It was also ground and sieved to N300-mesh size. Under RT, the CP powder was treated with potassium carbonate or phosphoric acid in a 1:1.5 ratio (w/w) for 12 h [15]. Inside a programmed muffle furnace, the pretreated biomass was heated to 972 K at a constant heating cycle of 283 K/min with a N2 flow rate of 10 cm3/min. The furnace’s temperature was held at 972 K for 2 h before continuing to drop to RT under nitrogen flow. The activated carbon was then drained with a 1% sodium bicarbonate (w/v) solution and boiled using double distilled water till the pH of the runoff was neutral (pH 7) [16]. It has been subsequently left to dry at 385 °F, during this time the mass remained unchanged. For adsorbent investigations, both potassium carbonate activated carbon (ACCO3) and phosphoric acid activated carbon (ACPO4) were sieved by b75 mesh and kept in a desiccator. Steps followed to obtain biochar from cassava peel are mentioned in Fig. 2.