Application Of Membrane Contactors Research Articles

Investigating the influence of CaCO3 nanoparticles on the performance of CO2 absorption in the PVC membrane contactors

The membrane contactor application to purify acid gases is a significant advancement in environmental protection and engineering processes. Notwithstanding the numerous privileges of membrane contactors, the wetting of the polymeric membrane is considered the main worry in developing the mentioned technology. The polymeric membrane wetting by liquid absorbents increases the membrane mass transfer resistance and decreases the gas absorption. In this study, hydrophobic PVC membranes including various amounts of CaCO3 nanoparticles were manufactured to reduce the wetting problem. The prepared membranes were evaluated using AFM, TEM, XRD, contact angle, SEM, and tensile strength measurements. The contact angle results illustrated that adding the nanoparticles enhanced the membrane contact angle; so that for nanocomposite membranes comprising 1.5 wt.% nanoparticles, the contact angle increased from about 77°–94°. Investigating the tensile strength results showed that the nanoparticle presence in the membrane structure raised the tensile strength by 10 MPa. Finally, the nanocomposite and pure membrane performance in CO2 absorption was evaluated in the system of membrane contactors. The findings exhibited that after 25 days of the gas absorption process, the permeate flux of pure membranes significantly decreased. However, the gas absorption flux in nanocomposite membranes containing 1.5 wt.% nanoparticles remained constant during this period.

Design principles and considerations of omniphobic membranes for membrane distillation and contactor

This paper presents design principles and considerations for robust omniphobic membrane fabrication for membrane distillation and contactor applications, based on a theoretical framework that links the membrane structure to the wetting resistance. First, the energy barrier against membrane wetting is depicted in relation to the membrane structure (re-entrant structure) and surface chemistry. The effect of liquid pressure (hydrostatic or hydraulic) on the energy barrier reduction is then illustrated, which shows that the pressure-induced liquid-gas interface distortion can reduce the energy barrier by nearly 10 times or more. Subsequently, the role of multi-level re-entrant structure to counteract the reduction and elevate the energy barrier is presented. Next, the framework is applied to deduce the key structural parameters of omniphobic membranes in the literature, where fibrous or microporous substrates were modified without and with nanoparticles to construct single- and multi-level re-entrant structures, respectively. The effectiveness of their re-entrant structure on enhancing the wetting resistance is then assessed. The analysis suggests that nanoparticle-based modifications in the literature led to rather low enhancement than anticipated, and can be further optimized to attain a greater wetting resistance. Finally, key considerations to fabricate robust omniphobic membranes are discussed.

Book Review Hollow Fiber Membrane Contactors: Module Fabrication, Design and Operation, and Potential Applications

The latest developments and applications of hollow fiber membrane contactors (HFMCs) were discussed in this recent published book. Membrane contactor provides gas–liquid or liquid–liquid contact without dispersion of one phase in another, which gives a higher mass transfer coefficient compared to the conventional contactors. Using a microporous hydrophobic or hydrophilic membrane, one of the fluids is immobilized in the pores where the mass transfer is occurred based on the concentration gradient. HFMC technology has been implemented in various applications including gas separation, fermentation, pharmaceuticals, wastewater treatment, chiral separation, semiconductor manufacturing, carbonation of beverages, metal ion extraction, protein extraction, VOC removal from waste gas, and osmotic distillation.

Mechanistic insights to the reversibility of membrane wetting in membrane distillation

Membrane wetting is an inevitable challenge in membrane distillation (MD). To overcome this challenge, a few dewetting techniques have been developed, but the reversibility of membrane wetting induced by various contaminants has not been well understood. Herein, we evaluate the reversibility of membrane wetting induced by different types of contaminants and elucidate the underlying mechanisms. From direct contact MD experiments and membrane wettability characterizations, membrane wetting induced by amphiphilic molecules, low-surface-tension liquids, and highly soluble salts can be easily reversed by 20-min DI water rinsing and oven drying, while to reverse membrane wetting induced by sparingly soluble salts, 3-h DI water rinsing and oven drying are required. Based on microscopic imaging and elemental mapping, the membrane wetting processes did not induce severe damage to membrane structure, and thus the hydrophobicity of the membrane can be restored after the contaminants were removed from the membrane. Furthermore, the mechanisms of the removal of different contaminants are elucidated. Specifically, after membrane rinsing and drying, the amphiphilic molecules automatically desorb from the dried membrane due to the disappearance of the underwater hydrophobic-hydrophobic interaction, while the low-surface-tension liquids leave the membrane pores because of evaporation. Additionally, during the membrane rinsing process, the highly soluble salts inside the membrane pores are dissolved, while the sparingly soluble salts detach from the membrane due to the hydrodynamic disturbance. The insights from this study shed lights on the development of effective dewetting techniques for hydrophobic membranes, which benefits not only MD but also membrane contactor applications.

Stability of Porous Polymeric Membranes in Amine Solvents for Membrane Contactor Applications.

Membrane gas-liquid contactors have great potential to meet the challenges of amine CO2 capture. In this case, the most effective approach is the use of composite membranes. However, to obtain these, it is necessary to take into account the chemical and morphological resistance of membrane supports to long-term exposure to amine absorbents and their oxidative degradation products. In this work, we studied the chemical and morphological stability of a number of commercial porous polymeric membranes exposed to various types of alkanolamines with the addition of heat-stable salt anions as a model of real industrial CO2 amine solvents. The results of the physicochemical analysis of the chemical and morphological stability of porous polymer membranes after exposure to alkanolamines, their oxidative degradation products, and oxygen scavengers were presented. According to the results of studies by FTIR spectroscopy and AFM, a significant destruction of porous membranes based on polypropylene (PP), polyvinylidenefluoride (PVDF), polyethersulfone (PES) and polyamide (nylon, PA) was revealed. At the same time, the polytetrafluoroethylene (PTFE) membranes had relatively high stability. On the basis of these results, composite membranes with porous supports that are stable in amine solvents can be successfully obtained to create liquid-liquid and gas-liquid membrane contactors for membrane deoxygenation.

Carbon dioxide capture in aqueous potassium serinate and piperazine solution using bubbling reactor for membrane contactor applications

There are various methods of CO2 removal, including absorption, adsorption, and membrane separation. A new method, membrane–solvent combination, involves the removal of CO2 using an absorbent in a membrane contactor. However, the absorbent causes membrane wetting, which reduces the CO2 removal efficiency. Accordingly, this study considered the use of potassium serinate (PS), an amino acid salt with high surface tension, to increase the surface tension of the absorbent and therefore reduce membrane wetting when used in a membrane contactor. Piperazine (Pz) was added to improve the absorption performance and prevent oxidative degradation. The concentration ranges of PS and Pz to apply at the membrane contactor were optimized based on the CO2 cyclic capacity and the calculated theoretical breakthrough pressure. Compared to a commercial CO2 absorbent, 30 wt% monoethanolamine (MEA), the PS + Pz absorbent had higher CO2 cyclic capacity and better wettability. Moreover, its oxidative degradation rate constant (k) in 720 h oxidative degradation experiments was 42.0 % lower than that of 30 wt% MEA, indicating that amino acid salt + Pz absorbents are promising for use in membrane contactors.

Study on robust absorption performance of hydrophilic membrane contactor for direct air capture

Increased atmospheric carbon dioxide (CO2) concentration constitutes a growing environmental and health concern. The absorption of CO2 from air requires a large gas–liquid contact area due to low driving force. Here, the membrane absorption was proposed to the removal of atmospheric CO2 using a ceramic membrane contactor, while NaOH serves as absorbent, performance of ceramic membrane absorption was study. In hydrophilic membrane, NaOH concentration of 2 mol⋅L−1 has the best absorption performance, which serves as initial concentration in absorption cyclic process, and when NaOH utilization reaches 75 %, it still has great absorption performance. In addition, suitable gas and liquid operating parameters of this work were also confirmed as 1000 mL⋅min−1 and 1 mL⋅min−1, respectively, corresponding mass transfer coefficient and CO2 absorption flux is 2.6 mm⋅s−1 and 0.096 mol⋅m−2⋅h−1, respectively. The great absorption stability shows the huge potential of ceramic membrane contactor application for direct air capture.

Membranes Based on PTMSP/PVTMS Blends for Membrane Contactor Applications.

In this work, perspective polymeric materials were developed for membrane contactor applications, e.g., for the dissolved oxygen removal from amine CO2 capture solvents. Several polymeric blends based on poly[1-trimethylsilyl-1-propyne] (PTMSP) and poly[vinyltrimethylsilane] (PVTMS) were studied. The gas and water vapor sorption and permeability coefficients for the PTMSP/PVTMS blend membranes at different PVTMS contents (0-100%) were obtained under temperatures of 30 and 60 °C for the first time. As the PVTMS content increases, the O2 and CO2 permeabilities decrease by 160 and 195 times at 30 °C, respectively. The fractional accessible volume of the polymer blends decreases accordingly. The transport of the CO2 capture solvent vapors through the PTMSP/PVTMS blend membranes were determined in thermo-pervaporation (TPV) mode using aqueous monoethanolamine (30%), N-methyldiethanolamine (40%), and 2-amino-2-methyl-1-propanol (30%) solutions as model amine solvents at 60 °C. The membranes demonstrated high pervaporation separation factors with respect to water, resulting in low amine losses. A joint analysis of the gas permeabilities and aqueous alkanolamine TPV data allowed us to conclude that the polymer blend composition of PTMSP/PVTMS 70/30 provides an optimal combination of a sufficiently high oxygen permeability and the pervaporation separation factor at a temperature of 60 °C.

Application of hollow fibre membrane contactor for ultra purification of 90Sr nitrate solution at bulk scale for 90Sr–90Y generator for societal use

Application of hollow fibre membrane contactor for ultra purification of 90Sr nitrate solution at bulk scale for 90Sr–90Y generator for societal use

Effect of amino acid additives in ammonia solution on SO2 absorption and ammonia escape using bubbling reactor for membrane contactor applications

Controlling the SO2 emissions is crucial because they result in several environmental problems and affect human health. Several techniques have been proposed for controlling SO2 emissions. Limestone or lime-based absorbents are widely used for SO2 removal. However, their low solubility limits their applications. Ammonia solution has attracted attention owing to its higher SO2 removal efficiency. However, owing to its high volatility, it has the propensity to escape, which can cause secondary environmental pollution. Therefore, we investigated the effect of six amino acid additives to improve the SO2 absorption performance and inhibit the ammonia escape in aqueous ammonia solution. The surface tension and theoretical breakthrough pressure of the amino acid-containing ammonia solutions was investigated to evaluate their applicability to a membrane contactor process. L-histidine (His) exhibited the best performance. Therefore, the effect of His concentration, inlet SO2 concentration, and absorption temperature on SO2 absorption performance was explored. The 13C nuclear magnetic resonance (NMR) and 1H NMR analyses were used to study the SO2 absorption mechanism. This study provides a strategy for preparing an eco-friendly and highly efficient SO2 absorbent that can overcome the disadvantage of current ammonia solutions for the removal of low-concentration SO2 from industrial gas emissions for the membrane contactor process application.

Hydrophobic Ag-Containing Polyoctylmethylsiloxane-Based Membranes for Ethylene/Ethane Separation in Gas-Liquid Membrane Contactor.

The application of gas-liquid membrane contactors for ethane-ethylene separation seems to offer a good alternative to conventional energy-intensive processes. This work aims to develop new hydrophobic composite membranes with active ethylene carriers and to demonstrate their potential for ethylene/ethane separation in gas-liquid membrane contactors. For the first time, hybrid membrane materials based on polyoctylmethylsiloxane (POMS) and silver tetrafluoroborate, with a Si:Ag ratio of 10:0.11 and 10:2.2, have been obtained. This technique allowed us to obtain POMS-based membranes with silver nanoparticles (8 nm), which are dispersed in the polymer matrix. The dispersion of silver in the POMS matrix is confirmed by the data IR-spectroscopy, wide-angle X-ray diffraction, and X-ray fluorescence analyses. These membranes combine the hydrophobicity of POMS and the selectivity of silver ions toward ethylene. It was shown that ethylene sorption at 600 mbar rises from 0.89 cm3(STP)/g to 3.212 cm3(STP)/g with an increase of Ag content in POMS from 0 to 9 wt%. Moreover, the membrane acquires an increased sorption affinity for ethylene. The ethylene/ethane sorption selectivity of POMS is 0.64; for the membrane with 9 wt% silver nanoparticles, the ethylene/ethane sorption selectivity was 2.46. Based on the hybrid material, POMS-Ag, composite membranes were developed on a polyvinylidene fluoride (PVDF) porous support, with a selective layer thickness of 5–10 µm. The transport properties of the membranes were studied by separating a binary mixture of ethylene/ethane at 20/80% vol. It has been shown that the addition of silver nanoparticles to the POMS matrix leads to a decrease in the ethylene permeability, but ethylene/ethane selectivity increases from 0.9 (POMS) to 1.3 (9 wt% Ag). It was noted that when the POMS-Ag membrane is exposed to the gas mixture flow for 3 h, the selectivity increases to 1.3 (0.5 wt% Ag) and 2.3 (9 wt% Ag) due to an increase in ethylene permeability. Testing of the obtained membranes in a gas-liquid contactor showed that the introduction of silver into the POMS matrix makes it possible to intensify the process of ethylene mass transfer by more than 1.5 times.

Hollow-Fiber Membrane Contactor for Biogas Recovery from Real Anaerobic Membrane Bioreactor Permeate.

This study demonstrates the application of hollow-fiber membrane contactors (HFMCs) for the recovery of biogas from the ultrafiltration permeate of an anaerobic membrane bioreactor (AnMBR) and synthetic effluents of pure and mixed CH4 and CO2. The developed membrane degassing setup was coupled with a pilot-scale AnMBR fed with synthetic domestic effluent working at 25 °C. The membrane degassing unit was able to recover 93% of the total dissolved CH4 and 83% of the dissolved CO2 in the first two hours of permeate recirculation. The initial recovery rates were very high (0.21 mg CH4 L−1 min−1 and 8.43 mg CO2 L−1 min−1) and the membrane was able to achieve a degassing efficiency of 95.7% for CH4 and 76.2% for CO2, at a gas to liquid ratio of 1. A higher mass transfer coefficient of CH4 was found in all experimental and theoretical evaluations compared to CO2. This could also be confirmed from the higher transmembrane mass transport resistance to CO2 rather than CH4 found in this work. A strong dependency of the selective gas transport on the gas and liquid side hydrodynamics was observed. An increase in the liquid flow rate and gas flow rate favored CH4 transport and CO2 transport, respectively, over each component. The results confirmed the effectiveness of the collective AnMBR and membrane degassing setup for biogas recovery. Still, additional work is required to improve the membrane contactor’s performance for biogas recovery during long-term operation.

Hydrophobic PVDF hollow fiber membrane modified with pulse inductively coupling plasma activation and chloroalkylsilanes for efficient dye wastewater treatment by ozonation membrane contactor

PVDF membranes were modified by pulse inductively coupled plasma (PICP) and followed by grafting by chloroalkylsilanes for hydrophobicity enhancement and applied to dye wastewater treatment by ozonation membrane contactor. Two plasma gases (oxygen and argon), two grafting chloroalkylsilanes (methyltrichlorosilane [MTCS] and trimethylchlorosilane [TMCS]), and a range of grafting times (0.5–4 h) were investigated. Hydrophobicity enhancement was influenced by the modification conditions including the type of plasma gas, the applied voltage and pressure, the number of plasma treatment shots, and the grafting agent and duration. The results revealed that oxygen-plasma activation was more effective than argon plasma for functionalizing MTCS for hydrophobicity enhancement. The hydrophobicity increased with MTCS grafting but not with TMCS grafting. Successful membrane modification using MTCS was confirmed by the presence of silicon using FT-IR and EDX analysis. Modifying membranes greatly increased the water contact angle, from 74.7° to 125.3° after activation by 2 shots of oxygen plasma under 10 kV/0.3 mbar followed by grafting with MTCS for 4 h. The duration of the exposure of the membranes to ozone determined the membrane properties. The modified membrane also had a higher and more stable ozone flux than the original membrane. Using the modified membrane, DB 71 decolorization by ozonation with membrane contactor was almost complete after 90 min. COD and TOC removals were 63% and 20%, respectively. This study demonstrates that membrane modification via PICP grafted with MTCS has the potential to improve hydrophobicity and membrane contactor applications.

Membrane Contactors for Maximizing Biomethane Recovery in Anaerobic Wastewater Treatments: Recent Efforts and Future Prospect

Increasing demand for water and energy has emphasized the significance of energy-efficient anaerobic wastewater treatment; however, anaerobic effluents still containing a large portion of the total CH4 production are discharged to the environment without being utilized as a valuable energy source. Recently, gas–liquid membrane contactors have been considered as a promising technology to recover such dissolved methane from the effluent due to their attractive characteristics such as high specific mass transfer area, no flooding at high flow rates, and low energy requirement. Nevertheless, the development and further application of membrane contactors were still not fulfilled due to their inherent issues such as membrane wetting and fouling, which lower the CH4 recovery efficiency and thus net energy production. In this perspective, the topics in membrane contactors for dissolved CH4 recovery are discussed in the following order: (1) operational principle, (2) potential as waste-to-energy conversion system, and (3) technical challenges and recent efforts to address them. Then, future efforts that should be devoted to advancing gas–liquid membrane contactors are suggested as concluding remarks.

Membrane Crystallization and Membrane Condenser: Two Membrane Contactor Applications

In recent years different new membrane processes have been designed and developed. In this paper two innovative processes (i.e., membrane condenser and membrane crystallization) will be described and discussed. Membrane crystallization can be used in desalination in combination with membrane distillation and pressure driven membrane processes (such as nanofiltration or reverse osmosis) to achieve high recovery factor combined to salt crystals production.The innovative membrane condenser can be used for the selective recovery of evaporated waste water and contaminants from industrial gases. This process can be also used for pre-treating gas streams that require further separation for the recovery of a defined species (such as pre-treatment of flue gas when used for CO2 capture, biogas for bio methane production, etc.). The current status, the separation principle, the utilized membrane materials and membrane configurations, and the application fields are described and discussed. The future development direction of these two processes is also given. Keywords: Membrane Crystallization; Membrane Condenser; Water recovery; Membrane Technologies;

The effects of 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide [emim] [NTf2] IL: acetone compositions on the amount, homogeneity and chemical stability of immobilized IL in hollow fiber-supported ionic liquid membranes (SILMs)

The use of supported ionic liquid membranes and solvents that possess good selectivity on capturing carbon dioxide from flue gases would have a potential to replace conventional absorption method. However, common good solvents for carbon dioxide capture will undergo degradation due to the presence of oxygen. In this work, the effect of binary mixtures of [emim] [NTf2] ionic liquid: acetone at different composition on the morphology of the supported ionic liquid membranes (SILMs) was investigated using field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray (EDX) analysis. To test the stability of the SILMs, membranes were submerged in a pure and aqueous solution of monoethanolamine (MEA) at 70 °C for 14 days. The maximum amount of ionic liquid immobilized within the particular membranes was acquired at [emim] [NTf2] IL: acetone; (80:20) composition and found to be homogeneously distributed. Based on the study, the SILMs were found to be more stable with 2 M MEA as its surrounding phase. These remarks were in agreement with the ionic liquid losses, as ascertained by mass balance. Results in this work ultimately suggest promising potentials of [emim] [NTf2]-SILMs for further evaluation work, especially for the prevention of oxidative degradation of the amine solvents in membrane contactor applications for CO2 capture.

Supported ionic liquid membranes (SILMs) as a contactor for selective absorption of CO2/O2 by aqueous monoethanolamine (MEA)

Application of membrane contactors in a combination of monoethanolamine as a solvent system for post-combustion CO2 capture has been extensively studied in the last decades. Due to the better performance to capture CO2 at low concentration, the potentialities of novel technology of supported ionic liquids membranes (SILMs) for absorption process in gas-liquid membrane contactor system are currently being explored to improve and compliment previous technology. In this study, a modified hydrophobic gas-liquid membrane contactor system was prepared using Liqui-Cel® parallel flow module as a membrane support and 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide [emim] [NTf2] ionic liquid as a supporting phase. Under moderate operating conditions, parallel flow mode and use of monoethanolamine (MEA) as an absorbent, the effects of absorbent temperature and gas velocity on the CO2 absorption efficiency and CO2/O2 selectivity were determined using this modified module. Further investigation to compare the performances of blank and modified membrane module was implemented at different temperatures (303–348 K) and gas velocities (4.63 × 10−6 to 3.70 × 10−5 m s−1). Results revealed that efficiency of the CO2 absorption process of the modified module is almost doubled with an average selectivity factor of CO2/O2 around 5 times compared to blank contactor system. Thus, this modified membrane contactor system had shown a great potential for further used in the real industrial CO2 capture and beneficial to bottleneck the issue of MEA oxidation that usually occurred in previous gas-liquid membrane contactor system.

Fabrication of hydrophobic PP/CH3SiO2 composite hollow fiber membrane for membrane contactor application

Polymeric membrane wetting by liquid absorbent is one of the major challenges of the gas- liquid membrane contactors. In order to overcome this issue, composite polypropylene (PP) hollow fiber membranes were prepared by incorporation of methyl grafted silica nanoparticles (CH3-g-silica NPs) via two treatment approaches including blending the NPs with dope solution before membrane fabricating (approach 1), and also coating the NPs on the surface of the prepared membrane (approach 2). The fabricated membranes were characterized by using ATR-FTIR, FESEM, TEM, AFM, porosity, contact angle, mechanical strength, breakthrough pressure, wetting resistance and gas permeation test. The obtained results from ATR-FTIR spectra confirmed the successful formation of the PP-CH3SiO2 composite hollow fiber membranes. It was seen that for composite membranes fabricated with approaches 1 and 2 the average contact angle increased from 124° to 145° and 168°, respectively. The fabricated membranes were also investigated for CO2 absorption process in gas- liquid membrane contactors. As a result, the gentle decrease in flux of composite membranes compare to the sharp flux drop of neat one confirmed the effective improvement in the non-wetting property of the membranes in the presence of inorganic particles.

Exploiting Fluoropolymers Immiscibility to Tune Surface Properties and Mass Transfer in Blend Membranes for Membrane Contactor Applications

Polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) and polyvinylidene fluoride (PVDF) blend membranes, with interconnected channels decorated with polymer crystallites, were produced by a tw...

Porous poly(vinylidene fluoride) membranes with tailored properties by fast and scalable non-solvent vapor induced phase separation

Hydrophobic and highly porous poly(vinylidene fluoride) (PVDF) membranes with isotropic cross section as well as tunable and narrow barrier pore size distribution in the range from ~0.1 to ~1 µm have been prepared using the non-solvent vapor induced phase separation (VIPS) technique. The process conditions have been tuned to suit an industrial scale up, using a short production time and dimethyl sulfoxide (DMSO) as solvent for PVDF, instead of commonly used hazardous chemicals. Factors like kind of solvent, the relative humidity of air, the exposure time to humid air and the mass fraction of PVDF in the casting solutions have been used to tune membrane characteristics. Interestingly, it was revealed that DMSO as a less common solvent for PVDF shows better qualities regarding upscaling than other more frequently used polar aprotic solvents (e.g. dimethylacetamide) when using VIPS under suited conditions. The phenomenon was explained through investigations of the membrane formation step, in particular by water uptake and cloud point measurements, as well as structure and performance analyses, e.g. by scanning electron microscopy, gas flow/liquid dewetting permpometry, gas and water vapor permeability analyses and liquid water entry pressure measurements. Lab-scale manufactured membranes showed pore characteristics and performance desired for membrane contactor applications. Furthermore, fabrication on a roll-to-roll machine using a nonwoven support and the established VIPS conditions was realized in a short manufacturing time; resulting membranes structure and characteristics were found to be similar to the ones for the lab-scale membranes. Overall, the combination of PVDF with DMSO gives promising opportunities for a more eco-friendly industrial fabrication of porous membranes with advanced properties via VIPS.