Bio‐Surfactant (Sophorolipids) Pre‐Coating for Thin‐Film Composite Membranes With Enhanced Dye Separation Performance

With increasing concerns over resource depletion and environmental pollution, resource recycling has emerged as a key strategy for promoting sustainable development. Nanofiltration (NF) membranes, characterized by their well‐defined pore size and surface charge, offer significant potential for small‐molecule separation and resource recovery. However, conventional polyamide (PA) NF membranes prepared via interfacial polymerization often exhibit dense selective layers, resulting in limited permeability and constrained practical application. In this study, a cost‐effective and biodegradable biosurfactant, sophorolipids, was employed as a pre‐coating agent on porous polyethersulfone (PES) substrates to modify the interfacial polymerization process. The resulting NF membranes demonstrated a nearly fivefold increase in water permeability (from 5 to 25 L m −2 h −1 bar −1 ) while maintaining excellent selectivity—achieving high rejection of large molecular dyes and low rejection of small molecular dyes. The membranes effectively separated dye mixtures containing Alcian blue (MW: 1298.86 g·mol −1 ) and crystal violet (MW: 407.98 g·mol −1 ), as well as dye/salt mixtures with sodium chloride, exhibiting outstanding dye/salt selectivity. These results highlight the strong potential of sophorolipids‐modified NF membranes for the sustainable treatment and resource recovery of textile dyeing wastewater.