(635f) Braided-Reinforced Thin Film Composite (TFC) Nanofiltration Hollow Fiber Membranes

Hollow fiber membranes are attractive for use in water treatment processes because of their high packing density relative to flat sheet and spiral wound configurations. They are also easily submersed in tanks for bioreactor applications. For water purification in particular, they are commonly use in microfiltration (MF) an ultrafiltration (UF) applications. To enable low pressure drop in fiber lumens, inner diameters of these fibers can be rather large, thus limiting the pressure tolerance of these membranes. Low pressure tolerance of larger capillary fibers has largely excluded the use of hollow fiber from higher pressure membrane processes reverse osmosis (RO) and nanofiltration (NF) except for cases where integrated asymmetric membranes are considered. Use of the thin-film composite (TFC) platform with polyamide based selective layers, while common with flat sheet membranes for RO an NF, have not found commercial success and have largely been relegated to the academic community for studies on forward osmosis (FO). In this work, we show that hollow fiber TFC membranes can be made for higher pressure applications. To address the pressure tolerance issues, we build our TFC using a commercial hollow fiber PVDF UF membrane that is reinforced with an embedded braid as a support. Onto this support is formed the selective barrier layer in-situ­ that from piperazine (PIP) an trimesoyl chloride (TMC) monomers. Through careful optimization the monomer concentration and reaction conditions, we have demonstrated softening with a 89 % MgSO₄ rejection and a permeance of 8 LMH/bar. This work represents the first time such a reinforce hollow fiber membrane has been used as a support for a TFC membrane and could broaden opportunities for hollow fiber membranes in processes where salt selection (RO, pressure retarded osmosis) is required.