Pervaporation and vacuum membrane distillation processes: Modeling and experiments

Khayet, M.; Matsuura, Takeshi

doi:10.1002/aic.10161

Cited by 158 publications

(78 citation statements)

References 29 publications

(96 reference statements)

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“…The membrane prevents the penetration of the aqueous solution into its dry pores by its hydrophobic nature until the liquid entry pressure of water (i.e., LEPw) is exceeded. Besides, the membrane properties, such as pore size, pore size distribution and porosity will also influence the MD performance [11][12][13][14]. Therefore, good hydrophobicity, appropriate pore size and narrow pore size distribution of microporous membranes are necessary to ensure the high permeate flux and rejection in MD process.…”

Section: Introductionmentioning

confidence: 99%

Fabrication and characterization of hydrophobic PVDF hollow fiber membranes for desalination through direct contact membrane distillation

Hou

Wang

et al. 2009

Separation and Purification Technology

132

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a b s t r a c tThe mixture of inorganic salt LiCl and soluble polymer polyethylene glycol (PEG) 1500 as non-solvent additive was introduced to fabricate hydrophobic hollow fiber membrane of polyvinylidene fluoride (PVDF) by phase inversion process, using N,N-dimethylacetamide (DMAc) as solvent and tap water as the coagulation medium. Compared with other three membranes from PVDF/DMAc, PVDF/DMAc/LiCl and PVDF/DMAc/PEG 1500 dope solution, it can be observed obviously by scanning electron microscope (SEM) that the membrane spun from PVDF/DMAc/LiCl/PEG 1500 dope had longer finger-like cavities, ultra-thin skins, narrow pore size distribution and porous network sponge-like structure owing to the synergistic effect of LiCl and PEG 1500. Besides, the membrane also exhibited high porosity and good hydrophobicity. During the desalination process of 3.5 wt% sodium chloride solution through direct contact membrane distillation (DCMD), the permeate flux achieved 40.5 kg/m 2 h and the rejection of NaCl maintained 99.99% with the feed solution at 81.8• C and the cold distillate water at 20.0 • C, this performance is comparable or even higher than most of the previous reports. Furthermore, a 200 h continuously desalination experiment showed that the membrane had stable permeate flux and solute rejection, indicating that the as-spun PVDF hollow fiber membrane may be of great potential to be utilized in the DCMD process.

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Section: Introductionmentioning

confidence: 99%

Fabrication and characterization of hydrophobic PVDF hollow fiber membranes for desalination through direct contact membrane distillation

Hou

Wang

et al. 2009

Separation and Purification Technology

132

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“…Furthermore, the SEM micrographs ( Figure 5.4) show that carbon was trapped inside the alumina substrate. In other words, the higher the carbon content, the higher is the resistance, leading to lower water fluxes, which is consistent with work published elsewhere (Bandini, Saavedra et al 1997;Urtiaga, Ruiz et al 2000;Khayet and Matsuura 2004;Hwang 2011). The ideal PV membrane for desalination should demonstrate high flux and high salt rejection.…”

Section: Analysis and Discussionsupporting

confidence: 77%

Carbon molecular sieve membranes for desalination

Song¹

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i This work reports on the development of novel carbon molecular sieve (CMS) membranes for desalination. The membranes were prepared by vacuum impregnation of precursor solutions containing phenolic resin into porous alumina tubes. Subsequently, the membrane tubes were calcined in an inert atmosphere, leading to the carbonisation of the resin impregnated into the porous alumina substrate. A systematic and parametric study was undertaken to investigate the effect of: (i) substrate porosity, (ii) precursor solution, (iii) vacuum impregnation time and (iv) carbonisation temperature on the performance of the resultant membranes. AbstractHigh quality CMS membranes were successfully prepared. High water fluxes were achieved using a pervaporation setup with values of 27 kg m -2 h -1 observed at 75 °C whilst delivering salt rejection in excess of 96% for a synthetic aqueous solution of 0.3 wt% NaCl chosen to represent brackish water. Increasing the salt concentration resulted in the water flux reducing, which was most likely due to salt concentration polarisation. However, the CMS membranes continued to perform well for processing sea water (3.5 wt% NaCl) at room temperature delivering water fluxes in the region of 9.4 kg m -2 h -1 with a salt rejection close to 100%. The high performance given by the CMS membranes in terms of water fluxes are at least one order of magnitude higher than those reported for other inorganic membranes derived from silica or zeolites.One important finding of this work is that the water flux increased by a factor of 70 as the concentration of the phenolic resin precursor solution decreased from 40 to 1 wt%. This result indicates that high resin concentration led to a higher amount of carbonised resin in the porous substrate and a higher resistance to water diffusion. The precursor solutions with a low resin concentration allowed for the formation of ideal CMS structures, which polymerised into the interparticle pore domains of the porous alumina substrate. As such a molecular sieving structure was formed as it preferentially allowed for the diffusion of the smaller molecule water with a kinetic diameter of 2.6 Å, and to a higher degree rejected the passage of hydrated ions with sizes in excess of 7 Å.A second important finding is that the functionality of the carbonised resin plays a role in delivering CMS membranes with high performance. CMS materials carbonised at 500 °C still retained some functional aromatic groups which were hydrophilic and impacted on membrane performance.However, increasing the carbonisation temperature to 700 °C lead to optimal microporosity, enhanced surface area and reduced hydrophilicity as the functional groups were almost completely ii removed. Further increases of carbonisation temperature to 800 °C resulted in the formation of larger, mesoporous structures and the unfavourable reduction of salt rejection.A third important finding is that best CMS membranes were prepared by longer vacuum times of 300 to 600 s, instead of short times of 30 or 60 s. This result wa...

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“…The potential of membranes has been extended to the separation of volatile products by membrane distillation and pervaporation, respectively [21,22] . In both techniques the liquid feed is in contact with the upstream side of the membrane, while the permeated product is obtained as a vapor on the downstream side, which is then condensed.…”

Section: Membrane Distillation and Pervaporationmentioning

confidence: 99%

Downstream Processing in Industrial Biotechnology

Hatti‐Kaul

2010

Industrial Biotechnology

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Pervaporation and vacuum membrane distillation processes: Modeling and experiments

Abstract: Two separation processes, pervaporation (PV) and vacuum membrane distillation (VMD),

Cited by 158 publications

References 29 publications

Fabrication and characterization of hydrophobic PVDF hollow fiber membranes for desalination through direct contact membrane distillation

Fabrication and characterization of hydrophobic PVDF hollow fiber membranes for desalination through direct contact membrane distillation

Carbon molecular sieve membranes for desalination

Downstream Processing in Industrial Biotechnology

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