**3. Materials and Method**

#### *3.1. Preparation of Activated Carbon*

The leftover leaves of "*Lantana camara*" (24 g) were collected from SMME Department, NUST Islamabad, (latitude, 33.6360821; longitude, 72.9897282) Pakistan. The surfaces of the leaves were cleaned three times with distilled water to remove dust. Before being crushed, the leaves were dried out in the open atmosphere for 3 to 4 days. The dried leaves were crushed and sieved. After that, an H3PO4 (wt 50%) solution was used to activate the fine biomass powder. The initial concentration of the H3PO4 solution was 85%. The required H3PO4 volumes per (17.38 g) dry raw biomass material were 12.13 mL [45]. The slurrybased material was calcined in a box resistance furnace for two hours at 500–600 degrees Celsius. Then, the obtained char was rinsed with distilled water to remove extra H3PO4 from the char [46]. After that, it was dried for an hour at 110◦C to yield 4 g of activated carbon [45–47].
