Based on previous reports , we applied a mild hydrolysis treatment (120 minutes with NaOH 1.5 M at 50 °C) in order to favor the formation of COO -surface groups while preserving the HPAN membrane mechanical properties. Expectedly, new IR peaks highlighted the presence of carboxylic acid/carboxylate moieties at 1560, 1400 and around 3300 cm -1 51, , along with amides groups (characteristic peak at 1670 cm -1 ) coming from the partial surface hydrolysis of nitriles.