Enhanced performance of forward osmosis membranes by incorporating PVDF substrates with hydrophilic nanofillers

Abstract

a b s t r a c tHydrophilic attapulgite (AT) and functional oxidized multi-walled carbon nanotubes (O-MWCNTs) are introduced to the polyvinylidene fluoride (PVDF) substrates to prepare improved performance of thin-film composite (TFC) membranes for forward osmosis (FO) process. The improved hydrophilicity of substrates can make for forming free-defect polyamide (PA) layer and enhance the permeability performance of the as-prepared TFC membranes. The effects of the single or composite addition of two nanofillers on the hydrophilicity, membrane morphology, porosity and mechanical strength of as-prepared substrates are investigated in detail. The results show that hydrophilic, porous and high-flux substrates are prepared and the corresponding TFC membranes own improved water flux and better selectivity. In a word, the PVDF/AT/O-MWCNTs TFC membrane receives a better water flux (J v ) of 28.23 and 20.37 L.m -2 .h -1 and a lower reverse salt flux (J s ) of 9.5 and 6.5 g.m -2 .h -1 in pressure-retarded osmosis (PRO) mode (active layer facing draw solution, AL-DS) and FO mode (active layer facing feed solution, AL-FS). The draw solution and feed solution are 2M NaCl aqueous solution and deionized (DI) water, respectively. This study develops a brand-new way for preparing substrate for FO process.

Lyotropic Liquid Crystal (LLC)-Templated Nanofiltration Membranes by Precisely Administering LLC/Substrate Interfacial Structure

“…A conceptual model proposed by Ghosh and his coworkers [ 22 ] illustrated that the aqueous solution meniscuses in the hydrophilic and hydrophobic substrate pores are concave and convex, respectively, and therefore, more polyamide is formed in the pores of a hydrophilic substrate, as shown in Figure 3 E. The advantage of using a hydrophilic substrate for PA TFC is exhibiting better substrate/active layer adhesion, but a substrate that is too hydrophilic could lead to a thick PA layer and more penetration of PA in the pores [ 25 ]. Additionally, choosing a hydrophobic substrate has limitations due to poor quality layer formation and very low storage of amine monomer on the substrate, which usually exhibits very low rejection [ 100 , 101 ]. The optimum water contact angle values could be between 40° and 60° [ 102 ].…”

“…The advantage of using a hydrophilic substrate for PA TFC is exhibiting better substrate/active layer adhesion, but a substrate that is too hydrophilic could lead to a thick PA layer and more penetration of PA in the pores [25]. Additionally, choosing a hydrophobic substrate has limitations due to poor quality layer formation and very low storage of amine monomer on the substrate, which usually exhibits very low rejection [100,101]. The optimum water contact angle values could be between 40 • and 60 • [102].…”