ساخت ماژول مقیاس آزمایشی از غشای فیبر توخالی کامپوزیتی نازک برای فرآیندهای اسمز معکوس Fabrication of a pilot scale module of thin film composite hollow fiber membrane for osmotic pressure-driven processes

INTRODUCTION A hollow fiber (HF) membrane holds attractions with respect to structural advantages over a flat sheet membrane in packing density, spacer-free modulation, and diversity of module design.1 Since HFs have been produced by a nonsolvent or a thermal induced phase separation, they (with pore sizes larger than several tens of nanometers) have been typically used for size sieving filtration processes (e.g., microfiltration, ultra-microfiltration, membrane bioreactor, etc.).2–4 Once a coating process is introduced on HFs, it can be extended to a variety of separation processes [e.g., nanofilration, gas separation, forward osmosis (FO), or pressure-retarded osmosis].5–9 Among dense-coating materials based on solution-diffusion theory, polyamide (PA) has gained significant attention because its high performance has been proven by industry fields (i.e., reverse osmosis, RO) for water and wastewater treatment processes due to water crisis.10–13 However, there is no commercialized PA-HF module for seawater desalination because of limited operating pressures up to 70 bars. Recently, other PA-HFs for osmotic pressure-driven (OPD) process such as FO1,7 or pressure-retarded osmosis3,8 have been more intensive, because those are operated at relatively low operating pressures, and OPD/RO hybrid systems could reduce energy consumption compared to independent RO systems.1,2,5,8,9,14–18 PA thin film composites (TFC) are synthesized by an interfacial polymerization (IP) method. Basically, whatever the structure or geometry of supports are, three major steps must be performed in consecutive order: first, wetting with an amine aqueous solution; second, removing the excess amine aqueous solution; and finally, formation of an interface zone using immiscible acyl chloride solutions. The primary factors to consider for defectfree PA selective layers are the geometric position (e.g., interface zone formed above or below the top surface of a support layer) and the formation uniformity (e.g., continuous interface) of an interface zone on the porous supports.19 The interface zone for flat-sheet porous supports is relatively simply flattened by mechanical squeezing using a rubber roller or air blowing to remove excess presoaked solutions.