Abstract
Polyamide (PA) thin-film composite (TFC) membranes are commonly applied in reversed osmosis (RO) and nanofiltration (NF) applications due to their thin, dense top-layer, and high selectivity. Recently, the conventional organic phase (i.e., hexane) during interfacial polymerization (IP) was replaced by less toxic ionic liquids (ILs) which led to excellent membrane performances. As the high price of most ILs limits their up-scaling, the potential use of inexpensive Aliquat was investigated in this study. The thin-film composite (TFC) membranes were optimized to remove flavor compounds, i.e., ethyl acetate (EA) and isoamyl acetate (IA), from a fermentation broth. A multi-parameter optimization was set-up involving type of support, reaction time for IP, water content of Aliquat, and concentration of both monomers m-phenylenediamine (MPD) and trimesoylchloride (TMC). The membranes prepared using Aliquat showed similar fluxes as those prepared from a reference IL 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C4mpyr][Tf2N]) but with better EA and IA retentions, even better than for a commercial RO membrane (GEA type AF). Finally, the recently introduced epoxide-curing of Bisphenol A diglycidyl ether (BADGE) with 1,6-hexanediamine (HDA) was investigated using Aliquat as organic phase. It is the first time this type of IP was performed in combination with an IL as organic phase. The resulting membrane was used in the filtration of a 35 µM Rose Bengal (RB) in 20 wt% dimethylformamide/ water (DMF/H2O) feed mixture. A well-crosslinked poly(β-alkanolamine) film was obtained with a > 97% retention.
Highlights
Thin film composite (TFC) membranes consist of an ultrathin functional layer on top of a porous support [1,2,3,4]
Common monomers used are meta-phenylene diamine (MPD) for the aqueous phase and trimesoyl chloride (TMC) for the organic phase, generating a very thin, dense, and highly cross-linked polyamide (PA) top-layer (Figure 2). These membranes are mostly applied in pressure-driven membrane processes, such as reverse osmosis (RO), nanofiltration (NF), or solvent-tolerant or solvent-resistant nanofiltration (STNF and SRNF, respectively), to retain low molecular weight components [4,5,6,7,8,9]
When selecting an ionic liquids (ILs) as organic phase, following important properties of the IL are considered to influence the interfacial polymerization (IP) process: (i) water immiscibility to create a biphasic system during IP, (ii) dynamic viscosity (η) and surface tension (σ) which influence the solubility and diffusivity of the amine monomer in the reaction zone
Summary
Thin film composite (TFC) membranes consist of an ultrathin functional layer on top of a porous support [1,2,3,4]. Common monomers used are meta-phenylene diamine (MPD) for the aqueous phase and trimesoyl chloride (TMC) for the organic phase, generating a very thin, dense, and highly cross-linked polyamide (PA) top-layer (Figure 2). These membranes are mostly applied in pressure-driven membrane processes, such as reverse osmosis (RO), nanofiltration (NF), or solvent-tolerant or solvent-resistant nanofiltration (STNF and SRNF, respectively), to retain low molecular weight components [4,5,6,7,8,9]. Commercial PA-TFC membranes show very high salt rejections of 99.4–99.8% [4]
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