Facile Preparation of Antifouling Hollow Fiber Membranes for Sustainable Osmotic Power Generation

Organic fouling in the membrane support is one of the major causes for the flux decline and low efficiency in the pressure retarded osmosis (PRO) process for osmotic power generation, especially when the fouling is complicated by inorganic salt ions. A facile method to fabricate antifouling hollow fiber membranes was demonstrated in this study, which employed the readily available poly(vinyl alcohol) (PVA) as the modification agent. The poly(ether sulfone) (PES) support for the thin film composite (TFC) membranes was first coated by polydopamine (PDA) and then coated with PVA with the aid of glutaraldehyde (GA). PDA was found to detach from the support in the first 2 h and gradually stabilized at pH 2, verifying its applicability for PRO processes. In addition, the existence of a PVA layer was confirmed by X-ray photoelectron spectroscopy. It is important to note that by controlling the reaction conditions, the water flux and salt reverse flux in the PRO process were not sacrificed, proving that the modification can well maintain the porous structure of the support. The modified membranes showed significantly improved fouling resistance to not only alginate but also complex alginate-calcium solutions. The water flux remained ∼80% instead of ∼64% in the latter case. Moreover, much of the fouling was converted from irreversible to reversible, which helped enhance the efficiency of physical cleaning to ∼90%, and hence improved the sustainability of the PRO process.