Novel macrocyclic polyamines regulated nanofiltration membranes: Towards efficient micropollutants removal and molecular separation

The discharge of wastewater containing organic micropollutants not only causes severe environmental pollution, but also exacerbates the scarcity of freshwater resources and poses a serious threat to human health. The nanofiltration (NF) membrane has unique advantages and obvious energy-saving effects in the demineralization of organic micropollutants. Poly(piperazine) amide NF membrane exhibits the poor organic micropollutants/salt selectivity and low water permeance. Therefore, developing a novel NF membrane with high water permeance and superior selectivity is of significance. In this study, a loose nanofiltration (LNF) membrane is fabricated by interfacial polymerization with 1, 4, 7, 10-tetraazacyclododecane (Cyclen) as a new aqueous phase monomer to modulate the polyamide microstructure. The steric structure of Cyclen is larger than that of PIP, and the steric hindrance increases, resulting in a low stacking density of the formed polyamide polymer. Compared with the PIP-based NF membrane, the fabricated Cyclen-TMC LNF membrane has a smoother surface, a higher density of carboxyl groups, and a lower degree of cross-linking. The Cyclen-TMC membrane exhibits the considerable water permeance, with the corresponding rejection of 99.9% and 92.7% for methyl blue and tetracycline (pH = 9), respectively, while maintaining a low rejection for monovalent salts (e.g., 4.5% for NaCl). Furthermore, the LNF membrane shows a superior anti-fouling performance with the relatively smooth, highly negatively charged surface and low operation pressure. The novel LNF membrane exhibits a high potential for textile and pharmaceutical wastewater treatment. This study provides a new candidate to regulate the separation performance of NF membranes using new aqueous monomers.