Design and fabrication of thin film composite organic solvent nanofiltration membranes by making use of the chirality of trans-1,2-diaminocyclohexane; characterization and performance studies

Abstract

The current work has been focused on using 1,2-diamine with a chirality having trans stereochemistry where two amino (NH₂) groups are trans to each other on a cyclohexane ring. The thin film composite (TFC) polyamide (PA) membrane was fabricated on a hydrazine hydrate crosslinked polyacrylonitrile (HH-PAN) support by interfacial polymerization (IP) reaction between trans-1,2-diamniocyclohexane (Tans-Amine; t-DAC) and trimesoyl chloride (TMC). Owing to the trans-position of the two vicinal amino groups occupying opposite positions on the chair conformation of t-DAC, a dense and crosslinked active layer was grown on the ultrafiltration (UF) HH-PAN support. Organic solvent nanofiltration (OSN) experiments showed high rejection rates of Trans-Amine-TMC@HH-PAN TFC membrane for model solutes such as dyes with a molecular size of ≈ 700 Da were completely rejected. Among polar solvents, methanol showed a permeance of 4.2 L m⁻² h⁻¹ bar⁻¹ whereas among non-polar solvents, toluene showed a permeance of 6.4 L m⁻² h⁻¹ bar⁻¹. Current work shows the significance of making use of the chirality of reacting monomers during IP for developing promising PA TFC OSN membranes.