Polypropylene Hollow Fiber Membrane Contactor Research Articles

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.

Advanced Hybrid System for Ammonium Valorization as Liquid Fertilizer from Treated Urban Wastewaters: Validation of Natural Zeolites Pretreatment and Liquid-Liquid Membrane Contactors at Pilot Plant Scale.

This study evaluates a hybrid system combining zeolites as a sorption stage and a hollow fiber membrane contactor (HFMC) for ammonia (NH3) recovery from treated urban wastewater. Ion exchange with zeolites was selected as an advanced pretreatment and concentration step before the HFMC. The system was tested with wastewater treatment plant (WWTP) effluent (mainstream, 50 mg N-NH4/L) and anaerobic digestion centrates (sidestream, 600-800 mg N-NH4/L) from another WWTP. Natural zeolite, primarily clinoptilolite, demonstrated effective desorption of retained ammonium using a 2% NaOH solution in a closed-loop configuration, resulting in an ammonia-rich brine that enabled over 95% NH3 recovery using polypropylene HFMCs. A 1 m3/h demonstration plant processed both urban wastewaters, which were pretreated by ultrafiltration, removing over 90% of suspended solids and 60-65% of COD. The 2% NaOH regeneration brines (2.4-5.6 g N-NH4/L) were treated in a closed-loop HFMC pilot system, producing 10-15% N streams with potential use as liquid fertilizers. The resulting ammonium nitrate was free of heavy metals and organic micropollutants, making it suitable for use as liquid fertilizer. This comprehensive N management solution for urban wastewater applications can contribute to local economies while achieving reduced N discharge and circularity goals.

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.

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.

Optimizing SO2 Adsorption from Flue Gas Using Microporous Polypropylene Hollow Fiber Membrane Contactor

This study optimized the operational parameters of removing SO2 from flue gas via a polymeric hollow fiber membrane contactor (HFMC) using the response surface methodology (RSM). The distilled water and polypropylene hollow fibers were applied as the adsorbent and membrane material, respectively. Three experimental parameters were chosen as independent variables: liquid flow rate, gas flow rate, and initial SO2 concentration. The SO2 removal efficiency was significantly affected by the initial SO2 concentration. The optimal ratio of liquid-to-gas flow rate was found to be 0.25 to reach maximum separation efficiency (98.81%). The optimal value of the liquid flow rate was 33 l/h, and the optimal gas flow rate was 131 l/h. The effect of CO2 presence, module length, fibers number, temperature, and the adsorbent nature were also investigated under optimal values obtained for the ratio of liquid-to-gas flow rate. Results indicated that CO2 presence in the flue gas slightly affects SO2 removal using water as an absorbent in HFCM. Furthermore, it was indicated that the SO2 removal efficiency was a function of the flue gas temperature and number of fibers: it decreased as the temperature rose from 20 to 50°C and the fiber numbers increased from 300 to 1000. This study offers a model to predict the efficiency of SO2 removal using HFMC under different conditions and provides the ground to further explore the industrial applications of this technology.

Integration of a calcium carbonate crystallization process and membrane contactor–based CO2 capture

This research work presents the integration of polypropylene hollow fiber membrane contactor–based CO2 absorption unit using aqueous sodium hydroxide (NaOH) as the absorbent solution, and precipitation of high-quality calcium carbonate by addition of calcium chloride. The integrated crystallization process bypasses the need for cost-intensive energy regeneration of the absorbent solution. Given the lifetime of high added value precipitated calcium carbonate, the proposed approach for integrating solid particle formation and a carbon dioxide mitigation technique can be considered as a potential post-combustion technology for carbon capture, utilization and sequestration (CCUS). The overall CO2 mass transfer coefficient in the membrane contactor and subsequent crystallization process was investigated by conducting the experiments at different operating conditions. For a maximum hydroxide concentration of 5.01molL-1, an overall mass transfer coefficient of 2.25·10-4ms-1 and CO2 flux of 2.45·10-4molm-2s-1 were obtained for a 0.5Lmin-1 of gas flow rate. The proposed liquid–liquid crystallization process produces a narrow size distribution of micron-sized calcium carbonate with a mean diameter of 3–8 µm that can be used in the paper, coatings, food and biomedical industries.

The Management of Dissolved Oxygen by a Polypropylene Hollow Fiber Membrane Contactor Affects Wine Aging.

Background: Numerous oenological practices can cause an excess of dissolved oxygen in wine, thus determining sensory and chromatic defects in the short- to long-term. Hence, it is necessary to manage the excess of oxygen before bottling. Methods: In this study, the management of the dissolved oxygen content by a polypropylene hollow fiber membrane contactor apparatus was performed in two wines from different grape varieties (Aglianico and Falanghina). The wines were analyzed after an 11-month aging. Anthocyanins and acetaldehyde content were evaluated by HPLC. In addition, other phenolic compounds and chromatic characteristics were analyzed by spectrophotometric methods. NMR and HR ESIMS analyses were conducted to evaluate the amount of pyranoanthocyanins and polymeric pigments. Results: After 11 months of aging, in both wines a decrease of free and total SO2 with respect to initial values was detected. In the wines with the highest dissolved oxygen levels, a more remarkable loss was observed. No significant differences in terms of color parameters were detected. In red wine with the highest oxygen content, a massive formation of polymeric pigments and BSA reactive tannins was observed, as opposed to wines with lower oxygen levels. Conclusion: The study demonstrated that the membrane contactor can prove a successful tool to manage dissolved oxygen in wines as to prevent their oxidative spoilage.

Selective Sulfur Dioxide Absorption from Simulated Flue Gas Using Various Aqueous Alkali Solutions in a Polypropylene Hollow Fiber Membrane Contactor: Removal Efficiency and Use of Sulfur Dioxide.

Hollow fiber membrane contactors (HFMCs) provide a large specific surface area. Thus, their significantly reduced volume provides an advantage compared to the conventional gas–liquid contactor. In this study, the selective removal efficiency of flue gas, in which sulfur oxide (SO2) and carbon dioxide (CO2) coexist, was measured using a polypropylene (PP) HFMC with such advantages. To increase the selective removal efficiency of SO2, experiments were conducted using various alkaline absorbents. As a result, with 0.05 M ammonia solution, the removal efficiency of 95% or more was exhibited with continuous operation for 100 h or more. We confirmed that the absorbent saturated by the once-through mode was aqueous ammonium sulfate ((NH4)2SO4) solution and could be used as a fertilizer without additional processing.

Maximising resource recovery from wastewater grown microalgae and primary sludge in an anaerobic membrane co-digestion pilot plant coupled to a composting process

A pilot-scale microalgae (Chlorella spp.) and primary sludge anaerobic co-digestion (ACoD) plant was run for one year in an anaerobic membrane bioreactor (AnMBR) at 35 °C, 70 d solids retention time and 30 d hydraulic retention time, showing high stability in terms of pH and VFA concentration. The plant achieved a high degree of microalgae and primary sludge substrate degradation, resulting in a methane yield of 370 mLCH4·gVSinf−1. Nutrient-rich effluent streams (685 mgN·L−1 and 145 mgP·L−1 in digestate and 395 mgNH4-N·L−1 and 37 mgPO4-P·L−1 in permeate) were obtained, allowing posterior nutrient recovery. Ammonium was recovered from the permeate as ammonia sulphate through a hydrophobic polypropylene hollow fibre membrane contactor, achieving 99% nitrogen recovery efficiency. However, phosphorus recovery through processes such as struvite precipitation was not applied since only 26% of the phosphate was available in the effluent. Composting process of the digestate coming from the ACoD pilot plant was assessed on laboratory-scale Dewar reactors, as was the conventional sludge compost from an industrial WWTP digestion process, obtaining similar values from both. Sanitised (free of Escherichia coli and Salmonella spp.) and stable compost (respirometric index at 37 °C below 0.5 mgO 2 g organic matter−1·h−1) was obtained from both sludges.

Study of intrinsic oxygen mass transfer characteristic and model on polypropylene hollow fiber membrane contactor

The oxygen mass transfer characteristics of a membrane contactor with a hydrophobic polypropylene hollow fiber membrane are experimentally studied herein. The examination focuses on influences of oxygen intake pressure (0.12, 0.13, and 0.14 MPa) and water flux (from 100 L/h to 320 L/h) on oxygen mass transfer coefficient. Experimental results indicate that the inflection point of oxygen mass transfer coefficient shows up when water flux increases under specific intake gas pressures. The mass transfer coefficient goes up remarkably along with rise of oxygen intake pressure. A novel mass transfer model based on the concept of the liquid film renewal time (△tj) and the solubility equilibrium time (△t⁎) is proposed. In this model, the total mass transfer rate is influenced both by liquid film renewal rate between fluid bulk region and liquid film at the gas–liquid interface, and by oxygen diffusion rate in the twice interface renewal process. The model interprets the experimental mass transfer phenomena well.

CO2 Desorption Performance from Imidazolium Ionic Liquids by Membrane Vacuum Regeneration Technology.

In this work, the membrane vacuum regeneration (MVR) process was considered as a promising technology for solvent regeneration in post-combustion CO2 capture and utilization (CCU) since high purity CO2 is needed for a technical valorization approach. First, a desorption test by MVR using polypropylene hollow fiber membrane contactor (PP-HFMC) was carried out in order to evaluate the behavior of physical and physico-chemical absorbents in terms of CO2 solubility and regeneration efficiency. The ionic liquid 1-ethyl-3-methylimidazolium acetate, [emim][Ac], was presented as a suitable alternative to conventional amine-based absorbents. Then, a rigorous two-dimensional mathematical model of the MVR process in a HFMC was developed based on a pseudo-steady-state to understand the influence of the solvent regeneration process in the absorption–desorption process. CO2 absorption–desorption experiments in PP-HFMC at different operating conditions for desorption, varying vacuum pressure and temperature, were used for model validation. Results showed that MVR efficiency increased from 3% at room temperature and 500 mbar to 95% at 310 K and 40 mbar vacuum. Moreover, model deviation studies were carried out using sensitivity analysis of Henry’s constant and pre-exponential factor of chemical interaction, thus as to contribute to the knowledge in further works.

Mathematical modeling of CO2 membrane absorption system using ionic liquid solutions

This research presents a 2D mathematical modeling based on finite difference method (FDM) for absorption of CO2 into aqueous solution of ionic liquids ([bmim][BF4] and [bmim][PF6]) by means of hydrophobic polypropylene hollow fiber membrane contactor (HFMC). Governing equations with their corresponding boundary conditions were solved and the results were validated against reported experimental data and excellent agreement was found. This study has provided an opportunity to investigate the effects of various ionic liquids with different concentrations as well as liquid and gas flow rate on CO2 absorption system in membrane contactors. The results demonstrated that molar flux of carbon dioxide for 25 wt% and 50 wt% solution of [bmim][PF6] is 1.29 and 1.98 times that of pure water, respectively. Also [bmim][BF4] has a weaker performance than [bmim][PF6] due to lower carbon dioxide solubility, and the addition of 50 wt% of it to the pure water has increased the absorption rate by 32 %. Overall and liquid phase mass transfer coefficient has decreased in ionic liquid solutions. Reynolds number in tubes has been decreased by increasing of ionic liquid mass fraction and also a sharp decrease in the Reynolds number can be observed in the ionic liquids mass fractions greater than 60 wt%.

Pomegranate juice concentration using osmotic distillation with membrane contactor

This study aims at evaluating the effect of fouling on the performance of polypropylene hollow fiber membrane contactor with feed-in-shell flow configuration for the concentration of pomegranate juice through osmotic distillation (OD). The juice was concentrated to 52.0 ± 0.3°Brix, reaching a maximum flux of 1.053 kg.m−2.h−1 at a temperature of 25 °C, stripping solution (CaCl2) concentration of 6 M and feed and stripping solution flow rates of 0.012 m3.h−1 in a total recycled processing time of 310 min. Scanning Electron Microscopy analysis showed that the fouling caused the membrane pores to be blocked during the prolonged operation. Repeated experimentation showed that the stringent membrane cleaning protocol almost doubled the water flux. The quality parameters (total soluble solids, total acidity, and total sugars) were well retained after concentration of pomegranate juice through the OD process.

Membrane Absorption Coupling Process for CO2 Capture: Application of Water-Based ZnO, TiO2, and Multi-Walled Carbon Nanotube Nanofluids

In this work, stable water-based zinc oxide (ZnO), titania (TiO2), and multi-walled carbon nanotube (MWCNT) nanofluids are prepared and examined as CO2 absorbents in a polypropylene hollow fiber membrane contactor. Different operating variables, such as liquid flow rate, gas flow rate, and concentration of nanoparticles, and their effects on CO2 molar flux are investigated. The long-term stability of nanofluids is monitored using ultraviolet–visible spectroscopy. Also, ζ-potential measurements and sediment photography are applied to confirm the results of nanofluid stability. Dynamic light scattering is used to determine the size distribution of dispersed nanoparticles. The results show that the increase in the nanoparticle concentration to 0.15 wt % has a favorable effect on CO2 absorption efficiency as a result of the increase in Brownian motion and other related mechanisms. However, it adversely affects the CO2 absorption by lowering the nanofluid stability at higher concentrations. The obtained result...

Experimental investigation and mathematical modeling of CO2 sequestration from CO2/CH4 gaseous mixture using MEA and TEA aqueous absorbents through polypropylene hollow fiber membrane contactor

In the current study, experimental and mathematical results of a counter-current contact between CO2/CH4 gaseous mixture and aqueous liquid absorbents (MEA and TEA) through a microporous polypropylene hollow fiber membrane contactor are presented to evaluate the sequestration percentage of CO2 acidic pollutant from gaseous mixture. One of the aims of this paper is to experimentally and mathematically study the effects of gas flow rate, aqueous liquid absorbents' flow rate and also inlet CO2 concentration on the removal efficiency of CO2. In order to carry out this, a two dimensional mathematical model is developed to predict the experimental results. The experimental results show that MEA absorbent has higher superiority for efficient removal of CO2 acidic gas compared to TEA absorbent. Based on the experimental results, the sequestration efficiency of CO2 from gaseous mixture applying MEA and TEA aqueous absorbents is about 92% and 62%, respectively. The simulated results of CO2 sequestration in wide ranges of gas flow rate, inlet CO2 concentration and liquid absorbents' flow rate demonstrate an excellent agreement with those of experimentally measured ones with average absolute relative errors (AAREs) of 4.3%, 4.4% and 3.6% for employing MEA and 6.9%, 3.4% and 5.2% for using TEA absorbents, respectively. Additionally, this article aims to study the influence of momentous operational parameters such as number of fibers, module length and also membrane porosity and tortuosity on the CO2 separation efficiency. Based on the experimental and the numerical simulated results, increase in the gas flow rate, the membrane tortuosity and the CO2 inlet concentration significantly deteriorates the sequestration efficiency of CO2 while increment of the fibers counts, the membrane module length, the membrane porosity and the liquid flow rate positively encourages the CO2 sequestration percentage.

Experimental study on the effects of an ionic liquid for CO2 capture using hollow fiber membrane contactors

Ionic liquids are considered as new absorbents with high solubility for separation of CO2 from flue gases. In this study, the effect of an ionic liquid ([Bmim][BF4]) on the absorption of CO2 using polypropylene hollow fiber membrane contactors was studied. Aqueous solutions of ionic liquid and mixture of ionic liquid with methyldiethanolamine were applied as physical and chemical absorbents, respectively. The effects of different parameters including concentration of ionic liquid in water and aqueous solution of methyldiethanolamine as base fluids, liquid and gas flow rates, and flow direction were investigated. The results showed that a 25 wt% solution of ionic liquid can increase the absorption efficiency about 20% and 15% compared to pure water in co-current and counter-current flows, respectively. It was also observed that a mixture containing 20 wt% of ionic liquid and 10 wt% of methyldiethanolamine can improve the absorption capacity about 10% compared to a 10 wt% MDEA aqueous solution without ionic liquid.

A novel process for oxygen absorption from air using hollow fiber gas-liquid membrane contactor

Abstract In this study, the absorption of oxygen from air flowing through polypropylene hollow fiber membrane contactor was investigated using slaughterhouse wastewater, including about 90% (v/v) blood, as an absorbent. The effect of operating parameters on process performance was examined in two modes of absorbent flowing through both the lumen and shell of the membrane contactor. In addition, some experiments were carried out to examine the long term performance of the system. Removal efficiency and absorption flux were determined for investigation of the process performance. Results showed decrease in gas flow rate and increase in liquid flow rate resulted in higher removal efficiency, respectively. Moreover, absorption flux was increased by augmenting both gas and liquid flow rate. Furthermore, the removal efficiency of near 78% was obtained for mode of wastewater flowing through the lumen side. No considerable variations in removal efficiency were observable for long term operation.

Denitration by oxidation-absorption with polypropylene hollow fiber membrane contactor

Development of cost-efficient denitration technologies has been a challenging task in chemical industry. Here we proposed a new denitration method by using polypropylene hollow fiber membrane contactor, through which the NO gas from a simulative flue gas was absorbed into a saline aqueous solution, and then oxidized by the added H2O2. We demonstrated that the numerous pores in the semipermeable membrane and the addition of NaCl gave rise to a high-efficient oxidation-absorption process. By combining with a theoretical study upon both classical and quantum density functional theories, we extensively examined the effects of different operation parameters including the gas and liquid flow rates, the concentrations of H2O2 and NaCl in the solution and SO2 in the mimic flue gas, the absorption temperature and the circulating time. The optimal operation parameters were identified. Finally, along with a designed industrial flow chart we evaluated the cost-efficiency of this proposed method, and found that this method could be more competitive than the current mainstream technologies for flue gas denitration.

Modeling SO2 absorption into water accompanied with reversible reaction in a hollow fiber membrane contactor

The authors developed an efficient flue gas desulfurization (FGD) process employing a hydrophobic polypropylene hollow fiber membrane contactor (HFMC) using deionized water as scrubbing liquid. A novel mathematical reactor model for gas absorption accompanied by a reversible reaction in an HFMC was developed for the first time. This new model employed the resistance-in-series theory, along with partial pore wetting, and a chemical enhancement factor for an instantaneous reversible reaction. This model was validated agreeably with experimental data. The validated reactor model was then employed to investigate the resistance distribution along the main axis and the effects of temperature on SO2 removal efficiency. It was shown that the reactor model with the assumption of non-wetted pores overestimated the absorption efficiency, and a wetted pore length between 6.25–9.75% would yield a very good agreement with the experimental data. The deviations between the predicted and experimental values were less than ±3.0% with an exception of 3.4% at the highest gas rate for gas flow rates ranging from 1.38×10−4 to 3.01×10−4m3s−1, liquid flow rates between 3.00×10−6−8.00×10−6m3s−1, and the inlet SO2 concentration of 2000 ppmv. Furthermore, the reactor model described the impact of inlet SO2 concentration on the SO2 removal efficiency within ±0.5% of measured values for liquid rates between 4.35×10−6 and 5.50×10−6m3s−1 under a gas flow rate of 1.90×10−4m3s−1. The resistances of shell side, fiber side and membrane are all important due to high solubility of SO2 and partial pore wetting. The SO2 removal efficiency decreased gradually as the temperature increased from 283 to 333K based on model predictions.

Practical designs of membrane contactors and their performances in CO2/CH4 separation

Porous polypropylene (PP) hollow fiber membrane contactors operated by either single absorption processes or combined absorption/desorption processes using water have been investigated for use in the production of biomethane from simulated biogas. To observe the effect of operating parameters on the membrane contactors, the connection of modules, flow rates, and operating pressures were tuned. For CO2/CH4 separation, operations using single absorption processes produced a good yield (85%) of high purity CH4 (97%). Connections in series containing two absorption modules facilitated CO2 absorption due to an increase in contact area at the liquid–gas interface. In the combined absorption/desorption processes, CH4 was recovered in 75% yield and 98% purity using two 1″ absorption modules and four 2″ desorption modules connected in series. Although the results were somewhat poorer than those of the single absorption processes due to limits in desorption performance, the combined process provided the potential for producing renewable methane as a fuel for vehicles. Furthermore, for the single absorption processes, the PP hollow fiber membrane contactor was operated continuously, while the membrane used in the combined absorption/desorption processes required periodic maintenance to maintain an acceptable performance.