Polyester-amide nanofiltration membranes tailored via doping with D-mannitol increased mono−/divalent anion selectivity and chlorine resistance

Conventional polyamide (PA) nanofiltration (NF) membranes suffer from insufficient mono−/divalent anion selectivity and poor chlorine resistance, limiting their water treatment applications. Herein, a polyester–amide (PEA) NF membrane was fabricated via interfacial polymerization using piperazine and hydroxyl-rich D-mannitol as aqueous comonomers. Compared with the traditional PA membrane, the optimal PEA membrane exhibited higher surface roughness, greater thickness, looser structure, stronger hydrophilicity, and higher electronegativity. Specifically, the optimal PEA membrane delivered a water permeability of 21.9 L⋅m −2 ⋅h −1 ⋅bar −1 and an outstanding NaCl/Na 2 SO 4 selectivity of 68.4. This optimal PEA membrane maintained stable performance under chlorination across a wide pH range and showed excellent alkali stability after 20 h in NaOH solution at pH = 12.0. Furthermore, the optimal PEA membrane exhibited better antifouling properties with smaller decline in flux and greater flux recovery. Additionally, stable flux and rejection were observed for the optimal PEA membrane over 28 days of continuous cross-flow filtration. This work offers a facile strategy to develop high-performance PEA NF membranes with increased anion selectivity and chlorine resistance.