%0 Journal Article
%T Gypsum (CaSO4¡¤2H2O) Scaling on Polybenzimidazole and Cellulose Acetate Hollow Fiber Membranes under Forward Osmosis
%A Si Cong Chen
%A Jincai Su
%A Feng-Jiang Fu
%A Baoxia Mi
%A Tai-Shung Chung
%J Membranes
%D 2013
%I MDPI AG
%R 10.3390/membranes3040354
%X We have examined the gypsum (CaSO 4¡¤2H 2O) 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¡ã ¡À 14.85¡ã after the addition of hydrophilic POSS nanoparticles and 3 min thermal treatment at 95 ¡ãC. 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.
%K forward osmosis
%K fouling
%K gypsum scaling
%K polybenzimidazole
%K polyhedral oligomeric silsesquioxane
%K cellulose acetate
%U http://www.mdpi.com/2077-0375/3/4/354