Influences of impregnation ratio and activation time on ultramicropores of peanut shell active carbons

• Peanut shell active carbons containing ultramicropores were made by KOH activation.
• We studied effects of impregnation ratio (IR) and activation time on ultramicropores.
• Increasing IR varied ultramicropore volume (V<0.7 nm) and ultramicropore fraction.
• Prolonging the activation time varied ultramicropore fraction, not varying V<0.7 nm.
• The highest V<0.7 nm was obtained by activation for 1–2 h using an IR of 2.

We studied effects of impregnation ratio and activation time on ultramicropores of KOH-activated peanut shell active carbons (ACs). The ultramicropores were characterized in terms of ultramicropore volume (V<0.7 nm), ultramicropore fraction (V<0.7 nm/Vt), and pore size distribution. The ultramicropores of the ACs were mostly in the range of 0.45–0.70 nm. Increasing the impregnation ratio from 1 to 3 first increased the V<0.7 nm and V<0.7 nm/Vt, and then decreased them. Prolonging the activation time from 1 h to 2 h resulted in a minimum V<0.7 nm/Vt, but hardly affected the V<0.7 nm. The AC with the highest V<0.7 nm (0.11 ml/g) was obtained by activation for 1–2 h at an impregnation ratio of 2. The V<0.7 nm bore a linear relationship with the CO2 uptakes at 0.1 and 0.2 bar (0 °C). This research was significant for preparation of ACs with developed ultramicropores.