Novel thin-film composite tri-bore hollow fiber membrane fabrication for forward osmosis

We have developed novel tri-bore thin-film composite (TFC) hollow fiber (HF) membranes for forward osmosis (FO) processes by employing a specially designed tri-bore blossom spinneret. The resultant hollow fibers exhibit evenly-distributed three inner bores with an either round or triangle outer geometry. The newly developed triangle tri-bore hollow fibers have impressive mechanical strength with enhanced permeation properties better than the round ones. Further efforts were given to investigate the effects of glycerol treatment and surfactant concentration during the interfacial polymerization. The new developed TFC tri-bore HF membranes exhibit high water fluxes of 50.5 LMH and 11.8 LMH with salt leakages as low as 3.5 gMH and 2.5 gMH, in pressure retarded osmosis (PRO) and FO modes, respectively, when using 2 M NaCl as the draw solution and pure water as the feed. The potential of using the triangle TFC membrane for desalination is also investigated. It could reach a water flux of 5.8 LMH using a 2 M NaCl draw solution and a model seawater solution as the feed. In addition, much more fibers can be packed in a FO module if TFC tri-bore HF membranes have a triangle shape instead of a round one. Theoretical calculations suggest that water output of the module consisting of triangle membranes would double the one comprising round membranes at a 40% packing density. This may enlighten the advantages of triangle tri-bore configuration for FO applications.