Promoting mechanism of SO2 and NO adsorption on activated carbon at sub-zero temperature

The adsorption of SOS and NO on activated carbon (AC) was studied between -40 degrees C and 20 degrees C. The results showed that the adsorption capacity of AC-2-750 (AC reacted with a 2:1 ratio of KOH at 750 degrees C) for SO2 and NO were 374.2 mg/g and 83.1 mg/g at -40 degrees C, respectively. As the temperature decreased, the van der Waals and electrostatic forces strengthened while molecular movements weakened, favouring low-temperature adsorption. During co-adsorption, SO2 was preferentially adsorbed in ultramicropores, whereas NO was primarily adsorbed in supermicropores. When NO was oxidised to NO2, it occupied the original adsorption sites of SO2, leading to a reduction in SO2 adsorption. The presence of NO2 favoured the adsorption of the entire system. This study provided directions for the design of activated carbon for LAS (low-temperature adsorption) technology and illustrated its mechanism at the microscopic level.