Interfacial polymerization-based NF/LNF membranes for selective dye/salt fractionation: From dye properties and membrane design to industrial translation

Driven by the increasing demand for green and low-carbon manufacturing and the pursuit of near-zero liquid discharge (NZLD), the valorization of hypersaline textile wastewater streams through the simultaneous reclamation of high-purity salts, residual dyes, and purified water has emerged as a critical frontier in environmental engineering. Nanofiltration (NF) and loose nanofiltration (LNF) membranes, which rely on synergistic mechanisms such as size exclusion and electrostatic interactions, have demonstrated strong potential for efficient dye/salt separation and resource recovery. This review comprehensively summarizes recent advances and application prospects of NF/LNF membranes for textile wastewater treatment. First, the physicochemical characteristics of major dye classes are discussed, with emphasis on their influence on membrane transport behavior and separation performance. Subsequently, the underlying separation mechanisms, including steric hindrance, Donnan exclusion, dielectric effects, and dye-aggregation-induced sieving, are systematically analyzed. Particular attention is given to interfacial polymerization (IP)-based strategies for tailoring polyamide NF/LNF membranes, including monomer selection, additive incorporation, and nanomaterial integration. Moreover, permeance–dye/salt selectivity plots were established for representative NF/LNF membranes to comparatively evaluate membrane performance and application potential under different fabrication strategies. In addition, the relationships between membrane pore structures, surface physicochemical properties, and separation performance are systematically summarized. Finally, future perspectives for improving membrane and system performance are proposed from mechanistic, material, and system-level viewpoints. Overall, this review provides valuable guidance for the rational design of next-generation NF/LNF membranes and their practical implementation for sustainable dye/salt separation, resource recovery, and water reuse.