Effect of heat-press conditions on electrospun membranes for desalination by direct contact membrane distillation

Lee, Tae-Min; Woo, Yun Chul; Tijing, Leonard D.; Shim, Wang Geun; Choi, June-Seok; Kim, Seung‐Hyun; Shon, Ho Kyong

doi:10.1016/j.desal.2015.09.025

Cited by 98 publications

(59 citation statements)

References 31 publications

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“…Consistent with the previous study [24], Figure 6 shows that the LEP of the neat membrane was the lowest, contributing to the rapid wetting in DCMD. After the membrane was heat-pressed, the LEP increased dramatically from 73 kPa to 91 kPa owing to the vastly decreased average pore diameter and increased crystallinity, although the contact angle decreased from 153 • to 142 • owing to the reduced roughness [24]. Annealing the HP membranes does not result in a significant change of the LEP as the effect of the increased pore sizes is offset by the increase in the hydrophobicity of the membranes, indicated by the increased contact angle.…”

Section: Lep and Contact Anglesupporting

confidence: 79%

“…The as-spun membrane has an average pore diameter of 1.3 µm and a much wider range (from 0.8 µm to 2.2 µm) than the other samples. The heat-pressed membrane (HP) has the smallest average pore size (1.1 µm) and a much smaller range of the pore diameter compared with the neat membranes because the fibers were deformed and widened under high pressure at 150 • C [24]. Annealing the HP membranes for one day can further narrowed the pore size distribution, although the mean pore diameter increased slightly from 1.1 µm to 1.2 µm.…”

Section: Improvement Of Membrane Propertiesmentioning

confidence: 99%

“…where e is the density of the ethanol (g/m 3 ) and p is the density of the PVDF-HFP (g/m 3 ) [16,24].…”

Section: Direct Contact Membrane Distillation (Dcmd) Testmentioning

confidence: 99%

“…Contact angle, which was generally used to indicate hydrophobicity of membrane surface, was measured by Theta Lite 100 (Attension) (Biolin Scientific, Paramus, NJ, USA) with sessile drop method [24,26]. Then 5~8 µL of water droplet was placed onto the membrane surface for analysis.…”

Section: Characterizationmentioning

confidence: 99%

“…As-spun, heat-pressed and annealed membrane samples was measured with a lab-made setup for their liquid entry pressure [9,24]. A gas supply was connected to a hollow stainless plate by a tube, with a digital gauge standing as the intermediate between them.…”

Section: Characterizationmentioning

confidence: 99%

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

et al. 2017

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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.

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Section: Lep and Contact Anglesupporting

confidence: 79%

Section: Improvement Of Membrane Propertiesmentioning

confidence: 99%

“…where e is the density of the ethanol (g/m 3 ) and p is the density of the PVDF-HFP (g/m 3 ) [16,24].…”

Section: Direct Contact Membrane Distillation (Dcmd) Testmentioning

confidence: 99%

Section: Characterizationmentioning

confidence: 99%

Section: Characterizationmentioning

confidence: 99%

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

et al. 2017

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Tailoring the Surface Properties of Micro/Nanofibers Using 0D, 1D, 2D, and 3D Nanostructures: A Review on Post‐Modification Methods

Schneider

Facure

Chagas

et al. 2021

Adv Materials Inter

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Micro‐ and nanofibers produced by electrospinning and solution blow spinning (SBS) are highly suitable platforms for diverse applications due to their advantageous properties, including the high surface area to volume ratio, high porosity, and flexibility. To render them additional functionalities, distinct pre‐ or post‐modification processes have been proposed for modifying such micro‐ and nanofibers with 0D, 1D, 2D, and 3D nanostructures. The pre‐modification requires the addition of 0D–3D nanostructures (or their precursors) into the polymeric phase before the spinning process, which can demand laborious solubilization and requires changes in experimental spinning parameters, with impact on morphology, spinnability, and properties. Post‐modification methods, on the other hand, enable the fabrication of composite fibers without the need to optimize the spinning parameters, allowing a simple and efficient surface modification. Herein, recent advances on post‐modification methods of spun fibers, including wet chemistry, grafting, crosslinking, click chemistry, oxidations, hydrolysis and reduction strategies, dip‐coating, layer‐by‐layer, electro/air‐spray, atomic layer deposition, and plasma techniques aiming at the surface functionalization with 0D–3D nanostructures are surveyed. Recent results, trends, and challenges on the application of such surface‐modified fibers for environmental, industrial, and medical applications, including as adsorbent and filtering membranes, catalysts for pollutants degradation, and wearable sensors are examined.

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Effective modeling and optimization of PVDF–PTFE electrospinning parameters and membrane distillation process by response surface methodology

Hassan

et al. 2018

J of Applied Polymer Sci

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Ploy(vinylidene fluoride)-polytetrafluoroethylene nanofibrous membrane fabrication and direct contact membrane distillation (DCMD) process were simulated and optimized by response surface methodology (RSM). Analysis of variance was applied to develop and verify the models that predict the objectives. The three-dimensional response surfaces of different objectives were obtained. Results showed that the membrane with thickness of 70.7 μm, contact angle of 146.2 , and liquid entry pressure of 53.5 kPa was obtained within investigated experimental range under the optimum electrospinning conditions. Rejection rate of 99.99% and the permeate flux of 67.5 kg m −2 h −1 were gained under the optimum membrane distillation (MD) process parameters. The actual and predicted values show good consistency verifying the accuracy of the models. In addition, an overall investigation of the influence of heat-press temperature on the morphological and mechanical properties of electrospun membrane was carried out. Results indicated that electrospinning process and MD performance can be enhanced after the corresponding variables were optimized by RSM. This study provides a scientific way to optimize the electrospinning and DCMD parameters.

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Effect of heat-press conditions on electrospun membranes for desalination by direct contact membrane distillation

Cited by 98 publications

References 31 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

Tailoring the Surface Properties of Micro/Nanofibers Using 0D, 1D, 2D, and 3D Nanostructures: A Review on Post‐Modification Methods

Effective modeling and optimization of PVDF–PTFE electrospinning parameters and membrane distillation process by response surface methodology

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