Membrane scaling in Vacuum Membrane Distillation - Part 2: Crystallization kinetics and process performance

Kiefer, Florian; Präbst, Alexander; Sattelmayer, Thomas

doi:10.1016/j.memsci.2019.117293

Cited by 7 publications

(8 citation statements)

References 15 publications

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“…20−23 Because of the high concentration, the crystal growth rate of highly soluble salt is much faster than that of sparingly soluble salt. 19 This rapid growth of the crystal, on the one hand, facilitates the formation of scale layer, and, on the other hand, may quickly block the membrane pore and hinder the continuous growth of crystals into membrane pores. Therefore, some studies reported no observation of the wetting phenomenon by NaCl.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Therefore, some studies reported no observation of the wetting phenomenon by NaCl. 19,24,25 With limited studies and inconsistent results, the wetting behavior of highly soluble salts in MD is still unclear. The dynamic process and governing mechanism of highly soluble salt-induced wetting still need further study.…”

Section: ■ Introductionmentioning

confidence: 99%

“…In real high-salinity wastewater, however, the content of highly soluble salts (e.g., NaCl) is usually 2 orders of magnitude higher than that of sparingly soluble salts . These highly soluble salts can also crystallize on the membrane surface after concentration and then potentially induce pore wetting . For example, several studies have reported the wetting phenomena in MD fed with pure NaCl solution. − Because of the high concentration, the crystal growth rate of highly soluble salt is much faster than that of sparingly soluble salt .…”

Section: Introductionmentioning

confidence: 99%

“…These highly soluble salts can also crystallize on the membrane surface after concentration and then potentially induce pore wetting . For example, several studies have reported the wetting phenomena in MD fed with pure NaCl solution. − Because of the high concentration, the crystal growth rate of highly soluble salt is much faster than that of sparingly soluble salt . This rapid growth of the crystal, on the one hand, facilitates the formation of scale layer, and, on the other hand, may quickly block the membrane pore and hinder the continuous growth of crystals into membrane pores.…”

Section: Introductionmentioning

confidence: 99%

“…This rapid growth of the crystal, on the one hand, facilitates the formation of scale layer, and, on the other hand, may quickly block the membrane pore and hinder the continuous growth of crystals into membrane pores. Therefore, some studies reported no observation of the wetting phenomenon by NaCl. ,, With limited studies and inconsistent results, the wetting behavior of highly soluble salts in MD is still unclear. The dynamic process and governing mechanism of highly soluble salt-induced wetting still need further study.…”

Section: Introductionmentioning

confidence: 99%

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Unique Behaviors and Mechanism of Highly Soluble Salt-Induced Wetting in Membrane Distillation

Shi

Gong

Qing

et al. 2022

Environ. Sci. Technol.

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Scaling-induced wettinggreatly limits the application of membrane distillation (MD) for the desalination of high-salinity feed. Although highly soluble salts (e.g., NaCl) have high concentrations in this water, their scaling-induced wetting remains overlooked. To unravel the elusive wetting behaviors of highly soluble salts, in this study, we systematically investigated the scaling formation and wetting progress by in situ observation with optical coherence tomography (OCT). Through examining the influence of salt type and vapor flux on the wetting behavior, we revealed that highly soluble salt-induced wetting, especially under high vapor flux, shared several unique features: (1) occurring before the bulk feed reached saturation, (2) no scale layer formation observed, and (3) synchronized wetting progress on the millimeter scale. We demonstrated that a moving scale layer caused these interesting phenomena. The initial high vapor flux induced high concentration and temperature polarizations, which led to crystallization at the gas–liquid interface and the formation of an initial scale layer. On the one hand, this scale layer bridged the water into the hydrophobic pores; on the other hand, it blocked the membrane pores and reduced the vapor flux. In this way, the decreased vapor flux mitigated the concentration/temperature polarizations, and consequently led to the dissolution of the feed-facing side of the scale layer. This dissolution prevented the membrane pores from being completely blocked, facilitating the transportation and crystallization of salts at the distillate-facing side of the scale layer (i.e., the gas–liquid interface), thus the proceeding of the wetting layer.

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Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%