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Reverse osmosis (RO), as an energy efficient desalination technology that is critical to mitigate water scarcity, encounters feedwater containing both organic foulants and inorganic scalants. However, comparing with extensive studies on individual fouling or scaling, our knowledge of the behavior and mechanisms associated with combined organic fouling and mineral scaling is still lacking. Due to the potential occurrence of mineral formation in both bulk solution and on the membrane surface, a complete, mechanistic understanding of combined fouling and scaling requires decoupling of surface and bulk phenomena. Herein, our study employed a comprehensive investigation to delve into the intricate interplay of gypsum scaling and organic fouling in RO process. Our systematic approach is accomplished through three sets of experiments that include static experiments and two types of dynamic experiments (i.e., (1) combined fouling and scaling, and (2) gypsum scaling on foulant-conditioned membranes). A variety of model foulants including humic acid, alginate, bovine serum albumin (BSA), and lysozyme were used to investigate the effects of foulant type. Our results demonstrate that the behavior of combined organic fouling and gypsum scaling aligns more with that of gypsum scaling on foulant-conditioned membranes rather than static experiments where bulk nucleation occurs, indicating the predominance of surface nucleation in RO. BSA exhibited a remarkable hindering effect on gypsum scaling, whereas other foulants displayed an additive effect. The lack of scaling mitigation by lysozyme suggests that molecular properties of protein must play a role in regulating the behavior of combined fouling and scaling. Results from multiple characterization techniques reveal the foulant-scalant interactions by delineating the morphological and chemical features of the fouling/scaling layers. Our study not only elucidates the mechanisms of combined organic fouling and gypsum scaling but also sheds light on potential strategies for membrane scaling control in RO desalination.
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This content will become publicly available on January 1, 2026
A tale of two minerals: contrasting behaviors and mitigation strategies of gypsum scaling and silica scaling in membrane desalination
Abstract Mineral scaling represents a major constraint that limits the efficiency of membrane desalination, which is becoming increasingly important for achieving sustainable water supplies in the context of a changing climate. Different mineral scales can be formed via distinct mechanisms that lead to a significant variation of scaling behaviors and mitigation strategies. In this article, we present a comprehensive review that thoroughly compares gypsum scaling and silica scaling, which are two common scaling types formed via crystallization and polymerization respectively, in membrane desalination. We show that the differences between scale formation mechanisms greatly affect the thermodynamics, kinetics, and mineral morphology of gypsum scaling and silica scaling. Then we review the literatures on the distinct behaviors of gypsum scaling and silica scaling during various membrane desalination processes, examining their varied damaging effects on desalination efficiency. We further scrutinize the different interactions of gypsum and silica with organic foulants, which result in contrasting consequences of combined scaling and fouling. In addition, the distinctive mitigation strategies tailored to controlling gypsum scaling and silica scaling, including scaling-resistant membrane materials, antiscalants, and pretreatment, are discussed. We conclude this article with the research needs of attaining a better understanding of different mineral scaling types, aiming to inspire researchers to take scale formation mechanism into consideration when developing more effective approaches of scaling control in membrane desalination.
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- PAR ID:
- 10582585
- Publisher / Repository:
- Springer Nature
- Date Published:
- Journal Name:
- Frontiers of Environmental Science & Engineering
- Volume:
- 19
- Issue:
- 1
- ISSN:
- 2095-2201
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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