Cellulose Acetate-Based Polyamide Nanofiltration Membranes by Diethylenetriamine-Assisted Interfacial Polymerization for Effective Removal of Dyes and Salt Ions

Abstract

In this study, cellulose acetate (CA)-based polyamide (PA) nanofiltration membranes (CA-NF-2/0.4) with enhanced antifouling and separation performance were prepared through the interfacial polymerization of diethylenetriamine (DETA) and 1,3,5-benzenetricarbonyl chloride (TMC) for the effective removal of dyes and salt ions. Benefiting from the three reaction sites (primary and secondary amino groups) of DETA, a PA layer with a three-dimensional network structure formed on the CA substrate, imparting the CA-NF-2/0.4 membranes with a strong negative charge (−24.8 mV at pH 7) and a defect-free morphological feature. Consequently, the CA-NF-2/0.4 membranes exhibited high removal efficiencies for various dyes (99% for Rose Bengal and Congo Red, 95.5% for Methyl Orange, and 96.1% for Methylene Blue), as well as various monovalent and divalent salts, including MgCl₂ (84.2%), Na₂SO₄ (92.7%), MgSO₄ (91.8%), and NaCl (54.1%). Additionally, the CA-NF-2/0.4 membranes demonstrated excellent antifouling properties [the flux recovery ratio (flux recovery rate > 98.5%), long-term durability, and stability under high operational pressures and salt concentrations] due to their good hydrophilicity (water contact angle of 39.8°) and the hydrogen bonding interaction between the active amine groups of DETA and the –OH groups of the CA support layer. This study presents an effective method for fabricating cellulose-based NF membranes with high separation and antifouling performance, offering insights into the high-value utilization of cellulose-based materials.