Robust hollow fiber nanofiltration membranes with high stability for wastewater process by dynamic layer-by-layer assembly

The stability of nanofiltration membranes in wastewater treatment represents a primary constraint to their development. In this work, hollow fiber nanofiltration membranes with robust stability were prepared by dynamic layer-by-layer (LBL) assembly of poly (sodium 4-benzenesulfonate) (PSS) and poly (diallyldimethyl ammonium chloride) (PDDA) on the internal surface of poly (ether sulfone) (PES) hollow fiber ultrafiltration membranes. The effect of different coating layers on the membrane performance was assessed, and the findings revealed that the LBL membrane with the optimal coating layer of 2 had a pure water permeance of 9.59 L m⁻² h⁻¹ bar⁻¹ with rejection of 92.11 % and 87.28 % for Na₂SO₄ and MgSO₄, respectively. Consistent pure water permeance was attained even after four cycles of anti-fouling testing, at varied pH values and backwashing. In the actual wastewater treatment, the membrane still maintained a stable permeance, the rejection of Ca²⁺, Mg²⁺ and SO₄²⁻ ions in the wastewater were 81.25 %, 87.81 % and 76.79 % respectively, and the rejection of total organic carbon reached up to 92.90 %. In summary, the membranes that had been developed exhibit economic efficiency and held significant potential for use in industrial production and real wastewater treatment procedures.