Flat Membrane Module Research Articles

Lithium solvent extraction by a novel multiframe flat membrane contactor module

Comparing to conventional liquid–liquid extraction, membrane extraction is an efficient and environmentally friendly separation technique to recover lithium from the salt-lake brine. Development of suitable hydrophilic solvent resistant nanoporous membranes for membrane extraction has been based on bench-scale small module. Because module design has significant impact on the performance, this work reported a novel multiframe flat membrane contactor module (MFMC) for lithium extraction from synthetic brine. The hydrophilic poly (ethylene-co-vinyl alcohol)/sulfonated poly(etheretherketone) membrane supported with polypropylene nonwoven (EVAL/SPEEK-NW) was prepared for module evaluation. The membrane mass transfer coefficients km of 1.1 × 10-6 m/s was obtained by Wilson plot. The global mass transfer coefficient Ke increased from 4.5 × 10-7 m/s to 9.9 × 10-7 m/s following the flow velocity from 0.4 to 1.8 cm/s in membrane extraction. We further evaluated the characteristics of MFMC via height of transfer units (HTU) and module efficiency (ME). High module efficiency of 90% was obtained, demonstrating MFMC’s efficient flow distribution. HTU of 28 m was estimated and was expected to decrease to 3 m by optimizing thickness of gasket and spacer as well as membrane performance. The MFMC module effectively reduced the loss of tributyl phosphate (TBP) by 91% comparing to liquid–liquid extraction. The research presented herein provides a flat membrane module design for potential future application of membrane extraction in wide applications.

Characteristics of Water Transport of Membrane Electrolyte over Selected Temperature for Proton Exchange Membrane Fuel Cell.

The water contents at both the anode and cathode of PEMFCs depend on the water-transport mechanism at the membrane. The humidity at the outside layers of the membrane determines the diffusion of water through it. The operating temperatures and pressures regulate the humidity conditions in the system. Because these parameters are nonlinear, the water-transport mechanism is analyzed via the difference in the water concentration on each side of the membrane. In this work, an experimental configuration is designed to investigate the diffusion mechanism of water through the membrane. A flat membrane module is tested in an isothermal test chamber to test the influence of temperature on the water-absorption and -transport characteristics of Nafion 117 and Nafion 211 membranes. A parametric study is conducted to test the water-transport mechanism at an operating pressure of 1 bar; temperatures of 30 °C, 50 °C, 70 °C and 90 °C; and a relative humidity ranging from 10% to 100%. The results indicate that the water content of Nafion 211 is higher than that of Nafion 117. The water content and diffusion coefficient are proportional to the operating temperature. In addition, the diffusion coefficient reaches its peak at conditions of 1 bar, 100% humidity, and 90 °C for both membrane types.

Fouling Mitigation via Chaotic Advection in a Flat Membrane Module with a Patterned Surface.

Fouling mitigation using chaotic advection caused by herringbone-shaped grooves in a flat membrane module is numerically investigated. The feed flow is laminar with the Reynolds number () ranging from 50 to 500. In addition, we assume a constant permeate flux on the membrane surface. Typical flow characteristics include two counter-rotating flows and downwelling flows, which are highly influenced by the groove depth at each . Poincaré sections are plotted to represent the dynamical systems of the flows and to analyze mixing. The flow systems become globally chaotic as the groove depth increases above a threshold value. Fouling mitigation via chaotic advection is demonstrated using the dimensionless average concentration () on the membrane and its growth rate. When the flow system is chaotic, the growth rate of drops significantly compared to that predicted from the film theory, demonstrating that chaotic advection is an attractive hydrodynamic technique that mitigates membrane fouling. At each Re, there exists an optimal groove depth minimizing and the growth rate of . Under the optimum groove geometry, foulants near the membrane are transported back to the bulk flow via the downwelling flows, distributed uniformly in the entire channel via chaotic advection.

Experimental investigation of the thermal performance of new flat membrane module designs for membrane distillation

Novel designs of a flat membrane module were realized by creating on the membrane surface specific patterns for the feed flow, with the aim to improve the heat transfer of the process by acting on the fluidodynamic of the hot stream. Their performance was, then, studied in Direct Contact Membrane Distillation (DCMD) tests by sending distilled water at different temperatures and flow rates. The investigated layouts were compared in terms of trans-membrane flux, permeate production, specific energy consumption, pressure drops, and the most effective design was identified.

A novel corrugated wall channel module for external concentration polarization mitigation in forward osmosis process.

Much work has been conducted on the topic of forward osmosis (FO), but only a few studies have focused on mitigating external concentration polarization (ECP). This study introduced a simple structure, the corrugated wall channel, to the design of FO module, to induce vortex, and then mitigate ECP. In this study, the corrugated wall channel module (CWCM) was tested under given conditions, with a traditional flat membrane module (FMM) as control. CWCM could mitigate ECP and then enhance water flux. When deionized water was taken as feed solution (FS) and 2-M NaCl solution as draw solution (DS), the water flux enhancement was 16.49 and 18.51% in FO mode (active layer facing FS) and PRO mode (active layer facing DS), respectively. When 0.5-M NaCl solution was taken as FS, the corresponding values were 15.92 and 17.13%, respectively. Computational fluid dynamics (CFD) analysis showed that the CWCM could induce vortex, promote the mixing of the solution in the module, and further contribute to the increase of water flux. The specific shape of CWCM affected its performance on mitigating ECP. Also, the more tortuous CWCM exhibited higher water flux. In addition, CWCM could lessen membrane fouling.

Numerical simulation of aeration flow phenomena in bench-scale submerged flat membrane bioreactor

The aeration rates in the membrane bioreactor is an important management-point that can reduce the maintenance costs and the membrane fouling by changing the reactor flow patterns and the shear stresses in the vicinity of the membrane surface. In the present study, COMSOL, a finite element analysis (FEA) program was used to analyze the velocity distribution, the shear stresses between the membranes and the baffle, and the shear stresses between the membranes in a system in which two flat membrane modules are installed within a bench-scale submerged flat membrane reactor for aeration at the bottom. The diameters and velocities of the bubbles that develop the velocities within the reactor were measured through image analysis and the results were applied to numerical analysis. The shear stresses between the membrane and the baffle showed relatively high values ranging from 0Pa to 0.1Pa at the 1/3 point from the bottom of the membrane module and showed high shear stresses in some of the top part of the membrane module too. However, the shear stresses between the membranes were formed to be lower than the shear stresses between the membranes and the baffle. This is disadvantageous to the reduction of fouling on the surfaces of the membranes where permeation fluxes exist.

Removing toxic contaminants from groundwater by graphene oxide nanocomposite in a membrane module under response surface optimization

A novel graphene oxide nanocomposite was investigated in a flat membrane module with cross-flow pattern for decontamination of water on optimization of the operating conditions. Response surface optimization methodology was followed in arriving at the best operating conditions. The best module performance in terms of flux and rejection was obtained at the optimum set of operating conditions comprising a pH of 8.0, operating pressure of 14 bars and an hourly cross-flow of 800 L. At the end of a 96-h run, the observed drop in flux was a negligible 3.4%. On rinsing and backwashing at the end of this period, the net drop could be limited to within 2%. The module succeeded in selectively removing 98.5% of arsenic, 96.7% of fluoride, 96–97% of iron and suspended solids from contaminated groundwater while permeating more than 79–81% of the useful calcium and 87–90% of magnesium minerals as desired in potable water. The study shows that if run under properly optimized conditions, a flat membrane module with cross-flow pattern and equipped with the graphene oxide nanocomposite can be a potential technology in producing healthy, tasty and non-toxic drinking water from contaminated groundwater even in the remote areas.

Enhanced treatment performance of coking wastewater and reduced membrane fouling using a novel EMBR

A novel EMBR (electric field applied in MBR) by placing stainless steel mesh cathode inside a flat membrane module and stainless steel mesh anode outside the module was built and operated to enhance the treatment performance of coking wastewater containing phenol, pyridine and quinoline and reduce the membrane fouling. The degradation rates of COD, phenol, pyridine and quinoline in EMBR with electric field (reactor A) were significantly higher than the sum of EMBR without electric field (reactor B) and only electro-catalytic degradation during the long-term treatment, confirming that a coupling effect was existed between biodegradation and electro-catalytic degradation process. Illumina sequencing data revealed that bacterial community was richer and more diverse in reactor A. Comamonas strain JB as the inoculums was the most dominant genus in each reactor and electric field applied in reactor A further improved the abundance of strain JB. The membrane fouling in reactor A was reduced.

Simulation of helium-methane mixture separation on selectively permeable membranes

In the article, the helium-methane mixture separation on the various types of membranes was considered. A flat membrane module was studied. It was made of two channels connected by a semipermeable membrane. It was shown that high membrane selectivity could not always provide a high degree of mixture separation.

Degradation Efficiency of Textile and Wood Processing Industry Wastewater by Photocatalytic Process Using In Situ Ultrafiltration Membrane

The hybrid membrane photocatalytic reactor (MPR) in this study was constructed by submerging a flat polyethersulfone membrane module into a ZnO or TiO2 slurry photocatalytic reactor for raw wastewater treatment. The short and long term MPR performance was investigated for the degradation of textile and wood processing industry wastewater. The different operational parameters such as the catalyst type, catalyst loading, initial wastewater concentration, light type, and semiconductor powder type affecting the performance of the reactor were initially evaluated using a batch system without a membrane module. After the optimization of the operating conditions, the long term studies were performed by the MPR. Nearly 100% color and 30–55% chemical oxygen demand (COD) removal could be reached at a hydraulic retention time of 6 h for both wastewater effluents. Moreover, reverse osmosis experiments were applied on MPR ultrafiltration effluent for further COD removal and up to 88% COD removal efficiency could be obtained. The color and organic matter degradation efficiency showed that the catalyst can be reused effectively in MPR. In this hybrid design, the membrane module served also as a separator which is very advantageous in keeping catalyst powder in suspension during the operation. The results indicated that the effluent water can be used as process water in the industry.

Studies on simulation and experiments of ethanol–water mixture separation by VMD using a PTFE flat membrane module

Model parameters modification and numerical simulation based on the Knudsen–viscous transition model to predict the vacuum membrane distillation (VMD) performance of ethanol–water mixture and experiments were studied in a polytetrafluoroethylene flat-sheet membrane module. A novel approach to determine the model parameters K and B (modified Knudsen diffusion and viscous flow membrane characteristics, respectively) consisted of membrane morphological parameters was especially developed by fitting the water VMD experimental results. Furthermore, linear relations between the modified model parameter K or B and feed temperature were first established, and then successfully employed to predict by simulation the separation performances of 5wt% ethanol–water mixture. The experiments of ethanol–water VMD demonstrated that the fluxes of ethanol and water both increased with temperature or vacuum degree, but the separation factor decreased. The simulation values agree quite well with experimental ones, finding the minimum and maximum discrepancies are 0.5% and 9.6% for flux and separation factor, respectively.

Influence of Geometry Structures on the Transfer and Flow Characteristics of Membrane Modules

AbstractThe effects of different inlet/outlet features and helical structures on the flow pattern and transfer performance of membrane modules were investigated with both three‐dimensional computational fluid dynamics and experimental methods. In a circular flat membrane module, two types of inlet/outlet with single‐port or three‐port configuration were used to evaluate the influence of small differences in the opening area structure of the inlet/outlet on the flow patterns. Although the transfer regions differ, large flow swirls appear in both systems, leading to stagnation regions and causing significant back‐mixing. To alleviate the swirls and improve the flow pattern, a helix clapboard was used to separate the membrane feed channel as spiral channel. Both the numerical and experimental results indicate that the helical structure can greatly enhance the transfer performance and increase the permeation rate while the increment in energy consumption is very small.

Effect of air sparging on flux enhancement during tangential flow filtration of degreasing effluent

The favorable effects of air sparging to reduce deposition on the membrane and consequent fouling during membrane separation are studied, first with a model solute (pectin), followed by degreasing effluent from a tannery. Directly injecting air into the feed stream enhances the permeate flux and the performance of the separation process in a rectangular flat sheet tangential flow membrane module. The effects of various operating parameters, namely, gas velocity, membrane surface orientations with respect to the flow direction, transmembrane pressure, cross-flow velocity, and model solute concentration, are quantified. The concentrations of pectin solutions used herein are chosen such that they behave similar to the degreasing effluent in terms of gel layer-type deposition on the membrane surface. Also, there are significant changes in the permeate quality (80 mg/l) by using air sparging in the flow channel which is below Indian discharge standards (250 mg/l). There are appreciable changes in the permeate quality when air sparging is employed compared to membrane separation without aeration. Image analyzing video microscopy is effectively used to precisely measure variation in deposition thicknesses on surface of the membrane as functions of operating parameters. Once the effectiveness of the method is established, the technique is successfully used, with significant flux enhancement, to treat degreasing effluent from a tannery.

Modeling the performance of flat and capillary membrane modules in vacuum membrane distillation

This paper deals with the modeling of the performance, in terms of energy consumptions and distillate flow rate produced, of flat and capillary membrane modules in vacuum membrane distillation (VMD). The developed model was validated by experimental tests carried out at lab-scale on a lab-made flat module of 40cm2 membrane area, equipped with a commercial polypropylene membrane (pore size, 0.2μm), and on a commercial capillary Microdyn module of 0.1m2 membrane area.Once validated, the mathematical model was used to predict the performance of modules with higher membrane areas (up to 5m2). The flat module resulted to perform better than the capillary one in terms of energy consumption/permeate flow rate ratios, the lowest value being 130kWh/m3distillate for a 5m2 membrane area, at 80°C of feed temperature and 10mbar of vacuum pressure.

Vacuum membrane distillation for purifying waters containing arsenic

In this work, the potentialities of Vacuum Membrane Distillation (VMD) for treating water containing arsenic, both in the trivalent and pentavalent form, were analyzed, with the aim of producing a purified permeate working at low feed temperatures (20°C–40°C). Experimental tests were carried out on a commercial flat membrane module varying the arsenic concentration, the arsenic form (trivalent or pentavalent), the membrane, the operating temperatures and flow-rates. Long-term tests were also performed. The membrane area was of 180cm2 and the vacuum pressure was fixed at 10mbar. In all tests, no arsenic was detected in the permeate and the highest flux ranged between 3 and 12.5kg/hm2 at 20°C and 40°C, respectively.

REMOVED: Modeling the Performance of Flat and Capillary Membrane Modules in Vacuum Membrane Distillation

This article has been removed: please see Elsevier Policy on Article Withdrawal ( http://www.elsevier.com/locate/withdrawalpolicy ). This article has been removed at the request of the Executive Publisher. This article has been removed because it was published without the permission of the author(s).

Minute electric field reduced membrane fouling and improved performance of membrane bioreactor

Effective application of a low voltage and low intensity electric field in EMBR (a membrane bioreactor attached with electric field) may reduce fouling, energy consumption, while enhance treatment efficiency. For that, electrodes and membrane modules were re-arranged in EMBR to maintain constant electrophoresis forces against deposition/adsorption of extra-cellular polymeric substances (EPS) or sludge particles on the membrane. The copper wire cathode inside a flat membrane module and stainless steel mesh anode outside the module were effectively used in fouling reduction in treating simulate municipal wastewater. The applied electric field significantly enhanced the permeate flux of polypropylene (PP) non-woven (0.036V/cm, extended the operating cycle 7days) or polyester membrane (0.073V/cm, 1.2 times), reduced sludge EPS production and membrane fouling, extended the filtration cycle and enhanced sludge activity. The irreversible membrane fouling was effectively reduced.

Amine/glycol liquid membranes for CO 2 recovery form air

Liquid membranes of amine liquids with glycol compounds were used for the separation of CO 2 from atmospheric air. Because the CO 2 concentration in atmospheric air is only 400 ppm, CO 2 separation based on a facilitated transport mechanism by an amine compound has an advantage. The 3-layered construction consists of a thin liquid membrane of uniform thickness. Using a flat membrane module containing the amine/glycol liquid membrane, CO 2 in the air was enriched in the sweep air that passed through the permeate side of the membrane module. The membrane durability, amine concentration and molecular structures of the amine components were investigated in terms of the CO 2 concentration ratio in the sweep air. The present process for CO 2 obtaining from air will be used for the forced culture of vegetables or strawberries in greenhouses.

Membrane contactors for the oxygen and pH control in desalination

The use of membrane contactors for the oxygen removal, as well as the pH control, in a reverse osmosis (RO) desalination plant was studied. Experimental tests were carried out in a lab set-up using a flat membrane module with 40 cm 2 of membrane area, by feeding in a counter-current mode the liquid and a gas stream of CO 2 or N 2. Several operating conditions were varied, such as temperature, streams flow rates and liquid composition. The liquid streams sent to the system were distilled water and synthetic solutions (prepared for simulating the reverse osmosis permeate and brine and the nanofiltration permeate). Four different hydrophobic membranes (PVDF, PVDF-treated, acrylic-based, and PTFE membranes) were characterized in terms of water uptake, CAM and SEM analysis, tested in the membrane contactor and, finally, compared. Based on the experimental results, the application of membrane contactors for the pH adjustment in the pre-treatment line of a desalination plant when coagulation is used, was considered as case study.

A new helical membrane module for increasing permeate flux

The membrane separation process such as MBR (membrane bioreactor) in wastewater treatment would be more competitive and environmental friendly, if membrane fouling was reduced and higher permeate flux was maintained without consuming extra material or extra energy. For this, a new helical membrane module with an inside helical spacer and outside cover membrane was designed which reduced filtration resistance. It increased mass transfer coefficients by 1.46–1.69 times that of flat membrane modules, when aeration level was at 0.2 m 3/h and the liquid cross flow rate was low (∼12 cm/h). Similarly increased were the ratios of pseudo-steady flux to initial flux ( F s /F o) for the helical membranes when the final helical angle was between 45° and 180° during the 1 or 2 h dynamic filtration of 500 mg/L kaolin suspension under constant trans-membrane pressure (2.8 or 3.2 kPa). The increased mass transfer is affected by liquid cross flow. When the cross flow rate was more than doubled (29 cm/h), the 90° helical membrane could maintain a relatively higher flux than the flat membrane at lower aeration intensity (0.1 m 3/h). The increase of aeration levels from 0.1 to 0.14 and to 0.2 m 3/h reduced cake layer deposition and fouling in the 135° helical membranes than in the flat membranes. More obvious decrease of filtration resistance in helical membranes than the flat membrane is attributed to the effectively enhanced turbulent mass transfer by the helical membrane surface distribution in the flow field, and the intensified interfacial turbulence/reduced boundary layer thickness by aeration bubbles and liquid flow. The maximal 48–69% flux increase obtained without extra energy consumption is a real advantage of the helical membranes.