In Process Wetting Prevention in Membrane Distillation

A special issue of Membranes (ISSN 2077-0375). This special issue belongs to the section "Membrane Processing and Engineering".

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 7165

Special Issue Editors

Institute of Process Engineering (IVT), Johannes Kepler University Linz, Altenberger Str. 69, A-4040 Linz, Austria
Interests: membrane distillation
Institute of Process Engineering (IVT), Johannes Kepler University Linz, Altenberger Str. 69, A-4040 Linz, Austria
Interests: membrane distillation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear colleagues,

The wetting phenomenon is wildly recognized as the core hindrance in the real industrial application of the membrane distillation process. This Special Issue provides a forum for publishing papers that advance our understanding of the wetting mechanism and wetting prevention in membrane distillation in a variety of applications. Publications are expected to cover the broad aspects of the science and technology of wetting dynamics, in-process wetting prevention and reversal in water, environment, energy, and food industry applications. The articles in this issue aim to illustrate some of the current developments in the field.

Prof. Dr. Wolfgang M. Samhaber
Dr. Mohammad Rezaei
Guest Editors

Manuscript Submission Information

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Keywords

  • Membrane Distillation 
  • Wetting phenomenon 
  • In-process wetting prevention

Published Papers (2 papers)

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Research

21 pages, 7191 KiB  
Article
Long-Running Comparison of Feed-Water Scaling in Membrane Distillation
by Mohammad Rezaei, Albraa Alsaati, David M. Warsinger, Florian Hell and Wolfgang M. Samhaber
Membranes 2020, 10(8), 173; https://doi.org/10.3390/membranes10080173 - 31 Jul 2020
Cited by 11 | Viewed by 4033
Abstract
Membrane distillation (MD) has shown promise for concentrating a wide variety of brines, but the knowledge is limited on how different brines impact salt scaling, flux decline, and subsequent wetting. Furthermore, past studies have lacked critical details and analysis to enable a physical [...] Read more.
Membrane distillation (MD) has shown promise for concentrating a wide variety of brines, but the knowledge is limited on how different brines impact salt scaling, flux decline, and subsequent wetting. Furthermore, past studies have lacked critical details and analysis to enable a physical understanding, including the length of experiments, the inclusion of salt kinetics, impact of antiscalants, and variability between feed-water types. To address this gap, we examined the system performance, water recovery, scale formation, and saturation index of a lab-scale vacuum membrane distillation (VMD) in long-running test runs approaching 200 h. The tests provided a comparison of a variety of relevant feed solutions, including a synthetic seawater reverse osmosis brine with a salinity of 8.0 g/L, tap water, and NaCl, and included an antiscalant. Saturation modeling indicated that calcite and aragonite were the main foulants contributing to permeate flux reduction. The longer operation times than typical studies revealed several insights. First, scaling could reduce permeate flux dramatically, seen here as 49% for the synthetic brine, when reaching a high recovery ratio of 91%. Second, salt crystallization on the membrane surface could have a long-delayed but subsequently significant impact, as the permeate flux experienced a precipitous decline only after 72 h of continuous operation. Several scaling-resistant impacts were observed as well. Although use of an antiscalant did not reduce the decrease in flux, it extended membrane operational time before surface foulants caused membrane wetting. Additionally, numerous calcium, magnesium, and carbonate salts, as well as silica, reached very high saturation indices (>1). Despite this, scaling without wetting was often observed, and scaling was consistently reversible and easily washed. Under heavy scaling conditions, many areas lacked deposits, which enabled continued operation; existing MD performance models lack this effect by assuming uniform layers. This work implies that longer times are needed for MD fouling experiments, and provides further scaling-resistant evidence for MD. Full article
(This article belongs to the Special Issue In Process Wetting Prevention in Membrane Distillation)
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24 pages, 9739 KiB  
Article
Mitigation of Membrane Wetting by Applying a Low Temperature Membrane Distillation
by Marek Gryta
Membranes 2020, 10(7), 158; https://doi.org/10.3390/membranes10070158 - 21 Jul 2020
Cited by 12 | Viewed by 2445
Abstract
The formation of deposits on the membrane surface during membrane distillation is considered as one of the main reasons for membrane wetting. To assess the intensity of this phenomenon, long-term studies were performed comparing the membrane wettability with non-fouling feed (NaCl solutions) and [...] Read more.
The formation of deposits on the membrane surface during membrane distillation is considered as one of the main reasons for membrane wetting. To assess the intensity of this phenomenon, long-term studies were performed comparing the membrane wettability with non-fouling feed (NaCl solutions) and feeds containing various foulants (lake and Baltic Sea water). The polypropylene membranes used were non-wetted by NaCl solutions during several hundred hours of water desalination. However, the occurrence of CaCO3 or other salt crystallization caused the membranes to be partially wetted, especially when periodical membrane cleaning was applied. The scaling intensity was significantly reduced by lowering the feed temperature from 353 to 315 K, which additionally resulted in the limitation of the degree of membrane wetting. Full article
(This article belongs to the Special Issue In Process Wetting Prevention in Membrane Distillation)
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