Effect of temperature-dependent microstructure evolution on pore wetting in PTFE membranes under membrane distillation conditions

Saffarini, Rasha B.; Mansoor, Bilal; Thomas, Rinku M.; Arafat, Hassan A.

doi:10.1016/j.memsci.2012.11.049

Cited by 165 publications

(75 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The increase in the average pore size may be due to the further decrease in the membrane thickness from 39 µm to 37 µm, which might be caused by the release of internal stress generated during heat-pressing; the other possible cause could be the supplementary merging of the crystalline phase of the PVDF which was converted from the amorphous phase during annealing [30]. The results were consistent with the study of Saffarini et al, as it was found that an increase in the annealing temperature would lead to an increase in the average pore size of the membranes [35]. Further annealing for another day led to a greater decrease in the range of the pore diameter and a sharp peak appeared, although the average mean pore size was further slightly increased to 1.3 µm (which was same as that of the neat membrane).…”

Section: Improvement Of Membrane Propertiessupporting

confidence: 89%

“…The existence of the α phase PVDF can increase the liquid entry pressure and, hence, the wetting resistance, contributing to better long-term MD performance. Saffarini et al stated that annealing could also affect the microstructure evolution [35], which benefits the long-term MD operation as well. By increasing the crystallinity and releasing the internal stresses caused by the heat-pressing, the thermal stability of the membrane could be improved, preventing the LEP from dropping rapidly owing to distortion at a high feed temperature.…”

Section: Increased Crystallinity and Appearance Of α Phase After Annementioning

confidence: 99%

See 1 more Smart Citation

Improving Nanofiber Membrane Characteristics and Membrane Distillation Performance of Heat-Pressed Membranes via Annealing Post-Treatment

et al. 2017

View full text Add to dashboard Cite

Electrospun membranes are gaining interest for use in membrane distillation (MD) due to their high porosity and interconnected pore structure; however, they are still susceptible to wetting during MD operation because of their relatively low liquid entry pressure (LEP). In this study, post-treatment had been applied to improve the LEP, as well as its permeation and salt rejection efficiency. The post-treatment included two continuous procedures: heat-pressing and annealing. In this study, annealing was applied on the membranes that had been heat-pressed. It was found that annealing improved the MD performance as the average flux reached 35 L/m 2 ·h or LMH (>10% improvement of the ones without annealing) while still maintaining 99.99% salt rejection. Further tests on LEP, contact angle, and pore size distribution explain the improvement due to annealing well. Fourier transform infrared spectroscopy and X-ray diffraction analyses of the membranes showed that there was an increase in the crystallinity of the polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) membrane; also, peaks indicating the α phase of polyvinylidene fluoride (PVDF) became noticeable after annealing, indicating some β and amorphous states of polymer were converted into the α phase. The changes were favorable for membrane distillation as the non-polar α phase of PVDF reduces the dipolar attraction force between the membrane and water molecules, and the increase in crystallinity would result in higher thermal stability. The present results indicate the positive effect of the heat-press followed by an annealing post-treatment on the membrane characteristics and MD performance.

show abstract

Section: Improvement Of Membrane Propertiessupporting

confidence: 89%

Section: Increased Crystallinity and Appearance Of α Phase After Annementioning

confidence: 99%

Improving Nanofiber Membrane Characteristics and Membrane Distillation Performance of Heat-Pressed Membranes via Annealing Post-Treatment

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Although wetting prevention in MD is the main process requirement, it has not been comprehensively studied and relatively few investigations have attempted to solve the wetting problems in MD membranes [12][13][14][15][16][17][18][19][20]. Some authors have investigated the improvement of hydrophobic properties of membranes employing novel materials or applying surface modification through manipulating surface chemistry and surface geometry by nanoparticle coating and surface fluorination [21][22][23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Wetting prevention in membrane distillation through superhydrophobicity and recharging an air layer on the membrane surface

Rezaei

Warsinger

Lienhard

et al. 2017

Journal of Membrane Science

126

View full text Add to dashboard Cite

Although membrane distillation offers distinctive benefits in some certain areas, i.e., RO concentrate treatment, concentrating solutions in the food industry and solar heat utilization, the occurrence of wetting of the hydrophobic membrane hinders its potential industrial applications.Therefore, wetting prevention is a vital criterion for the treatment of solutions with lower surface tension than water. The present work examines the effect of recharging air bubbles on the membrane surface for the wetting incidence when a surfactant (sodium dodecyl sulfate, SDS) exists in a highly concentrated NaCl aqueous solution. This study shows that the presence of the air bubbles on the surface of the superhydrophobic membrane in a direct contact membrane distillation setup inhibited the occurrence of wetting (~100% salt rejection) even for high concentrations of the surface-active species (up to 0.8 mM SDS) in the feed solution while no undesirable influence on the permeate flux was observed. Introducing air into the feed side of the membrane displaces the liquid which partly tends to penetrate the macroporous structure with air bubbles and therefore increases the liquid entry pressure, and in addition, the simultaneous use of a superhydrophobic membrane enhances the solution contact angle.

show abstract

“…Traditionally, stretched membranes (e.g., PTFE) with small curvature radius were assigned B values of 0.5-0.6 or even smaller (0.4-0.46) [12]. According to this model, two membranes, X and Y, with similar CA and r max , but with X having round pores and Y having stretched (i.e., more elliptically shaped) pores, will have different LEP values.…”

Section: Introductionmentioning

confidence: 99%

“…There is also lack of information as to how to evaluate the membrane characteristics in order to apply the models and, in general, how the different pore structures may affect the LEP. There is also the common notion that LEP should be determined experimentally for each particular membrane rather than trusting the predicted values, as several researchers reported wetting to occur at lower pressures than the LEP values predicted by these models [12].…”

Section: Introductionmentioning

confidence: 99%

Membrane structure and surface morphology impact on the wetting of MD membranes

Guillén-Burrieza

Servi

Lalia³

et al. 2015

Journal of Membrane Science

Self Cite

View full text Add to dashboard Cite

Effect of temperature-dependent microstructure evolution on pore wetting in PTFE membranes under membrane distillation conditions

Cited by 165 publications

References 26 publications

Improving Nanofiber Membrane Characteristics and Membrane Distillation Performance of Heat-Pressed Membranes via Annealing Post-Treatment

Improving Nanofiber Membrane Characteristics and Membrane Distillation Performance of Heat-Pressed Membranes via Annealing Post-Treatment

Wetting prevention in membrane distillation through superhydrophobicity and recharging an air layer on the membrane surface

Membrane structure and surface morphology impact on the wetting of MD membranes

Contact Info

Product

Resources

About