2.3.1. HPAN membrane preparation
The PAN membranes were hydrolyzed by immersing them in a 1 M NaOH solution for 2 h followed by immersing them in a 1 M HCl solution for 12 h to acidify PAN. During the acidification process, the sodium carboxylate groups transformed into carboxylic acid groups. The hydrolyzed and acidified PAN membranes will be henceforth denoted as HPAN membranes. Subsequently, the prepared HPAN membranes were thoroughly washed with DI water.