Preparation and characterization of activated carbon modified by potassium for carbon dioxide/methane adsorption and separation

In this study, potassium nitrate, which was confirmed feasible to improve the adsorption capacity of carbon dioxide and separation of carbon dioxide/methane mixture, was utilized to modify the commercial coconut shell activated carbon. Three parameters, including potassium ion concentration, modification temperature and modification time, were investigated. The best sample is obtained when impregnating in potassium nitrate solution of 0.1 mol L−1 at 55 °C for 12 h according to its adsorbed amount capacity and separation effect. The saturated adsorbed amount of carbon dioxide on the optimal sample reaches up to 12.25 mmol g−1. In addition, the selectivity for a binary mixture with volume ratio of 60/40, 50/50 and 40/60, which is considered in the range of typical landfill gas, are 6.86, 6.62 and 6.39, increasing by 45.9 %, 43.6 % and 41.4 %, respectively. The adsorbent obtained in this study is promising in the adsorption and separation of carbon dioxide and methane industrially. Moreover, the method of modifying by potassium ion provides a potential way in improving the property of the adsorbents.