Brominated monomer-enabled polyester tight ultrafiltration membranes for efficient dye/salt separation and anti-fouling performance

Tight ultrafiltration (TUF) membranes with rational structures exhibited considerable promise in the selective dye/salt fractionation during textile wastewater desalination. However, conventional polymeric ultrafiltration membranes suffer from severe fouling and limited dye/salt selectivity. Herein, we employed a controllable interfacial polymerization (IP) strategy using a brominated monomer, 2,6-dibromo-3,5-dihydroxybenzoic acid (DBHBA), as an aqueous monomer to react with trimesoyl chloride (TMC) for the fabrication of a series of polyester-based TUF membranes. The incorporation of bromine substituents into DBHBA induced electron-withdrawing and steric effects, which reduced its reactivity with TMC, thereby enabling it to construct a loose and hydrophilic polyester active layer with precisely tunable pore structures. The optimized DBHBA TUF membrane exhibited an exceptional water permeance of 92.9 L m −2  h −1  bar −1 , a high dye rejection (>98 %), and a low Na 2 SO 4 rejection (<3 %), achieving a separation factor of 32.8 for selective dye/salt fractionation. More importantly, the smooth and hydrophilic membrane surface endowed superior anti-fouling capability with a flux recovery ratio of >94.4 % in cyclic fouling–cleaning tests. These results demonstrate that regulating the IP process using functionalized monomers is an effective strategy for designing advanced TUF membranes featuring excellent dye/salt selectivity and robust fouling resistance, offering a promising route for sustainable textile wastewater desalination.