scholarly journals Effect of on the Membrane Distillation of PVDF Membrane Material Enhanced by Gas-Liquid Two-Phase Flow

2018 ◽  
Vol 2 (1) ◽  
Keyword(s):  
Membrane Surface ◽  
Threshold Level ◽  
Membrane Distillation ◽  
Permeate Flux ◽  
High Concentration ◽  
Two Phase ◽  
Flux Enhancement ◽  
Membrane Performance ◽  
Flux Decline ◽  
Sweeping Gas

This study investigates the membrane performance and fouling control in the bubble-assisted sweeping gas membrane distillation with high concentration saline (333 K saturated solution) as feed. The results show that longer bubbling interval (3 min) at a fixed bubbling duration of 30s can most efficiently increase the the flux enhancement ratio up to 1.518. Next, the flux increases with the gas flowrate under a relatively lower level, but tends to a plateau after the threshold level (1.2 L•min-1). Compared to non-bubbling case, the permeate flux reaches up to 1.623 fold at a higher bubble relative humidity of 80 %. It was also found that greater flux enhancement can be achieved and meanwhile dramatic flux decline can be delayed for an intermittent bubbling system with a smaller nozzle size. These results accord well with the observations of fouling deposition in situ on the membrane surface with SEM.

scholarly journals Effect of bubble characteristics and nozzle size on the membrane distillation enhanced by gas–liquid two-phase flow

2019 ◽  
Vol 9 (3) ◽  
pp. 292-300
Author(s):  
Dashuai Zhang ◽  
Xiaopeng Zhang ◽  
Li Chen ◽  
Wang Lili ◽  
Wu Di ◽  
...  
Keyword(s):  
Gas Flow ◽  
Membrane Surface ◽  
Threshold Level ◽  
Membrane Distillation ◽  
Permeate Flux ◽  
High Concentration ◽  
Two Phase ◽  
Flux Enhancement ◽  
Nozzle Size ◽  
Sweeping Gas

Abstract This study investigates the membrane performance and fouling control in bubble-assisted sweeping gas membrane distillation with high concentration saline (333 K saturated solution) as feed. The results show that a longer bubbling interval (3 min) at a fixed bubbling duration of 30 s can most efficiently increase the flux enhancement ratio up to 1.518. Next, the flux increases with the gas flow rate under a relatively lower level, but tends to plateau after the threshold level (1.2 L·min−1). Compared to the non-bubbling case, the permeate flux reaches up to 1.623-fold at a higher bubble relative humidity of 80%. It was also found that greater flux enhancement can be achieved and, meanwhile, dramatic flux decline can be delayed for an intermittent bubbling system with a smaller nozzle size. These results accord well with the observations of fouling deposition in situ on the membrane surface with scanning electron microscope (SEM).

scholarly journals Concentration of FeSO4 spent solutions by membrane distillation

2007 ◽  
Vol 9 (2) ◽  
pp. 15-18 ◽  
Author(s):  
Marek Gryta
Keyword(s):  
Potential Application ◽  
Ph Value ◽  
Membrane Surface ◽  
Membrane Distillation ◽  
Permeate Flux ◽  
Salt Solutions ◽  
Iron Compounds ◽  
Fast Decline ◽  
Waste Salt

Concentration of FeSO4 spent solutions by membrane distillation The possibility of potential application of membrane distillation for the concentration of waste salt solutions has been presented in this work. It was found that the oxidation of iron compounds takes place during the process that was associated with the formation of a layer of oxides on the membrane surface. A fast decline of the permeate flux was observed due to the scaling phenomena. The problem of scaling was eliminated by the acidification with H2SO4 of the feed to the pH value of 2.

Electroflocculation as potential pretreatment in colloid ultrafiltration

2006 ◽  
Vol 6 (1) ◽  
pp. 69-78 ◽  
Author(s):  
T. Harif ◽  
M. Hai ◽  
A. Adin
Keyword(s):  
Membrane Fouling ◽  
Colloidal Suspension ◽  
Membrane Surface ◽  
Constant Current ◽  
Permeate Flux ◽  
Batch Mode ◽  
Membrane Behavior ◽  
Flux Decline ◽  
Stainless Steel Cathode ◽  
Marginal Improvement

Electroflocculation (EF) is a coagulation/flocculation process in which active coagulant species are generated in situ by electrolytic oxidation of an appropriate anode material. The effect of colloidal suspension pretreatment by EF on membrane fouling was measured by flux decline at constant pressure. An EF cell was operated in batch mode and comprised two flat sheet electrodes, an aluminium anode and stainless steel cathode, which were immersed in the treated suspension, and connected to an external DC power supply. The cell was run at constant current between 0.06–0.2A. The results show that pre-EF enhances the permeate flux at pH 5 and 6.5, but only marginal improvement is observed at pH 8. At all pH values cake formation on the membrane surface was observed. The differences in membrane behavior can be explained by conventional coagulation theory and transitions between aluminium mononuclear species which affect particle characteristics and consequently cake properties. At pH 6.5, where sweep floc mechanism dominates due to increased precipitation of aluminium hydroxide, increased flux rates were observed. It is evident that EF can serve as an efficient pretreatment to ultrafiltration of colloid particles.

The new concept of flux enhancement during cell separation with MF/UF processes

2001 ◽  
Vol 1 (5-6) ◽  
pp. 381-386
Author(s):  
A. Kołtuniewicz
Keyword(s):  
Cell Separation ◽  
High Efficiency ◽  
Membrane Surface ◽  
Cross Flow ◽  
Dry Mass ◽  
High Energy ◽  
Process Conditions ◽  
Permeate Flux ◽  
Flux Enhancement ◽  
Flow Systems

The microfiltration and ultrafiltration processes are considered as matured membrane processes that are well established in industrial practice. Nevertheless, the main obstacles of their further development in the new competitive implementations are the economical problems. The key economic factors are permeate flux and energy consumption. However, although the cross-flow systems enable us to attain higher flux, it is usually very expensive. The high energy is consumed to maintain circulation velocity of the retentate that is sufficient for sweeping out the retained component from the membrane surface. Moreover in the case of cells separation the high intensity of the fouling and low cake permeability makes it necessary to apply additional efforts, such as backflushing, backpulsing, promoters of turbulence, vibrations, ultrasounds and many other. Therefore, dead-end systems are still quite competitive with cross-flow, especially for diluted (less than 0.5% of dry mass) suspensions or solutions. Cell separation with membranes is one of the most vivid problems for modern biotechnology, wastewater and water treatment. Membranes offer mild process conditions and high selectivity of separation. This enables us to solve a variety of problems such as cell culturing, fractionation, concentration, purification and sterilisation. The selected cells may be precisely separated from other components of broth and subsequently directed into the reaction space again in good conditions to ensure a quasi-continuous mode of operation. Moreover, membranes enable us to attain high efficiency of the bioconversion by removal of all product and inhibitors directly from the bioreactor. This is the reason for the huge interest in cell separation with membranes. The idea of the paper was to present the new concept of flux enhancement for cell separation on membranes. This concept lies in taking advantage of the specific rheological nature of biopolymers, which are the main foulants. The biopolymers retained on the membrane surface (i.e. on the top layer) can be applied as a lubricant for the cells that can settle on such a ‘movable layer’. As is shown, further in the paper, the thickness of the moving layer is lower and the flux is greater. The common movement of the cells and gel layer is very convenient from the cells integrity point of view. However the hydrodynamic conditions always play an important role in cross-flow systems; the resistance of ultrafiltration membranes may be reduced much more when compared with more open microfiltration membranes.

Influence of humic acid on the long-term performance of direct contact membrane distillation

2018 ◽  
Vol 30 (1) ◽  
pp. 109-120 ◽  
Author(s):  
Dong-Wan Cho ◽  
Gihoon Kwon ◽  
Jeongmin Han ◽  
Hocheol Song
Keyword(s):  
Humic Acid ◽  
Membrane Fouling ◽  
Coalbed Methane ◽  
Direct Contact ◽  
Membrane Surface ◽  
Membrane Distillation ◽  
Permeate Flux ◽  
Direct Contact Membrane Distillation ◽  
High Level

In this study, the influence of humic acid on the treatment of coalbed methane water by direct contact membrane distillation was examined with bench-scale test unit. During short-term distillation (1000 min), high level of humic acid above 50 ppm resulted in significant decrease in permeate flux, while low level of humic acid (∼2 ppm) had little influence on the flux. For the long-term distillation (5000 min), the flux decline began at 3400 min in the presence of 5 ppm humic acid and 5 mM Ca2+, and decreased to ∼40% of initial flux at 5000 min. The spectroscopic analysis of the membrane used revealed that the surface was covered by hydrophilic layers mainly composed of calcite. The membrane fouling effect of humic acid became more significant in the presence of Ca2+ due to more facile calcite formation on the membrane surface. It was demonstrated that humic acid enhanced CaCO3 deposition on the membrane surfaces, thereby expediting the scaling phenomenon.

Experimental Study and Numerical Simulation of the Air Gap Membrane Distillation (AGMD) Process

2016 ◽  
Vol 11 (1) ◽  
pp. 41-45 ◽  
Author(s):  
Ehsan Karbasi ◽  
Javad Karimi-Sabet ◽  
J. Mohammadi Roshandeh ◽  
M. A. Moosavian ◽  
H. Ahadi
Keyword(s):  
Numerical Simulation ◽  
Membrane Surface ◽  
Membrane Distillation ◽  
Air Gap ◽  
Operating Conditions ◽  
Permeate Flux ◽  
Air Gap Membrane Distillation ◽  
Temperature Polarization ◽  
Output Ratio ◽  
Cfd Method

Abstract Some challenges, including inappropriate distribution of currents on the membrane surface, poor hydrodynamics and existing severe temperature polarization (TP) phenomenon in MD modules, impede industrialization of MD process. Computational fluid dynamics (CFD) method was used for numerical simulation of hydrodynamics in air gap membrane distillation modules. One of two simulated modules in this work is a novel developed one in which heat and mass transfer data was compared with available literature data. Moreover, the effect of using baffles in module was investigated. Comparison between the novel module and conventional module indicates higher trans-membrane mass flux and gained output ratio (GOR) coefficient by 7% and 15%, respectively. Moreover, the effects of different operating conditions including feed temperatures and feed flow rates on permeate flux were investigated.

Chemical pretreatment of feed water for membrane distillation

2008 ◽  
Vol 62 (1) ◽  
Author(s):  
Marek Gryta
Keyword(s):  
Membrane Fouling ◽  
Membrane Surface ◽  
Membrane Distillation ◽  
Feed Water ◽  
Chemical Pretreatment ◽  
Permeate Flux ◽  
Membrane Scaling ◽  
Water Pretreatment ◽  
Energy Dispersion Spectrometry ◽  
Process Operation

AbstractMembrane distillation was used to produce demineralized water from ground water. The influence of feed water pretreatment carried out in a contact clarifier (softening with Ca(OH)2 and coagulation with FeSO4 · 7H2O) followed by filtration, on the process effectiveness was evaluated. It was found that the chemical pretreatment decreased the membrane fouling; however, the degree of water purification was insufficient because precipitation of small amounts of deposit on the membrane surface during the process operation was still observed. The permeate flux was gradually decreasing as a result of scaling. The morphology and composition of the fouling layer were studied using scanning electron microscopy coupled with energy dispersion spectrometry. The presence of significant amounts of silica, apart from calcium and magnesium, was determined in the formed deposit. The removal of foulants by heterogeneous crystallization performed inside the filter (70 mesh), assembled directly at the module inlet, was found to be a solution preventing the membrane scaling.

scholarly journals Modification of porous polyetherimide hollow fiber membrane by dip-coating of Zonyl® BA for membrane distillation of dyeing wastewater

2021 ◽  
Author(s):  
S. A. Mousavi ◽  
Z. Arab Aboosadi ◽  
A. Mansourizadeh ◽  
B. Honarvar
Keyword(s):  
Pore Size ◽  
Hollow Fiber ◽  
Hollow Fiber Membrane ◽  
Membrane Surface ◽  
Pure Water ◽  
Dip Coating ◽  
Membrane Distillation ◽  
Permeate Flux ◽  
Fiber Membrane ◽  
Air Gap Membrane Distillation

Abstract Wetting and fouling have significantly affected the application of membrane distillation (MD). In this work, a dip-coating method was used for improving surface hydrophobicity of the polyetherimide (PEI) hollow fiber membrane. An air gap membrane distillation (AGMD) process was applied for treatment of the methylene blue (MB) solution. The porous PEI membrane was fabricated by a dry-wet spinning process and the hydrophobic 2-(Perfluoroalkyl) ethanol (Zonyl® BA) was used as the coating material. From FESEM, the modified PEI-Zonyl membrane showed an open structure with large finger-like cavities. The modified membrane displayed a narrow pore size distribution with mean pore size of 0.028 μm. The outer surface contact angle of the PEI-Zonly membrane increased from 81.3° to 100.4° due to the formation of an ultra-thin coated layer. The pure water flux of the PEI-Zonyl membrane was slightly reduced compared to the pristine PEI membrane. The permeate flux of 6.5 kg/m2 h and MB rejection of 98% was found for the PEI-Zonyl membrane during 76 h of the AGMD operation. Adsorption of MB on the membrane surface was confirmed based on the Langmuir isotherm evaluation, AFM and FESM analysis. The modified PEI-Zonyl membrane can be a favorable alternative for AGMD of dyeing wastewaters.

Channel Length Influence on the Performance of the Vacuum Membrane Distillation

2020 ◽  
Author(s):  
Abdulaziz M. Alasiri ◽  
Umar Alqsair ◽  
Sertac Cosman ◽  
Robert Krysko ◽  
Alparslan Oztekin
Keyword(s):  
Membrane Surface ◽  
Membrane Distillation ◽  
Channel Length ◽  
Water Vapor Transport ◽  
Membrane Thickness ◽  
Local Concentration ◽  
Permeate Flux ◽  
Hydrophobic Membrane ◽  
Vapor Flux ◽  
Temperature Polarization

Abstract The demand for freshwater has been increased globally. Membrane distillation (MD) technique can be an attractive option for desalination applications. MD is defined as a thermal-driven separation process that implements a hydrophobic membrane for allowing only water vapor transport through the membrane. VMD system is investigated in this study to examine its sensitivity toward the channel design. PTFE membrane is employed and treated as a functional surface where its main properties, such as porosity, tortuosity, pore diameter, and membrane thickness are defined. Different flow rates and inlet temperatures of the feed solution are involved to intensely study the effect of the channel length on VMD performance. The local concentration and temperature polarization coefficient and mass flux along the membrane surface are presented and discussed. With the increasing length of the module, concentration and temperature polarization levels are increased, and the vapor flux is decreased. It is shown that the permeate flux decreases linearly with the channel length. The slope of the permeate flux with length can be used to estimate the flux performance of modules with varying length.

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