Aminated substrate based thin film composite nanofiltration membrane with high separation performance by chemically inhibiting the intrusion of polyamide

In this study, aminated PES substrates were prepared and applied for the investigation on the interfacial polymerization of piperazine (PIP) and 1,3,5-benzenetricarbonyl trichloride (TMC) thereon, with relatively low (PIP: 0.1 wt%, TMC: 0.01 wt%) and high (PIP: 0.5 wt%, TMC: 0.05 wt%) monomer concentration. In low concentration condition, thin, dense, and defect-free selective layers were synthesized on the aminated substrates. In high concentration condition, thin film composite (TFC) membranes with thin selective layers and without the intrusion of polyamide into the substrates were formed. The reactions between the aminated substrate and selective layer were confirmed by XPS analysis on the back surface of the selective layer. The aminated substrates based TFC membrane (TFC-48-H) showed high separation performance, including high water permeability as 20.6 ± 0.1 L/m2 h bar and high Na2SO4 to NaCl selectivity as 86.7, indicating the application potential in divalent to monovalent salts separation process. A conceptual model was proposed to highlight the role of the aminated substrates in the interfacial polymerization process as (1) PIP loaders, (2) PIP diffusion hinders, and (3) polyamide intrusion chemically inhibitors in high monomer concentration condition.