High-permeability vacuum membrane distillation utilizing mechanically compressed carbon nanotube membranes

Jung, Woo-Sang; Choe, Younjeong; Kim, Taewoo; Ok, Jong G.; Lee, Hong H.; Kim, Yong Hyup

doi:10.1039/d1ra08042c

Cited by 8 publications

(5 citation statements)

References 32 publications

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“…However, other models such as the Hertz model cannot be used as we have observed adhesion (∼15 nN) between the probe and the sample, and the JKR model is applicable to soft samples with high adhesion, where significant deformation occurs at the contact zone during pull-off which is not the case in our samples. Moreover, there are other parameters such as areal density of VACNTs in the range of 200−400 CNT/μm 2 , 29 and we assume that the VACNTs have uniform structure in the microscale, and the gap between the CNTs can be ignored as it is nearly 5−10 nm.…”

Section: Resultsmentioning

confidence: 99%

Frictional Behavior of Alumina-Coated Vertically Aligned Carbon Nanotube Forests: Implications for Micro and Nano Electromechanical Devices

Verma

Rai

Gosvami

et al. 2022

ACS Appl. Nano Mater.

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In this work, we report the role of alumina coating on frictional behavior of vertically aligned carbon nanotube (VACNT) forests sliding against an alumina microsphere as a counter surface using atomic force microscopy. A high coefficient of friction (COF) of ∼2.13 is observed for VACNT forest, while the COF reduced significantly to ∼0.45 for 20 nm alumina-coated VACNT forests. The fivefold reduction in the COF can be explained by considering the changes in the contact area and lateral stiffness. The effect of sliding speed on the COF is also investigated on both bare and alumina-coated VACNT forest samples. The COF does not show any dependency on sliding speed and confirms the consistent difference in friction force between bare and alumina-coated VACNTs over the investigated range of sliding speeds.

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Section: Resultsmentioning

confidence: 99%

Frictional Behavior of Alumina-Coated Vertically Aligned Carbon Nanotube Forests: Implications for Micro and Nano Electromechanical Devices

Verma

Rai

Gosvami

et al. 2022

ACS Appl. Nano Mater.

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“…However, these membranes often encounter issues such as pore wetting and scaling during a prolonged operation. − Consequently, intensive efforts have been made on the construction of biomimetically rough surfaces with nanomaterials (e.g., micro/nanoscale nanotubes/silica, SiC@graphene), aiming to improve the wetting and scaling resistance of the membrane. − However, low-surface-energy substrates such as polydimethylsiloxane (PDMS), − hexadecyltrimethoxysilane (HDTMS), and fluoroalkylsilane , are commonly utilized to modify the surface or as binders to immobilize nanomaterials. In this case, the micro/nanostructure of the membrane could be partially obscured, potentially reducing surface roughness, increasing mass transfer resistance, and consequently leading to a decrease in water vapor flux. − Reported membranes made of nanomaterials without polymers, such as alumina-supported metal–organic framework (MOF) membranes and carbon nanotube membranes, can exhibit a good water flux. Inspired by the above, it is urgent to develop simple approaches using low-cost materials that can be combined with nanomaterials to prepare antiwetting membranes. − …”

Section: Introductionmentioning

confidence: 99%

“…In this case, the micro/nanostructure of the membrane could be partially obscured, potentially reducing surface roughness, increasing mass transfer resistance, and consequently leading to a decrease in water vapor flux. 21−23 Reported membranes made of nanomaterials without polymers, such as aluminasupported metal−organic framework (MOF) membranes 24 and carbon nanotube membranes, 25 can exhibit a good water flux. Inspired by the above, it is urgent to develop simple approaches using low-cost materials that can be combined with nanomaterials to prepare antiwetting membranes.…”

Section: Introductionmentioning

confidence: 99%

“Two Birds One Stone” Strategy: PTFE Nanorods for Assembling Nanomaterials and Constructing Hydrophobic Porous Membranes for High-Performance Membrane Distillation

Lai,

Wang,

et al. 2024

Ind. Eng. Chem. Res.

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The promising development of porous hydrophobic membranes hybridized with nanomaterials is of great value for desalinating in membrane distillation (MD). The surface morphology of nanomaterials is frequently covered by polymer binders during the assembly process, resulting in reduced mass transfer efficiency. Herein, we constructed a hybridized membrane featuring lotus leaf mimetic hierarchies by vacuum filtration of a commercial polytetrafluoroethylene (PTFE) nanorod emulsion containing wrinkled reduced graphene oxide (rGO) microspheres on a microfiltration substrate. The PTFE nanorods playing the role of "two birds one stone" not only allowed the microspheres to be tightly attached to the substrate without the use of a polymer binder, but they generated a wrinkled rGO microsphere−PTFE nanorod layer with a loose and porous structure as well. Such membrane exhibits strong hydrophobicity (a water contact value of ∼142.6°) and excellent salt rejection of 99.75% with a high water flux of 35.73 kg•m −2 •h −1 for separating a 3.5 wt % NaCl solution (70 °C) in a vacuum MD (VMD). It also retains a stable performance after a 700 h continuous operation. An in-depth analysis of the mass transfer process was further performed by theoretical calculation, providing inspiration for constructing high-performance membranes for desalination.

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“…Depending on the approach for vapor condensation, MD can be classified into four major configurations [ 13 ], including air gap membrane distillation (AGMD) [ 14 , 15 , 16 , 17 ], sweeping-gas membrane distillation (SGMD) [ 12 , 18 , 19 , 20 , 21 , 22 ], direct contact membrane distillation (DCMD) [ 12 , 23 , 24 , 25 , 26 , 27 ], and vacuum membrane distillation (VMD) [ 12 , 28 , 29 , 30 , 31 , 32 ]. Recently, a new MD configuration that combined the features of AGMD and DCMD processes was introduced and named water gap membrane distillation (WGMD) [ 33 , 34 , 35 ] or permeate gap membrane distillation (PGMD) [ 36 , 37 , 38 , 39 ], or liquid gap membrane distillation (LGMD) [ 40 , 41 , 42 , 43 ].…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of a Plate–Frame Water Gap Membrane Distillation System for Seawater Desalination

Lawal,

Abdulazeez,

Alsalhy

et al. 2023

Membranes

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This study presented a detailed investigation into the performance of a plate–frame water gap membrane distillation (WGMD) system for the desalination of untreated real seawater. One approach to improving the performance of WGMD is through the proper selection of cooling plate material, which plays a vital role in enhancing the gap vapor condensation process. Hence, the influence of different cooling plate materials was examined and discussed. Furthermore, two different hydrophobic micro-porous polymeric membranes of similar mean pore sizes were utilized in the study. The influence of key operating parameters, including the feed water temperature and flow rate, was examined against the system vapor flux and gained output ratio (GOR). In addition, the used membranes were characterized by means of different techniques in terms of surface morphology, liquid entry pressure, water contact angle, pore size distribution, and porosity. Findings revealed that, at all conditions, the PTFE membrane exhibits superior vapor flux and energy efficiency (GOR), with 9.36% to 14.36% higher flux at a 0.6 to 1.2 L/min feed flow rate when compared to the PVDF membrane. The copper plate, which has the highest thermal conductivity, attained the highest vapor flux, while the acrylic plate, which has an extra-low thermal conductivity, recorded the lowest vapor flux. The increasing order of GOR values for different cooling plates is acrylic < HDPE < copper < aluminum < brass < stainless steel. Results also indicated that increasing the feed temperature increases the vapor flux almost exponentially to a maximum flux value of 30.36 kg/m2hr. The system GOR also improves in a decreasing pattern to a maximum value of 0.4049. Moreover, a long-term test showed that the PTFE membrane, which exhibits superior hydrophobicity, registered better salt rejection stability. The use of copper as a cooling plate material for better system performance is recommended, while cooling plate materials with very low thermal conductivities, such as a low thermally conducting polymer, are discouraged.

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High-permeability vacuum membrane distillation utilizing mechanically compressed carbon nanotube membranes

Abstract: High-permeable vacuum membrane distillation by applying vertically aligned carbon nanotube for the first time.

Cited by 8 publications

References 32 publications

Frictional Behavior of Alumina-Coated Vertically Aligned Carbon Nanotube Forests: Implications for Micro and Nano Electromechanical Devices

Frictional Behavior of Alumina-Coated Vertically Aligned Carbon Nanotube Forests: Implications for Micro and Nano Electromechanical Devices

“Two Birds One Stone” Strategy: PTFE Nanorods for Assembling Nanomaterials and Constructing Hydrophobic Porous Membranes for High-Performance Membrane Distillation

Experimental Investigation of a Plate–Frame Water Gap Membrane Distillation System for Seawater Desalination

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