Modification of Nanofiber Support Layer for Thin Film Composite Forward Osmosis Membranes via Layer-By-Layer Polyelectrolyte Deposition

Abstract

Electrospun nanofiber-supported thin film composite membranes are among the most promising membranes for seawater desalination via forward osmosis. In this study, a high-performance electrospun polyvinylidenefluoride (PVDF) nanofiber-supported TFC membrane was successfully fabricated after molecular layer-by-layer polyelectrolyte deposition. Negatively-charged electrospun polyacrylic acid (PAA) nanofibers were deposited on electrospun PVDF nanofibers to form a support layer consisted of PVDF and PAA nanofibers. This resulted to a more hydrophilic support compared to the plain PVDF nanofiber support. The PVDF-PAA nanofiber support then underwent a layer-by-layer deposition of polyethylenimine (PEI) and PAA to form a polyelectrolyte layer on the nanofiber surface prior to interfacial polymerization, which forms the selective polyamide layer of TFC membranes. The resultant PVDF-LbL TFC membrane exhibited enhanced hydrophilicity and porosity, without sacrificing mechanical strength. As a result, it showed high pure water permeability and low structural parameter values of 4.12 Lm and 221 µm, respectively, significantly better compared to commercial FO membrane. Layer-by-layer deposition of polyelectrolyte is therefore a useful and practical modification method for fabrication of high performance nanofiber-supported TFC membrane.

Fabrication of a graphene oxide-embedded separation bilayer composite nanofiltration membrane using a combination of layer-by-layer self-assembly and interfacial polymerization

“…Compared with a pristine blank PVDF membrane, the pure water flux was increased by 119%, and the rejection rate of NaCl was increased from 95.17% to 96.43%. 11 Ormanci-Acar et al used a positively charged hollow fiber membrane as the support layer, and firstly generated a poly(diallyldimethylammonium chloride)/poly(4styrene sulfonate) (PDDA/PSS) or PEI/PSS PE interlayer containing 3.5 bilayers by LbL self-assembly, and then a top functional layer of PA was generated on the PE layer using the IP method. The obtained composite hollow fiber RO membrane increased the retention of NaCl from 94% to 97% and the removal rate of micro-pollutants increased from 96% to 98%, although the permeability decreased slightly (from 0.9 L m −2 h −1 bar −1 to 0.7 L m −2 h −1 bar −1 ).…”

Development of forward osmosis membranes modified by cross-linked layer by layer assembly for brackish water desalination

“…This might be due to a trade-off between water flux and reverse solute flux. Gonzales [13] proposed a novel LBL method by coating the PVDF-PAA nanofiber support layer with polyethylenimine (PEI) and PAA to construct a polyelectrolyte layer underneath the polyamide selective layer. The hydrophilicity and porosity of the novel membrane were significantly improved resulting in superior water permeation and low structural parameter of 221 µ m. The water flux was recorded as 37.8 and 45.2 LMH and the reverse solute flux as 4.5 and 4.9 g m -2 h -1 when using 1.5 M NaCl and 2.0 M NaCl as the DS and DIwater as the FS.…”

Development of thin-film composite membrane for forward osmosis process

“…In addition to perm-selectivity, FO membranes should possess good mechanical properties to maintain membrane integrity and ensure stable operations [134][135][136][137]. In order to minimize the impact of ICP on the performance of asymmetric membranes in the FO process, the support layer of the membrane has to be thin, highly porous and comprises highly interconnected pore structures.…”