Electrically conductive hydrophobic membrane cathode for membrane distillation with super anti-oil-fouling capability: Performance and mechanism

Membrane distillation (MD) purifies water by transporting its vapor through a hydrophobic membrane. An ideal MD membrane poses high water flux and high fouling, scaling, and wetting resistances. In this study, we develop polyvinylidene fluoride (PVDF) membranes for MD by focusing on reduction of PVDF degree of crystallinity. We explore the roles of dope solution temperature in dictating the phase separation mechanisms as well as the structure and the performance of semicrystalline PVDF membranes. DSC spectra show that higher dope solution temperature depresses crystallinity via formation of imperfect crystal. Such findings were also supported by FTIR and XRD results. The SEM images reveal formation of spherulite-like morphology in the membrane matrices for membranes prepared from high temperature dope solutions. A good balance between solid-liquid and liquid-liquid phase separations that offers low degree of crystallinity was found at a dope solution temperature of 60°C (PVDF-60), which showed the MD flux of 18 l/m2 h (vs. 6 l/m2 h for temperature of 25°C, as a benchmark) and nearly complete salt rejection when run at hot and cold temperatures of 65°C and 25°C, respectively. The PVDF-60 shows a high wetting resistance and stable MD flux of 10.5 l/m2 h over a 50 h test for treating brine solution as the feed (70 g NaCl/l).

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Morphological Study of Fabricated PVDF Based Hydrophobic Membrane for Different Additives and Coagulation Bath Temperature

Asian Journal of Water Environment and Pollution ◽

10.3233/ajw210027 ◽

2021 ◽

Vol 18 (3) ◽

pp. 39-47

Author(s):

Meenakshi Yadav ◽

Sushant Upadhyaya ◽

Kailash Singh ◽

Manish Vashishtha

Keyword(s):

Contact Angle ◽

Water Content ◽

Temperature Difference ◽

Synergistic Effects ◽

Weight Percent ◽

Membrane Distillation ◽

Coagulation Bath ◽

Hydrophobic Membrane ◽

Sem Micrograph ◽

Dope Solution

The demand of membrane distillation (MD) has increased since last few decades for numerous applications. The membrane used in MD is hydrophobic; therefore, the focus has been emphasised on the development of a suitable membrane with desired microstructure. In this study, the flat sheet hydrophobic membrane of suitable properties has been casted with various additives such as water, ethane-di-ol, and propan-2-ol in dope solution using a non-solvent induced phase separation (NIPS) technique. The effect of water content in dope solution has been studied on casted membrane porosity and contact angle. The maximum contact angle and porosity were found to be 96° and 53.23% at 4 weight percent of water content in dope solution of PVDF polymer and di.methyl.acetamide as solvent. It was found that SEM micrograph when ethane-di-ol and propan-2-ol are used as an additive shows more finger-like pores and nodules, respectively, in the microstructure of the casted membrane. Furthermore, synergistic effects using water with other additives were also identified using SEM micrograph of casted membrane and it was observed that water with ethane-di-ol and propan-2-ol form contact angle of 98° and 105°, respectively, for 2 weight percent each additive in dope. In this study, the membrane was also cast by dissolving PVDF powder in di.methyl.acetamide solvent with lithium chloride and the effect of the temperature difference between coagulation bath and film temperature was investigated using an SEM micrograph. Overall, it was found that water content and temperature difference aid in developing hydrophobic porous membrane of desired properties for MD applications.

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Refinery processed water treatment via the low energy Direct Contact Membrane Distillation (DCMD)

Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles ◽

10.2516/ogst/2018077 ◽

2019 ◽

Vol 74 ◽

pp. 3 ◽

Cited By ~ 2

Author(s):

Khadije El Kadi ◽

Isam Janajreh ◽

Raed Hashaikeh ◽

Rizwan Ahmed

Keyword(s):

Water Treatment ◽

Pore Size ◽

Mass Flux ◽

Thermal Efficiency ◽

Membrane Distillation ◽

Low Energy ◽

Water Separation ◽

Oil Water Separation ◽

Oil Water ◽

Oil Fouling

The amount of refinery water discharged to the environment from oil industry has increased vigorously in current times. Recent research has been focusing on the use of membrane technology for the refinery processed water treatment. Membrane Distillation (MD) is an emerging technology that has been highly marked by its low-energy requirement and high desalination efficiency. However, conventional MD membranes (i.e. PVDF) are not feasible for oil-water separation processes. That is due to the oleo-philic property of the membrane and thus, causes membrane fouling and halts the production of mass flux. An anti-oil-fouling membrane is essential for a successful oil-water separation by MD. Underwater-oleophobic as well as omniphobic are two different approaches in fabricating such membranes. The former approach is based on the asymmetric surface wettability, whereas the latter is attributed to the surface structure that is characterized by having a very large contact angle for all liquids. However, such composite membranes are characterized by their lower porosity, smaller pore size, but with unique surface slippage, in comparable with the conventional PVDF membranes. As such, in this work, high fidelity numerical simulation of DCMD is performed using non-isothermal Computational Fluid Dynamics (CFD) validated model in order to assess the role of the anti-oil-fouling membrane properties on the performance of the DCMD. Results are presented in terms of temperature polarization coefficient, mass flux, latent heat flux, and thermal efficiency. Results show the compromising effect of membrane porosity to 45% reduces the mass flux and thermal efficiency respectively by 68% and 40%, and reduction of pore size to the half (i.e. 50 nm) can cause a reduction by 50.6% in mass flux and 24.18% in thermal efficiency compared to the baseline (i.e. 100 nm). On the other hand, the omniphobic slippage effect leads to a noticeable gain of 16% in DCMD mass flux with slight gain in thermal efficiency. This can maximize mass flux and thermal efficiency to be as much as 50.3 kg/m2 h and 69%, respectively.

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Electrically conductive membranes for in situ fouling detection in membrane distillation using impedance spectroscopy

Journal of Membrane Science ◽

10.1016/j.memsci.2018.03.069 ◽

2018 ◽

Vol 556 ◽

pp. 66-72 ◽

Cited By ~ 4

Author(s):

Farah Ejaz Ahmed ◽

Nidal Hilal ◽

Raed Hashaikeh

Keyword(s):

Impedance Spectroscopy ◽

Membrane Distillation ◽

Electrically Conductive ◽

Conductive Membranes

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Analysis and optimization of a new cylindrical air gap membrane distillation system

Water Science & Technology Water Supply ◽

10.2166/ws.2019.164 ◽

2019 ◽

Vol 20 (1) ◽

pp. 361-371 ◽

Cited By ~ 3

Author(s):

Vandita T. Shahu ◽

S. B. Thombre

Keyword(s):

Flow Rate ◽

Membrane Separation ◽

Negative Impact ◽

Membrane Distillation ◽

Air Gap ◽

Cylindrical Shape ◽

Hydrophobic Membrane ◽

Tube Heat Exchanger ◽

Whole Process ◽

Air Gap Membrane Distillation

Abstract Membrane distillation is a rate-governed non-isothermal membrane separation technique that utilizes trans-membrane temperature difference for evaporating water and thereby separating it from brackish feed for reproducing fresh water. A novel design of a cylindrical air gap membrane distillation module is presented. The module is fabricated in a way similar to a shell and tube heat exchanger. A PTFE hydrophobic membrane is used and is formed in a cylindrical shape. Design of experiments (DOE) is used to design the experiments statistically and to identify the significant operating parameters. Experiments were performed according to the Taguchi design approach using an L16 orthogonal array. Optimization of the whole process is performed by response surface methodology. It is shown that the feed temperature and feed flow rate have a positive effect, whereas the salinity has a negative impact on flux. The maximum value of flux achieved with this system is 3.6 kg/m2 hr. A high value of flux of 2.6 kg/m2 hr was achieved under optimum conditions at a temperature of 45 °C and a flow rate of 1.5 lpm with a salinity of 5 g/litre.

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Biomimetic hydrophobic membrane: A review of anti-wetting properties as a potential factor in membrane development for membrane distillation (MD)

Journal of Industrial and Engineering Chemistry ◽

10.1016/j.jiec.2020.08.005 ◽

2020 ◽

Vol 91 ◽

pp. 15-36 ◽

Cited By ~ 1

Author(s):

Wan Aisyah Fadilah Wae AbdulKadir ◽

Abdul Latif Ahmad ◽

Ooi Boon Seng ◽

Nuur Fahanis Che Lah

Keyword(s):

Membrane Distillation ◽

Hydrophobic Membrane ◽

Wetting Properties ◽

Potential Factor ◽

Membrane Development

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Development of Nano-Carbon Bucky-Paper Membranes for Membrane Distillation

Materials Science Forum ◽

10.4028/www.scientific.net/msf.724.408 ◽

2012 ◽

Vol 724 ◽

pp. 408-411 ◽

Cited By ~ 3

Author(s):

Jae Wuk Koo ◽

Ji Hee Han ◽

Sang Ho Lee ◽

Jin Sik Sohn ◽

June Seok Choi

Keyword(s):

Polyvinylidene Fluoride ◽

Membrane Distillation ◽

Practical Implementation ◽

Vapor Permeability ◽

Feed Water ◽

Hydrophobic Membrane ◽

Salt Rejection ◽

Multi Stage ◽

And Performance ◽

Bucky Paper

Membrane distillation (MD) is a special evaporation process to produce fresh water from seawater or contaminated water using membranes. MD has advantages over other evaporation technologies such as multi-stage flash vaporization (MSF) and multi-effect distillation (MED) due to its relatively low energy requirements, allowing the use of solar energy as its heat source. Nevertheless, lack of membrane materials for MD process hinders its practical implementation for desalination and water treatment. In this study, membranes made of carbon nanotube (CNT) are presented for MD. Flat sheet hydrophobic membranes made of polyvinylidene fluoride (PVDF) were selected as supports for bucky-paper membranes, allowing formation of CNT bucky-paper without chemical reactions. Laboratory-scale systems were used to evaluate their potential and performance in direct contact MD. Water permeability and salt rejection were analyzed for each case. D.I water and synthetic feed water were used for the lab-scale tests. It was demonstrated that the physical immobilization of CNT on a hydrophobic membrane changed led to an increase in vapor permeability while improving salt rejection.

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Performances of air gap and water gap MD desalination modules

Water Practice & Technology ◽

10.2166/wpt.2018.034 ◽

2018 ◽

Vol 13 (1) ◽

pp. 200-209 ◽

Cited By ~ 1

Author(s):

Atia E. Khalifa

Keyword(s):

Specific Energy Consumption ◽

Membrane Distillation ◽

Air Gap ◽

Dominant Factor ◽

Feed Water ◽

Permeate Flux ◽

Hydrophobic Membrane ◽

Air Gap Membrane Distillation ◽

Gap Width ◽

Feed Temperature

Abstract Membrane distillation (MD) is a promising thermally-driven membrane separation technology for water desalination. In MD, water vapor is being separated from the hot feed water solution using a micro-porous hydrophobic membrane, due to the difference in vapor pressures across the membrane. In the present work, experiments are conducted to compare the performance of water gap membrane distillation (WGMD) and air gap membrane distillation (AGMD) modules under the main operating and design conditions including the feed and coolant temperatures, membrane material and pore sizes, and the gap width. Results showed that the WGMD module produced higher fluxes as compared to the AGMD module, for all test conditions. The feed temperature is the dominant factor affecting the system flux. The permeate flux increases with reducing the gap width for both water and air gap modules. However, WGMD module was found to be less sensitive to the change in the gap width compared to the AGMD module. The PTFE membrane produced higher permeate flux as compared to the PVDF membrane. Bigger mean pore diameter enhanced the permeate flux, however, this enhancement is marginal at high feed temperatures. With increasing the feed temperature, the GOR values increase and the specific energy consumption decreases.

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