Corncob, a widespread and inexpensive natural resource in China, was used to prepare activated carbon (AC) by chemical activation with potassium hydroxide (KOH). The adsorption equilibrium and kinetics of H2, CH4, and CO2 on AC were investigated at different temperatures. Adsorption isotherms of H2, CH4, and CO2 were correlated with the Langmuir and Freundich equations, and the heat of adsorption was determined. It was revealed that the Freundich adsorption equation was more apt to describe the adsorption procedure of H2, CH4, and CO2 compared to the Langmuir equation. Two simplified kinetic models including pseudo-first-order and -second-order equations were used to evaluate the adsorption processes. The results indicated that the adsorption of H2, CH4, and CO2 could be described properly by a pseudo-second-order equation. The kinetic parameters of this model were calculated and discussed.

The key step for the adsorption-desorption engineering process is the reversible in-situ desorption of the adsorbent without VOCs (volatile organic compounds) accumulation. Our previous results show that the mesoporous silica gel performs well in adsorbing and desorbing the VOCs due to their capillary condensation in the mesopores. However, the microporous silica performs better in adsorbing though poorer in desorbing VOCs because of the direct interaction between VOCs molecules and the adsorbent wall in the micropores. Herein, the adsorption and desorption of o-xylene on two silica gels (SG) with different pore size distribution by vacuum swing adsorption (VSA) has been systematically studied. The equilibrium adsorption and desorption experiments of two kinds of silica gels at different loading heights in fixed bed show that the concentration front of o-xylene in microporous SG disperses slowly. However, the concentration front of o-xylene in mesoporous SG is significantly dispersed. To improve the overall efficiency of adsorptiondesorption, the mesoporous and microporous SGs are loaded together in the fixed bed. It was found that the increase in the microporous SG loading percentage facilitated the adsorption capacity but deteriorated its desorption efficiency, while the opposite occurs to the mesoporous SG. After optimization, it was observed that minimal energy consumption (1.295 kWh/m 3 VOCs gas) was used when the adsorption column is loaded with 60% SG B at the inlet and 40% of the SG A at the outlet end for o-xylene vapour adsorption. This finding will be useful for designing adsorbent loading in the adsorption column.