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1. Pattern size relative to oil droplet size effect on oil fouling in nanofiltration

   https://doi.org/10.1016/j.memsci.2024.123457  

   Ward, Lauren M ; Martin, Catherine C ; Weinman, Steven T ( February 2025 , Journal of Membrane Science)

   Membrane fouling is a major issue in many membrane applications. There are numerous methods used in attempt to mitigate membrane fouling, with one method being membrane surface patterning. However, it is still unclear how the ratio of foulant size to pattern size affects membrane fouling. In this study, we investigated constant foulant size while varying the pattern size on the membrane surface to be smaller than (300-nm), equal to (10-μm), and larger than (50-μm) the foulant (10-μm) on polyamide nanofiltration membranes. These membranes were compared to a commercial nanofiltration membrane and a control flat synthesized membrane. The membranes were tested with water, 2000 ppm Na2SO4, and three cycles of a n-dodecane (as oil) brine solution in a dead-end cell to assess the fouling resistance and flux recovery ability of each polyamide membrane type. From the fouling experiments, it was determined that none of the pattern sizes significantly affect the flux recovery ratio, but smaller than and larger than patterns decreased the fouling rate on the polyamide membranes by a small margin. 

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2. A comprehensive study on combined organic fouling and gypsum scaling in reverse osmosis: Decoupling surface and bulk phenomena

   https://doi.org/10.1016/j.memsci.2023.122399  

   Park, Shinyun ; Saavedra, Mayca ; Liu, Xitong ; Li, Tianshu ; Anger, Bridget ; Tong, Tiezheng ( February 2024 , Journal of Membrane Science)

   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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3. Raman imaging of membrane fouling

   https://doi.org/https://doi.org/10.1016/j.seppur.2020.116763  

   Azizighannad, S. ; Intrchomb, W. ; Mitra, S. ( February 2020 , Separation and purification technology)

   Membrane processes are widely used in industrial applications such water purification, food processing and pharmaceutical manufacturing. During their operation, the accumulation of foulants in membrane pores and on membrane surfaces lead to the reduction in flux, membrane lifetime and increase in operational cost, and the understanding of the fouling phenomenon is important for mitigating these problems. In this paper we report the application of Raman chemical imaging as a means of identify and map foulants on a membrane surface. The surface of a Polytetrafluoroethylene (PTFE) membrane was studied by Raman chemical imaging before and after fouling during desalination via membrane distillation. Information about location and concentration of three different salts namely CaSO4, BaSO4 and CaCO3 was studied. The three salts showed different distribution patterns, and their distribution was analyzed by correlation mapping and multivariate curve resolution. It was observed that CaSO4 agglomerated in specific places while the BaSO4 and CaCO3 were more distributed. Raman imaging appears to be a powerful tool for studying membrane foulants and can be effective in identifying the distribution of different species on a membrane surface. 

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4. Mechanical Vibration for the Control of Membrane Fouling in Direct Contact Membrane Distillation

   https://doi.org/10.3390/sym11020126  

   Huang, Frank ; Medin, Carolyn ; Arning, Allie ( February 2019 , Symmetry)

   One of the biggest challenges for direct contact membrane distillation (DCMD) in treating wastewater from flue gas desulfurization (FGD) is the rapid deterioration of membrane performance resulting from precipitate fouling. Chemical pretreatment, such as lime-soda ash softening, has been used to mitigate the issue, however, with significant operating costs. In this study, mechanical vibration of 42.5 Hz was applied to lab-scale DCMD systems to determine its effectiveness of fouling control for simulated FGD water. Liquid entry pressure and mass transfer limit of the fabricated hollow fiber membranes were determined and used as the operational constraints in the fouling experiments so that the observed membrane performance was influenced solely by precipitate fouling. Minimal improvement of water flux was observed when applying vibration after significant (~16%) water-flux decline. Initiating vibration at the onset of the experiments prior to the exposure of foulants, however, was promising for the reduction of membrane fouling. The water-flux decline rate was reduced by about 50% when compared to the rate observed without vibration. Increasing the module packing density from 16% to 50% resulted in a similar rate of water-flux decline, indicating that the fouling propensity was not increased with packing density in the presence of vibration. 

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5. Process- and Product-Related Foulants in Virus Filtration

   https://doi.org/10.3390/bioengineering9040155  

   Isu, Solomon ; Qian, Xianghong ; Zydney, Andrew L. ; Wickramasinghe, S. Ranil ( April 2022 , Bioengineering)

   Regulatory authorities place stringent guidelines on the removal of contaminants during the manufacture of biopharmaceutical products. Monoclonal antibodies, Fc-fusion proteins, and other mammalian cell-derived biotherapeutics are heterogeneous molecules that are validated based on the production process and not on molecular homogeneity. Validation of clearance of potential contamination by viruses is a major challenge during the downstream purification of these therapeutics. Virus filtration is a single-use, size-based separation process in which the contaminating virus particles are retained while the therapeutic molecules pass through the membrane pores. Virus filtration is routinely used as part of the overall virus clearance strategy. Compromised performance of virus filters due to membrane fouling, low throughput and reduced viral clearance, is of considerable industrial significance and is frequently a major challenge. This review shows how components generated during cell culture, contaminants, and product variants can affect virus filtration of mammalian cell-derived biologics. Cell culture-derived foulants include host cell proteins, proteases, and endotoxins. We also provide mitigation measures for each potential foulant. 

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