Sodium lignosulfonate modified loose nanofiltration membranes with excellent antifouling performance for dye/salt separation

Loose nanofiltration (LNF) membrane, which combines high permeate flux with excellent separation selectivity, is an ideal technical approach for efficient separation of dyes and inorganic salts. Here, sodium lignosulfonate (SL) as the aqueous phase additive, a novel polyamide-based LNF membrane with a thin polyamide separation layer was fabricated by delaying the interfacial polymerization (IP) reaction of piperazine. The resulting membrane exhibits excellent pure water permeance (82.77 LMH bar −1 ), impressive dye rejection of >99 % and low rejection for inorganic salts (Na₂SO₄, MgSO₄, MgCl₂, and NaCl, all below 10 %), demonstrating extremely high dye/salt selectivity (Congo Red/Na₂SO₄: 258.5). Additionally, the membrane maintained a CR rejection exceeding 99 % during continuous 40 h treatment of CR mixed salt solutions. As-prepared membrane exhibits excellent antifouling performance, with a flux recovery rate of up to 96.7 %, which is considerably higher than that of commercial NF270 membranes. With the help of the introduction of SL, a SL-decorated LNF with high hydrophilicity and surface negative charge promises great application potential in the field of textile wastewater treatment.