Preparation of activated carbon
Corncob used in this study as precursor was sourced locally.
These were cut into small pieces, washed severally with distilled
water to remove surface-adhered particulate matter and watersoluble
impurities and dried to constant weight in an oven at
70 ◦C. The dried samples were ground and sieved to particle size
of 500–710 m and further dried in the oven. The sample was then
soakedinorthophosphoric acid(H3PO4) withanimpregnationratio
of 1:1 (w/w)for 24 h and dehydrated in an oven overnight at 105 ◦C.
The choice ofH3PO4 as activating agent was because ofthe excellent
results obtained withitinpreliminary studies. The resultant sample
was activated in an electric tubular furnace at 500 ◦C with constant
heating rate of 10 ◦C/min, under purified nitrogen (99.995%) flow of
150 cm3/min for 2 h. The AC produced was cooled to room temperature
and washed with 0.1 M HCl and successively with hot distilled
water. Washing with distilled water was done repeatedly until the
pH of the filtrate reached 6–7. The final product was dried in an
oven at 105 ◦C for 24 h and kept in an airtight container for further
use.