For the preparation of the KOH-activated carbon,
the biomass was previously pyrolyzed at 400 ํC for 4 h and subsequently impregnated with a saturated solution of potassium hydroxide 1 mL/g of carbon and continuously stirred for 2 h at 60 ํC.
The samples were then dried for 24 h in an air circulation oven at 120 ํC,
ground,
sieved (100–150 mesh) and pyrolyzed again at 500 ํC (CAK5) and 700 ํC (CAK7).
To clean up the surface,
the resulting carbons were washed alternately with hot and cold deionized water until neutralization pH was reached.
Finally,
the activated carbons were dried at 105 ํC for 24 h to remove moisture.