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A New Method for Quantitative Evaluation Concentration Polarization Under Different Conditions for the Forward
1Green Intelligence Environmental School, Yangtze Normal University, No. 16 Juxian Road, Fuling District, Chongqing 408100, China.
Membranes
|August 27, 2025
Summary
Concentration polarization significantly impacts forward osmosis (FO) membrane performance. This study quantifies how internal and external concentration polarization affects osmotic pressure, revealing internal CP
Area of Science:
- Membrane Science and Technology
- Water Treatment Technologies
- Chemical Engineering
Background:
- Concentration polarization (CP) is a major challenge in forward osmosis (FO) membrane processes, reducing operational efficiency.
- Quantitative evaluation of CP is crucial for understanding its detrimental effects on FO performance.
Purpose of the Study:
- To systematically investigate the impact of different concentration polarization types on osmotic pressure drop in FO.
- To analyze the influence of draw solution (DS) and feed solution (FS) characteristics on CP effects.
- To compare CP effects in FO and pressure-retarded osmosis (PRO) modes.
Main Methods:
- Utilized the water transmission coefficient (ηWT) to quantify water flux relative to theoretical flux.
- Investigated varying concentration gradients between DS and FS.
- Employed organic FS and deionized (DI) water for comparative analysis.
- Examined effects of different salts (CaCl2 vs. NaCl) as DS.
Main Results:
- Water transmission coefficient (ηWT) decreased with increasing concentration gradients.
- Dilutive internal CP (ICP) proportion increased, while concentrative external CP (ECP) proportion decreased with different DSs in FO mode.
- Organic FS and higher FS concentrations exacerbated CP effects, reducing water flux.
- CaCl2 as DS caused greater efficiency reduction than NaCl.
- PRO mode showed higher water flux but also greater flux decline compared to FO mode.
Conclusions:
- Both ECP and ICP reduce osmotic pressure, with ICP exerting a dominant influence.
- Dilutive ICP negatively impacts osmotic pressure in FO mode, while dilutive ECP is dominant in PRO mode.
- Understanding and mitigating CP is essential for optimizing FO and PRO processes.
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