(iii) The
carbonization was put into KOH solution with the quantity ratio
of 1/4, and then dried in an oven at 105 ◦C for 24 h. The
samples were calcinated in a furnace at 800 ◦C for 2 h with
the heating ramp of 10 ◦C/min, and then cooled to room temperature
and washed by dilute hydrochloric acid to neutrality.
In the end, the sample was dried in an oven at 105 ◦C for 24 h,
obtaining the modified activated carbon (signed as K-AC).