scholarly journals The Formation of Polyvinylidene Fluoride Membranes with Tailored Properties via Vapour/Non-Solvent Induced Phase Separation

Membranes ◽  
2018 ◽  
Vol 8 (3) ◽  
pp. 71 ◽  
Author(s):  
Tiziana Marino ◽  
Francesca Russo ◽  
Alberto Figoli
Keyword(s):  
Phase Separation ◽  
Polyvinylidene Fluoride ◽  
Pore Diameter ◽  
Membrane Properties ◽  
Triethyl Phosphate ◽  
Time Intervals ◽  
Membrane Morphology ◽  
Dope Solution ◽  
Bicontinuous Structure ◽  
Preparation Techniques

The present investigation reports as it is possible to prepared polyvinylidene fluoride (PVDF) membranes for microfiltration (MF) and ultrafiltration (UF) applications, by using triethyl phosphate (TEP) as non–toxic solvent in accordance with the Green Chemistry. Casting solutions containing different concentrations of polyethylene glycol (PEG) were prepared in order to study its effect on the final membrane morphology and properties. The possibility to finely modulate membrane properties was also investigated by applying two different membrane preparation techniques, the Non-Solvent Induced Phase Separation (NIPS) and its coupling with Vapour Induced Phase Separation (VIPS). Membranes’ morphology was detected by Scanning Electron Microscopy (SEM). Thickness, porosity, contact angle, pore size and water permeability were also recorded. Both the PEG content in the dope solution and the selected time intervals during which the nascent films were exposed to established relative humidity and temperature were found to play a crucial role in membrane formation. In particular, it was demonstrated as, by varying PEG content between 10 and 20 wt %, and by setting the exposure time to humidity at 0/2.5/5/7.5 min, membranes with different pore diameter and bicontinuous structure, suitable for UF and MF applications, could be easily obtained.

scholarly journals Preparation and Characterization of TiO2-PVDF/PMMA Blend Membranes Using an Alternative Non-Toxic Solvent for UF/MF and Photocatalytic Application

Molecules ◽  
2019 ◽  
Vol 24 (4) ◽  
pp. 724 ◽  
Author(s):  
Ouassila Benhabiles ◽  
Francesco Galiano ◽  
Tiziana Marino ◽  
Hacene Mahmoudi ◽  
Hakim Lounici ◽  
...  
Keyword(s):  
Phase Separation ◽  
Vinylidene Fluoride ◽  
Membrane Surface ◽  
Polymer Concentration ◽  
Inversion Method ◽  
Membrane Morphology ◽  
Photocatalytic Application ◽  
Poly Vinylidene Fluoride ◽  
Dope Solution ◽  
Phase Inversion Method

The approach of the present work is based on the use of poly (methylmethacrylate) (PMMA) polymer, which is compatible with PVDF and TiO2 nanoparticles in casting solutions, for the preparation of nano-composites membranes using a safer and more compatible solvent. TiO2 embedded poly (vinylidene fluoride) (PVDF)/PMMA photocatalytic membranes were prepared by phase inversion method. A non-solvent induced phase separation (NIPS) coupled with vapor induced phase separation (VIPS) was used to fabricate flat-sheet membranes using a dope solution consisting of PMMA, PVDF, TiO2, and triethyl phosphate (TEP) as an alternative non-toxic solvent. Membrane morphology was examined by scanning electron microscopy (SEM). Backscatter electron detector (BSD) mapping was used to monitor the inter-dispersion of TiO2 in the membrane surface and matrix. The effects of polymer concentration, evaporation time, additives and catalyst amount on the membrane morphology and properties were investigated. Tests on photocatalytic degradation of methylene blue (MB) were also carried out using the membranes entrapped with different concentrations of TiO2. The results of this study showed that nearly 99% MB removal can be easily achieved by photocatalysis using TiO2 immobilized on the membrane matrix. Moreover, it was observed that the quantity of TiO2 plays a significant role in the dye removal.

scholarly journals Influence of Preparation Temperature on the Properties and Performance of Composite PVDF-TiO2 Membranes

Membranes ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 876
Author(s):  
Duc-Trung Tran ◽  
Jean-Pierre Méricq ◽  
Julie Mendret ◽  
Stephan Brosillon ◽  
Catherine Faur
Keyword(s):  
Phase Separation ◽  
Membrane Properties ◽  
High Porosity ◽  
Permeate Flux ◽  
Preparation Temperature ◽  
Membrane Formation ◽  
Compression Behavior ◽  
Membrane Morphology ◽  
Ternary Phase Diagrams ◽  
And Performance

Composite PVDF-TiO2 membranes are studied extensively in literature as effective anti-fouling membranes with photocatalytic properties. Yet, a full understanding of how preparation parameters affect the final membrane structure, properties and performance has not been realized. In this study, PVDF-TiO2 membranes (20 wt% TiO2/PVDF) were fabricated via the non-solvent-induced phase separation (NIPS) method with an emphasis on the preparation temperature. Then, a systematic approach was employed to study the evolution of the membrane formation process and membrane properties when the preparation temperature changed, as well as to establish a link between them. Typical asymmetric membranes with a high porosity were obtained, along with a vast improvement in the permeate flux compared to the neat PVDF membranes, but a reduction in mechanical strength was also observed. Interestingly, upon the increase in preparation temperature, a significant transition in membrane morphology was observed, notably the gradual diminution of the finger-like macrovoids. Other membrane properties such as permeability, porosity, thermal and mechanical properties, and compression behavior were also influenced accordingly. Together, the establishment of the ternary phase diagrams, the study of solvent–nonsolvent exchange rate, and the direct microscopic observation of membrane formation during phase separation, helped explain such evolution in membrane properties.

scholarly journals A Single Step Preparation of Photothermally Active Polyvinylidene Fluoride Membranes Using Triethyl Phosphate as a Green Solvent for Distillation Applications

Membranes ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 896
Author(s):  
Marcello Pagliero ◽  
Antonio Comite ◽  
Camilla Costa ◽  
Ilaria Rizzardi ◽  
Omar Soda
Keyword(s):  
Phase Separation ◽  
Polyvinylidene Fluoride ◽  
Water Shortage ◽  
Membrane Distillation ◽  
Single Step ◽  
Green Solvent ◽  
Triethyl Phosphate ◽  
Nacl Solution ◽  
Preparation Conditions ◽  
Vacuum Membrane Distillation

Membrane distillation is a growing technology that can address the growing problem of water shortage. The implementation of renewable energy and a reduction in the environmental impact of membrane production could improve the sustainability of this process. With this perspective, porous hydrophobic polyvinylidene fluoride (PVDF) membranes were prepared using triethyl phosphate (TEP) as a green solvent, using the non-solvent induced phase separation technique. Different amounts of carbon black were added to dope solutions to improve the photothermal properties of the membranes and to enable direct heating by solar energy. By optimizing the preparation conditions, membranes with porosity values as high as 87% were manufactured. Vacuum membrane distillation tests carried out using a concentrated NaCl solution at 50 °C showed distillate fluxes of up to 36 L/m2 h and a complete salt rejection. Some preliminary studies on the photothermal performance were also conducted and highlighted the possibility of using such membranes in a direct solar membrane distillation configuration.

scholarly journals Exploiting the Interplay between Liquid-Liquid Demixing and Crystallization of the PVDF Membrane for Membrane Distillation

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
N. I. M. Nawi ◽  
M. R. Bilad ◽  
N. A. H. M. Nordin ◽  
M. O. Mavukkandy ◽  
Z. A. Putra ◽  
...  
Keyword(s):  
Polyvinylidene Fluoride ◽  
Water Flux ◽  
High Water ◽  
Membrane Distillation ◽  
Degree Of Crystallinity ◽  
Solution Temperature ◽  
Hydrophobic Membrane ◽  
Sem Images ◽  
Cold Temperatures ◽  
Dope Solution

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).

Solidification characteristics of polymer solution during polyvinylidene fluoride membrane preparation by nonsolvent-induced phase separation

2013 ◽  
Vol 438 ◽  
pp. 77-82 ◽  
Author(s):  
Toru Ishigami ◽  
Keisuke Nakatsuka ◽  
Yoshikage Ohmukai ◽  
Eiji Kamio ◽  
Tatsuo Maruyama ◽  
...  
Keyword(s):  
Phase Separation ◽  
Polymer Solution ◽  
Polyvinylidene Fluoride ◽  
Membrane Preparation
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