Unique Behaviors and Mechanism of Highly Soluble Salt-Induced Wetting in Membrane Distillation
Document Type
Article
Publication Date
10-18-2022
Abstract
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.
Identifier
85139209113 (Scopus)
Publication Title
Environmental Science and Technology
External Full Text Location
https://doi.org/10.1021/acs.est.2c03348
e-ISSN
15205851
ISSN
0013936X
PubMed ID
36154007
First Page
14788
Last Page
14796
Issue
20
Volume
56
Grant
52070147
Fund Ref
National Natural Science Foundation of China
Recommended Citation
Shi, Danting; Gong, Tengjing; Qing, Weihua; Li, Xianhui; and Shao, Senlin, "Unique Behaviors and Mechanism of Highly Soluble Salt-Induced Wetting in Membrane Distillation" (2022). Faculty Publications. 2586.
https://digitalcommons.njit.edu/fac_pubs/2586
