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Membranes 2013, 3(4), 354-374; doi:10.3390/membranes3040354
Article

Gypsum (CaSO4·2H2O) Scaling on Polybenzimidazole and Cellulose Acetate Hollow Fiber Membranes under Forward Osmosis

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Received: 12 October 2013; in revised form: 29 October 2013 / Accepted: 1 November 2013 / Published: 8 November 2013
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Abstract: We have examined the gypsum (CaSO4·2H2O) scaling phenomena on membranes with different physicochemical properties in forward osmosis (FO) processes. Three hollow fiber membranes made of (1) cellulose acetate (CA), (2) polybenzimidazole (PBI)/polyethersulfone (PES) and (3) PBI-polyhedral oligomeric silsesquioxane (POSS)/polyacrylonitrile (PAN) were studied. For the first time in FO processes, we have found that surface ionic interactions dominate gypsum scaling on the membrane surface. A 70% flux reduction was observed on negatively charged CA and PBI membrane surfaces, due to strong attractive forces. The PBI membrane surface also showed a slightly positive charge at a low pH value of 3 and exhibited a 30% flux reduction. The atomic force microscopy (AFM) force measurements confirmed a strong repulsive force between gypsum and PBI at a pH value of 3. The newly developed PBI-POSS/PAN membrane had ridge morphology and a contact angle of 51.42° ± 14.85° after the addition of hydrophilic POSS nanoparticles and 3 min thermal treatment at 95 °C. Minimal scaling and an only 1.3% flux reduction were observed at a pH value of 3. Such a ridge structure may reduce scaling by not providing a locally flat surface to the crystallite at a pH value of 3; thus, gypsum would be easily washed away from the surface.
Keywords: forward osmosis; fouling; gypsum scaling; polybenzimidazole; polyhedral oligomeric silsesquioxane; cellulose acetate forward osmosis; fouling; gypsum scaling; polybenzimidazole; polyhedral oligomeric silsesquioxane; cellulose acetate
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Chen, S.C.; Su, J.; Fu, F.-J.; Mi, B.; Chung, T.-S. Gypsum (CaSO4·2H2O) Scaling on Polybenzimidazole and Cellulose Acetate Hollow Fiber Membranes under Forward Osmosis. Membranes 2013, 3, 354-374.

AMA Style

Chen SC, Su J, Fu F-J, Mi B, Chung T-S. Gypsum (CaSO4·2H2O) Scaling on Polybenzimidazole and Cellulose Acetate Hollow Fiber Membranes under Forward Osmosis. Membranes. 2013; 3(4):354-374.

Chicago/Turabian Style

Chen, Si C.; Su, Jincai; Fu, Feng-Jiang; Mi, Baoxia; Chung, Tai-Shung. 2013. "Gypsum (CaSO4·2H2O) Scaling on Polybenzimidazole and Cellulose Acetate Hollow Fiber Membranes under Forward Osmosis." Membranes 3, no. 4: 354-374.


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