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Integral hollow fiber membrane with chemical cross-linking for pressure retarded osmosis operated in the orientation of active layer facing feed solution
- Li, Ye, Zhao, Shanshan, Setiawan, Laurentia, Zhang, Lizhi, Wang, Rong
- Journal of membrane science 2018 v.550 pp. 163-172
- artificial membranes, crosslinking, energy, fouling, harvesting, porosity, reverse osmosis, sodium chloride, wastewater
- Pressure retarded osmosis (PRO) is an innovative technique to yield osmotic energy. Nevertheless, the PRO performance is exacerbated by the severe membrane fouling occurring within the porous support. It is a potential alternative for sustainable power harvesting to change the membrane orientation from active layer facing draw solution (AL−DS) or PRO mode to active layer facing feed solution (AL−FS) or FO mode for a low-fouling propensity. A novel integral PRO hollow fiber membrane was developed in this work by phase inversion and followed with a facile cross-linking post-treatment. The structure and properties of the resultant membrane were systematically investigated using a series of characterization protocols. The PRO performance of the membrane was studied under various hydraulic pressures at the AL−FS orientation. The results reveal that the substrate with sponge-like structure and relatively dense inner surface can better withstand high pressure in PRO process. Two steps of cross-linking endowed the membrane with a smaller pore size on the outer surface that exhibits high rejection against various inorganic salts. The novel integral membrane can achieve a stable power density output around 4.3Wm−2 at 12 ~ 13bar hydraulic pressure, using a real wastewater reverse osmosis (RO) retentate and 1.0M sodium chloride as the feed and draw stream, correspondingly. This result demonstrates that the PRO operation in the AL−FS orientation (FO mode) offers a significant advantage over the AL−DS orientation (PRO mode) by eliminating the pretreatment of the feed water or/and other measures associated with membrane fouling control in the PRO mode. To implement the PRO operation with the AL−FS orientation, developing a robust membrane with an integral structure is critical. The newly developed integral hollow fiber membrane via chemical cross-linking presents the potential for PRO operation in the AL−FS orientation.