Polyethyleneimine‐Mediated Polyamide Composite Membrane with High Perm‐Selectivity for Forward Osmosis

Abstract

Thin‐film composite (TFC) membranes comprised of a polyamide (PA) selective layer upon a porous substrate dominate the forward osmosis (FO) membrane market. However, further improvement of perm‐selectivity still remains a great challenge. Herein, a polyethyleneimine (PEI) interlayer is intentionally designed prior to interfacial polymerization (IP) to tailor the PA layer, which thus improves the separation performance. The PEI interlayer not only improves the substrate hydrophilicity for adsorbing more diamine monomer and controlling its release rate, but also participates in IP reaction by crosslinking with acyl chloride (TMC). Furthermore, it can decrease the electronegativity of the substrate for decreasing reverse salt diffusion. Consequently, a denser, thinner and smoother PA layer is formed due to the uniform distribution, controllable release of diamine monomer and the extra crosslinking between PEI and TMC. Furthermore, the PA layer becomes more hydrophilic with PEI involvement. As a result, the asprepared TFC membrane exhibits a favorable water flux of 16.1 L m−2 h−1 and an extremely low reverse salt flux (1.25 g m−2 h−1). Meanwhile, it achieves an excellent perm‐selectivity with a ratio of water to salt permeability coefficient of 8.25 bar−1. Moreover, it exhibits an outstanding antifouling capacity. The work sheds light on fabricating high perm‐selective membranes for desalination.

Recent advances in thin film nanocomposite membranes containing an interlayer (TFNi): fabrication, applications, characterization and perspectives

“…This approach enabled the substrate to adsorb more amine monomers from aqueous solution and control the IP reaction with the release rate. 53 …”

“…51 PEI deposition of a carboxylated polyacrylonitrile (PAN) substrate was used to control the subsequent IP reaction by modulating the diffusion rate of the -NH 2 monomer with PEI. 53,54 In addition, the hydrophilic interlayer formed by PEI and PDA codeposition also controls the subsequent IP reaction. 47,48,55,56 Dopamine self-polymerizes into PDA under weakly alkaline conditions at pH = 8, and the surface of the substrate forms a stable surface coating.…”

“…This approach enabled the substrate to adsorb more amine monomers from aqueous solution and control the IP reaction with the release rate. 53 TpPa is a COF, and it is oen used in membrane separations because can be synthesized at normal temperature and pressure and loaded onto the surface of the substrate through in situ growth without affecting the membrane structure. [66][67][68][69][70][71] Wang et al constructed structurally complete and stable TpPa interlayers on a PI substrate in a manner similar to that reported by Yang et al to control the IP process.…”

A Comprehensive Review of Performance of Polyacrylonitrile-Based Membranes for Forward Osmosis Water Separation and Purification Process

“…In another study, the TFC membrane of a commercial PAN substrate exhibited a favorable water permeability flux of 16.1, LMH, and an extremely low reverse salt flux (1.25 gMH). Within this, polyethyleneimine (PEI) was utilized as an interlayer prior to the IP reaction to tailor the PA layer, which thus improved TFC-PAN membrane perm-selectivity performance due to the formed denser, thinner, and smoother PA layer [154]. The same modification technique was followed by Farman et al [155], in which the modified membrane showed a reasonable performance for concentrating the orange juice via the FO process.…”

Construction of facilitated mass transfer composite membranes with triple-layer water nanochannel architecture for forward osmosis process using cGO-coated polysulfone separation membrane as the substrate

“…In addition, the hydrophilic modification of the substrate surface by coating method can also enhance the permeability of the substrate without changing its pore structure in the matrix. At present, researchers have successfully coated polyethyleneimine (PEI) on PAN, 24 polydopamine (PDA) on PVC, 25 carbon nanotubes (CNTs) on PES, 12 and PDA nanoparticles on PAN nanofibers 26 in order to enhance the hydrophilicity and permeability of the substrate.…”