Facile fabrication of tight polyethersulfone-based ultrafiltration membranes for dye/salt separation via phase separation

Tight ultrafiltration (UF) membranes and loose nanofiltration membranes demonstrate significant potential for the efficient separation of dye/salt wastewater mixtures. However, the development of high-performance membranes suitable for industrial-scale production remains a challenge. In this study, a self-supporting tight UF membrane was fabricated for the separation of dyes and salts using a simple phase separation method. A series of carboxylate-functionalized polyaromatic ether sulfone (PAES) polymers with varying carboxylate (−COO − ) content were synthesized as hydrophilic additives to prepare polyethersulfone (PES) blend membranes. The effects of the carboxylate content in the synthesized polymer, additive blend ratio, and dope concentration on the morphology, mechanical strength, hydrophilicity, surface composition, zeta potential, and permeation and rejection performances were systematically investigated. Experimental results revealed that the − COO − content in the polymer additive is the dominant factor for achieving tight UF membranes suitable for dye/salt separation, rather than the dope concentration or blend ratio. The optimal membrane exhibited a desirable pure water permeability of 64 L·m −2 ·h −1 ·bar −1 , with a high rejection rate of 96 % for Congo red dye and a low salt rejection rate of 9.0 % for Na 2 SO 4 . Furthermore, the membrane demonstrates excellent long-term filtration stability and considerable anti-fouling properties against bovine serum albumin solutions, highlighting its promising application potential.