Adenine-modified sulfonated poly(ether ether ketone) membranes with phytic acid doping for efficient acid recovery

Electrodialysis provides a sustainable strategy for acid recovery with operational simplicity and energy efficiency. This study utilized adenine’s basic sites to anchor phytic acid (IP6) and prepared phytic acid-doped adenine-modified sulfonated poly ether ether ketone (SPEEK x A/IP6) membranes with varying adenine substitutions. The acid-base crosslinking among adenine, phytic acid, and sulfonic acid groups enhances membrane mechanical characteristics and dimensional stability. The breaking strength increased 8 %–22 % relative to the pure SPEEK. The interactions between phytic acid and SO 3 H groups with adenine promote proton transport, while the large planar cationic structure of protonated adenine enhances membrane permselectivity. The SPEEK-40A/IP6 membrane exhibited superior H + flux (2.16 mmol m −2 s −1 ) and H + /Fe 2+ permselectivity (58.5), which is 1.72 times higher than the original SPEEK and surpasses both ASTOM (38.9) and recent reported membranes. These findings indicate the significant potential of SPEEK- x A/IP6 membranes for acidic wastewater acid recovery.