Exploring the potential of commercial polyethylene membranes for desalination by membrane distillation

Nature-mimetic hydrophobic membranes with high wetting resistance have been designed for seawater desalination via vacuum membrane distillation (VMD) in this study. This is achieved through molecular engineering of metal-organic framework (MOF)-functionalized alumina surfaces. A two-step synthetic strategy was invented to design the hydrophobic membranes: (1) to intergrow MOF crystals on the alumina tube substrate and (2) to introduce perfluoro molecules onto the MOF functionalized membrane surface. With the first step, the surface morphology, especially the hierarchical roughness, can be controlled by tuning the MOF crystal structure. After the second step, the perfluoro molecules function as an ultrathin layer of hydrophobic floss, which lowers the surface energy. Therefore, the resultant membranes do not only possess the intrinsic advantages of alumina supports such as high stability and high water permeability, but also have a hydrophobic surface formed by MOF functionalization. The membrane prepared under an optimum condition achieved a good VMD flux of 32.3 L/m 2 -h at 60 • C. This study may open up a totally new approach for design of next-generation high performance membrane distillation membranes for seawater desalination.

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“…Figure 2 shows the lab-made setup [36,37]. A 200 mL stainless steel cylinder was used as the reservoir of salt water containing 3.5% NaCl.…”

Section: Membrane Characterizationsmentioning

confidence: 99%

Metal–Organic Framework-Functionalized Alumina Membranes for Vacuum Membrane Distillation

Zuo

Chung

2016

Water

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“…In light of the vast amount of seawater, much research has been conducted to desalinate seawater via processes such as reverse osmosis (RO) (Fritzmann et al, 2007;Sirkar et al, 1982;Kang and Cao, 2012), multi-effect distillation (MED) (Al-Shammiri and Safar, 1999), membrane distillation (MD) (Khayet and Matsuura, 2011;Wang and Chung, 2015;Zuo et al, 2016) and forward osmosis (FO) (Zhao et al, 2012;Valladares Linares et al, 2014;McGovern and Lienhard V, 2014). However, these processes also face challenges of either high-energy consumption or severe membrane fouling.…”

Section: Introductionmentioning

confidence: 99%

Freeze desalination of seawater using LNG cold energy

et al. 2016

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With the aid of cold energy from regasification of liquefied natural gas (LNG), freeze desalination (FD) is an emerging technology for seawater desalination because of its low energy characteristics and insensitivities to fouling problems. This work aims to investigate the major operating parameters of FD such as coolant temperature, freezing duration, supercooling, seeding, agitation, crystallizer material and subsequent washing procedure on ice production and water quality. It was found that the optimal freezing duration per batch was 1 h for an iron crystallizer and 1.5 h for a glass crystallizer. The optimal coolant temperature should be around -8 °C. The optimal amount of washing water to clean the raw ice was about 50 wt% of the raw ice. Over 50 wt% of the feed could be recovered as raw ice within 1 h, which means an overall ice recovery rate of higher than 25% (of the original seawater), considering the consumption of washing water. Both artificial and real seawater were tested under the optimized conditions. The total dissolved solid in the product ice was around 300 ppm, which met the World Health Organization (WHO) potable water salinity standard of 500 ppm. Therefore, the process parameters optimized in this study can be directly used for the freeze desalination of seawater.

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“…Much research effort is currently directed towards improved membranes, tailored to yield increasingly higher vapour fluxes [16]. However, as the membrane performance increases, the issue of temperature polarization acquires an increasing importance since it may become the limiting factor for performance, and thus the issue of module hydrodynamics has to be more and more carefully addressed.…”

Section: Introductionmentioning

confidence: 99%

Performance comparison between overlapped and woven spacers for membrane distillation

Gurreri¹,

Tamburini²,

Cipollina³

et al. 2017

dwt

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a b s t r a c tThe sustainable production of freshwater from seawater desalination is receiving increasing attention. Recently, some desalination technologies are taking advantage from the coupling with renewable resources; among them, membrane distillation (MD) is one of the most promising since it can be easily powered by low-grade thermal energy. MD being an emerging technology, efforts are required to optimize geometry and operating conditions of real units in order to reduce the unitary freshwater production cost. In particular, temperature polarization is a well-known detrimental effect for the process driving force; spacers are traditionally used to enhance mixing and make temperature boundary layers thinner, at the cost of higher pressure losses. The present work is devoted to testing and comparing the performance of two different two-layer net spacers: overlapped and woven. Investigations were carried out both by experiments and by computational fluid dynamics (CFD) at different Reynolds numbers, ranging from creeping flow to turbulent flow regimes. Experiments (for intermediate to high Re) made use of thermochromic liquid crystals along with digital image processing. Computational results (for low to intermediate Re) were obtained via steady state (low Re) or direct numerical simulations (intermediate Re) along with the unit cell approach. A good agreement between experiments and CFD results was obtained in the range of superposition. Results showed that woven spacers guarantee a better mixing than overlapped ones, especially in the low to intermediate Re range, thus resulting in Nusselt numbers 2.5-3 times higher. On the other hand, the less disturbed flow field induced by overlapped spacers was found to yield friction coefficients up to 4 times lower, thus allowing lower pumping costs. The choice between the two configurations depends crucially on the relative importance attributed to savings in membrane surface area and in pumping energy for any specific application.

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Exploring the potential of commercial polyethylene membranes for desalination by membrane distillation

Cited by 150 publications

References 47 publications

Metal–Organic Framework-Functionalized Alumina Membranes for Vacuum Membrane Distillation

Metal–Organic Framework-Functionalized Alumina Membranes for Vacuum Membrane Distillation

Freeze desalination of seawater using LNG cold energy

Performance comparison between overlapped and woven spacers for membrane distillation

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