Alicyclic polyamide nanofilms with asymmetric structure for Cl-/SO42- separation

Abstract

Separation of mixed ion, especially Cl- and SO42-, is essential for reduced energy consumption and achievement of the minimal or zero-liquid discharge. Membrane technology has attracted significant attention in this respect owing to its good system coupling and maturity. However, it remains challenging to fabricate highly selective nanofilm with fine-tuning pore and structure that is suitable for the separation of Cl- and SO42-. Herein, we report an asymmetric alicyclic polyamide nanofilm with enhanced interconnectivity pore by manipulating the molecular geometry structure, composed of the porous aromatic polyamide dendrimer layer, and the dense alicyclic polyamide layer with hollow stripes. This resulted membrane shows a 107.14% separation rate of Cl- and SO42-, and a water flux (for Na2SO4) of ~2.2 times that of the pristine polyamide membrane. We estimate this fine-tuning pore approach resulting from alicyclic structure also might be employed in other separation membranes such as gas, solvent or neutral molecules.

Aminal‐Linked Covalent Organic Framework Membranes Achieve Superior Ion Selectivity

“…[10] However, commercial polyamide-based NF membranes generally display somewhat low water permeances of below 10 L m −2 h −1 bar −1 and Cl − /SO 4 2− selectivity below 35. [11] Existing research on polyamide-based thin-film nanocomposite (TFN) membranes and polyamide-based thin-film composite (TFC) membranes is focused predominately on strategies to coordinate the trade-off between water permeance and salt rejection. [12] However, the development of NF membranes with high permeance and ion selectivity remains a major challenge due to the size similarity between monovalent and divalent ions, and the heterogenous pore size distribution of polyamide-based membranes.…”

Solvation‐amination‐synergy that neutralizes interfacially polymerized membranes for ultrahigh selective nanofiltration

“…IP is a rapid (~seconds) reaction process, whose kinetics are challenging to be controlled 11,12 . In a typical NF membrane formation process, amines diffuse from the water inside the porous substrate into the oil phase and polycondensate with acyl chlorides, forming a polyamide network 13–15 . The amine diffusion has been controlled well by adding inhibitors to the aqueous phase, such as polyvinyl alcohol 16 and cucurbituril, 17 which constructs the high‐performance NF membranes with Turing structures.…”

“…11,12 In a typical NF membrane formation process, amines diffuse from the water inside the porous substrate into the oil phase and polycondensate with acyl chlorides, forming a polyamide network. [13][14][15] The amine diffusion has been controlled well by adding inhibitors to the aqueous phase, such as polyvinyl alcohol 16 and cucurbituril, 17 which constructs the highperformance NF membranes with Turing structures. However, the nascent polymerized layer impedes the transport of amines across the film, so that the excess acyl chlorides do not participate in the reaction.…”