Modulating hydrophobicity of composite polyamide membranes to enhance the organic solvent nanofiltration

Interfacially Polymerized Thin‐Film Composite Membranes for Organic Solvent Nanofiltration

“…[ 2 ] Various polymers have been explored as the substrate of a TFC membrane, as listed in Table 1 . Conventional polymers, such as polyetherimide (PEI), [ 24,75,76–79 ] polysulfone (PSf), [ 83 ] polyethersulfone (PES), [ 84 ] PEEK, [ 47 ] and poly(m‐phenylene isophthalamide) (PMIA) [ 81,82 ] are generally used as the substrate matrix without covalent crosslinking because of the absence of active covalent crosslinking sites in the macromolecular backbone chains. Consequently, the drawbacks of the non‐cross‐linked polymeric‐based TFC membranes can be identified.…”

“…Nanofiltration experiments demonstrated that the TFC membrane had an adequate separation performance in DMSO. Based on the cross‐linked PEI substrate, PEI TFC [ 77 ] and PA TFC [ 24,90 ] nanofilms were also reported with good resistance in mild solvents and strong solvents such as acetone or THF.…”

“…The typical example is the aromatic diamine of m ‐phenylenediamine (MPD). Increasing the aromatic rings could reduce the solubility of diamines in aqueous solution, such as 4,4′‐diaminodiphenylme‐thane [ 24 ] and 4,4′‐oxydianiline. [ 77 ] Aromatic amines with more than two benzene rings, therefore, have to be dissolved in an organic solvent (methanol) or DMF/water mixture prior to the IP reaction.…”

“…also compared two routes to modulating a new PA surface hydrophilicity by grafting two different chemicals 4,4′‐diaminodiphenylme‐thane and 2,2,2‐trifluoroethylamine, respectively. [ 24 ] The former chemical contains abundant ‐OH groups while the latter contains ‐F groups. As expected, the hydrophilic membrane had an enhanced permeance for polar solvents, like methanol, ethanol, and acetone, while the hydrophobic membrane had an increased permeance for lower polarity solvents, such as THF and ethyl acetate.…”

“…[ 20 ] Additionally, the thickness, pore size/free volume, microporosity, and surface chemistry of the selective layer of a composite membrane also play a significant role in solvent transport. [ 8,21–24 ] More details about the effects of the membrane surface properties such as surface charge, surface hydrophilicity/hydrophobicity, and surface roughness on the separation performance of OSN can be found in a systematic review by Amirilargani et al. [ 25 ] Despite the better understanding of the mechanisms in OSN membrane separation, devising a solvent stable, scalable membrane with high permeability and excellent selectivity is still a continuous challenge for energy‐efficient membrane separations.…”