Facile construction of novel poly(ether sulfone ether ketone ketone) loose nanofiltration membrane for efficient dye/salt separation

The growing complexity of dyeing and printing effluents has presented considerable challenges for their effective treatment and recycling. Recently, there has been a notable increase in the development of loose nanofiltration (NF) membranes, which are characterised by their exceptional environmental resilience, high throughput, and superior dye/salt selectivity. This work presents the development of a new loose NF membrane prepared from a modified polymer called poly(ether sulfone ether ketone ketone) (PESEKK). The membrane features a dense-loose-support structure and is prepared through a straightforward one-step, non-solvent induced phase separation (NIPS) technique, eliminating the need for heating or post-treatment. Precise regulation of membrane pore size down to 4.27 nm can be achieved through modulation of PESEKK and pore-former composition. The membranes could separate positively and negatively charged dyes in mixed dye solutions accurately and selectively. Additionally, the membrane demonstrated exceptional dye/salt selective separation with a high water flux of 230.7 L m −2  h −1  bar −1 , Congo red rejection of 99.91 ± 0.13 %, NaCl rejection of 2.71 ± 0.23 %, and a separation factor (α) of 347.4, outperforming state-of-the-art membranes. Remarkably, PESEKK membrane maintained outstanding stability and separation performance for up to 200 h under extreme environments, including NaOH solution (up to 9 mol L −1 ), NaClO solution (up to 40,000 mg L −1  h), n-hexane, isopropanol, and methanol. This high-performing loose NF membrane, developed using innovative polymer materials, offers a promising solution for treating the challenging wastewater generated by printing and dyeing processes.