*2.2. Preparation of the Activated Carbon*

The preparation process of the AC (Figure 1) has two steps: carbonization and activation. In the first step, argan was crushed and sieved to get a particle size ranging between 80 and 100 μm. Then it was washed with distilled water and dried at 60 ◦C for 24 h. In the second step, the chemical impregnation was done in a round-bottom flask reactor, where 60 g of argan reacted with an H3PO4 solution 85% (1:3) for 24 h at an ambient temperature of 25 ◦C. After impregnation, the solid was filtered under a vacuum to remove the excess phosphoric acid. Then the argan's powder was pyrolyzed at 575 ◦C for 90 min in a muffle furnace (PR Series Hobersal). Furthermore, the carbon was completely washed with ultra-pure water in order to remove the remaining phosphoric acid until reaching a pH of (6.5). Finally, the samples were dried in the oven at 105 ◦C for 24 h.
