One-step fabrication of acid-resistant tight ultrafiltration membrane for efficient dye/salt separation at high salinity

A key challenge in textile wastewater treatment lies in developing membranes’ tolerance both under acidic and high-salinity conditions. Taking advantage of the acid stability of amidine and reactivity of polyacrylonitrile (PAN), an innovative tight ultrafiltration (TUF) membrane with dual acid and salt resistance was prepared via the in-situ crosslinking of PAN with diamines. The optimized TUF membrane (PAN-HMDA) was simply prepared from solution of PAN crosslinked by 1,6-hexamethylenediamine (HMDA) through non-solvent induced phase separation (NIPS). Respective rejections of >99.5% and ∼5% for dyes exceeding 460 Da in molecular weight and salts (MgSO 4 , NaCl, and Na 2 SO 4 ) were achieved by PAN-HMDA with permeance of 20.5 LMH/bar. Notably, excellent Congo Red/salt separation selectivity was demonstrated by PAN-HMDA (α CR/MgCl2  = 175.2, α CR/MgSO4  = 316.7, α CR/NaCl  = 318.0, α CR/Na2SO4  = 963.0). Stability tests confirmed its robust performance under harsh conditions, maintaining >99.4% rejection of CR after 60-day immersion in 2 M H 2 SO 4 or 2 M HCl. Meanwhile, stable performance was maintained after 48-h continuous filtration in 1 M H 2 SO 4 and under 80 g/L high-salinity conditions. Moreover, after simple washing with DI water, the FRR of PAN-HMDA for SA, HA and BSA were stabilized at 88.1%, 96.6% and 82.5%, respectively, showing considerable potential in treating real textile wastewater. This work paved a new way for efficient treatment of acidic and high-salinity textile wastewater.