Lysine‐Functionalized Boehmite/Polysulfone Nanofiltration Membranes with Enhanced Dye Rejection and Salt Separation Performance

ABSTRACT

Polysulfone (PSF) nanofiltration membranes incorporating L‐lysine‐functionalized boehmite nanoparticles (Lys‐BM) were developed to improve dye and salt removal from water. Lysine functionalization enhanced nanoparticle dispersion and compatibility within the PSF matrix. Membranes containing 0–1 wt.% Lys‐BM were fabricated by phase inversion and characterized using XRD, FT‐IR, TGA, and SEM. The membranes exhibited an asymmetric structure with a dense skin layer, porous sublayer, and finger‐like pores. The 0.5 wt.% Lys‐BM membrane showed the best overall performance, while higher loading (1 wt.%) caused minor agglomeration and reduced efficiency. Lys‐BM incorporation significantly enhanced membrane hydrophilicity, reducing the contact angle from 65.06° to 50.31°, while increasing porosity and approximately doubling pure water flux. Antifouling properties also improved substantially, with flux recovery ratio increasing from 52.85% for pristine PSF to 92.32%. The modified membranes achieved >95% Methylene Blue rejection and >90% MgSO4 and MgCl2 rejection. Zeta‐potential analysis confirmed surface charge reversal following Lys‐BM incorporation, supporting improved separation performance. Moreover, long‐term cross‐flow filtration showed that the optimized membrane retained 88–90% of its initial flux, compared with approximately 60% for pristine PSF. Overall, Lys‐BM modification provides an effective strategy for producing high‐performance and operationally stable nanofiltration membranes for advanced water treatment.