The chars were produced in a rotary oven (5 °C/min up to 850 °C
with a soaking time of 30 min) and in a nitrogen atmosphere as explained in a previous paper [26]. Physical activation was also carried
out in the rotary oven at 850 °C with a flow of 250 ml/min of CO2 for
various periods of time in order to obtain different degrees of burn-off
expressed on an ash free basis (B.O.) throughout the manuscript.