranes and modules in the industry for MABR. The developed products are expected to be applied in the actual separation process.

Characterization and comparative evaluation of polysulfone and polypropylene hollow fiber membranes for blood oxygenators

AbstractBlood oxygenators are used to saturate oxygen levels and remove carbon dioxide from the body during cardiopulmonary bypass. Although the natural lung is hydrophilic, commercially used oxygenator materials are hydrophobic. Surface hydrophobicity weakens blood compatibility, as long‐term contact with the blood environment may lead to different degrees of blood activity. Polysulfone may be considered an alternative hydrophilic material in the design of oxygenators. Therefore, it may be directed toward developing hydrophilic membranes. This study aims to investigate the feasibility of achieving blood gas transfer with a polysulfone‐based microporous hollow fiber membrane and compare it with the commercially available polypropylene membranes. Structural differences in the membrane morphology, surface hydrophilicity, tortuosity, mass transfer rate, and material properties under different operation conditions of temperature and flow rates are reported. The polysulfone membrane has a water contact angle of 81.3°, whereas a commercial polypropylene membrane is 94.5°. The mass transfer resistances (s/m) for the polysulfone and polypropylene membranes are calculated to be 4.8 × 104 and 1.5 × 104 at 25°C, respectively. The module made of polysulfone was placed in the cardiopulmonary bypass circuit in parallel with the commercial oxygenator, and pH, pO2, pCO2 levels, and metabolic activity were measured in blood samples.

A novel tunable polypropylene hollow fiber membrane with gradient structure for extracorporeal membrane oxygenation applications

High gas permeability and excellent resistance to plasma leakage are expected from polypropylene (PP) hollow fiber membranes (HFMs) used in extracorporeal membrane oxygenation (ECMO) systems. This study successfully prepared a novel PP HFMs with tunable and gradient structures using oleic acid (OA) and methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate (RhodiasolvⓇ PolarClean) (PL) as binary diluents via the hybrid induced phase separation (HIPS) method. The phase-separation behavior of the PP-OA/PL system was studied using a phase diagram and the resultant membrane structure. As the concentration of PL in the binary diluents increased, the phase separation mechanism changed from solid–liquid (S–L) to liquid–liquid (L–L), and the structure of PP HFMs changed from crystalline to cellular or bi-continuous. Moreover, the effects of PP concentration and air gap distance on the membrane structure and performance were investigated. In particular, the obtained HFMs showed a clear gradient configuration. The results showed that when the PP concentration, OA to PL mass ratio, and air gap were set to 35 wt%, 7/3, and 10 mm, respectively, the PP HFM exhibited the optimal performance with a high N2 permeability of 23.42 ± 0.98 ml/(min cm2 bar) and resistance to simulated plasma leakage of 4300 min.

Resource recovery from landfill leachate by two-stage of direct contact membrane distillation

Landfill leachate (LL) is a high organic matter and ammonia strength wastewater. The recovery of ammonia and water as by-products can be a path to a more sustainable management of LL. This study aims to evaluating the performance of a two-stage of Direct Contact Membrane Distillation for resource recovery from LL. In the first stage, the hot LL flows through the shell side of the polypropylene hollow fiber membrane module while the sulfuric acid solution passes through the lumen side. Ammonia is recovered as ammonium sulfate. In the second stage, the hot effluent from the first stage flows through the hot channel of the poly(tetrafluoroethylene) flat sheet membrane module, while cooled distillate water flows through the other side in countercurrent. The water evaporates and cross the membrane from the hot to the cold channel where it condenses. The results revealed the ammonia recovery rate was 87.38 % in the first stage, then, for each 1 m3 of LL, 2.20 kg of ammonia could be recovered. The water recovered (flux of 11.7 kg m−2 h−1) showed high quality, due to the great membrane rejection rate of colour (99.99 %), turbidity (99.88 %), TOC (99.98 %), NH3 (99.85 %) and phosphorus (99.88 %).

Evaluation of a hollow fiber membrane contactor reactor for reactive extraction in biodiesel production

A polypropylene hollow fiber membrane contactor reactor (HF-MCR) was used to evaluate the performance of a reactive extraction process for biodiesel production. The process involved the transesterification of soybean oil with methanol, catalyzed by sodium hydroxide. The experimental methodology assessed the impact of oil flow rate and methanol/oil molar ratio on the biodiesel (FAME) production rate, triglyceride reaction rate, and glycerin concentration in the final biodiesel product. The results demonstrated that, by employing a countercurrent configuration, is possible to extract the glycerin from the biodiesel-rich phase with methanol, achieving both the reaction and the separation stages in the same equipment. The best results were obtained at a methanol/oil molar ratio of 4:1 and an oil flow rate of 0.4 L h−1, leading to a triglyceride conversion rate of 0.14 mol h−1 and a FAME production rate of 0.24 mol h−1, equivalent to 34 % conversion and 56 % yield, respectively. The final biodiesel product showed a low concentration of glycerin, measuring only 0.06 % wt. This investigation highlights the potential of employing membrane contactors technology for the biodiesel production process, reducing the processing time by eliminating the biodiesel/glycerol separation stage, and therefore bringing down the load of downstream purification operations.

Preparation of Hyflon AD/Polypropylene Blend Membrane for Artificial Lung.

A high-performance polypropylene hollow fiber membrane (PP-HFM) was prepared by using a binary environmentally friendly solvent of polypropylene as the raw material, adopting the thermally induced phase separation (TIPS) method, and adjusting the raw material ratio. The binary diluents were soybean oil (SO) and acetyl tributyl citrate (ATBC). The suitable SO/ATBC ratio of 7/3 was based on the size change of the L-L phase separation region in PP-SO/ATBC thermodynamic phase diagram. Through the characterization and comparison of the basic performance of PP-HFMs, it was found that with the increase of the diluent content in the raw materials, the micropores of outer surface of the PP-HFM became larger, and the cross section showed a sponge-like pore structure. The fluoropolymer, Hyflon ADx, was deposited on the outer surface of the hollow fiber membrane using a physical modification method of solution dipping. After modification, the surface pore size of the Hyflon AD40L modified membranes decreased; the contact angle increased to around 107°; the surface energy decreased to 17 mN·m-1; and the surface roughness decreased to 17 nm. Hyflon AD40L/PP-HFMs also had more water resistance properties from the variation of wetting curve. For biocompatibility of the membrane, the adsorption capacity of the modified PP membrane for albumin decreased from approximately 1.2 mg·cm-2 to 1.0 mg·cm-2, and the adsorption of platelets decreased under fluorescence microscopy. The decrease in blood cells and protein adsorption in the blood prolonged the clotting time. In addition, the hemolysis rate of modified PP membrane was reduced to within the standard of 5%, and the cell survival rate of its precipitate was above 100%, which also indicated the excellent biocompatibility of fluoropolymer modified membrane. The improvement of hydrophobicity and blood compatibility makes Hyflon AD/PP-HFMs have the potential for application in membrane oxygenators.

Determination of polycyclic aromatic compounds from a solid-waste dumpsite fire smoke using hollow-fibre membranes sampling coupled to gas chromatography and mass spectrometry

ABSTRACT Improperly managed solidwaste dumpsites are a potential time bomb as these can pose serious deleterious hazards to the neighbouring communities. This was the case in Maseru Lesotho one warm afternoon when the dumpsite caught fire with no clear human activity, producing dark smoke that covered the residential area around the site. The current study reports the use of simple passive samplers composed of polypropylene hollow fibre membranes impregnated with dodecane for screening of polycyclic aromatic hydrocarbons in this dumpsite fire smoke. The fibres were suspended at different sampling locations at the dumpsite and inside and outside the surrounding households and left there to sample for 6 hours after which 1-cm pieces were placed in headspace vials for desorption and further analysed by gas chromatography and mass spectrometry. The detected compounds were annotated using the NIST 2017 MS library comparison and the following compounds were found: acenaphthene, naphthalene, biphenylene, flourene, phenanthrene, flouranthene, benzoflouranthene, pyrene and clopentapyrene. Given there were no standards available, the compounds could not be quantified. Nonetheless, the results demonstrated the potential for a simple hollow-fibre liquidphase microextraction technique for use in the screening of PAHs in smoke. Most importantly, they reflect the importance of negative impact of the dumpsite smoke being so rich in these compounds that have been classified as carcinogens.

Nitrogen recovery from sludge centrate by membrane contactor: Influence of operating parameters and cleaning conditions

In urban wastewater treatment, the sludge generated is treated by anaerobic digestion, to be subsequently dehydrated by centrifuges. Currently, the liquid fraction obtained in this dehydration process is recirculated at the head of the treatment plant. However, its high nitrogen and phosphorus content makes it an effluent with high added value. The recovery of these nutrients could be an excellent alternative for the production of fertilizers or other industrial applications. In this study, the use of a liquid-liquid phase membrane contactor is presented as a favorable solution for the recovery of ammoniacal nitrogen from sludge centrated. The polypropylene hollow fiber membrane was evaluated considering its ammonia removal and recovery capacity. For this, different parameters were evaluated: the influence of the type and concentration of the acid solution, the wastewater pH, the flow rates of feeding and the acid stripping solution, and the contact time. Results showed that with a contact time of 65 min, ammonia removal and recovery percentages of the order of 90% were achieved. The flow rates of the stripping and feed solutions together with the acid concentration did not have a significant influence on the removal but on the recovery. Concerning used acid, sulphuric and phosphoric acid solutions achieved better results than nitric acid solution. The most critical parameter was the pH, obtaining the highest removal and recovery of ammonium at the highest pH. Finally, a stable cleaning protocol was obtained, between preventive and moderate cleanings to avoid severe cleanings, keeping the membrane at its maximum capacity.

Janus hollow fibre membranes with intrusion anchored structure for robust desalination and leachate treatment in direct contact membrane distillation

High-performance Janus membranes have been intriguing for membrane distillation due to its distinctive features for improving fouling and wetting resistance. However, long-term structural stability remains challenging owing to delamination caused by the opposite affinity between the two different kinds of materials. Herein, a physically-anchored hydrophilic layer containing graphene oxide (GO)/poly(vinyl alcohol) (PVA)/sulfosuccinic acid (SSA) i.e., GOSP layer was formed on the surface of a microporous polypropylene (PP) hollow fibre membrane. Meanwhile, the nanostructure of the GOSP layer could be tuned from 2-dimensional lamellar to 3-dimensional mixed matrix, exhibiting various water transport properties. As a result, the fabricated Janus membrane with the partially intruded pore channels exhibited superior antiwetting and antifouling performance for desalination and wastewater treatment in the direct contact membrane distillation process. For surfactant containing saline water, the GOSP/PP Janus membrane with optimised PVA/GO ratio possessed noticeably enhanced anti-wetting property compared to pristine PP membrane. In particular for leachate treatment, the GOSP/PP membrane produced high quality permeate with <1 mg/L ions and 10 mg/L total organics and maintained stable water flux while the leachate was concentrated by 5 times (80 % water recovery), providing great potential for using membrane distillation towards zero liquid discharge.

A new superhydrophobic polypropylene hollow fiber membrane preparation method and its application in the treatment of brine with high salt concentration

A simple and effective strategy combining etching, electrostatic adsorption, and dip-coating methods was developed in this paper to prepare uniform and stable superhydrophobic surfaces on polypropylene hollow fiber membranes (PPHFM) for desalination of highly concentrated salt solutions (3.5 wt% − 15 wt%). A number of appropriate evaluation methods were used to characterize the membrane, and the results confirmed that the composite membrane was successfully modified. Compared with PPHFM, the water contact angle (WCA) was increased from 119° to 165°; the surface roughness was increased from 0.198 µm to 0.961 µm; the mean pore size was increased from 0.16 µm to 0.24 µm; the porosity was increased from 53% to 70%. The PPHFM and composite membranes were applied to a long-term (80 h) vacuum membrane distillation (VMD) with a salt concentration of 15 wt%. The average permeates flux of the composite membrane increased from 4.27 kg (m2 h)−1 to 12.33 kg (m2 h)−1 compared to the PPHFM, while the composite membrane had superior resistance to wetting and stability.

Dynamic Modeling of CO2 Absorption Process Using Hollow-Fiber Membrane Contactor in MEA Solution

In this work, a comprehensive mathematical model was developed in order to evaluate the CO2 capture process in a microporous polypropylene hollow-fiber membrane countercurrent contactor, using monoethanolamine (MEA) as the chemical solvent. In terms of CO2 chemical absorption, the developed model showed excellent agreement with the experimental data published in the literature for a wide range of operating conditions (R2 &gt; 0.96), 1–2.7 L/min gas flow rates and 10–30 L/h liquid flow rates. Based on developed model, the effects of the gas flow rate, aqueous liquid absorbents’ flow rate and also inlet CO2 concentration on the removal efficiency of CO2 were determined. The % removal of CO2 increased while increasing the MEA solution flow rate; 81% of CO2 was removed at the high flow rate. The CO2 removal efficiency decreased while increasing the gas flow rate, and the residence time in the hollow-fiber membrane contactors increased when the gas flow rate was lower, reaching 97% at a gas flow rate of 1 L‧min−1. However, the effect was more pronounced while operating at high gas flow rates. Additionally, the influence of momentous operational parameters such as the number of fibers and module length on the CO2 separation efficiency was evaluated. On this basis, the developed model was also used to evaluate CO2 capture process in hollow-fiber membrane contactors in a flexible operation scenario (with variation in operating conditions) in order to predict the process parameters (liquid and gaseous flows, composition of the streams, mass transfer area, mass transfer coefficient, etc.).

Chemical and Physical Ionic Liquids in CO2 Capture System Using Membrane Vacuum Regeneration.

Carbon Capture Utilization and Storage technologies are essential mitigation options to reach net-zero CO2 emissions. However, this challenge requires the development of sustainable and economic separation technologies. This work presents a novel CO2 capture technology strategy based on non-dispersive CO2 absorption and membrane vacuum regeneration (MVR) technology, and employs two imidazolium ionic liquids (ILs), [emim][Ac] and [emim][MS], with different behavior to absorb CO2. Continuous absorption–desorption experiments were carried out using polypropylene hollow fiber membrane contactors. The results show the highest desorption behavior in the case of [emim][Ac], with a MVR performance efficiency of 92% at 313 K and vacuum pressure of 0.04 bar. On the other hand, the IL [emim][MS] reached an efficiency of 83% under the same conditions. The MVR technology could increase the overall CO2 capture performance by up to 61% for [emim][Ac] and 21% for [emim][MS], which represents an increase of 26% and 9%, respectively. Moreover, adding 30%vol. demonstrates that the process was only favorable by using the physical IL. The results presented here indicate the interest in membrane vacuum regeneration technology based on chemical ILs, but further techno-economic evaluation is needed to ensure the competitiveness of this novel CO2 desorption approach for large-scale application.

Process Scale‐Up of an Energy‐Efficient Membrane Solvent Extraction Process for Rare Earth Recycling from Electronic Wastes

This study reports the process scale‐up and long‐term performance of an energy‐efficient and cost‐effective membrane solvent extraction (MSX) process for separation and recovery of high purity rare earth oxides (REOs) from scrap permanent magnets (SPMs). The rare earth elements (REEs), including dysprosium, neodymium, and praseodymium, are recovered from SPMs using a neutral extractant, tetraoctyl diglycolamide (TODGA) embedded in a microporous polypropylene hollow fiber membrane module. The MSX process performance is demonstrated with bench scale module with membrane surface area of 1.4 m2 to industrial scale modules with membrane surface area of up to 20 m2 to enable the processing of up to 1 ton month−1 of SPMs. The purity and the yield of the recovered REOs are &gt;99.5 wt% and &gt;95%, respectively. The average extraction rate of REOs is &gt;10 g m−2 hr−1. A skid of MSX system is assembled with a membrane area of 40 m2. The MSX skid successfully recovers REOs with a capacity of 300 kg REOs/month. Finally, it is determined that the organic phase containing the extractant maintains its performance up to 250 h. The results suggest that the MSX process is an economically viable and environmentally friendly process for separation and recovery of REOs from electronic wastes.

Application of an improved hollow fiber liquid phase microextraction technique coupled to LC-MS/MS to studying migration of fluorescent whitening agents from plastic food contact materials

In this paper, a new hollow fiber liquid-phase microextraction method was developed to improve the extraction of five fluorescent whitening agents that migrated from plastics food contact materials. Influencing factors, such as the types of membrane, the extraction solvent, the stirring speed, the addition of salt ion, and extraction time, were investigated in detail. Under the optimal conditions, high enrichment factors (71–205) can be obtained with 15 μL extraction solvent. The new method is advantageous; the polypropylene hollow fiber membrane modified by sepiolite nanoparticles had excellent solvent binding force and mass transfer effect compared with the conventional extraction technique. The extracts were analyzed by high performance liquid chromatography–tandem mass spectrometry, the limits of detection were 0.3 or 0.9 ng kg−1 with good correlation coefficients (r 2 ≥ 0.9940) for the five fluorescent whitening agents. The intra-day and inter-day recoveries ranged between 82.6% and 112%, with a relative standard deviation of less than 12%. The established method was successfully applied to the analysis of fluorescent whitening agent migration from four types of plastic food contact materials immersed in three food simulants.

Polypropylene Hollow Fiber Membrane by Dissolution-Inducing Pore Methods.

Plasma leakage limits the development of polypropylene membranes as oxygenated membranes. Here, a new method named the dissolution-induced pore method was adapted to prepare polypropylene hollow fiber membranes: after polypropylene and polyvinyl chloride were melt-blended and extruded, the polyvinyl chloride was removed by N, N-dimethylacetamide to obtain a porous polypropylene membrane material. The variation of membranes has been explored in detail with respect to the influence of different parameters on the flux and mechanical properties of membranes and the feasibility of the polyvinyl chloride recovery. The resulting polypropylene hollow fiber membrane shows that plasma penetration was zero within 6 h of test, gas flux can reach 189,000 L/(m2·h·0.1 MPa), and its strength at break reaches 65 MPa and the elongation at break is 890%; polyvinyl chloride recovery achieves more than 99%. This research has developed a promising and low-cost extracorporeal membrane oxygenation material, which provides benefits for patients with less capacity for medical expenditure.

Polypropylene Hollow-Fiber Membrane Made Using the Dissolution-Induced Pores Method.

The efficient preparation of hydrophilic polypropylene membranes has always been a problem. Here, a twin-screw extruder was used to melt-blend ethylene-vinyl alcohol copolymer and polypropylene; then, hollow fibers were extrusion-molded with a spinneret and taken by a winder; after this, dimethyl sulfoxide was used to dissolve the ethylene-vinyl alcohol copolymer of the fiber to obtain a polypropylene hollow-fiber membrane. This procedure was used to study the effects of different contents and segment structure of ethylene-vinyl alcohol copolymer on the structure and filtration performance of the membranes; furthermore, the embedded factor and blocked factor were used to evaluate the ethylene-vinyl alcohol copolymer embedded in the matrix without dissolving and or being completely blocked in the matrix, respectively. The results show that the increase in ethylene-vinyl alcohol copolymer could reduce the embedded factor and increase the blocked factor. The increase in the polyethylene segments of ethylene-vinyl alcohol copolymer could increase both the embedded factor and blocked factor. The water permeation of the membrane reached 1300 Lm−2·h−1·bar−1 with a 100% rejection of ink (141 nm) and the elongation at break reached 188%, while the strength reached 22 MPa. The dissolution-induced pores method provides a completely viable alternative route for the preparation of polypropylene membranes.

Sono-hollow fiber membrane contactors: A new approach for CO2 separation by physical/chemical absorbents

Herein, the nano adsorbents of Fe3O4 and Fe3O4@SiO2–NH2 were first synthesized and then dispersed in distilled water as a base fluid for Carbon dioxide (CO2) separation from a gas stream using a polypropylene hollow fiber membrane contactor (PP HFMC) and the separation experiment was performed under non-ultrasonic/ultrasonic irradiation for the first time. The impacts of varying liquid and gas flow rates, nanoparticles (NPs) loading, absorbents viscosity, NPs stability, and ultrasonic irradiation intensity were evaluated on the performance of Fe3O4 and Fe3O4@SiO2–NH2 nanofluids in CO2 separation. According to the obtained results, Fe3O4@SiO2–NH2 nanofluid was considerably powerful compared to Fe3O4 nanofluid due to the advantage of chemical reaction with CO2. Furthermore, ultrasound irradiation effectively raised the CO2 absorption capacity of Fe3O4 and Fe3O4@SiO2–NH2 nanofluids up to 13.37 and 16.41%, respectively. Ultimately, at the best operational condition, the CO2 separation enhancement factors of 58.44 and 84.45% were achieved by Fe3O4@SiO2–NH2 nanofluid under non-ultrasonic irradiation and ultrasonic irradiation conditions.

Construction of superhydrophobic micro/nano-structure surface on polypropylene hollow fiber membrane and its application in membrane distillation

Construction of superhydrophobic micro/nano-structure surface on polypropylene hollow fiber membrane and its application in membrane distillation

Comprehensive insights into performance of water gap and air gap membrane distillation modules using hollow fiber membranes

A commercially available microporous polypropylene hollow fiber membranes were employed for air gap and water gap membrane distillation (i.e., AGMD and WGMD, respectively) processes. In both configurations, the outer surface of commercially available dense polypropylene hollow fibers was used as the condensing surface of the permeate. The performance levels of the AGMD and WGMD processes utilizing microporous polyvinylidene fluoride membranes fabricated in-house were compared with those using polypropylene membranes. Under the given specific operating conditions, the maximum mean permeation flux values in AGMD and WGMD using polypropylene hollow fiber membranes were approximately 24 and 27 kg/m2h, respectively. In addition, theoretical studies on AGMD and WGMD using the designed hollow fiber module configuration were performed. The predicted results were found to well agree with the experimental results, thus verifying their validity. Moreover, parametric studies were conducted to identify the optimum evaporation-to-condensation surface area ratio (i.e., optimum numbers of hollow fiber membranes and hollow fiber condensers) in terms of specific energy consumption.